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.
Persistent Müllerian duct syndrome deficiency of fetal anti-Müllerian hormone (AMH) effect due to mutations of the gene for AMH or the anti-Müllerian hormone receptor, but may also be as a result of insensitivity to AMH of the target organ. Persistent Mullerian Duct Syndrome (PMDS), also known as Persistent Oviduct Syndrome, is a congenital disorder related to male sexual development. PMDS usually affects phenotypically normal male individuals with the karyotype (46, XY) and is a form of pseudohermaphroditism. PMDS has various causes to do with AMH or receptors abnormalities. For example, AMH has failed to synthesis, failed to release or was secreted at the wrong