Insulin-like growth factor (IGF)-I and IGF-binding protein-3 in relation to hemoglobin concentration in healthy term infants.

In order to evaluate the role of insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) in the maintenance of blood Hb concentration in infants, we studied the serum concentrations of IGF-I and IGFBP-3 in relation to blood hemoglobin values in 25 healthy term infants at birth and two months of age. The mean concentration of IGF-I was 18.6+/-7.1 ng/ml and IGFBP-3 was 1240+/-498 ng/ml at birth. Positive correlation was observed between the blood Hb concentrations and both IGF-I (r = 0.56, p = 0.004) and IGFBP-3 levels (r = 0.38, p = 0.04) at the first examination. Our results show that blood Hb is positively correlated to serum IGF-I levels indicating indirectly the involvement of mediators of growth hormone in the regulation of physiologic Hb concentrations at birth. As no relationship was found between IGF-I, IGFBP-3 and Hb levels at the second examination, the same association could not be demonstrated at two months of age.