IGFs and IGF-binding proteins in the regulation of human ovarian and endometrial function.

The key function of reproduction is to propagate inheritable characteristics to new generations. The human female reproductive system consists of the hypothalamic– pituitary–ovarian axis and end organs such as the uterus and fallopian tubes. The endocrine axis involves both peptide hormones (gonadotropin-releasing hormone, follicle-stimulating hormone (FSH) and luteinizing hormone (LH)) and steroid hormones (estradiol and progesterone). In addition, numerous growth factors, including the insulin-like growth factors (IGFs) and IGFbinding proteins (IGFBPs), play an important role at the tissue and cellular level through autocrine and/or paracrine mechanisms. There is substantial evidence that IGFs and IGFBPs are involved in follicular growth/development and steroidogenesis in the ovary, in proliferation and differentiation of the uterine endometrium, and in the implantation of the embryo.