The objective of this study was to elucidate the relationship and role of insulin-like growth factor-1 (IGF-1), IGF binding protein-1 (IGFBP-1), insulin and luteinizing hormone (LH) in the pathogenesis of polycystic ovary syndrome (PCOS). In a pilot study, serum concentrations of IGF-1 were determined in women with PCOS (n = 10), hypopituitarism (n = 12) and normal controls (n = 10). In the main study, serum concentrations of IGF-1, IGFBP-1, insulin and LH in women with anovulation associated (n = 23) and not associated (n = 47) with PCOS were determined. Serum concentrations of IGF-1 were not different in women with PCOS, anovulatory non-PCOS and healthy women but were low in those with hypopituitarism. Mean serum IGFBP-1 in PCOS (33.8 +/- 21.2 micrograms/l) was decreased compared with anovulatory non-PCOS (60.0 +/- 22 micrograms/l) (P = 0.0001), and correlated negatively with insulin concentrations (r = -0.67, P = 0.0006). Patients with PCOS could be separated into those with high LH and those with high insulin levels. It was concluded that women with PCOS have normal serum IGF-1 concentrations but IGFBP-1 levels, regulated by insulin, are low. Hyperinsulinaemia and raised LH are independently capable of stimulating ovarian androgen production. Growth factors may have an important role in the pathogenesis of PCOS.