title: Age, genetic, and nongenetic factors influencing variation in serum sex steroids and zonal volumes of the prostate and benign prostatic hyperplasia in twins.
abstract: 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.
  
  
  METHODS
  The contribution of genetic and nongenetic familial factors on the variation of plasma sex steroid concentrations and of the volume of zones of the prostate measured by transrectal ultrasound (TRUS) has now been investigated in pairs of male monozygotic (MZ) and dizygotic (DZ) twin pairs between age 25-75 years. Bioelectric impedance permitted quantitation of body fat, lean body mass, and water. Morphometrics and testicular volume were also determined.
  
  
  RESULTS
  The intraclass correlation (rI) was > 0.40 for the variation of the total volume (TV), the 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 variation of the PZ and TZ and 30% of the ratio of TZ/PZ. None of the TV and environmental factors influenced the remainder of the variation. Heredity accounted for 25% or more of the variation of dihydrotestosterone (DHT), and the ratios of DHT/testosterone (T), estradiol (E2)/T, androstanediol glucuronide, sex hormone-binding globulin (SHBG)-bound T, T/SHBG, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and dehydroepiandrosterone sulfate (DHEA-S). In MZ twin pairs the variation 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 mass, body mass/fat, and testicular size.
  
  
  CONCLUSIONS
  Our results indicated that both MZ and DZ twin pairs had zonal prostate volumes more like their twin pair than like unrelated twins. However, nongenetic factors exerted stronger influences than genetic factors on zonal volumes of the prostate. In contrast, hereditary factors had stronger influences on determining the variation of many sex hormones and morphometric characteristics than did nongenetic factors.
authors.affiliation: Department of Medicine, University of Utah School of Medicine, Salt Lake City 84132, USA.
authors.forename: A W
authors.initials: AW
authors.lastname: Meikle
authors.forename: R A
authors.initials: RA
authors.lastname: Stephenson
authors.forename: C M
authors.initials: CM
authors.lastname: Lewis
authors.forename: G A
authors.initials: GA
authors.lastname: Wiebke
authors.forename: R G
authors.initials: RG
authors.lastname: Middleton
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000097:blood* / Q000502:physiology; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology; D019314:Dehydroepiandrosterone Sulfate / Q000097:blood; D013196:Dihydrotestosterone / Q000097:blood; D017097:Electric Impedance; D004777:Environment; D004958:Estradiol / Q000097:blood; D005640:Follicle Stimulating Hormone / Q000097:blood; D012739:Gonadal Steroid Hormones / Q000097:blood*; D006801:Humans; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000378:metabolism / Q000473:pathology* / Q000502:physiology; D011470:Prostatic Hyperplasia / Q000097:blood* / Q000235:genetics* / Q000473:pathology; D012738:Sex Hormone-Binding Globulin / Q000032:analysis / Q000378:metabolism; D013739:Testosterone / Q000097:blood; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic
chemical_list: D012739:Gonadal Steroid Hormones; D012738:Sex Hormone-Binding Globulin; D013196:Dihydrotestosterone; D013739:Testosterone; D004958:Estradiol; D019314:Dehydroepiandrosterone Sulfate; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone