Normal age-dependent values of serum insulin growth factor-I: results from a healthy Italian population.
Serum IGF-I levels were measured in 547 non-hypopituitaric, non-acromegalic healthy subjects of both sexes in Italy to develop reference values in relation to age and sex. Participant subjects were stratified in three age classes (25- 39, 40-59 and >or=60 yr) and IGF-I assay was carried out by double-antibody radio immunoassay. Pearson's correlation coefficient between age and IGF-I values was calculated by sex and predefined age ranges. IGF-I levels significantly decreased with age (p<0.001, Kruskal-Wallis test) while sex was not a significant factor. The median IGF-I levels were 206 ng/ml in the 25-39 yr range, 147 ng/ml in the 40-59 yr range and 103 ng/ml in the >or=60 yr range. Pearson's correlation coefficient confirmed the negative correlation between age and IGF-I levels in the total sample of subjects (r=-0.529). The r coefficient between age and IGF-I levels did not differ between sexes (r=-0.570 in males and r=-0.529 in females), thus reflecting no sex-effect on IGF-I levels decline over years. No correlations were found in the 25-39 yr range (r=-0.036) or in the 40-59 yr range (r=-0.080) either, while in subjects aged >60 yr, IGF-I levels tended to further decrease with increased age (r=0.389). Ranges of normal values set at the 2.5th-97.5th percentile in the three age ranges were 95.6-366.7 ng/ml between 25 and 39 yr, 60.8-297.7 ng/ml between 40 and 59 yr and 34.5-219.8 ng/ml in subjects aged >or=60 yr. This study may contribute to the development of age-specific reference ranges for IGF-I determination in serum of normal subjects of both sexes in Italy.
Aimaretti
G
G
Endocrinology, Department of Clinical and Experimental Medicine, University of Piemonte Orientale, 28100 Novara, Italy. gianluca.aimaretti@med.unipmn.it
Boschetti
M
M
Corneli
G
G
Gasco
V
V
Valle
D
D
Borsotti
M
M
Rossi
A
A
Barreca
A
A
Fazzuoli
L
L
Ferone
D
D
Ghigo
E
E
Minuto
F
F
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006262:Health; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D007558:Italy; D008297:Male; D008875:Middle Aged; D011863:Radioimmunoassay / Q000379:methods; D012016:Reference Values; D012727:Sex Characteristics
D007334:Insulin-Like Growth Factor I