プロフィール紹介文
Many androgen actions in the body are mediated by binding to the androgen receptor, a nuclear receptor that modulates transcription of responsive genes (Rommets, 2004). The science of testosterone production and detection continues to shape current policy towards testosterone in sports. Although anabolic agents are banned from competition by most international sports federations, numerous competitors test positive every year. Although gender verification has not identified any normal man competing as a woman, this process has identified women athletes with DSD. For many years, female competitors have been subject to tests of sexual genotype and phenotype known as gender verification. Endogenous androgen production is dynamically regulated by both exercise and winning in competition. However, due to variability in endogenous secretion, and similarities with exogenous testosterone, it has been challenging to establish allowable limits for testosterone in competition.
The use of testosterone in sports has been banned by the World Anti-Doping Agency (WADA) and other sports organizations due to its performance-enhancing effects and potential health risks. Understanding how hormone levels, such as testosterone, growth hormone, estradiol and others correlate with performance indicators including speed and strength is crucial for optimizing athletic abilities. By Barr body screening, male competitors with Klinefelter's syndrome or female athletes with CAH are identified as female, but women with AIS are identified as male.
Testosterone can be described as having anabolic and androgenic (virilising) effects, though these categorical descriptions are somewhat arbitrary, as there is a great deal of mutual overlap between them. In general, androgens such as testosterone promote protein synthesis and thus growth of tissues with androgen receptors. It is also used illicitly to enhance physique and performance, for instance in athletes. In addition to its role as a natural hormone, testosterone is used as a medication to treat hypogonadism and breast cancer.
Gender verification for all female competitors was finally dropped from Olympic competition in 1999 (Dickinson et al, 2002). Later tests screened female athletes for the presence of a Y chromosome, and subsequently for the SRY gene on the Y chromosome (Simpson et al, 2000). Such tests would have potential to identify as males both XX athletes with masculinization due to CAH, and XY competitors with incomplete AIS or partial genital masculinization due to 5a-reductase deficiency. In the 1930's, concerns were raised about the masculine appearance of several female athletes, most notably two competitors in the 100 meter event at the 1936 Olympic games in Berlin (Ritchie et al, 2008). Lacking DHT, the external genitalia of XY males are feminized at birth, although the testes descend into the labia majora under the influence of testosterone (Wilson et al, 1993).
There may be other important functions of this hormone that have not yet been discovered. For example, the genitals may not enlarge, facial and body hair may be scant, and the voice may not deepen normally. Adolescent boys with too little testosterone may not experience normal masculinization. A "feedback loop" closely regulates the amount of hormone in the blood.
