Are all males equal? Anatomic and functional basis for sexual orientation in males

The etiology of male homosexuality

This hypothesis agrees with Le Vay's suggestion that the two phenomena of childhood behavior and adult sexuality are induced by separate events rather than being two events in a single chain. However, it differs from Le Vay in that it includes the postnatal period, as being of crucial importance in the development of adult sexuality. Male homosexuality is portrayed as a biological variation of human sexuality and the hormonal changes which may produce it are described. It is postulated that sexual preference is dictated by testosterone action on the brain possibly commencing prenatally but certainly continuing during a critical postnatal period. It is proposed that reduction in testosterone action results in reduced proliferation of hypothalamic nuclei, which play a vital role in psycho-sexual orientation. The cause of this reduction in testosterone is the prolongation of hyperprolactinemia during this critical postnatal period, which is deemed to be secondary to prolactin microadenomata stimulated to secrete prolactin by high estrogen levels at the end of pregnancy and failing to turn off this secretion until after this critical postnatal period. It is postulated that there is a temporal dissociation between the development of masculine behaviour and psycho-sexual orientation, but that hormonal influences may overlap these periods. Hyperprolactinemia, caused by stress upon the infant, may also influence psycho-sexual orientation.

The effect of non-steroidal antiandrogen flutamide on luteinizing hormone pulsatile secretion in male-to-female transsexual subjects

We evaluated LH pulsatile patterns before and 4 weeks after the oral administration of flutamide (750 mg/day) in 9 male-to-female transsexuals (age range 17-28 yr) requesting gender reassignment. Flutamide was given to explore the feedback role of androgens on the LHRH-LH unit in LH pulsatility in transsexuals. Seven normal age-matched men served as a control group, without receiving flutamide, due to ethical considerations. LH pulsatility was evaluated on samples collected every 15 min for 360 min. FSH, PRL, cortisol, SHBG and sex steroids were evaluated on pooled samples. LH pulses were analyzed by the Santen and Bardin algorithm, slightly modified. No differences in FSH, PRL, total- or free-testosterone, estradiol and SHBG levels were noted between transsexuals and controls. Normal circadian cortisol decline was observed in all subjects. Mean LH levels (p < 0.05) and LH pulses (p < 0.01) were significantly lower in transsexuals. Flutamide induced an increase in mean LH and testosterone levels (p < 0.01). After flutamide administration there was an increase in LH pulse frequency (P < 0.01) and the frequency and amplitude of LH pulses in transsexuals were restored to levels observed in controls. No differences in FSH, PRL or estradiol levels were found after flutamide. These data suggest that a decrease in LH pulse frequency could be an endocrine marker in male-to-female transsexuals. An increase in endogenous androgen negative feed-back could be speculated in these subjects. However, normal testosterone levels indirectly suggest that a normal that a normal qualitative LH secretion is maintained.(ABSTRACT TRUNCATED AT 250 WORDS)