Lifestyle determinants of 5 alpha-reductase metabolites in older African-American, white, and Asian-American men

Men with higher endogenous 5 alpha -reductase activity may have higher pros tate cancer risk. This hypothesis raises two questions: (a) Could racial di fferences in 5 alpha -reductase activity explain the observed racial differ ences in prostate cancer risk? and (b) Could a man reduce his activity leve l by modifying his lifestyle? To address these questions, we measured two h ormonal indices of 5 alpha -reductase activity [serum levels of androstane- 3 alpha -17 beta -diol glucuronide (3 alpha -diol G) and androsterone glucu ronide (AG)] in healthy older African-American, white, and Asian-American m en, who are at high, intermediate, and low prostate cancer risk, respective ly. We also examined associations between these metabolite levels and such Lifestyle characteristics as body size and physical activity as well as sel ect aspects of medical history and family history of prostate cancer. Men i ncluded in this cross-sectional analysis (rr = 1054) had served as control subjects in a population-based ease-control study of prostate cancer we con ducted in California, Hawaii, and Vancouver, Canada and provided informatio n on certain personal attributes and donated blood between March 1990 and M arch 1992, In this study, concentrations of 3 alpha -diol G declined signif icantly with age and increased significantly with body mass index. Mean lev els of 3 alpha -diol G, adjusted for age and body mass index, were 6.1 ng/m l in African-Americans, 6.9 ng/ml in whites and 4.8 ng/ml in Asian-American s. These differences were statistically significant (African-Americans vers us whites: P < 0.01; whites versus Asian-Americans: P < 0.001). Concentrati ons of AG decreased significantly with age, but only in whites, and were un related to any of the reported personal attributes. Mean levels of AG, adju sted for age, were 44.1 ng/ml in African-Americans, 44.9 ng/ mi in whites, and 37.5 ng/ml in Asian-Americans (Asian-Americans versus whites, P < 0.001 ), In conclusion, older African-American and white men have similar levels of these two indices of 5 alpha -reductase activity, and these levels are h igher than those of older Asian-American men. This difference may be relate d to the lower prostate cancer risk in Asian-Americans.