Tuesday, February 15, 2005

Here's some interesting research findings regarding transsexuals (and transgenders by definition).

Transsexuals have, often from childhood onward, the strong feeling of having been born the wrong sex. Their desire to resemble the opposite sex is so strong that they are even willing to undergo major surgery and hormone treatments to achieve this end. This gender-identity problem has been proposed to develop as a result of a disturbed interaction between the developing brain and sex hormones. The search for structures that may be directly related to gender identity, i.e., structures whose anatomy is “female” in genetically male transsexuals, has so far led to our studies of the central nucleus of the bed nucleus of the stria terminalis (BSTc). A female-sized nucleus was found in male-to-female transsexuals. The size of the BSTc was not influenced by sex hormones in adulthood and was independent of sexual orientation. Similar results were obtained when the total number of somatostatin neurons was determined in the BSTc. In the BSTc of one female-to-male transsexual a male volume and somatostatin neuron number was found; (Zhou et al., 1995b; Kruijver et al., 2000). Although the BSTc may be one of many structures involved in the phenomenon of gender identity, these results do support the hypothesis that gender identity develops as a result of an interaction between the developing brain and sex hormones.

(Structural and Functional Sex Differences In the Human Hypothalamus
Dick F. Swaab,*, 1 Wilson C. J. Chung,*, † Frank P. M. Kruijver,* Michel A. Hofman,* and Tatjana A. Ishunina*, ‡ *Graduate School Neurosciences Amsterdam, Netherlands Institute for Brain Research, Meibergdreef 33, 1105 AZ Amsterdam, The Netherlands; †Department of Psychology, University of Massachusetts, Amherst, Massachusetts; and ‡Department of Histology And Embryology, Kursk State Medical University, Kursk, Russia Received August 9, 2000; accepted March 1, 2001)

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