Differences in reproductive endocrinology between Asian men and Caucasian men--a literature review.

This review provides an overview of the literature on aspects of reproductive endocrinology wherein Asian men may differ from Caucasian, notably, prostatic neoplasm and the sensivity to pharmacological regimens of male contraception. Both genetic and environmental factors, such as nutrition, might be relevant. Asian men residing in Asia seem to be relatively protected from clinical prostatic neoplasm while the prevalence of preclinical prostatic neoplasm is not different. Migration to an area with a higher prevalence reduces this difference but does not undo it. With regard to prostatic neoplasm the following factors have been considered as relevant in Asian men: 1) a reduction in 5 alpha-reductase level, 2) decreased levels of androgenic ketosteroid precursors of 5 alpha-reduced androgen metabolites, 3) the decreased presence of a P53 mutation, 4) a higher CAG-repeat length of the androgen receptor, 5) a possible higher level of physical activity, 6) differences in sexual activity. Furthermore, Asian men respond to a higher degree with azoospermia in response to contraceptive steroids. Possible explanations offered for the more pronounced response to contraceptive steroids are: 1) differences in testicular structure and decreased spermatogenic potential, 2) an earlier and more marked suppression in LH secretion by exogenous androgens. The differences may be due to genetical and/or environmental factors influencing the peripheral testosterone metabolism. Dietary factors such as the higher intake of phytoestrogens in Asians might exert effects on 5 alpha-reductase activity and/or on sex hormone binding globulin (SHBG) levels, thus having an impact on the biological efficacy of circulating androgens.