Altered Regulation of Insulin-Like Growth Factor Binding Protein-I in Patients With Polycystic Ovary Syndrome

Abstract

Insulin-like growth factor (IGF-I) action is influenced by circulating as well as tissue levels of its binding proteins. Because serum IGF binding protein-1 (IGFBP-1) levels have been found to be decreased in patients with polycystic ovary syndrome (PCOS), we tested the hypothesis that regulation of IGFBP-1 secretion may be different in patients with PCOS compared with normal women. We studied 15 normal ovulatory women and 15 women with PCOS of similar age (21 +/- 1 and 22 +/- 1 years, respectively). All subjects were studied after an overnight fast between days 5-8 after spontaneous or progestin-induced menses. Perturbations included the administration of insulin intravenously, maintenance of a euglycemic clamp, and, in a subsequent cycle, the administration of a long-acting somatostatin analogue (octreotide, 100 micrograms) given subcutaneously. Blood samples were collected before treatment, every 15 minutes for 6 hours after insulin, and every 30 minutes for 3 hours after octreotide administration. Serum levels of IGF-I, IGFBP-1, IGFBP-3, and insulin were measured by specific immunoassays. Compared with the controls, patients with PCOS had significantly higher insulin levels, similar IGF-I and IGFBP-3 levels, and significantly lower IGFBP-1. Insulin did not change serum IGF-I levels in either group, although a significant decrease in IGFBP-1 levels occurred in normal women but not in patients with PCOS. Octreotide treatment also did not change serum IGF-I levels in either group, but serum insulin levels decreased significantly and IGFBP-1 levels increased significantly in both groups; this response was significantly greater in controls. Our data are compatible with the notion that regulation of IGFBP-1 is altered in women with PCOS and that several factors may be involved.