Study of the effect of estradiol on gonadotrophin levels in untreated male-to-female transsexuals.

This project was an attempt to test Dörner's theory that aspects of gender identity and sexual behavior depend on a defect in a normal imprinting mechanism of testicular testosterone (T) on the male hypothalamus. It has been suggested that such an action by T is incomplete in male-to-female transsexuals and that in this disorder the hypothalamus retains a cyclic pattern of gonadotrophin secretion and a positive feedback response to estrogens, such as is seen in the normal female. Five untreated male-to-female transsexuals and five normal male controls were each given 2 mg IM of estradiol, and T, estradiol, LH, and FSH globulin was measured serially over the following five days. No significant differences were found in the gonadotrophin or any of the other hormone responses in the transsexuals compared to normal controls. If there is a defect in imprinting of the hypothalamus in transsexual men, it does not seem to affect the basal levels of gonadotrophins or the pattern of their response to estrogen, at least in the intact male.