Pränatale Hormone und Verhalten

Eine Metastudie in der Zeitschrift „Neuroscience and Behavioral Review“ (Impact Factor: 10.284) aus dem Jahr 2004 fasst noch einmal den Stand bezüglich Pränataler Hormone und ihrer Auswirkungen auf Geschlechterunterschiede zusammen:

There is now good evidence that human sex-typed behavior is influenced by sex hormones that are present during prenatal development, confirming studies in other mammalian species. Most of the evidence comes from clinical populations, in which prenatal hormone exposure is atypical for a person’s sex, but there is increasing evidence from the normal population for the importance of prenatal hormones. In this paper, we briefly review the evidence, focusing attention on the methods used to study behavioral effects of prenatal hormones. We discuss the promises and pitfalls of various types of studies, including those using clinical populations (concentrating on those most commonly studied, congenital adrenal hyperplasia, androgen insensitivity syndrome, ablatio penis, and cloacal exstrophy), direct measures of hormones in the general population (assayed through umbilical cord blood, amniotic fluid, and maternal serum during pregnancy), and indirect measures of hormones in the general population (inferred from intrauterine position and biomarkers such as otoacoustic emissions, finger length ratios, and dermatoglyphic asymmetries). We conclude with suggestions for interpreting and conducting studies of the behavioral effects of prenatal hormones.

Quelle: Prenatal sex hormone effects on child and adult sex-typed behavior: methods and findings

In der Einleitung wird bereits noch einmal einiges zusammengefasst:

There is now good evidence from human and nonhumanspecies that events occurring during prenatal developmentcan have life-long effects on an organism. These effects are not limited to physical characteristics, but extend to a variety of behavioral traits. Thus, as described in several papers inthis special issue and elsewhere, physical and emotionalstressors experienced by pregnant rodent, monkey, andhuman females are associated with behavioral problems inoffspring throughout life [1–3]. The physical and behavioral effects of prenatal stress appear to be mediated by hormone induced changes to the developing hypothalamic–pituitary–adrenal axis [3,4].Long-term effects of prenatal events extend beyond exposure to stress hormones. There are also marked physical and behavioral consequences of prenatal exposure to another category of hormones, those produced by thegonads (‘sex hormones’). In all mammalian species studied,sexual differentiation of the reproductive system depends largely on the amount of androgens present during critical periods of prenatal life. In human beings, this critical period begins at about 7–8 weeks of gestation when the testes develop and begin to secrete testosterone [5]. The external genitalia are undifferentiated until then, and the amount of testosterone (or other androgens) determine whether they differentiate into male-typical or female-typical genitalia. With high levels of testosterone, the genitalia become the penis, scrotum, and urogenital sinus, where as low or absent testosterone results in the development of the clitoris, labiamajora, and separate vaginal and urethral canals. Intermediate levels of testosterone result in ambiguous genitalia,e.g. an enlarged clitoris with fused labia, a small penis. Sexhormones also affect the development of the internal reproductive structures. Parallel behavioral studies in nonhuman mammals clearly show that the same prenatal hormones responsible for sexual differentiation of the body are also involved insexual differentiation of behavior [for reviews, see 6–8]. Inrodents, females injected with high doses of androgens inthe newborn period show behavior more typical of malesthan of other females, and males that are castrated or givenanti-androgens show behavior more typical of females thanof other males. The behaviors involved include adult sexual behavior, juvenile rough play, adult aggression and maze performance. These effects are also found in rodents naturally exposed to atypical hormone levels from gestatingnext to opposite-sex littermates, as described below.Behavioral effects of early hormones are also found innonhuman primates: female monkeys exposed to androgensearly in development are masculinized with respect tosexual behavior, rough play, grooming [9], and somelearning abilities [10,11]. Studies in monkeys confirm andextend studies in rodents in two important ways. First, they illustrate the complexity of timing effects and show that there may be several distinct sensitive periods for androgen effects on behavior, even within the prenatal period, so thatsome behaviors are masculinized by exposure early (but notlate) in gestation, whereas other behaviors are masculinized by exposure late (but not early) in gestation [9]. For example, monkeys that received androgens early indevelopment and had masculinized genitals showed increased mounting of peers and mothers and less grooming behavior, where as those exposed later in development had normal-looking genitals but showed increased rough play and mounting of peers, but not mounting of mothers. Second, studies in monkeys show the importance of environmental context in modifying the behavioral effects of hormones. For example, the social environment of juvenile monkeys modifies the expression of behavior that is influenced by hormones [12]. The behaviors that are the least variable across social contexts are the most affected by prenatal hormones.

Hier wird also noch einmal einiges dargelegt, was ich hier schon häufiger dargestellt habe: Der Mechanismus zeigt sich bei den Säugetieren an sich, was stark dafür spricht, dass er auch bei Menschen besteht. Und weitere Untersuchungen zeigen, dass dies auch tatsächlich der Fall ist.

Hier eine Tabelle zu den Unterschieden zwischen Männern und Frauen:

Männer Frauen Unterschiede

Männer Frauen Unterschiede

 Hier zeigen sich also einige Unterschiede, Mädchen sind besser im einigen sprachlichen Bereichen, Erinnerung und Auffassungsgabe und interessieren sich sehr deutlich mehr für mädchentypische Aktivitäten, Jungs sind besser in bestimmten Bereichen des räumlichen Denkens, sind aggressiver, Suchen eher nach neuen Erlebnissen und Erfahrungen und interessieren sich eher für typische Jungenaktivitäten. Beide Geschlechter bevorzugen ihre eigenen Geschlechtsgenossen als Spielgefährten und werden von dem anderen Geschlechts stark sexuell angesprochen.

Insgesamt eine interessante Studie.