title: Twenty-four-hour mean plasma testosterone concentration declines with age in normal premenopausal women.
abstract: The 24-h mean plasma concentration of total testosterone (T) was measured in 33 healthy, regularly cycling, nonobese women between 21 and 51 yr of age. Percent free T was measured in 17 of them. Plasma dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) were measured in 24 of them, and the DHEA-to-T and DHEAS-to-T ratios were calculated. It was found that the concentration of total T showed a steep decline with age; the regression equation was: T (nanomoles per L) = 37.8 x age-1.12 (r = -0.54; P < 0.003). According to this equation, the expected T concentration of a woman of 40 would be 0.61 nmol/L, about half that of a woman of 21 (1.3 nmol/L). The percent free T did not vary significantly with age, so free T concentration likewise showed a steep decline with age. The DHEA-to-T and DHEAS-to-T ratios were both age invariant, clearly because the levels of DHEA and DHEAS also decline steeply with age, as previously reported.
authors.affiliation: Department of Medicine, Beth Israel Medical Center, New York, New York 10003, USA.
authors.forename: B
authors.initials: B
authors.lastname: Zumoff
authors.forename: G W
authors.initials: GW
authors.lastname: Strain
authors.forename: L K
authors.initials: LK
authors.lastname: Miller
authors.forename: W
authors.initials: W
authors.lastname: Rosner
mesh_terms: D000328:Adult; D000375:Aging / Q000097:blood*; D002940:Circadian Rhythm; D003687:Dehydroepiandrosterone / Q000031:analogs & derivatives / Q000097:blood; D019314:Dehydroepiandrosterone Sulfate; D005260:Female; D006801:Humans; D008875:Middle Aged; D009994:Osmolar Concentration; D017697:Premenopause / Q000097:blood*; D012016:Reference Values; D013739:Testosterone / Q000097:blood*
chemical_list: D013739:Testosterone; D003687:Dehydroepiandrosterone; D019314:Dehydroepiandrosterone Sulfate