Study: Male TSs Brains Resemble Women's
Date: Mon, 6 Nov 95 15:05:47 -0800
From: Peter Langston <psl>
Subject: Study: Male TSs Brains Resemble Women's
Forwarded-by: "email@example.com" <firstname.lastname@example.org>
Forwarded-by: email@example.com (Paula Stockholm)
[Forwards pondering their own physiology.]
Study: Male transsexuals' brains resemble women's
Scientists in Holland have found preliminary evidence that male transsexuals
-- men who identify sexually with women -- have a strikingly different brain
structure from "ordinary" men, at least in one key area about one-eighth of
an inch wide.
In today's issue of the journal Nature, a team of researchers from Amsterdam
reports that it conducted post-mortem exams on the brains of six
male-to-female transsexuals. Specifically, the researchers studied one
particular part of the hypothalamus, called the central division of the bed
nucleus of the stria terminalis (BSTc).
This area, which is thought to influence sexual behavior, is on average 44
percent larger in men than in women. Yet all six subjects had BSTc regions
that were the size of women's, Dick Swaab of the Netherlands Institute for
Brain Research and colleagues found.
BSTc volume is not related to homosexuality, the researchers concluded from
post-mortem analyses of 36 other brains, including those of gay men and
heterosexuals of both sexes: "The BSTc was 62 percent larger in homosexual
men than in heterosexual women." Nor does it appear to be a factor in sexual
orientation in general. Of the six transsexuals, three had been attracted
to women, two were attracted to men and one was bisexual.
Psychiatrist Sandra Witelson of McMaster University in Hamilton, Ontario,
said the work adds "to the body of knowledge that has been accumulating in
the past five or six years, all of which shows that there are biological
correlates to variation in human sexual behavior."
The authors of today's paper argue that the transsexuals' "feminine" BSTc
volume arose from biochemical conditions early in life -- perhaps during
fetal development. The findings, they conclude, "support the hypothesis that
gender identity develops as a result of an interaction between the
developing brain and sex hormones."
© 1995 Peter Langston