Controversy over Biological Theories of Sexual Orientation

• The full text of Tahir's article HOMOSEXUALITY - An Analysis of Biological Theories of Causation is worth reading. He provides detailed criticisms of genetic, hormonal and neuroanatomical studies which claim that homosexual behavior is an innate characteristic like race or gender.
• Newspaper report of Swaab's work on brain anatomy in transsexuals.
  Abstract: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. 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.
• Here is an article that provides a summary of Tahir's critique of Swaab's work on transsexuals and LeVay's work on homosexuals
  Abstract:Critics of Swaab's transsexual study state that the study was performed on a small number of specimens and the results may have been skewed by other factors. For one, only six brains of transsexuals were autopsied. Secondly, all the transsexuals had been exposed to large quantities of estrogen, the feminizing hormone. Hormones can alter the state of the brain and scientists questioned whether the discovered results could have been the result of estrogen use within the samples. Further tests to confirm the results will have to be made before these findings can be seriously analyzed.
  A 1991 published study by Simon LeVay that claimed that an area of the hypothalamus known as INAH3 is smaller in homosexual men and heterosexual women. The report was the result of the study of the brains from 41 cadavers and stated that there was a similarity in the size of the hypothalamus in the gay men and heterosexual women, both smaller than that of the heterosexual men. Tahir again disputes these findings by stating that the study had too many unknown factors to make them valid. For one he states that the sexual histories of the subjects were not absolutely known. Secondly he states that the 19 homosexual subjects had died of AIDS and studies have shown that brain tissue has been documented to deteriorate in patients with AIDS and may have affected the study's results. Lastly, the hypothalamus was larger in 3 of 19 of the homosexual men than in the mean size of the heterosexual men. Dr. Paul Cameron states, "According to [LeVay's] theory, 3 of the 'heterosexuals' should have been homosexual, and 3 of the homosexuals should have been heterosexual. When you completely misclassify 6 of 35, you don't have much of a theory." Both agree the study cannot be considered valid.

Frequently Asked Questions (FAQ): Hormone Therapy for Transsexuals

• FAQ: Hormone Therapy for Female to Male Transsexuals
  Abstract This document contains a list of frequently asked questions and their answers regarding hormone therapy (secondary sexual reassignment) for female-to-male transsexuals. More generally, this document contains information about gonadal hormones and anti-hormones, so it can be a helpful reference for the treatment of androgen and estrogen-sensitive conditions--for example, certain cancers of the reproductive organs and breasts.
• FAQ: Hormone Therapy for M2F Transsexuals
  Abstract This document contains a list of frequently asked questions and their answers regarding hormone therapy (secondary sexual reassignment) for male-to-female transsexuals. More generally, this document contains information about gonadal hormones and anti-hormones, so it can be a helpful reference for the treatment of androgen and estrogen-sensitive conditions--for example, certain cancers of the reproductive organs and breasts.

The Endocrine Society Factsheets

• Congenital adrenal hyperplasia
  What is CAH?
  CAH is a disease that affects the manufacture of the "stress" hormone, cortisol. Cortisol is produced by the adrenal gland, a small organ near the kidney. CAH occurs in two forms: severe or "classical" and mild or "nonclassical." Girls with classical CAH are born with masculine-appearing external genitals but with female internal sex organs. Boys with classical CAH look normal at birth, so their diagnosis of CAH is sometimes missed. People with CAH are likely to have trouble retaining salt, a condition that can be life-threatening. Everyone with CAH also has unusually high levels of the male sex hormone testosterone in their blood. Among the difficulties it causes are infertility, excessive hair growth, acne, and early growth of sexual hair. In addition, adrenal crises can occur and result in death.
• Turner's syndrome
  What is Turner's syndrome?
  Turner's syndrome is a relatively common disease in females, affecting many body systems. In this genetic disorder, the absence of all or part of one sex chromosome is associated with short stature and failure to mature sexually. Other problems can include learning difficulties, heart and kidney abnormalities, infertility, and thyroid dysfunctions.