Transgender hormone therapy (male-to-female) males is associated with higher serum estrogen. Both estrogen and testosterone help to stimulate bone formation, especially during puberty. Estrogen is the predominant sex hormone that slows bone loss, even in men. In spite of the induction of breast development, transgender women who undergo HRT do not have an increased risk of breast cancer. Only a handful of cases of breast cancer have ever been described in transgender women who have undergone male-to-female HRT. This is in accordance with research in cisgender men in which gynecomastia has been found not to be associated with an increased risk of breast cancer,
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.