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

Abstract

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.

The insulin-like growth factor-1 and expression of its binding protein-3 in chronic hepatitis C and hepatocellular carcinoma

“…In liver diseases, serum level of IGF-1 is thought to provide a useful marker of the organ function, independently of etiology and patient age (20,24,42). In the CH-C group, our investigations confirmed the negative correlation between concentration of S-IGF-1 and patient age described by other authors (43,44). Moreover, in the CH-C group, we demonstrated that mean S-IGF-1 concentration is higher in women as compared to men.…”

Normal values of serum IGF-1 in adults: results from a Brazilian population

“…The maximum difference in the upper limit (97.5th percentile) was 7 µg/L (20 to 30 years) and the maximum difference in the lower limit (2.5th percentile) was 10 µg/L (21 to 25 years). Therefore, similar to previous studies (7)(8)(9)(10)(11)(12)(13)(14), the IGF-1 reference values are reported according to age group, without distinction between genders ( Table 2). The curves representing the 97.5th, 50th (median) and 2.5th percentiles of IGF-1 as a function of age are shown in figure 1.…”

“…Many other studies also failed to demonstrate such difference and their results were reported without distinction between genders (7)(8)(9)(10)(11)(12)(13)(14). The hypothesis of a consistent and plausible difference between genders is also weakened by the fact that eventual small differences are not uniform, with some reporting higher IGF-1 levels in men or women depending on their age (10,15) or even on the assay used (10).…”

“…The Student t-test and Kruskal-Wallis test were used to determine differences between groups according to gender (10)(11)(12)14). The two-tailed Pearson correlation coefficient test was used to analyze the correlation between age and IGF-1 values in both genders (14) and between the first and second measurement after 12 weeks (18).…”

“…The values should be assay-specific (9,10), should be reported according to age (7)(8)(9)(10)(11)(12)(13)(14)(15)(16), and should preferentially be population-specific (17). The sample from which these values are extracted should be of adequate size (7,9) and the subjects should be selected rigorously, excluding conditions known to interfere with the levels of this hormone (6).…”