Temporal changes in insulin-like growth factors I and II and in insulin-like growth factor binding proteins 1, 2, and 3 in human milk.

AIM: To evaluate the postpartum time course of changes in insulin-like growth factors (IGFs) and their binding proteins (IGFBPs). METHODS: Breast milk IGF-I and IGF-II and IGFBP-1, IGFBP-2, and IGFBP-3 levels were determined in 23 women with babies born at term, from day 4 until up to 9 months after birth. RESULTS: The IGFBP-3 levels were highest from day 4 to day 6 and then decreased by days 10-12. In contrast, IGF-I and IGF-II and IGFBP-1 and IGFBP-2 showed little change over the first 2 weeks after birth. Subsequently, all the IGF components showed a moderate decline over approximately the first 1-3 months and then stable levels up to 9 months after birth. CONCLUSION: Although the possibility cannot be excluded that these changes in levels of IGFs and their binding proteins in human milk represent passive loss from the mammary gland, we speculate that higher early levels of the human milk IGF system contribute to maturation of the infant gut.