Biology and sexual orientation INAH3 weight for the heterosexual male brains was significantly larger than for the heterosexual female brains, while the results for the gay male group were between those of the other two groups but not quite significantly different from either. The neuron count also found a male-female difference in INAH3, but found no trend related to sexual orientation. A 2010 study, Garcia-Falgueras and Swaab asserted that "the fetal brain develops during the intrauterine period in the male direction through a direct action of testosterone on the developing nerve cells, or in the female direction through the absence of this hormone surge.
Transgender hormone therapy (male-to-female) produce full progestogenic effects with oral administration. Some progestins, such as medroxyprogesterone acetate and hydroxyprogesterone caproate, are or can be used by intramuscular or subcutaneous injection instead. Almost all progestins, with the exception of dydrogesterone, have antigonadotropic effects. The main effects of hormone therapy in transgender women are feminization and demasculinization, and are as follows: Breast, nipple, and areolar development varies considerably depending on genetics, body composition, age of HRT initiation, and many other factors. Development can take a couple years to nearly a decade for some. However, many transgender women report there is often a "stall" in breast growth