[The role of insulin-like growth-factor binding proteins in normal and polycystic ovaries]

The insulin-like growth factor binding proteins are single chain polypeptides, that can bind insulin-like growth factors, but not insulin. They can serve as autocrine or paracrine regulators of the actions of insulin-like growth factor. The human granulosa cells produce insulin-like growth factor-II but not insulin-like growth factor-I, while the human theca cells produce insulin-like growth factor-I and II. Polycystic ovarian syndrome is a disorder which is characterised by hyperandrogenism and anovulation. In polycystic ovarian syndrome there is a disorder of follicular development, with the accumulation of antral follicles within the ovary which fail to respond appropriately to endogenous follicle-stimulating hormone. Significance is given to insulin-like growth factor binding proteins, which have an inhibitory action on follicle-stimulating hormone. No differences were found in the total level of insulin-like growth factor binding proteins follicular profiles between women with polycystic ovarian syndrome and without it. Serum insulin-like growth factor binding protein-I levels are lower in polycystic ovarian syndrome with hyperinsulinaemia, probably as a consequence of insulin-mediated suppression of insulin-like growth factor binding protein-I. Consequently, serum free insulin-like growth factor-I levels are higher. This alteration may cause an excessive thecal androgen production. The alterations in the insulin-like growth factor-insulin-like growth factor binding proteins axis may be one of several mechanisms that help to sustain the steady state of anovulation and follicular dysmaturation that are characteristic of this syndrome.