Meyer Bahlburg (1979) reviewed the findings, among others, of the psychoendocrine data on transsexual women. About one third of the subjects had elevated androgen levels. He reviewed two reports which suggested "abnormalities of the neuroendocrine regulation of luteinizing hormone [LH] secretion in female transsexuals."

In girls with adrenogenital syndrome (caused by a genetic defect) the adrenal cortices cannot synthesize cortisol, and instead produce a substance which has the same action as androgen. Consequently, these girls are masculinized and must be treated with cortisone therapy. Money and Ehrhardt (ibid) noted that "there are some who, lacking serious symptoms [which can be as severe as having salt and fluid imbalance and lacking blood pressure regulation] , escape recognition and grow up successfully as boys."

Hereditary factors (i.e. genetic chromosomal sex), the neurohormonal system and the psychoendocrine milieu, cytogenetic disorders and chromosomal defects, pre and postnatal hormones, and the hypothalamicpituitary gonadotrophin axis have been hypothesized to playa major role in the evolution of female transsexualism and in other female gender identity disturbances.

Given the masculine character of many female transsexuals, it had been speculated that they may have been virilized by their higher base levels of androgen. Since it is quite unlikely that such a complex process as gender identity differentiation should be based on a single biological substratum (no less on such an innocuous factor as increased androgen levels a hormone readily found in small quantities in all females), the research into this area is highly speculative.

In spite of evidence suggesting a possible psychological etiology of their gender identity disturbances, Spate chose to focus on the women's EEG abnormalities as the cause of their transsexualism. He viewed early developmental cerebral insult as affecting the limbic system adversely, leading to gender pathology, and believed that such insult left the individual susceptible in later life to a sexual aberration which could be documented by an abnormal EEG.

The most obvious place for researchers to look for organic deficit in transsexualism is the brain. Kluver and Bucy (1939) had already demonstrated a variety of behaviors, including bizarre and hyper sexuality, in monkeys who had bilateral temporal lobectomies. Subsequent research into human analogues suggested that individuals with a variety of sexual psycho pathology (including transvestism and fetishism) had either abnormal EEGs or temporal lobe disorders.

In an intriguing paper Baker and Stoller (1968) described six individuals "who were raised as members of their assigned sex but who felt that they belonged to the opposite sex [and] at puberty all developed some sort of cross sex change, in effect confirming their earliest gender wishes." When examined these patients revealed a variety of hidden conditions which contributed to their gender aberrations, including a "girl" who had a clitoris the size of a penis.

For more than two decades a select group of researchers has pursued the idea that a biological disorder may be the cause of female transsexualism (Blumer, 1969; Money and Ehrhardt, 1972; Jones, 1974). While this approach might seem too reductionistic, the clinical case material in transsexual research has always had a compelling biological aspect.

The value of the single case approach is that it provides us with an intensive understanding of the complex forces at work in determining a given woman's female transsexualism. This approach typifies biological research in the sense that a phenomenon need only be shown to exist once in order to prove its existence.

Indeed, a given female transsexual's MMPI profile (Minnesota Multiphasic Personality Inventory) might be totally different from the mean score. However, while it is common practice to use such a mean profile to describe a clinical reference group (and it has a certain validity and usefulness), it may be misleading for a given female transsexual who may be much more seriously disturbed than the mean profile would suggest.