Stimulation of androgen-sensitive hair follicles is mediated by dihydrotestosterone (DHT), which is formed in these tissues by 5-reduction of testosterone. A possible mechanism for increased body hair in some human populations might, therefore, be an increase in 5α-reductase activity, resulting in elevated tissue levels of DHT. If present, this finding could have other important clinical implications, since the 5α-reductase enzyme is pivotal in the pathophysiology of prostatic disease. To explore differences in clinical and biochemical parameters of androgen action, we conducted a study of 184 Caucasian and Chinese subjects in whom we evaluated chest hair density and serum levels of androgen precursors and 5α-reduced androgen metabolites. Differences in chest hair density were most notable in the men, in whom comparative mean chest hair scores (using a scale of 0-4) were 3.0 vs. 0.8 (P < 0.0001), Caucasian vs. Chinese. Levels of 5α-reduced androgen products were also strikingly higher in the Caucasian vs. Chinese subjects. Serum 3α-androstanediol glucuronide levels (nanomoles per L) were 34.7 ± 2.4 vs. 19.7 ± 0.9 (P < 0.001) for the men and 21.5 ± 3.2 vs. 9.4 ± 0.6 (P < 0.001) for the women, and serum levels of androsterone glucuronide (nanomoles per L) were 179 ± 26 vs. 107 ± 7 (P < 0.01) for the Caucasian vs. Chinese men and 173 ± 23 vs. 81 ± 9 (P < 0.001) for the women. Serum levels of total and bioavailable testosterone did not differ between the racial groups, but serum levels of the precursor androgens, dehydroepiandrosterone sulfate and androstenedione, were significantly higher in the Caucasian vs. Chinese men, but not in the women. We conclude that increased serum levels of 5α-reduced androgen metabolites in Caucasians vs. Chinese subjects provide circumstantial evidence for a racial difference in 5α-reductase activity and suggest a mechanism for the increased body hair observed in the Caucasian men. Increased levels of precursor androgens may also play a role.
All Science Journal Classification (ASJC) codes
- Endocrinology, Diabetes and Metabolism
- Clinical Biochemistry
- Biochemistry, medical