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 ≥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 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 ≥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.