Should cross-sex hormone treatment of transsexual subjects vary with ethnic group?

In general, goals are induction of breast formation, elimination of sexual hair growth, and a more female fat distribution. Sexual hairiness is much less of a problem in people in SE Asia compared with Caucasians. Furthermore, Asian males have more subcutaneous fat in adulthood than Caucasians. 2 The induction of breast formation amounts to pharmacologically mimic the pathophysiology of gynecomastia: an increase of the estrogen stimulus and reduction of the inhibitory effect of androgens on breast tissue. 3 While administration of estrogens alone will decrease androgen production, a combination with a gonadotropin-releasing hormone analogue or a compound that suppresses androgen production or activity, appears more effective. Male contraceptive studies show some baseline differences in the male reproductive system between different ethnic groups, including differences in testicular structure and testosterone metabolism predisposing East Asian men to a higher sensitivity to steroidal contraceptives. 4 Studies of serum hormone levels and production rates of testosterone showed that young Chinese men residing in China have lower testosterone production rates, total testosterone and sex hormone-binding globulin (SHBG) levels compared with Chinese or Caucasian men living in the United States, probably explained by environmental/dietary factors. 4 The 5α-reduced steroids dihydrotestosterone, 3α-17β androstanediol glucuronide and androsterone glucronide levels and their ratios to testosterone are lower in East Asian men, suggestive of lower 5α-reductase enzyme activity in East Asians. 4 There is no evidence that MtoF transsexual people differ biologically from men. For optimal feminization with G uidelines for cross‑sex hormone treatment of transsexual people have been developed, but no attention has b e en p ai d to the sp e cif i cs of ethnic groups. South East (SE) Asian male‑to‑female (MtoF) transsexual people may be able to transition to the female sex with lower doses of estrogens/progestins than Caucasians thus reducing health risks. Female‑to‑male (FtoM) may virilize less profoundly with standard doses of androgens, but this is probably sufficient to pass acceptably as men in view of the less pronounced sex differences in physique in Asians compared with Caucasians. It is timely that studies in Asians are conducted to get a better insight into their specific needs and risks of cross‑sex hormone treatment. In the biomedical sciences, it is widely assumed that (patho) physiological mechanisms reliably established in a certain ethnic group (practically almost always Caucasians), carry a general validity for other groups, regardless of their ethnic background. In its generality this is a workable …