Normal age-dependent values of serum insulin growth factor-I: Results from a healthy Italian population

• Published in: Journal of endocrinological investigation Vol. 31; no. 5; pp. 445 - 449
• Main Authors: Aimaretti, G., Boschetti, M., Corneli, G., Gasco, V., Valle, D., Borsotti, M., Rossi, A., Barreca, A., Fazzuoli, L., Ferone, D., Ghigo, E., Minuto, F.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.05.2008
• Subjects: Adult; Age Factors; Aged; Aged, 80 and over; Endocrinology; Female; Health; Humans; Insulin-Like Growth Factor I - analysis; Italy; Male; Medicine; Medicine & Public Health; Metabolic Diseases; Middle Aged; Original Articles; Radioimmunoassay - methods; Reference Values; Sex Characteristics; Italy; normal range; healthy subjects; IGF-I
• ISSN: 0391-4097; 1720-8386
• DOI: 10.1007/BF03346389

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 <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 ≥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 2.5 th –97.5 th 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.