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.
Biology and sexual orientation male sexual orientation. The research consisted of 1,077 homosexual men and 1,231 heterosexual men. A gene named SLITRK6 on chromosome 13 was identified, and contains an area or DNA sequence which is different for gay men than for heterosexual men. The research supports another study which had been done by Simon levay. Levay's research suggested that the hypothalamus of gay men is different from straight men. The SLITRK6 is active in the mid-brain where the hypothalamus is. The researchers found another gene, named "thyroid stimulating hormone receptor" (TSHR) on chromosome 14 which dna sequence is different also for gay men.