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 (2539, 4059 and≥60 years) and IGF-I assay was carried out by double-antibody radio immunoassay. The Pearsons 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 2539 years, 147 ng/ml in the range 4059 years and 103 ng/ml in the range≥60 years. The Pearsons 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 2539 years (r=−0.036) and in the 4059 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 2.5th97.5th percentile in the 3 age ranges were 95.6366.7 ng/ml between 2539 years, 60.8297.7 ng/ml between 4059 years and 34.5219.8 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.
28 Apr - 02 May 2007
European Society of Endocrinology