In a previous study we found androgen receptor
(AR) sex differences in several regions throughout the human hypothalamus.
Generally, men had stronger nuclear AR immunoreactivity (AR-ir) than women.
The strongest nuclear labeling was found in the caudal hypothalamus in the
mamillary body complex (MBC), which is known to be involved in aspects of
cognition and sexual behavior.
The present study was carried out to
investigate whether the sex difference in AR-ir of the MBC is related to
sexual orientation or gender identity (i.e. the feeling of being male or
female) or to circulating levels of androgens, as nuclear AR-ir is known to
be up-regulated by androgens. Therefore, we studied the MBC in postmortem
brain material from the following groups: young heterosexual men, young
homosexual men, aged heterosexual castrated and noncastrated men, castrated
and noncastrated transsexuals, young heterosexual women, and a young
virilized woman.
Nuclear AR-ir did not differ significantly
between heterosexual and homosexual men, but was significantly stronger than
that in women. A female-like pattern of AR-ir (i.e. no to weak nuclear
staining) was observed in 26- to 53-yr-old castrated male-to-female
transsexuals and in old castrated and noncastrated men, 67--87 yr of age. In
analogy with animal studies showing strong activational effects of androgens
on nuclear AR-ir, the present data suggest that nuclear AR-ir in the human
MBC is dependent on the presence or absence of circulating levels of
androgen. The group data were, moreover, supported by the fact that a
male-like AR-ir (i.e. intense nuclear AR-ir) was found in a 36-yr-old
bisexual noncastrated male-to-female transsexual and in a heterosexual
virilized woman, 46 yr of age, with high levels of circulating testosterone.
In conclusion, the sexually dimorphic AR-ir
in the MBC seemed to be clearly related to circulating levels of androgens
and not to sexual orientation or gender identity. The functional
implications of these alterations are discussed in relation to reproduction,
cognition, and neuroprotection.
Citation:
J Clin Endocrinol Metab 2001 Feb;86(2):818-27 an
article published on the Internet by Journal of Clinical Endocrinological
Metabolism <http://jcem.endojournals.org/cgi/content/full/86/2/818>
