Age-related decline of plasma bioavailable testosterone in adult men.
Plasma bioavailable and total testosterone (T), gonadotropins (FSH, LH) and prolactin (PRL) were determined in 70 ambulatory men subdivided into 3 groups according to age: group I (n = 22; age 20-35 yr), group II (n = 22; age: 36-50 yr) and group III (n = 26; age 51-70 yr). Bioavailable T levels declined significantly with age (r = -0.42; P less than 0.01) while those of total T decreased less significantly (r = -0.28; P less than 0.05). In addition, the decrease of bioavailable T occurred earlier. FSH was shown to increase with age (r = 0.41; P less than 0.01) whereas LH and PRL were not found to change significantly. Bioavailable T was correlated with total T (r = 0.25; P less than 0.05) and inversely correlated with FSH (r = -0.26; P less than 0.05). No correlation could be demonstrated between LH and either bioavailable or total T. In view of the age-related increase of sex hormone binding globulin, a fact generally observed in the literature, bioavailable T may be considered a more reliable index than total T for the evaluation of T production. Thus it may be concluded that the early decrease of bioavailable T in ambulatory men not known to have any pathology or any medication altering testicular function corresponds in fact to age-related decline of T secretion by the testes.
Nahoul
K
K
Fondation de Recherche en Hormonologie, Fresnes, France.
Roger
M
M
D000328:Adult; D000368:Aged; D000375:Aging / Q000097:blood*; D001682:Biological Availability; D005640:Follicle Stimulating Hormone / Q000097:blood; D006062:Gonadotropins / Q000097:blood; D006801:Humans; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D008875:Middle Aged; D011388:Prolactin / Q000097:blood; D013739:Testosterone / Q000097:blood*
D006062:Gonadotropins; D013739:Testosterone; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone