AGE, GENETIC, AND NONGENETIC FACTORS INFLUENCING VARIATION IN SERUM SEX STEROIDS AND ZONAL VOLUMES OF THE PROSTATE AND BENIGN PROSTATIC HYPERPLASIA IN TWINS

BACKGROUND. We have observed that hereditary and environmental factors have a substantial influence on the plasma content of sex steroids in normal male twins and in men of families with prostatic disease. METH ODS. The contribution of genetic and nongenetic familial factors on th e variation of plasma sex steroid concentrations and of the volume of zones of the prostate measured by transrectal ultrasound (TRUS) has no w been investigated in pairs of male monozygotic (MZ) and dizygotic (D Z) twin pairs between age 25-75 years. Bioelectric impedance permitted quantitation of body fat, lean body mass, and water. Morphometrics an d testicular volume were also determined. RESULTS. The intraclass corr elation (r(1)) was >0.40 for the variation of the total volume (TV), t he transition zone (TZ), the peripheral zone (PZ), and the ratio of TZ /PZ in both MZ and DZ twins, and heredity affected 22% of the variatio n of the PZ and TZ and 30% of the ratio of TZ/PZ. None of the TV and e nvironmental factors influenced the remainder of the variation. Heredi ty accounted for 25% or more of the variation of dihydrotestosterone ( DHT), and the ratios of DHT/testosterone (T), estradiol (E2)/T, andros tanediol glucuronide, sex hormone-binding globulin (SHBG)-bound T, T/S HBG, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and dehydroepiandrosterone sulfate (DHEA-S). In MZ twin pairs the variati on of the volumes of the prostate became greater with age. In contrast , the variation of the sex hormone concentrations did not show greater variation with age. Heredity also affected >30% of the variation for waist measurement, weight, body fat, body mass, water and lean body ma ss, body mass/fat, and testicular size. CONCLUSIONS. Our results indic ated that both MZ and DZ twin pairs had zonal prostate volumes more li ke their twin pair than like unrelated twins. However, nongenetic fact ors exerted stronger influences than genetic factors on zonal volumes of the prostate. In contrast, hereditary factors had stronger influenc es on determining the variation of many sex hormones and morphometric characteristics than did nongenetic factors. (C) 1997 Wiley-Liss, Inc.