Association of serum insulin-like growth factor-I and erythropoiesis in relation to body iron status.

This study investigated the associations between serum insulin-like growth factor-I (IGF-I) concentrations and erythropoietic activities in relation to body iron status. Serum IGF-I concentrations, free erythrocyte protoporphyrin (FEP), hemograms, and serum iron markers were measured in 71 female adolescents, age 14 to 17 yr. No significant differences were observed in hemograms, iron parameters, or FEP between the subjects with IGF-I <681.2 ng/ml and IGF-I 681.2 ng/ml. However, blood hemoglobin and serum iron concentrations averaged 13.4 +/- 0.8 g/dl and 93.7 +/- 41.2 microg/dl in the subjects with IGF-I >809 ng/ml, which were above the values in those with IGF-I <523 ng/ml (12.3 +/- 0.9 g/dl and 50.5 +/- 30.8 microg/dl, p < 0.05, respectively). On the other hand, FEP was significantly lower in the adolescents with IGF-I >809 ng/ml than in those with IGF-I <523 ng/ml (38.9 +/- 16.2 microg/dl vs 63.4 +/- 23.1 microg/dl, p <0.05). Prevalences of iron deficiency or iron deficiency anemia were 3- or 5-fold higher in the subjects with IGF-I <523 ng/ml, compared to those with IGF-I >809 ng/ml. Serum IGF-I correlated significantly with FEP (r = -0.45, p <0.05) and serum iron concentrations (r = 0.40, p <0.05) in iron deficient subjects. In summary, IGF-I seems to have an important relationship to iron metabolism and protoporphyrin synthesis in adolescents.