The Neuroendocrine Response of Luteinizing Hormone to Estrogen Administration in Heterosexual, Homosexual, and Transsexual Subjects

The neuroendocrine response of LH to estrogen administration may be related to sexual dimorphism of the brain, and therefore, homosexual and especially transsexual individuals may differ from heterosexual individuals in their responses. This study failed to find such differences among groups of female heterosexuals, homosexuals, and transsexuals. Specifically, after single dose estrogen administration, all subjects had an initial decline in serum LH levels, followed by a brisk rise of equal magnitude. Among males, the type of response was less uniform. After an initial fall in serum LH levels, the individual responses varied. In 12 of 23 male homosexuals, 10 of 15 male heterosexuals, and all 6 genetic male transsexuals studied, serum LH levels remained below pretreatment levels. In the remaining 11 male homosexuals and 5 of the heterosexuals, serum LH levels increased to values exceeding those before treatment, resembling the response found in the 3 groups of women. Those homosexual and heterosexual men with a rise in serum LH levels to above pretreatment values also had the greatest fall in testosterone levels after estrogen administration, while these same men had the lowest testosterone response to hCG stimulation. I conclude from these results that 1) the similarity of LH responses to estrogen administration in all groups of women studied does not support a theory of brain androgenization as a factor in the establishment of gender identity of sexual orientation; and 2) individual differences in men in the type of LH response to estrogen administration can be satisfactorily explained by endocrine factors, such as Leydig cell function, and need not be related to gender identity, sexual orientation, or other possible causes.