Involvement of insulin-like growth factors in the interactions between nutrition and reproduction in female mammals.

The effects of nutrition on the reproductive system of female mammals are discussed in an attempt to determine the importance of the role of the insulin-like growth factor (IGF) system of proteins in the physiological mechanisms. The IGF system comprises IGF-I, IGF-II, their receptors and binding proteins. For this review, insulin and its receptors have been included in this system. The reproductive responses have been separated into two classes, based on fundamental differences in the reproductive biology and physiological mechanisms underlying them. The first involves the effects of nutrition on the induction of ovulation, at puberty or postpartum. In this case, the question is whether or not the animal will reproduce. The second class of response, changes in ovulation rate, involves consideration of reproductive efficiency in animals in which ovulation is inevitable.