Decreased 34K insulin-like growth factor binding protein in polycystic ovarian disease

Insulin and insulin-like growth factor I (IGF-I) have been implicated in ovarian androgen production. Insulin is closely related to IGF-I and cross-reacts with its receptor. The 34K IGF-binding protein (34K IGF-BP) has been shown to inhibit the binding of IGF-I to its receptor. The authors evaluated the role of insulin in the regulation of serum levels of 34K IGF-BP in patients with polycystic ovarian disease (PCOD). 34K IGF-BP levels during an oral glucose tolerance test (OGTT) were measured in 15 PCOD (8 obese and 7 nonobese) patients and in 10 healthy control subjects. The fasting level of 34K IGF-BP was decreased in nonobese PCOD patients (2.4 +/- 0.3 micrograms/l) (mean +/- standard error) (P = 0.02) and obese PCOD patients (0.59 +/- 0.2 micrograms/l) (P less than 0.001) as compared with healthy controls (4.8 +/- 0.9 micrograms/l). Both nonobese PCOD patients and normal controls demonstrated a significant decrease in 34K IGF-BP following OGTT. An insulin-related decrease in 34K IGF-BP may allow an increased pool of IGF-I able to bind to its receptor. This would provide a mechanism for increased ovarian androgen production via IGF-I stimulation of its receptor.