ANDROGENS AND THE EVOLUTION OF MALE-GENDER IDENTITY AMONG MALE PSEUDO-HERMAPHRODITES WITH 5-ALPHA-REDUCTASE DEFICIENCY

To determine the contribution of androgens to the formation of male-gender identity, we studied male pseudohermaphrodites who had decreased dihydrotestosterone production due to 5α-reductase deficiency. These subjects were born with female-appearing external genitalia and were raised as girls. They have plasma testosterone levels in the high normal range, show an excellent response to testosterone and are unique models for evaluating the effect of testosterone, as compared with a female upbringing, in determining gender identity. Eighteen of 38 affected subjects were unambiguously raised as girls, yet during or after puberty, 17 of 18 changed to a male-gender identity and 16 of 18 to a male-gender role. Thus, exposure of the brain to normal levels of testosterone in utero, neonatally and at puberty appears to contribute substantially to the formation of male-gender identity. 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. (N Engl J Med 300:1233–1237, 1979) MALE pseudohermaphrodites with a deficiency of the enzyme 5α-reductase1 2 3 raised as girls provide a unique opportunity for evaluation of the effects of testosterone and the sex of rearing in the determination of gender identity in man. Because of a deficiency in the activity of this enzyme, there is decreased in utero production of dihydrotestosterone, which results in severe ambiguity of the external genitalia of the affected male fetus. Thus, at birth, many affected infants were thought to be girls and were raised accordingly. However, since the biosynthesis and peripheral action of testosterone are normal, prenatal, neonatal and pubertal exposure to. © 1979, Massachusetts Medical Society. All rights reserved.