title: Serum total and free testosterone level of Japanese men: a population-based study.
abstract: BACKGROUND
  There has never been a large scale population-based study of serum levels of total testosterone (TT) and free testosterone (FT) in Japanese men.
  
  
  METHODS
  We determined serum levels of TT and FT of 1120 Japanese men aged 40-79 years using radioimmunoassay (RIA), as a part of a population-based longitudinal study of aging. Of these, sex hormone binding protein (SHBG) was also measured by RIA in 471 men. For the latter group, the calculated free testosterone (cFT) was determined by a formula using serum level of albumin, TT and SHBG.
  
  
  RESULTS
  The mean +/- 2 SD of TT, FT and cFT were 513 +/- 326 ng/dL (187-839 ng/dL), 13.2 +/- 7.8) pg/mL (5.4-21.0 pg/mL) and 77.0 +/- 43.4 pg/mL (33.6-120.4 pg/mL), respectively. While TT did not relate to age, FT and cFT decreased with age. FT in the 40-49 years age group was 15.1 +/- 8.4 pg/mL (6.7-23.5 pg/mL), in the 50-59 years age group was 13.9 +/- 6.8 pg/mL (7.1-20.7 pg/mL), in the 60-69 years age group was 12.0 +/- 6.6 pg/mL (5.4-18.6 pg/mL) and in the 70-79 years age group was 11.5 +/- 7.0 pg/mL (4.5-18.5 pg/mL). FT significantly correlated with cFT (Spearman's r = 0.803). The correspondence rates were 92.3% at the mean -1 SD and 98.7% at the mean -2 SD level.
  
  
  CONCLUSIONS
  We determined the mean and standard deviation of TT, FT and cFT in Japanese men aged 40 years or older. It is supposed that FT determined by RIA would be useful for diagnosing partial androgen deficiency of aging males.
authors.affiliation: Division of Urology, Department of Surgery and Intensive Care, and Department of Epidemiology, National Center for Geriatrics and Gerontology, Japan. kokamura@chubu-nh.go.jp
authors.forename: Kikuo
authors.initials: K
authors.lastname: Okamura
authors.forename: Fujiko
authors.initials: F
authors.lastname: Ando
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shimokata
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D006801:Humans; D007564:Japan; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D013739:Testosterone / Q000097:blood*
chemical_list: D013739:Testosterone