Paracrine actions of insulin-like growth factors and IGF binding protein-1 in non-pregnant human endometrium and at the decidual-trophoblast interface.

Insulin-like growth factors, IGF-I, IGF-II, and IGF binding protein (IGFBP-1) appear to play major roles in endometrial development during the menstrual cycle and in the process of implantation. The mitogenic, differentiative, and anti-apoptotic properties of these growth factors, as well as their spatial and temporal expression in cycling endometrium, suggest that they may participate in endometrial growth, differentiation, inhibition of apoptosis, and perhaps angiogenesis. IGFBP-1 is a major protein product of non-pregnant endometrium during the mid-late secretory phase and occurs in abundance in decidua. Its roles as an IGF-binding protein and as a trophoblast integrin ligand suggest that it may have multiple roles in endometrial development and in interactions between the decidua and the invading trophoblast. Precise elucidation of the mechanisms underlying IGF and IGFBP-1 action at the decidual-trophoblast interface in early pregnancy awaits further investigation. The future also awaits elucidation of the potential predictive utility of IGFBP-1 in serum and in decidua in, for example, pre-eclampsia and perhaps implantation failure.