Ethnicity and migration as determinants of human prostate size.

The roles of ethnicity and migration in determining the size of human prostate zones during midlife were explored. Prostate size was measured by planimetric ultrasound in 163 men residing in Sydney who were either Australian non-Chinese (AR; n = 116) or Chinese migrants (ACM; n = 47) and had lived in Australia for a median of 7.3 yr (range, 0.2-25 yr). These were compared with Chinese men residing in China (CR; n = 210). Central and total prostate volumes were estimated by a single observer using the same equipment at both sites. After adjustment for age, central and total prostate volumes were significantly smaller, and plasma prostate-specific antigen and 5alpha-dihydrotestosterone (DHT) concentrations and International Prostate Syndrome Scores were significantly lower, in CR compared with either ACM or AR, whereas the scores of the latter two groups were similar. Almost all of the population difference in total prostate volumes could be accounted for by differences in central prostate volumes. The strongest correlates of age-adjusted prostate volume were prostate-specific antigen and DHT, the latter presumably reflecting the quantitative importance of prostatic stromal type II 5alpha-reductase activity to circulating DHT concentrations. Sex hormone-binding globulin concentrations were significantly higher in CR and significantly lower in ACM compared with those in AR, but the significance of these observations is unclear. These findings highlight the importance of the central zone of the prostate as well as provide evidence for an environmental factor influencing prostate growth. This factor operates over a relatively short time period compared with the evolution of prostate disease. Hence, this study provides evidence that ethnicity and geographical factors, such as migration, can influence the growth of the normal human prostate during midlife and may facilitate future studies of the origins and pathogenesis of human prostate disease.