COMPARATIVE RATES OF ANDROGEN PRODUCTION AND METABOLISM IN CAUCASIAN AND CHINESE SUBJECTS

Clinically apparent prostate cancer occurs more commonly among Caucasi ans living in Western countries than in Chinese in the Far East. Prior studies demonstrated diminished facial and body hair and lower levels of plasma 3 alpha-androstanediol glucuronide and androsterone glucuro nide in Chinese than in Caucasian men. Based upon these findings, inve stigators postulated that Chinese men could have diminished 5 alpha-re ductase activity with a resultant decrease in prostate tissue dihydrot estosterone levels and clinically apparent prostate cancer. An alterna tive hypothesis suggests that decreased 3 alpha-androstanediol glucuro nide and androsterone glucuronide levels might reflect reduced product ion of androgenic ketosteroid precursors as a result of genetic or env ironmental factors. The present study examined 5 alpha-reductase activ ity, androgenic ketosteroid precursors, and the influence of genetic a nd environmental/dietary factors in groups of Chinese and Caucasian me n. We found no significant differences in the ratios of 5 beta:5 alpha -reduced urinary steroids (a marker of 5 alpha-reductase activity) bet ween Chinese subjects living in Beijing, China, and Caucasians living in Pennsylvania. To enhance the sensitivity of detection, we used an i sotopic kinetic method to directly measure 5 alpha-reductase activity and found no difference in testosterone to dihydrotestosterone convers ion ratios between groups. Then, addressing the alternative hypothesis , we found that the Caucasian subjects excreted significantly higher l evels of individual and total androgenic ketosteroids than did their C hinese counterparts. To distinguish genetic from environmental/dietary factors as a cause of these differences, we compared Chinese men livi ng in Pennsylvania and a similar group; living in Beijing, China. We d etected a reduction in testosterone production rates and total plasma testosterone and sex hormone-binding levels, but not in testosterone M CRs in Beijing Chinese as a opposed to those living in Pennsylvania. C omparing Pennsylvania Chinese with their Caucasian counterparts, we de tected no significant differences in total testosterone, free and weak ly bound testosterone, sex hormone-binding globulin levels, and testos terone production rates. Taken together, these studies suggest that en vironmental/dietary, but not genetic, factors influence androgen produ ction and explain the differences between Caucasian and Chinese men.