Growth hormone response to L-dopa and pyridostigmine in women with polycystic ovarian syndrome

Objective: To evaluate the GH secretion and clarify the factors influencing the GH secretion in women with polycystic ovarian syndrome (PCOS). Design: Comparison of the GH response to L-dopa with or without pyridostigmine (inhibitor of acetylcholinesterase) pretreatment and insulin response to oral glucose tolerance test in patients with PCOS and matched controls. Setting: Outpatients and healthy volunteers studied at a clinical research unit of a university hospital. Patients, Participants: Ten women with PCOS and 9 controls with regular cycles were recruited. Interventions: After an overnight fast, each subject underwent a GH stimulation test with L- dopa with or without pyridostigmine pretreatment. Plasma insulin and glucose levels were measured after a 75-g glucose load. Main Outcome Measures: Plasma GH, insulin-like growth factor I (IGF-I), insulin, and nonesterified fatty acids. Results: Growth hormone responses and GH area under the response curve (AUC) to L-dopa were significantly lower in PCOS than those in controls. Pyridostigmine enhanced the GH response to L-dopa significantly in PCOS. Insulin responses and insulin AUC to oral glucose load were significantly higher in PCOS than those in controls. Plasma IGF-I levels of PCOS were significantly higher than controls. Insulin AUC had a positive correlation with plasma IGF-I levels but an inverse correlation with GH AUC in PCOS and controls. Conclusion: Our result indicated that decreased GH secretion of PCOS may be associated with a high somatostatin activity and a high plasma IGF-I level.