Prenatal Testosterone Part II

Do prenatal testosterone levels cause transgender behavior? Is MTF transgenderism caused by low prenatal testosterone levels and FTM transgenderism caused by levels that are too high. The Prenatal Testosterone Theory of Transgenderism was developed by some East German scientists in an effort to please their socialist and Soviet masters during the 1960’s that recommended that testosterone be given to pregnant mothers of male children in order to avoid MTF transgenderism. Last post I detailed the somewhat sordid history of this issue. In this post, I will tell you about the science and answer some of the questions I received regarding Part I.

There are several lines of evidence that refute the Prenatal Testosterone Theory of Transgenderism (PTTT): 

1. The science cited for this theory involves the sex life of rats and guinea pigs. Animals have sex but they do not have gender and therefore cannot be transgender. You should remember from previous posts that sex refers to sexual organs and intercourse and gender refers to culturally defined gender behavior categories. Rodents such as rats and guinea pigs have sex because it is innate. When automatic hormonal cycles cause female rodents to be in estrous and receptive to sexual intercourse. Estrous causes female reflexes that allow them to rear up to improve access for intercourse. Male rodents are attracted by the smell of a receptive female and his penile reflexes are activated. That is probably more than you really wanted to know about rodent sex.
   Animals do not have gender, at least gender like humans do. Human gender behavior categories are invented by human cultures. So animal research cannot be cited to support the Prenatal Testosterone Theory of Transgenderism.
2. Kallmann’s syndrome provides a “natural experiment” which demonstrates that low prenatal testosterone does not cause MTF Transgenderism. People with Kallmann’s syndrome have a genetic defect that severely reduces testosterone levels. Females with Kallman’s are unaffected but males have low testosterone levels such that they do not complete normal male development.
   There have only been 2 reported cases in the past 60 years in which a male with Kallmann’s syndrome was transgender, indicating that low prenatal testosterone does not cause MTF transgenderism.
3. Congenital adrenal hyperphasia (CAH) is a genetic disorder which causes high prenatal testosterone, starting in utero. People with CAH have a genetic defect that prevents their brains from sensing the chemical cortisol which is normally manufactured and released by the adrenal glands. Your adrenal glands are located above the kidneys and regulate many hormonal mechanisms. The result of the genetic defect is that the brain keeps sending chemical messages to the adrenals to release cortisol but the adrenals do not stop there. They also release high levels of testosterone.  Bet you might not have know that your adrenal glands make testosterone as well as the testes. CAH is easily treated with a drug that interferes with the over-secretion of testosterone and cortisol but it is often not discovered until puberty. CAH has minimum effects on males but female brains are bathed in an unusually high level of testosterone, starting as a fetus and ending when they get the drug which stops the over-secretion of testosterone.
   So do females whose brains are bathed in testosterone from an early prenatal age have higher rates of transgenderism and transsexualism?  The answer is no. The frequency of MTF transgenderism is no higher in females with CAH. Such females do tend to engage in sports and male occupations but in modern Western society these behaviors are well within the feminine gender behavior category. The high levels of testosterone may have influenced the brain mechanisms involved in aggression but not those involved in gender.
4. There is now some doubt about the experimental results upon which the East Germans based the Prenatal Testosterone Theory of Transgenderism because we now know that testosterone does not directly cause masculinization of the brain and organization of sex reflexes. It is counterintuitive, but estrogens act directly on the brain to cause masculinization of the brain. Because estrogens are stopped from entering the brain by an active mechanism, the estrogen that causes masculinization is manufactured from testosterone.Testosterone does penetrate the brain.  If it is hard for you to understand that estrogens cause masculinization of the brain from converted testosterone, you are in good company. My biopsychology class at Georgia Tech never got it.
   The result of these discoveries is that the feminization of brain reflexes reported in the experiments that were cited to support the Prenatal Testosterone Theory of Transgenderism, is in doubt. If estrogens did get in the brain, it would cause masculinization, not feminization.
5. The Prenatal Testosterone Theory of Transgenderism has not and cannot be proven by direct measurement of fetal testosterone. So far, we do not have the techniques to actually make such measurements. The measurement of finger length ratios has been used as a surrogate for prenatal testosterone. Finger length ratios are correlated with transgenderism, but all of the finger length ratio science can be explained by genetic causes.

I had a comment about administration of testosterone to pregnant women but, as far as I can tell, this was never actually done. At least I hope not. A powerful estrogen-like compound (diethylstilbestrol) was administered to pregnant mothers to prevent miscarriage from the 1940’s to 1972. Use of this drug was discontinued because it causes birth defects and increased incidence of cancer in offspring. It may cause transgenderism but that is another long tale. If testosterone was administered to pregnant mothers to avoid transgenderism or homosexuality it would be a well-known horror story, equivalent to the diethylstilbestrol story. We now tell females to avoid their own or their husbands testosterone drugs over concern that the drugs will cause birth defects.

I also had a comment about a hypothesis from the same East German scientists that formulated the Prenatal Testosterone Theory of Transgenderism. These scientists hypothesized that there should be a higher incidence of homosexuality during wars because of maternal stress that would reduce fetal testosterone levels.  However, in 1995 Schmidt and Clement conducted a study that compared the incidence of homosexuality during war and peace.  The hypothesis was not confirmed.

References

Schmidt, G., & Clement, U.  (1995). Does peace prevent homosexuality? Journal of Homosexuality.  28(3-4), 269-275.

Tags: estrogen, featured, testosterone, Transgender

Category: Transgender Body & Soul