Geschlechterrollenwechsel in der Pubertät aufgrund 5a-reductase-2 Ausfall (5a-RD-2)

Ein interessanter Bericht schildert den Verlauf einer biologischen Besonderheit,  der 5a-reductase-2 deficiency (5a-RD-2):

Ich hatte dazu schon einmal einen Artikel:

Gender development and 5a-reductase-2 deficiency (5a-RD-2) and 17bhydroxysteroid dehydrogenase-3 deficiency (17b-HSD-3) Children with 5α-RD-2 have an enzyme defect that prenatally blocks the conversion of testosterone into dihydrotestosterone. Consequently they are born with external genitals that are female in appearance. They are usually raised as girls and seem to have a female gender identity, but, if the condition is not discovered in childhood, these children develop male sex characteristics in puberty: growth of their “clitoris” and scrotum, lowering of the voice, beard growth, masculine muscle development, and masculine body fat distribution. After puberty, many of these youngsters start living as males and develop a sexual attraction toward females. These transitions have been primarily documented in non-Western cultures. When raised as boys, these children have a male identity and behave like boys.

Dazu dann aus dem Artikel:

A study of this form of pseudo-hermaphroditism in the Dominican Republic found 18 cases, all of whom had been unambiguously assigned a female sex and socialized as girls by parents who had no idea that their daughters might be sons. This occurred in a traditional, rural, unsophisticated, Latin American society with clear and distinct differences in male and female sex role behaviour. At the time of their sex change, several of the subjects were already engaged to be married to men. All had girls’ names, dressed as girls, and regarded themselves as girls until the sex change.

Following puberty, all the subjects developed male genitals along with the other secondary sexual characteristics of adolescent males. One of the first signs of the sex change in the erstwhile girls was a sudden interest in playing football! The ages at which subjects first experienced morning erections, nocturnal emissions, masturbation and sexual intercourse were not appreciably different between those raised as girls who changed to a male-gender identity and a control group raised as boys from the beginning.

Vermutlich würde man hier im feministischen sagen, dass eben die Zuordnung des Männlichen zu den Genitalien so eindeutig ist, dass sie trotz aller Erziehung ihre Rollen vergessen und männlich werden.

Dazu aus meinem Butlerartikel:

Butler überträgt diesen Gedanken, wie Foucault bereits vor ihr auf das Geschlechterverhältnis, wo nach ihrer Auffassung ebenfalls bestimmte Geschlechternormen errichtet worden sind, die die Errichtung der Geschlechter und deren Verhalten bewirken. Diese knüpfen an die unterschiedlichen Körper von Mann und Frau an, die aber insoweit lediglich das Unterscheidungsmerkmal bilden, dass dann über verschiedene kulturell geschaffene Regeln zur Errichtung der Geschlechterrollen führt. Körper materialisieren sich nie unabhängig von ihrer kulturellen Form, sind also immer an ihre kulturspezifische Wahrnehmung gebunden.
Diese kulturspezifischen Merkmale der Geschlechterrollen werden dann durch beständige Wiederholung gleichsam eingeübt.
Nach dieser Vorstellung gibt es ersteinmal keine Frau als Subjekt, sondern das was als Frau definiert wird ist beständig einer kulturellen Betrachtung und Veränderung unterworfen. Eine „Frau“ mit einem männlicheren Körper ist in dieser Hinsicht teilweise schon wieder den männlichen Regeln unterworfen, ist also nicht per se Frau, sondern irgendwo dazwischen. Ein Transsexueller wäre nach erfolgter Operation über seinen Körper neuen Geschlechternormen unterworfen, die aber wiederum im Fluss sind und wer welchen Normen unterworfen ist, ist ebenso im Fluss, was die Abgrenzung der Geschlechter schwierig macht. Allein der Diskurs kann nach diesen Vorstellungen festlegen, was eigentlich eine Frau und was ein Mann ist. Denn der Diskurs hätte nach diesen Theorien etwa die Macht, einem Mann mit einem zB geringen Bartwuchs die Männereigenschaft abzusprechen und ihn den Frauen zuzuordnen (wenn ich es richtig verstehe). Darauf, dass die Abgrenzung dennoch in den meisten Kulturen abgesehen von den geringen Zahlen der Intersexuellen und Transsexuellen unproblematisch ist, geht sie meines Wissens nach nicht ein.
Für Butler schafft der Diskurs damit auch gleichzeitig den Körper -durch die Sprache materialisert sich das Geschlecht, Diskurs und Materie sind insofern miteinander verbunden. Die Sprache und der Diskurs stehend damit auf einer Stufe mit der Materie. Das Sprache und Diskurs die Materie nicht verändern und die Materie unterschiedlich bleibt ist nicht relevant, weil das übergeordnete Subjekt aus den drei Elementen, Diskurs, Sprache und Materie, eben durch diese alle drei geschaffen wird. Eine Frau kann nicht Frau sein, wenn die Eigenschaft Frau nicht durch den Diskurs in seiner gerade gültigen Form geschaffen, dies durch Sprache vermittelt wird und die Unterscheidung zu anderen Geschlechtern anhand körperlicher Faktoren, an denen diese Normen ansetzen können, erfolgen kann. (vgl auch „Butler zur Konstruktion der Geschlechter„)

Weil also deren Körper männlicher werden übernehmen sie dann nach dieser Vorstellung auch männliche Normen. Allerdings scheint mir die Erklärung nach der Biologie wesentlich realistischer und natürlich müsste man sich dann auch entscheiden, ob Erziehung leicht änderbar ist, ebenso wie Geschlechterrollen oder nicht.

The study found that all but two (89 per cent) made a full sex-role change and were living with women at the time of the study despite parental consternation, their own initial shock, and social pressure not to do so.

Gerade wenn man diesen Druck dazu nimmt und auch berücksichtigt, dass sie nicht plötzlich körperlich Männer geworden sind, sondern nur männlicher, passen auch die oben genannten Theorien nach meiner Auffassung nicht. Eine so hohe Quote passt aber sehr gut zu den biologischen Theorien.

Auch die anderen beiden Personen haben aber erhebliche Veränderungen mit dem Einsetzen der Hormone erlebt.

One of the remaining two continued to dress as a woman, had sexual relations with women but not men, and had masculine ways. The other persisted in the female role and lived with a man for a year until he left her. She was described by the study as having masculine build and mannerisms but wore false breasts and at the time of the study desired a sex change operation to make her a more normal woman.

Auch sicherlich keine einfachen Schicksale plötzlich eine solche Umkrempelung des eigenen Lebens zu erfahren und alles auf den Kopf gestellt zu bekommen, was bisher galt.

Of the 18, she was the only one who persisted in all respects with the female sex role that she had been assigned at birth. The researchers conclude: “These subjects demonstrate that in the absence of sociocultural factors that could interrupt the natural sequence of events, the effect of testosterone predominates, over-riding the effect of rearing as girls.”

Es würde in der Tat ganz neue Modelle erfordern um diese Phänomene darzustellen, wenn man nur auf die Erziehung abstellt. Denn dieses Abstreifen der Erziehung scheint mir mit den bisherigen Theorien nicht wirklich zu erklären.

Ein anderes Beispiel:

The Simbari Anga of Papua New Guinea have a radically different culture from that of the Dominican Republic: after male initiation rites (prior to puberty) the two sexes are kept rigorously separate, and ritualized oral sex occurs between men from puberty until premarital age. Yet in spite of this barrier between the sexes,

most of the affected individuals changed their gender identities from female to male at puberty, albeit with much turmoil … The fact that these individuals adopted male gender identity at puberty suggests that prenatal exposure of the brain to testosterone, combined with normal activational events of male puberty, overrides any effect of rearing in the determination of adult gender identity.

Bei vollkommener Trennung konnten sie dennoch eine andere Geschlechteridentität entwickeln. Aber eben auch nur die davon betroffenen, die eine hormonelle Umstellung erlebten.

The researchers conclude:

It has been proposed that gender identity becomes fixed by 18 months to 4 years of age, at the approximate time of language development (…). During this time a child becomes aware of his or her gender. Awareness of one’s gender and being unalterably fixed in that gender appear to be two separate issues. Subjects with 5α-reductase deficiency who have undergone a gender change suggest that gender identity in man is not fixed in childhood but is continually evolving, becoming fixed with or following pubertal events.

In humans, androgens, and not just environmental or sociocultural factors, make a strong and definite contribution to the formation of a male gender identity (…).

Es ist ein interessanter Sonderfall, der sicherlich weiterer Forschung wert ist. Natürlich funktioniert ansonsten bei anderen Jungs und Mädchen auch die Umwandlung von Testosteron auch, so dass da bestimmte Abläufe früher beginnen und abgeschlossen werden könnten.

In terms of the diametric model(link is external), sexuality is a complex issue, as I argued in a previous post, with a real, mechanistic, genetically-determined part—sex—and an imaginary, mentalistic part—gender. Furthermore, as I also pointed out in another post, even the purely genetic/hormonal aspect of sex is much more complicated in reality than it might seem. But however you look at it, the score seems to be: Nature 9, Nurture 1! At the very least, it certainly isn’t the draw we’re usually told it is.

Es zeigt aus meiner Sicht auch die starke Wirkung der Biologie, die selbst einen so komplexen Wandel bewirken kann.

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Geschlechterunterschiede im Gehirn sind bereits im Alter von einem Monat vorhanden

Ein interessante Studie zu Geschlechterunterschieden im Gehirn bei Säuglingen:

The developing brain undergoes systematic changes that occur at successive stages of maturation. Deviations from the typical neurodevelopmental trajectory are hypothesized to underlie many early childhood disorders; thus, characterizing the earliest patterns of normative brain development is essential. Recent neuroimaging research provides insight into brain structure during late childhood and adolescence; however, few studies have examined the infant brain, particularly in infants under 3 months of age. Using high-resolution structural MRI, we measured subcortical gray and white matter brain volumes in a cohort (N = 143) of 1-month infants and examined characteristics of these volumetric measures throughout this early period of neurodevelopment. We show that brain volumes undergo age-related changes during the first month of life, with the corresponding patterns of regional asymmetry and sexual dimorphism. Specifically, males have larger total brain volume and volumes differ by sex in regionally specific brain regions, after correcting for total brain volume. Consistent with findings from studies of later childhood and adolescence, subcortical regions appear more rightward asymmetric. Neither sex differences nor regional asymmetries changed with gestation-corrected age. Our results complement a growing body of work investigating the earliest neurobiological changes associated with development and suggest that asymmetry and sexual dimorphism are present at birth.

Quelle: Investigation of brain structure in the 1-month infant (Scihub Volltext Link)

Aus der Studie:

Unterschiede Gehirn Mann Frau 1 Monat

Unterschiede Gehirn Mann Frau 1 Monat

Da geht es um die

  1. Größe des Gehirns von männlichen und weiblichen Babies nach Geburt.
  2. Das Volumen der weißen Substanz im Gehirn
  3. Das Volumen der grauen Substanz im Gehirn

Wie man sieht ist das Gehirn der männlichen Babies im Durchschnitt zB größer, und zwar über die hier erfassten Alter hinweg, auch wenn es einzelne männliche Babies mit relativ kleinen und einige Mädchen mit relativ großen Gehirnvolumen gibt. Der Trend ist aber recht deutlich.

Auch die Daten zu den verschiedenen Bereichen zeigen deutliche Unterschiede:

Unterschiede Gehirn Mann Frau 1 Monat

Unterschiede Gehirn Mann Frau 1 Monat

Es wird schwer das mit einer unterschiedlichen Sozialisiation zu erklären. Sie müsste dann wohl bereits im Mutterleib ansetzen. Was allerdings pränatale Hormone in der Tat machen, wie man beispielsweise an dem Testosteronspiegel sieht:

Testosteron Maenner Frauen

Testosteron Maenner Frauen

Aus einer Besprechung der Studie:

Dean’s team found that the boys’ brains were 8.3 per cent bigger, in line with the sex difference in brain volume found in adults and the few other available infant studies. Also as seen in adults, male brains had relatively more white matter (connecting tissue) and female brains more grey matter, relative to total brain size.

A number of specific neural areas were larger in males, such as parts of the limbic system involved in emotions, including the amygdala, insula, thalamus and putamen. The researchers also found evidence for relatively larger hippocampi, an area involved in memory, which has more commonly been found to be larger in females, although not universally so. Meanwhile female brains were relatively larger in other limbic areas such as parts of the cingulate gyrus, caudate and parahippocampal gyrus, and they had a few white-matter structures that were relatively larger.

These sex differences were smaller than has been observed in adults, which suggests that maturation continues this differentiation, likely through the high volume of sex steroid receptors in these brain areas. The alternative suggestion is that the subsequent differentiation is due to socialisation, but for the forces of socialisation to work along the same lines as pre-existing biological forces would suggest that socialisation is at most a feedback loop between biology and society.

There were a lot of brain areas that differed structurally between the sexes, but it would be irresponsible to draw any firm conclusions about what they might mean for function and behaviour. For instance,  what could differences in overall insula size possibly mean psychologically when the area is associated with “compassion and empathy, perception, motor control, self-awareness, cognitive functioning”, “interpersonal experience” and “psychopathology”?

Insofern liegt noch viel Arbeit vor den Forschern, bis sie die Unterschiede wirklich verstehen. Aber dennoch entzieht diese Studie vielen, die auf einen Blank Slate abstellen und annehmen, dass Geschlechterunterschiede nur auf Sozialisiation zurück gehen können einiges an Boden bzw. erfordert, dass diese ihre Thesen kritisch hinterfragen.

Vgl auch:

Homosexualität am Gesicht erkennen

Die Studie war bereits Thema in den Kommentaren:

We show that faces contain much more information about sexual orientation than can be perceived and interpreted by the human brain. We used deep neural networks to extract features from 35,326 facial images. These features were entered into a logistic regression aimed at classifying sexual orientation. Given a single facial image, a classifier could correctly distinguish between gay and heterosexual men in 81% of cases, and in 74% of cases for women. Human judges achieved much lower accuracy: 61% for men and 54% for women. The accuracy of the algorithm increased to 91% and 83%, respectively, given five facial images per person. Facial features employed by the classifier included both fixed (e.g., nose shape) and transient facial features (e.g., grooming style). Consistent with the prenatal hormone theory of sexual orientation, gay men and women tended to have gender-atypical facial morphology, expression, and grooming styles. Prediction models aimed at gender alone allowed for detecting gay males with 57% accuracy and gay females with 58% accuracy. Those findings advance our understanding of the origins of sexual orientation and the limits of human perception. Additionally, given that companies and governments are increasingly using computer vision algorithms to detect people’s intimate traits, our findings expose a threat to the privacy and safety of gay men and women.

Quote: Deep neural networks are more accurate than humans at detecting sexual orientation from facial images.

Aus dem Spiegelartikel dazu:

Sie zeigten, wie ein Computer mithilfe von Gesichterkennungssoftware die sexuelle Orientierung von Menschen erkennt.

Und das mit extrem hoher Trefferquote: Ausgehend von nur einem Foto erkannte das Programm 81 Prozent aller schwulen Männer und 74 Prozent aller homosexuellen Frauen. Menschliche Probanden, denen die gleichen Bilder vorgelegt wurden, kamen hier nur auf 61 und 54 Prozent Trefferquote. Noch gruseliger wurden die Ergebnisse, wenn man dem Rechner fünf Bilder einer Person vorlegte. Dann erkannte die Software 91 Prozent der homosexuellen Männer und 83 Prozent der Frauen.

Auch interessant: Das dort verlinkte Bild:

homosexuell Gesicht

homosexuell Gesicht

Das linke Gesicht wurde aus heterosexuellen Personen zusammengesetzt, das rechte aus homsoexuellen Personen.

Interessanterweise kommen mir in beiden Fällen die heterosexuellen Gesichter unattraktiver vor. Vielleicht auch nur, weil  sie jeweils dicker aussehen.

Aus meiner Sicht ein durchaus zu erwartendes Ergebnis:

Die vorherrschende Theorie führt an, dass Homosexualität in einer engen Verbindung mit insbesondere pränatalen Hormonen steht:

Und auch Gesichter sind männlicher oder weiblicher unter der Einwirkung der Hormone:

vgl zB diese Studie:

Prenatal testosterone may have a powerful masculinizing effect on postnatal physical characteristics. However, no study has directly tested this hypothesis. Here, we report a 20-year follow-up study that measured testosterone concentrations from the umbilical cord blood of 97 male and 86 female newborns, and procured three-dimensional facial images on these participants in adulthood (range: 21–24 years). Twenty-three Euclidean and geodesic distances were measured from the facial images and an algorithm identified a set of six distances that most effectively distinguished adult males from females. From these distances, a ‘gender score’ was calculated for each face, indicating the degree of masculinity or femininity. Higher cord testosterone levels were associated with masculinized facial features when males and females were analysed together (n = 183; r = −0.59), as well as when males (n = 86; r = −0.55) and females (n = 97; r = −0.48) were examined separately (p-values < 0.001). The relationships remained significant and substantial after adjusting for potentially confounding variables. Adult circulating testosterone concentrations were available for males but showed no statistically significant relationship with gendered facial morphology (n = 85, r = 0.01, p = 0.93). This study provides the first direct evidence of a link between prenatal testosterone exposure and human facial structure.

Ich hatte einmal zu den Gründen für Homosexualität ausgeführt:

1. Männliche Homosexualität:

  • Die Hoden des Fötus produzieren nicht genug Testosteron
  • Die Hoden des Fötus entwickeln sich zu spät und produzieren erst nach der entscheidenen Phase Testosteron
  • Das Testosteron wird mangels entsprechender Rezeptoren an der Blut-Hirn-Schranke/im ganzen Körper nicht erkannt.
  • Das Testosteron wird mangels entsprechender Rezeptoren an der Blut-Hirn-Schranke nur teilweise/abgeschächt erkannt
  • Das Östrogen wird im Gehirn mangels entsprechender Rezeptoren nicht erkannt.
  • Die Mutter stellt in der entscheidenden Phase nicht genug Testosteron bereit.
  • Der Schwellenwert ist überhoch eingestellt, so dass das weibliche Programm trotz ausreichend Testosteron nicht durchgeführt wird.
  • Antiandrogene blockieren die Rezeptoren in der entscheidenden Phase.
  • Medikamente/andere Stoffe senken den Testosteronspiegel in der entscheidenden Phase
  • Umweltbedingungen senken des Testosteronspiegel in der entscheidenden Phase
  • Ein Zusammenspiel dieser Faktoren

2. Weibliche Homosexualität:

  • Der Fötus hat einen erhöhten Testosteronspiegel (über eine Überproduktion der Nebennierenrinde und der Eierstöcke)
  • Die Mutter stellt ein Übermass an Testosteron bereit.
  • Der Schwellenwert für das 2.  Bauschema Mann ist in diesem Bereich extrem niedrig angesetzt.
  • Medikamente sorgen für eine Erhöhung des Testosteronspiegels in der empfindlichen Phase
  • überempfindliche Rezeptoren suggerieren einen erhöhten Testosteronspiegel.
  • Ein Zusammenspiel dieser Faktoren

Wie man sieht muss damit nicht zwangsläufig die Homosexualität sich auch im Gesicht zeigen. Etwa weil der „Schwellenwert“ niedrig angesetzt ist oder der Wert nur in einer bestimmten Phase sehr hoch ist. Gerade wenn der Hormonspiegel aber dauerhaft erhöht ist spricht vieles für eine Übereinstimmung.

Insofern aus meiner Sicht ein sehr nachvollziehbares Ergebnis

 

Studiensammlung 4: (Prenatale) Hormone und Geschlechterunterschiede im Gehirn und Verhalten

Und weil wir heute eh schon eine Studie hier zu Gehirnunterschieden haben hier ein paar weitere Studien:

1.

Fetal Testosterone Influences Sexually Dimorphic Gray Matter in the Human Brain

In nonhuman species, testosterone is known to have permanent organizing effects early in life that predict later expression of sex differences in brain and behavior. However, in humans, it is still unknown whether such mechanisms have organizing effects on neural sexual dimorphism. In human males, we show that variation in fetal testosterone (FT) predicts later local gray matter volume of specific brain regions in a direction that is congruent with sexual dimorphism observed in a large independent sample of age-matched males and females from the NIH Pediatric MRI Data Repository. Right temporoparietal junction/posterior superior temporal sulcus (RTPJ/pSTS), planum temporale/parietal operculum (PT/PO), and posterior lateral orbitofrontal cortex (plOFC) had local gray matter volume that was both sexually dimorphic and predicted in a congruent direction by FT. That is, gray matter volume in RTPJ/pSTS was greater for males compared to females and was positively predicted by FT. Conversely, gray matter volume in PT/PO and plOFC was greater in females compared to males and was negatively predicted by FT. Subregions of both amygdala and hypothalamus were also sexually dimorphic in the direction of Male > Female, but were not predicted by FT. However, FT positively predicted gray matter volume of a non-sexually dimorphic subregion of the amygdala. These results bridge a long-standing gap between human and nonhuman species by showing that FT acts as an organizing mechanism for the development of regional sexual dimorphism in the human brain.

Ergänzung:

(FT was measured from amniotic fluid samples collected between 13 and 20 weeks of gestation (mean FT, 0.79 nmol/L; SD, 0.34 nmol/L; range, 0.25–1.70 nmol/L).

2.

The Impact of Sex, Puberty, and Hormones on White Matter Microstructure in Adolescents

Background: During adolescence, numerous factors influence the organization of the brain. It is unclear what influence sex and puberty have on white matter microstructure, as well as the role that rapidly increasing sex steroids play. Methods: White matter microstructure was examined in 77 adolescents (ages 10–16) using diffusion tensor imaging. Multiple regression analyses were performed to examine the relationships between fractional anisotropy (FA) and mean diffusivity (MD) and sex, puberty, and their interaction, controlling for age. Follow-up analyses determined if sex steroids predicted microstructural characteristics in sexually dimorphic and pubertal-related white matter regions, as well as in whole brain. Results: Boys had higher FA in white matter carrying corticospinal, long-range association, and cortico-subcortical fibers, and lower MD in frontal and temporal white matter compared with girls. Pubertal development was related to higher FA in the insula, while a significant sex-by-puberty interaction was seen in superior frontal white matter. In boys, testosterone predicted white matter integrity in sexually dimorphic regions as well as whole brain FA, whereas estradiol showed a negative relationship with FA in girls. Conclusions: Sex differences and puberty uniquely relate to white matter microstructure in adolescents, which can partially be explained by sex steroids.

Ergänzung:

Hormonal Assessment
Four milliliters of blood was collected via venipuncture between the hours of 7:00 to 10:00 AM at the Oregon Clinical and Translational Research Institute in the same week as the imaging session.

3.

Regional sex differences in grey matter volume are associated with sex hormones in the young adult human brain

Previous studies suggest organizing effects of sex hormones on brain structure during early life and puberty, yet little is known about the adult period. The aim of the present study was to elucidate the role of 17β-estradiol, progesterone, and testosterone on cortical sex differences in grey matter volume (GM) of the adult human brain. To assess sexual dimorphism, voxel-based morphometry (VBM) was applied on structural magnetic resonance images of 34 healthy, young adult humans (17 women, 17 men, 26.6 ± 5 years) using analyses of covariance. Subsequently, circulating levels of sex hormones were associated with regional GM using linear regression analyses. After adjustment for sex and total GM, significant associations of regional GM and 17β-estradiol were observed in the left inferior frontal gyrus (β = 0.39, p = 0.02). Regional GM was inversely associated with testosterone in the left inferior frontal gyrus (β = −0.16, p = 0.04), and with progesterone in the right temporal pole (β = −0.39, p = 0.008). Our findings indicate that even in young adulthood, sex hormones exert organizing effects on regional GM. This might help to shed further light on the underlying mechanisms of both functional diversities and congruence between female and male brains.

4.

Pubertal hormones organize the adolescent brain and behavior

Maturation of the reproductive system during puberty results in elevated levels of gonadal steroid hormones. These hormones sculpt neural circuits during adolescence, a time of dramatic rewiring of the nervous system. Here, we review the evidence that steroid-dependent organization of the adolescent brain programs a variety of adult behaviors in animals and humans. Converging lines of evidence indicate that adolescence may be a sensitive period for steroid-dependent brain organization and that variation in the timing of interactions between the hormones of puberty and the adolescent brain leads to individual differences in adult behavior and risk of sex-biased psychopathologies.

5.

Prenatal hormones and childhood sex-segregation: Playmate and play style preferences in girls with congenital adrenal hyperplasia

We investigated playmate and play style preference in children with congenital adrenal hyperplasia (CAH) (26 females, 31 males) and their unaffected siblings (26 females, 17 males) using the Playmate and Play Style Preferences Structured Interview (PPPSI). Both unaffected boys and girls preferred same-sex playmates and sex-typical play styles. In the conflict condition where children chose between a same-sex playmate engaged in an other-sex activity or an other-sex playmate engaged in a same-sex activity, boys (both CAH and unaffected brothers) almost exclusively chose playmates based on the preferred play style of the playmate as opposed to the preferred gender label of the playmate. By contrast, unaffected girls used play style and gender label about equally when choosing playmates. Girls with CAH showed a pattern similar to that of boys: their playmate selections were more masculine than unaffected girls, they preferred a boy-typical play style and, in the conflict condition, chose playmates engaged in a masculine activity. These findings suggest that prenatal androgen exposure contributes to sex differences in playmate selection observed in typically-developing children, and that, among boys and girls exposed to high levels of androgens prenatally, play style preferences drive sex segregation in play.

6.

Prenatal Hormones and Postnatal Socialization by Parents as Determinants of Male-Typical Toy Play in Girls With Congenital Adrenal Hyperplasia

Toy choices of 3- to 10-year-old children with congenital adrenal hyperplasia (CAH) and of their unaffected siblings were assessed. Also assessed was parental encouragement of sex-typed toy play. Girls with CAH displayed more male-typical toy choices than did their unaffected sisters, whereas boys with and without CAH did not differ. Mothers and fathers encouraged sex-typical toy play in children with and without CAH. However, girls with CAH received more positive feedback for play with girls’ toys than did unaffected girls. Data show that increased male-typical toy play by girls with CAH cannot be explained by parental encouragement of male-typical toy play. Although parents encourage sex-appropriate behavior, their encouragement appears to be insufficient to override the interest of girls with CAH in cross-sexed toy

7.

Increased aggression and activity level in 3- to 11-year-old girls with congenital adrenal hyperplasia

Experimental research in a wide range of mammals has documented powerful influences of androgen during early development on brain systems and behaviors that show sex differences. Clinical research in humans suggests similar influences of early androgen concentrations on some behaviors, including childhood play behavior and adult sexual orientation. However, findings have been inconsistent for some other behaviors that show sex differences, including aggression and activity level in children. This inconsistency may reflect small sample sizes and assessment limitations. In the present study, we assessed aggression and activity level in 3- to 11-year-old children with CAH (38 girls, 29 boys) and in their unaffected siblings (25 girls, 21 boys) using a questionnaire that mothers completed to indicate current aggressive behavior and activity level in their children.

Data supported the hypotheses that:

  • 1. unaffected boys are more aggressive and active than unaffected girls;
  • 2. girls with CAH are more aggressive and active than their unaffected sisters; and
  • 3. boys with and without CAH are similar to one another in aggression and activity level.

These data suggest that early androgens have a masculinizing effect on both aggressive behavior and activity level in girls.

8.

Prenatal androgen exposure alters girls’ responses to information indicating gender-appropriate behaviour

Individual variability in human gender-related behaviour is influenced by many factors, including androgen exposure prenatally, as well as selfsocialization and socialization by others postnatally. Many studies have looked at these types of influences in isolation, but little is known about how they work together. Here, we report that girls exposed to high concentrations of androgens prenatally, because they have the genetic condition congenital adrenal hyperplasia, show changes in processes related to selfsocialization of gender-related behaviour. Specifically, they are less responsive than other girls to information that particular objects are for girls and they show reduced imitation of female models choosing particular objects. These findings suggest that prenatal androgen exposure may influence subsequent gender-related behaviours, including object (toy) choices, in part by changing processes involved in the self-socialization of gendered behaviour, rather than only by inducing permanent changes in the brain during early development. In addition, the findings suggest that some of the behavioural effects of prenatal androgen exposure might be subject to alteration by postnatal socialization processes. The findings also suggest a previously unknown influence of early androgen exposure on later processes involved in self socialization of gender-related behaviour, and thus expand understanding of the developmental systems regulating human gender development.

9.

How early hormones shape gender development

Highlights
Prenatal androgens influence sex-related characteristics to varying degrees.
• Androgens facilitate male-typed activities through interest in things versus people.
• Androgens are associated with some aspects of brain structure and activation.
• Current work is focused on interplay of hormones and social environment.
• Relevant to questions regarding sex-related psychopathology, prenatal programming.
 
Many important psychological characteristics show sex differences, and are influenced by sex hormones at different developmental periods. We focus on the role of sex hormones in early development, particularly the differential effects of prenatal androgens on aspects of gender development. Increasing evidence confirms that prenatal androgens have facilitative effects on male-typed activity interests and engagement (including child toy preferences and adult careers), and spatial abilities, but relatively minimal effects on gender identity. Recent emphasis has been directed to the psychological mechanisms underlying these effects (including sex differences in propulsive movement, and androgen effects on interest in people vs things), and neural substrates of androgen effects (including regional brain volumes, and neural responses to mental rotation, sexually arousing stimuli, emotion, and reward). Ongoing and planned work is focused on understanding the ways in which hormones act jointly with the social environment across time to produce varying trajectories of gender development, and clarifying mechanisms by which androgens affect behaviors. Such work will be facilitated by applying lessons from other species, and by expanding methodology. Understanding hormonal influences on gender development enhances knowledge of psychological development generally, and has important implications for basic and applied questions, including sex differences in psychopathology, women’s underrepresentation in science and math, and clinical care of individuals with variations in gender expression.

10.

The organizing actions of adolescent gonadal steroid hormones on brain and behavioral development

Highlights

• Adolescence is a sensitive period for the effects of hormones on brain and behavior.
• Testicular hormones masculinize and defeminize social and reproductive behaviors.
• Ovarian hormones have both feminizing and defeminizing effects on female behavior.
• Gonadal steroid hormones drive many brain structural changes during adolescence.
• Adolescence may be part of a protracted postnatal steroid-sensitive period.

Abstract
Adolescence is a developmental period characterized by dramatic changes in cognition, risk-taking and social behavior. Although gonadal steroid hormones are well-known mediators of these behaviors in adulthood, the role gonadal steroid hormones play in shaping the adolescent brain and behavioral development has only come to light in recent years. Here we discuss the sex-specific impact of gonadal steroid hormones on the developing adolescent brain. Indeed, the effects of gonadal steroid hormones during adolescence on brain structure and behavioral outcomes differs markedly between the sexes. Research findings suggest that adolescence, like the perinatal period, is a sensitive period for the sex-specific effects of gonadal steroid hormones on brain and behavioral development. Furthermore, evidence from studies on male sexual behavior suggests that adolescence is part of a protracted postnatal sensitive period that begins perinatally and ends following adolescence. As such, the perinatal and peripubertal periods of brain and behavioral organization likely do not represent two discrete sensitive periods, but instead are the consequence of normative developmental timing of gonadal hormone secretions in males and females.

11.

Effects of chromosomal sex and hormonal influences on shaping sex differences in brain and behavior: Lessons from cases of disorders of sex development

Sex differences in brain development and postnatal behavior are determined largely by genetic sex and in utero gonadal hormone secretions. In humans however, determining the weight that each of these factors contributes remains a challenge because social influences should also be considered. Cases of disorders of sex development (DSD) provide unique insight into how mutations in genes responsible for gonadal formation can perturb the subsequent developmental hormonal milieu and elicit changes in normal human brain maturation. Specific forms of DSDs such as complete androgen insensitivity syndrome (CAIS), congenital adrenal hyperplasia (CAH), and 5α-reductase deficiency syndrome have variable effects between males and females, and the developmental outcomes of such conditions are largely dependent on sex chromosome composition. Medical and psychological works focused on CAH, CAIS, and 5α-reductase deficiency have helped form the foundation for understanding the roles of genetic and hormonal factors necessary for guiding human brain development. Here we highlight how the three aforementioned DSDs contribute to brain and behavioral phenotypes that can uniquely affect 46,XY and 46,XX individuals in dramatically different fashions

Aus der Studie:

CAH ein Schaubild

CAH, CAIS und 5-alpha reductace Deficiency: ein Schaubild

Weiteres aus der Studie:

Research focused on cases of DSD have helped the scientific community better understand the interplay between gonadal hormones and sex chromosome complement with regard to generating some of the sex differences observed in humans. These works have shed light on the likelihood that testosterone exposure, as opposed to sex chromosomes, is a larger contributing factor for guiding one’s sexual orientation and to a lesser extent gender identity. We see that 46,XX CAH individuals that have been exposed to in utero testosterone experience a greater degree of dissatisfaction in gender assignment in addition to above-average levels of homosexual and bisexual fantasies, a proxy for sexual preference. As previously mentioned, other variables are present in CAH cases such as life-long medical interventions and psychosocial confounds. These variables may constitute an environmental factor that, when coupled with biological predispositions, generates variations in sexual orientation and gender identity. That sexual orientation is determined solely by in utero hormonal milieu is unlikely. We see that the vast majority of CAH women, despite having been exposed to above-average levels of testosterone, identify as heterosexual as measured by both partners and sexual fantasies. The science of sexual orientation is still weakly understood at the mechanistic level; however, considerable amounts of research have proposed many possibilities for the causes of same-sex attraction (LeVay, 2012; Bailey et al., 2016).

The strongest evidence that adds support for the influence of testosterone in structuring gender identity comes from the work focused on 46,XY CAIS, in which nearly all individuals researched indicate feelings typical of female gender. In addition to self-reports and clinical evaluations, recent fMRI studies have also demonstrated that CAIS women not only feel female but also neurologically respond more similarly to 46,XX women than to 46,XY men when observing sexual images. However, new studies are continually emerging suggesting that gender identity and sexual orientation in individuals with CAIS are not as clear as once thought, and the rates of nonheterosexual and gender dysphoria may be much higher than currently stated. In addition to CAH and CAIS, 5α-reductase deficiencies have also demonstrated the strong role of testosterone’s ability to organize the human brain hormonally and influence adult gender identity and behavior. If early in utero exposure had no influence in guiding brain gender, we would expect considerable difficulty with the female-to-male transition observed in pubertal years in those with 5α-reductase deficiency. What we observe, however, is that an overwhelming majority of individuals with this condition comfortably transitioned into the new gender role at puberty, a worldwide observation occurring throughout many different types of social environments. Despite the convincing findings for the role of testosterone in generating these observations, the influence of social and other environmental variables are also factors that require consideration.

Cognitive Conclusions
Studying cases of DSDs has also provided insight into some of the biological parameters that generate sex differences in cognitive abilities such as visuospatial awareness and targeting ability. From studies with 46,XX CAH individuals it has been well established that in utero androgen exposure seems to enhance the ability to mentally rotate objects as well as improving hand–eye coordination during targeting tasks. This trait appears to be dependent on sex chromosome complement in addition to hormone exposure, insofar as 46,XY males with CAH actually perform worse than their matched controls, which is unexpected given the fact that CAH males would have equal or elevated levels of circulating testosterone. This raises the notion, as mentioned above, that proper timing and dosage are also likely to be important for enhancing such abilities and that simply having above-average levels of testosterone during development would not generate a “super-male.” CAIS provides another insight into this matter, demonstrating that the ability to respond to testosterone on an XY background is critical to establishing baseline spatial performance abilities. fMRI studies demonstrate that 46,XY CAIS had less inferior parietal lobe neuroactivation when performing spatial rotation tasks, a feature that resembles 46,XX females more than control genetic males. These fMRI studies on CAIS individuals once again minimize social influences and allow for a more unbiased assessment of the requirement for testosterone over genetic composition for shaping these cognitive performance sex differences.
Structural Conclusions
From the MRI studies that have been conducted in patients with CAH, it is clear that DSDs affect more than gonadal development. As highlighted, the central nervous system is highly sensitive to various hormones, and imbalances of these can greatly affect downstream behavior as well as overall brain structure. Variations in amygdala volume seem to be present in some individuals with CAH; however the effect is different depending on sex chromosome composition. Specifically, 46,XY males with CAH show unilateral reductions in the left amygdala, whereas 46,XX females with CAH show bilateral reductions in overall volume. Alterations in amygdala volume seem to be consistent with long-term glucocorticoid replacement therapies because findings for non-CAH patients on such hormone regiments also show amygdala abnormalities. The documentations of white matter irregularities seem to be unaffected by chromosomal sex and to cause similar variations in both males and females with CAH. The explanations for these results are not agreed upon, and more research will be needed before causations can be associated with the unusual white matter findings. Although limited, these discoveries have opened a new area for potential investigation focusing on the role of glucocorticoid influences in the developing brain in addition to the more frequently studied gonadal hormonal contributions. Unfortunately, no extensive structural studies have been conducted in patients with CAIS or 5α-reductase deficiencies. These findings would be invaluable in determining the direct effect of testosterone on the structures that in MRI studies have shown alterations in CAH. Future work focusing on outcomes in individuals with DSD will continue to aid in deciphering the contributions of chromosomal sex and hormones to shaping the sexually dimorphic human brain.

12.

Feminists wrestle with testosterone: Hormones, socialization and cultural interactionism as predictors of women’s gendered selves 

Sociology of gender has developed beyond a personality-centered idea of ‘‘sex-roles’’ to an approach that stresses interaction and social structure. At the same time, there has been a concurrent development in the psychological sex-differences and medical literatures toward including the biological bases of sex-typed behavior and gender identities. In this paper, while we conceptualize gender as a social structure, we focus only on the individual level of analysis: testing the relative strength of (maternal circulating) prenatal hormones, childhood socialization, and the power of expectations attached to adult social roles (cultural interactionist) as explanations for women’s self-reported feminine and masculine selves. Our findings are complex, and support some importance of each theory. Prenatal hormones, childhood socialization, and cultural interactionism were all influential factors for gendered selves. While cultural expectations predicted only feminine selves, prenatal hormones were more robust predictors of masculine sense of self. While personality may be a relatively stable characteristic influenced by the body and childhood socialization, our results reinforce the importance of studying how the social world responds to and reinforces gendered personality.

12.

Genetic association suggests that SMOC1 mediates between prenatal sex hormones and digit ratio

Abstract

Men and women differ statistically in the relative lengths of their index and ring fingers; and the ratio of these lengths has been used as a biomarker for prenatal
testosterone. The ratio has been correlated with a wide range of traits and conditions including prostate cancer, obesity, autism, ADHD, and sexual orientation. In a genome-wide association study of 979 healthy adults, we find that digit ratio is strongly associated with variation upstream of SMOC1 (rs4902759: P = 1.41 9 10-8) and a meta-analysis of this and an independent study shows a probability of P = 1.5 9 10-11. The protein encoded by SMOC1 has recently been shown to play a critical role in limb development; its expression in prostate tissue is dependent on sex hormones, and it has been implicated in the sexually dimorphic development of the gonads. We put forward the hypothesis that SMOC1 provides a link between prenatal hormone exposure and digit ratio.

Anmerkung: Finde ich interessant: Wenn das Protein, welches Einfluss auf die Entwicklung der Gliedmaßen hat, wiederum abhängig von Testosteron ist, dann würde das durchaus erklären, warum die Digit Ratio ein Indikator  für pränatales Testosteron ist, es könnte je nach Zusammenspiel auch zeigen, warum es ein teilweise unzuverlässiger Anzeiger ist, eben weil die Mechanismen unterschiedlich sind.

13.

Exposure to prenatal life events stress is associated with masculinized play behavior in girls

Previous research has shown that prenatal exposure to endocrine-disrupting chemicals can alter children’s neurodevelopment, including sex-typed behavior, and that it can do so in different ways in males and females. Non-chemical exposures, including psychosocial stress, may disrupt the prenatal hormonal milieu as well. To date, only one published study has prospectively examined the relationship between exposure to prenatal stress and gender-specific play behavior during childhood, finding masculinized play behavior in girls who experienced high prenatal life events stress, but no associations in boys. Here we examine this question in a second prospective cohort from the Study for Future Families. Pregnant women completed questionnaires on stressful life events during pregnancy, and those who reported one or more events were considered “stressed”. Families were recontacted several years later (mean age of index child: 4.9 years), and mothers completed a questionnaire including the validated Preschool Activities Inventory (PSAI), which measures sexually dimorphic play behavior. In sex-stratified analyses, after adjusting for child’s age, parental attitudes towards gender-atypical play, age and sex of siblings, and other relevant covariates, girls (n=72) exposed to prenatal life events stress had higher scores on the PSAI masculine sub-scale (β=3.48, p=0.006) and showed a trend towards higher (more masculine) composite scores (β=2.63, p=0.08). By contrast, in males (n=74), there was a trend towards an association between prenatal stress and higher PSAI feminine sub-scale scores (β=2.23, p=0.10), but no association with masculine or composite scores. These data confirm previous findings in humans and animal models suggesting that prenatal stress is a non-chemical endocrine disruptor that may have androgenic effects on female fetuses and anti-androgenic effects on male fetuses.

Anmerkung: Die Werte sind allerdings anscheinend sehr gering

14.

Relations between prenatal testosterone levels and cognitive abilities at 4 years.

Relations between prenatal testosterone (T) levels and cognitive abilities at age 4 were examined for 28 girls and 30 boys. Prenatal T levels were measured in 2nd trimester amniotic fluid samples obtained by amniocentesis and were examined in relation to scores on tests of cognitive abilities. For girls, prenatal T levels showed a curvilinear (inverted U-shaped) relation to language comprehension and classification abilities. Linear relations also were observed in that prenatal T levels were inversely related to girls‘ scores on tasks assessing counting and number facts. Similarly, girls with high average block building scores had lower prenatal T and cognitive abilities were not observed. The observation of relations in girls and not boys is discussed, and the findings are examined in relation to theories of hormone-behavior relations.

15.

Relations between prenatal testosterone and cerebral lateralization in children.

Several theorists have proposed that the sex steroid testosterone acts on the fetal brain during a critical period of development to influence cerebral lateralization (N. Geschwind & A. M. Galaburda, 1987; M. Hines & C. Shipley, see PA, Vol 71:8996; S. F. Witelson, see PA, Vol 79:26441. In the present study. relations were examined between prenatal testosterone levels in 2nd trimester amniotic fluid and lateralization of speech, affect, and handedness at age 10. Girls with higher prenatal testosterone levels were more strongly right-handed and had stronger left-hemisphere speech representation. Boys with higher prenatal testosterone levels had stronger right-hemisphere specialization for the recognition of emotion. This pattern of results is most consistent with Witelson’s (1991) claim that prenatal testosterone leads to greater lateralization of function.

Testo-kain oder Koka-steron? Zur Wirkung von Testosteron

Dies ist ein Gastartikel von Nina Radtke

Vor nicht all zu langer Zeit habe ich Testosteron mit Kokain verglichen. Zu diesem Schluss bin ich gekommen, da ich, im Gegensatz zu den meisten Menschen, in meinem Leben bereits verschiedenste Mengen an Testosteron im Blut hatte.

Dazu muss ich nun erst einmal kurz meine Vorgeschichte erklären: Bis ich 21 wurde, war ich der männlichen Adoleszenz unterworfen. Je mehr die Männlichkeit mein Ich bestimmte, umso schlechter fühlte ich mich. Das lag allerdings an meinem inneren Konflikt, dem Umstand, das ich trotz bereits lange vorher bestehendem andersartigem Bedürfnis, ein Mann werden sollte statt eine Frau.

Nun, ich habe dann, zuerst in Eigenregie und später mit ärztlicher Unterstützung eine Hormontherapie begonnen (und viele Operationen mitgemacht), dabei war mein Androgenspiegel oft signifikanten Änderungen unterworfen und ich habe inzwischen Alles erlebt von Testosteron quasi auf 0 bis hin zu den furchtbar hohen Testosteronspiegeln die ich angesichts meiner damals sehr ausgeprägten Muskulatur und Maskulinität gehabt haben muss.

Natürlich ist Testosteron nur ein Faktor, auch die Östrogenspiegel sowie mein weiterer Lebensweg hatten und haben sicher einen Einfluss auf mein Verhalten.

Dennoch ist es meine persönliche Empfindung, das Testosteron / Dihydrotestosteron (Wird mit Hilfe einer Aromatase zB in Prostata und Haarfolikeln aus Testosteron hergestellt und wirkt deutlich stärker) folgendermaßen wirkt:

  • Testosteron gibt Selbstvertrauen
    Wenn mein Testosteronspiegel sehr sehr niedrig ist, dann geht mir zunehmend das Selbstvertrauen flöten. Als mein Testosteronspiegel deutlich höher war, hatte ich im Umgang mit Menschen keine Selbstzweifel. Und auch keine Selbstzweifel (nur Verbitterung) beim Blick in den Spiegel. Bei sehr niedrigem Testosteron fühle ich mich einfach nicht sicher, aber es ist mehr. Mit viel Testosteron hat mein Selbstvertrauen oft dazu geführt, das Leute ohne Wiederworte Dinge mitgemacht haben, um die ich sie jetzt wirklich bitten müsste. Ich stand auch sehr viel mehr im Mittelpunkt.
  • Testosteron macht aktiv
    Kaum Testo – Lange Schlafen | „Normales Testo“ (Wert den ich die meiste Zeit hatte, etwas über weibl. Norm) – Halbwegs Aktiv | Hohes Testo – Aufgedreht (zB hin und her laufen beim Warten) ——- Hab aber glaub ich auch ADHS was sich überwiegend in sprunghaften Gedanken aber auch in physischer Unruhe äußert
  • Testosteron macht Unangreifbar
    Keine Angriff hätte mein Ego treffen können. Sowieso ist Ego glaube ich ein Produkt des zirkulierenden Testosterons, jedenfalls hat der Wettbewerbsgeist und der Geltungswahn mit der Hormontherapie schrittweise abgenommen und hat nun (T < weibliche Norm) Nichts mehr zu sagen. Ich bin jetzt auf mein Potential fokussiert und nicht auf den Vergleich mit Anderen. Ich ordne mich ohne Hierachiebewusstsein in eine Gruppe ein, früher undenkbar, aber vielleicht war mein Fokus auf Hierachie auch teilweise durch die Tipps in den Flirtratgebern statt nur durchs Testosteron bestimmt.
  • Testosteron macht Triebhaft
    Drogen, Party, Alkohol, Fressen – früher konnte ich mir den Driss jeden Tag geben und habs auch getan weil ich immer Bock drauf hatte. Eine neurobiologische Erklärung könnte sein, das Testosteron die Dopaminausschüttung stimuliert: Der gleiche Belohnungsreiz wirkt mit viel Testosteron deutlich stärker als mit wenig Testosteron. Vermutlich ein Grund, warum exzessives Verhalten bei Männern verbreiteter ist: Mehr Dopamin = Mehr Risikobereitschaft.
  • Testosteron macht gefühllos
    Schlimmer als unter Antidepressiva hat das Testosteron damals wie eine unsichtbare Mauer meine Gefühle eingesperrt. Ich konnte Gefühle ansatzweise fühlen, aber es gab immer einen Punkt, wo die Gefühle geblockt waren. Nur besonders starke „Einschläge“ konnten mich emotional aus der Ruhe bringen. Emotionen sind unter Östrogen ohne Testosteron weit fließender und natürlicher.

Mehr kann ich dazu nicht sagen, es ist noch heftig wie stark anabol Testosteron wirkt, ich merke es innerhalb weniger Wochen wenn mein Testosteron mal wieder sinkt oder steigt, das die Einkaufstasche mal schwerer und mal leichter ist. Aber das weiß glaub ich Jeder über das Hormon Testosteron^^

Zur Ergänzung des Gastartikels noch einige Links:

Liebe als Sucht bzw. Sucht als Liebe und das Liebesleben von Wühlmäusen

Ich habe das sehr interessante Buch „The Chemistry between us“ gelesen, welches ich empfehlen kann. Es werden einige sehr interessante Punkte dargestellt, sowohl zur Forschung von Geschlechterunterschieden als auch insbesondere dazu, wie wir Lieben und wie sich Bindung entwickelt.

Es sind interessante Punkte in dem Buch enthalten, zu denen man dutzende Artikel schreiben könnte. Ich fange mal mit einem an, der auch in dieser Kurzzusammenfassung hier dargestellt wird:

Young has devoted his career to studying the behaviors and neural circuitry of love in the prairie vole, a rodent whose monogamous tendencies resemble our own. Once a prairie vole has found “the one,” the pair will most likely remain companions for life. Young’s research has implicated a range of chemical activities—mainly during sex—that build this lifelong bond. In particular, he uncovered how two hormones in the brain, vasopressin in male voles and oxytocin in female voles, regulate social behavior and memory—promoting the recognition of a loved one and the urge to cuddle or defend. In addition, the circulation of dopamine and opioids allows the vole to associate his or her partner with pleasure, thus strengthening their bond. Many of these molecules are identical to those activated in human bonding.

Interessant ist daran, dass es zwei Arten von Voles (Wühlmäuse) gibt, die eine ist monogam, die andere nicht. Der Wesentliche Unterschied ist wohl eben der, dass bei dem einen über Vasopressin und Oxytocin eine Bindung erfolgt und bei dem anderen nicht. Der Unterschied zwischen den beiden Arten ist relativ gering, die Unterschiede im Verhalten aber enorm.

Young führt dann verschiedene Tests auf, die nahelegen, dass die gleichen Mechanismen eben auch beim Menschen wirken.

That loving feeling comes at a price. A hormone called corticotropin-releasing factor, or CRF, builds up in the brains of paramours and parents alike. The CRF system activates a stress response, and this system elicits the painful sensations you feel when your baby cries or your boyfriend dumps you. The system may seem like a nasty trick, but it has its uses. Even when passion fades or a diaper needs changing, the sharp pangs of the CRF system keep families and loved ones together. The CRF system also contributes to the agony an addict feels after the elation wears off. Thus, the authors argue, the highs of intimacy and withdrawals of separation parallel the highs and lows that drug addicts experience.

Wenn ich mich recht erinnere, dann stellt der Autor es so dar, dass die erste Liebe (oder der erste Kick bei einer Droge) oft noch tatsächliches Glück ist, weil man in Oxytocin gebadet ist und andere glücklichmachende Hormone ausgeschüttet werden. Das bewirkt eine Bindung. Wie bei vielen positiven Reizen wird diese Ausschüttung von reinen Glückshormonen aber mit der „Gewöhnung“ an den Partner immer geringer. Es greift dann ein anderes System: Wenn man das, was einen bisher glücklich gemacht hat, nicht mehr hat, dann baut sich das oben genannte Stresshormon auf und dieser lässt dann nach, wenn man den „Reiz“ wieder ausgesetzt ist. Das bewirkt dann den Trennungsschmerz und kann in bestimmten Fällen zu einem „ich kann nicht mit ihr und ich kann nicht ohne sie“ führen: Wenn sie da ist hat man dann eben „Belohnungseffekt“ mehr, weil dieser zu abgestumpft ist, ist sie aber weg, dann stellt sich der Trennungsschmerz ein.

Ähnlich ist es wohl auch bei Drogennutzern, die eine Droge eben wie eine Liebe empfinden: Am Anfang ist es pures Glück, dann brauchen sie eine immer höhere Dosis und schließlich ist es schlicht der „Trennungsschmerz“ der bekämpft wird und man hält es nicht mehr aus und will diesen beseitigen. Hat man ihn beseitigt, dann meint man vielleicht jederzeit aufhören zu können, aber dann treten wieder die Entzugserscheinungen auf.

Hier eine andere Besprechung des Buches in der man auch sieht, wie sich dieser „Liebesentzug“ auswirkt:

To investigate the rodent version of getting hugs, and what happens in the absence of hugs from a bonded partner, Bosch took virgin males and set them up in vole apartments with roommates—either a brother they hadn’t seen in a long time or an unfamiliar virgin female. As males and females are wont to do, the boy-girl roommates mated and formed a bond. After five days, he split up half the brother pairs, and half the male-female pairs, creating what amounted to involuntary vole divorce. Then he put the voles through a series of behavioral tests.

The first is called the forced-swim test. Bosch likens it to an old Bavarian proverb about two mice who fall into a bucket of milk. One mouse does nothing and drowns. The other tries to swim so furiously the milk turns into butter and the mouse escapes. Paddling is typically what rodents will do if they find themselves in water; they’ll swim like crazy because they think they’ll drown if they don’t. (Actually, they’ll float but apparently no rodent floaters have ever returned to fill in the rest of the tribe.)

The voles that were separated from their brothers paddled manically. So did the voles who stayed with their brothers and the voles who stayed with their female mates. Only the males who’d gone through vole divorce floated listlessly as if they didn’t care whether they drowned.

„It was amazing,“ Bosch recalls. „For minutes, they would just float. You can watch the video and without knowing which group they were in, you can easily tell if it’s an animal separated from their partner, or still with their partner.“ Watching the videos of them bob limply, it’s easy to imagine them moaning out „Ain’t No Sunshine When She’s Gone“ with their tiny vole voices.

Die armen Wühlmäuse.

Man stelle es sich mit ihm an der Gitarre vor:

Prairie vole (Prärie Wühlmaus)

Prairie vole (Prärie Wühlmaus) (ein Bild mit Gitarre war nicht zu finden, aber er schaut immerhin traurig)

Das Leben von Laborwühlmäsuen ist allerdings auch so hart:

Next Bosch subjected the voles to a tail-suspension test. This test uses the highly sophisticated technique of duct taping the end of an animal’s tail to a stick and suspending it. As in the swim test, a rodent thus suspended will usually flail and spin his legs like a cartoon character who’s run off the edge of a cliff. Once again, though, while the other males did just that, the divorced males hung like wet laundry.

In a final behavior test, Bosch placed the voles on an elevated maze, like the ones we’ve already described that tested anxiety. On such a maze, the animal’s desire to investigate fights with its fear of exposed areas. Compared to the other voles, the divorced males were significantly less likely to explore the open arms of the maze.

All these tests, commonly used to test lab animals for depression, showed that if you separate a pair-bonded male vole from his mate, you’ll get a very mopey vole who uses what’s called passive-stress coping to deal with the overwhelming anxiety of partner loss. „When the separation takes place, this is what causes the animals to feel so bad,“ Bosch explains. „We found this increased depressive behavior and that tells us the animal is not feeling well.“ He doesn’t mean „under the weather,“ he means the divorced voles are emotionally miserable. „It is like when my wife went to the States for a post-doc for one year, so I knew I wouldn’t see her for at least six months. Well, I was sitting at home, laying on the couch, not motivated to do anything, not to go out and meet friends like I usually would.“

Es ist interessant, dass wir hier den Tieren ganz ähnlich sind und das in beiden Fällen bestimmte Chemikalien am Werk sind, ohne die wir uns nicht auf diese Weise verhalten würden (wie die andere Art von Voles zeigt, die nicht monogam ist).

Dann wurde versucht, die Wirkung mit Drogen nachzustellen:

Koob and others have used drugs to create the very same behavior in other lab animals. When the drugs are taken away from rats and mice, they display the same passive responses to elevated mazes. They withdraw socially. They mope. Human addicts do the same, Koob points out, mentioning characters in movies like Leaving Las Vegas and Trainspotting as examples.

To explain the physiology behind this passive depression state in the separated voles, Bosch checked their chemistry. The males separated from their mates had much higher levels of corticosterone, a stress chemical, in their blood than did any of the other groups, including voles separated from their brothers. Their HPA axis was working so hard, their adrenal glands weighed more. Bosch nailed CRF’s role in driving both the HPA axis overdrive and the mopey behavior by blocking CRF receptors in the voles‘ brains. When he did, the divorced voles no longer hung limply from the sticks. They didn’t float for as long in the water. They still remembered their mates, and were still bonded to them; they just didn’t worry about it when they left them.

Das finde ich recht eindrucksvoll: Wenn bestimmte Rezeptoren blockiert sind, dann gab es keinen Liebeskummer mehr. Was die „Macht“ biologischer Systeme aus meiner Sicht gut darlegt. Theoretisch könnte man dies sicherlich auch bei Menschen machen, aber entsprechende Tests wären unethisch. Ich würde aber vermuten, dass es Menschen mit einer geringeren Ausschüttung an Stresshormonen oder schwächeren Rezeptoren gibt, die dann eben eher auf „Short Time Mating“ setzen und nicht sehr anfällig für Liebeskummer sind. Ich vermute, dass sie dann eben auch ein anderes Verhalten zeigen.

But here’s the strange thing: both the voles who stayed with their female mates and the voles who were forced to split from the females had much more CRF in the BNST than did males who lived with, or were separated from, their brothers. In other words, loads of this stress-related hormone were being pumped in both the voles who got depressed after separation and voles who were still happily bonded and didn’t show signs of passive-stress coping.

„Bonding itself produces high CRF,“ Bosch says. „But this does not mean the system is also firing.“ There is something fundamental about living with a mate that results in more CRF stress hormone in the brain, but that also prevents the engagement of the HPA stress axis as long as the mates stay together. Using an interesting metaphor for bonding, Bosch says „I compare it to a rifle. As soon as they form a pair-bond, the rifle is loaded with a bullet. But the trigger isn’t pulled unless there is separation.“ He thinks that vasopressin serves as the chemical trigger to fire off the HPA axis during separation, though the exact roles of both oxytocin and vasopressin are still unclear.

Addicted drug users load the rifle, too. The gun won’t fire unless they stop taking the drug. For the bonded voles, „it won’t fire unless the partner leaves the nest,“ Bosch says.

Das ist ein interessanter Mechanismus. Er bewirkt zum einen Bindung, aber er lässt uns wahrscheinlich auch gleichzeitig eher die Möglichkeit, den Partner zu wechseln. Bei einem neuen Partner wird eben dann wieder Vasopressin, Oxytocin etc ausgeschüttet und damit das System wieder in Schach gehalten. Weswegen derjenige mit neuem Partner die Trennung auch besser verkraftet während der Verlassene das weit weniger kompensieren kann. Es verhindert also ein Verlassen sofern man nicht etwas besseres findet (statt wie beim ersten Verliebt sein den Partner unter der Ausschüttung der Hormone zu verklären). Wobei der Trennungsschmerz den Wechsel auch nicht zu einfach machen wird.