Background: Insulin-like growth factor-I (IGF-I) is present in the milk of several mammalian species including cow's milk and human milk. Enteral application of IGF-I promotes the proliferation of intestinal cells and increases intestinal villous height and disaccharidase activity in animal studies(1). Therefore, IGF-I may play a role in the nutrition of the newborn infant. Hypothesis: IGF-I is present in non-hydrolized protein infant formula based on cow's milk, but is not detectable in infant formula with hydrolized protein. Methods: IGF-I was measured in duplicate with a commercial radioimmunoassay (Mediagnost, Tübingen, Germany) in 5 hydrolized protein and 5 non-hydrolized protein infant formulas based on cow's milk. Results: In hydrolized protein formulas no immunoreactive IGF-I was detected (<0.048 nM). In contrast, in non-hydrolized protein formulas IGF-I concentrations were in the range found in mature human milk (mean±SD): A: 0.15±0.03 nM, B: 0.08±0.01 nM, C: 0.08±0.03 nM, D: 0.13±0.03 nM, E: 0.16±0.01 nM. Conclusions: We conclude that the hydrolysis of proteins in infant formula results in a loss of immunoreactivity of IGF-I. We speculate that this indicates a loss of function of IGF-I as well as the lack of also other polypeptide hormones in hydrolized formula.

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