Endocrine Abstracts (2007) 14 P453

Normal age-dependent values of serum insulin growth factor (IGF)–I: results from a healthy Italian population

V Gasco1, G Aimaretti2, M Boschetti3, G Corneli2, D Valle4, M Borsotti5, A Rossi4, S Rovere1, L Fazzuoli3, D Ferone3, E Ghigo1 & F Minuto3

1Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Turin, Torino, Italy; 2Endocrinology, Department of Clinical and Experimental Medicine, University of Piemonte Orientale, Novara, Italy; 3Endocrinology, DISEM, University of Genova, Genova, Italy; 4Eli Lilly Italia SpA, Sesto Fiorentino, FI, Italy; 5SOD Safety and Quality, Careggi Hospital, Firenze, Italy.

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 gender. Participant subjects were stratified in three age classes (25–39, 40–59 and≥60 years) and IGF-I assay was carried out by double-antibody radio immunoassay. The Pearson’s correlation coefficient between age and IGF-I values was calculated by sex and pre-defined age ranges. IGF-I levels significantly decreased with age (P<0.001, Kruskal-Wallis test) while age was not a significant factor. The median IGF-I levels were 206 ng/ml in the range 25–39 years, 147 ng/ml in the range 40–59 years and 103 ng/ml in the range≥60 years. The Pearson’s correlation coefficient confirmed the negative correlation between age and IGF-I levels in the total sample of subjects (r=−0.529), with no sex-effect (r=−0.570 in males and r=−0.529 in females). No correlations were also found in the 25–39 years (r=−0.036) and in the 40–59 years range (r=−0.080), while in subjects aged>60 years, 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 3 age ranges were 95.6–366.7 ng/ml between 25–39 years, 60.8–297.7 ng/ml between 40–59 years and 34.5–219.8 ng/ml in subjects aged≥60 years. This study may contribute in the development of age-specific reference ranges for IGF-I determination in serum of normal subjects of either sex, irrespective of the used method of assay.

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