This region is also different in humans, but the research involving hormone levels has not been done on humans (for obvious reasons). However, research, upon death, has delved into the sexually dimorphic regions of the brain. In 1980, Roger Gorski found that the interstitial nuclei of the anterior hypothalamus (INAH), numbers 2 and 3 (there are four of these nuclei, were sexually dimorphic. The size differential between males and females was most apparent in INAH 3. In males, this nucleus can be from two to three times larger than it is in females. This difference spans all age groups, meaning that the differentiation must occur at some time before birth.
Then, in 1991, Simon LeVay set out to find if the sexual dimorphism in INAH2 and 3 could be correlated with sexual orientation. He hypothesized that the size of this region in the brain in homosexual males would be similar in size to that in heterosexual females, and that it would be larger in heterosexual males and lesbians. He dealt mainly with the INAH 3, as it is more significantly different between males and females. He found that male homosexuals had INAH 3's that were comparable in size to heterosexual females. He didn't study lesbians. With results stating that this region of the brain is different in homosexual and heterosexual men, and the knowledge that the size of this same region in rats is determined in utero and directly following birth, the evidence seems to support the theory that homosexuals are "born that way."
http://www.goshen.edu/bio/Biol410/SrSempapers01/christiana.html