title: Effects of aging and sex on plasma insulin-like growth factor I (IGF-I) levels in normal adults.
abstract: Effects of aging and sex on total plasma IGF-I levels were studied in 207 normal adults (103 males and 104 females), aged 21 to 80 years. Plasma IGF-I concentrations were measured by specific radioimmunoassay after extraction with acid-ethanol. Plasma IGF-I levels ranged from 50.8 to 480.6 micrograms/l with a mean (+/- SD) value of 200.7 +/- 81.9 micrograms/l in these normal adults. The mean plasma IGF-I levels were higher in females than in males in the second decade (332.6 +/- 63.9 vs 252.4 +/- 45.2 micrograms/l, p less than 0.01), whereas there was no sex difference in plasma IGF-I levels in elderly subjects. In both sexes, plasma IGF-I levels declined with age. In females, the slope of the regression line was much steeper in the young group (aged 21 to 40 years) than in the middle-aged and elderly group (aged 41 to 80 years) (y = -11.3x + 641.7, r = -0.538, p less than 0.005 and y = -1.97x + 289.3, r = -0.308, p less than 0.01). In males, plasma IGF-I linearly declined with age and the slope of the regression line (y = -2.36x + 322.2, r = -0.480, p less than 0.005) was not considerably different from that of the middle-aged and elderly group in females.
authors.affiliation: Department of Medicine, Shimane Medical University, Izumo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Yamamoto
authors.forename: M
authors.initials: M
authors.lastname: Sohmiya
authors.forename: N
authors.initials: N
authors.lastname: Oka
authors.forename: Y
authors.initials: Y
authors.lastname: Kato
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood*; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D011863:Radioimmunoassay; D012044:Regression Analysis; D012727:Sex Characteristics
chemical_list: D007334:Insulin-Like Growth Factor I