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ObjectiveSeveral studies have reported that -aminobutyric acid (GABA) ergic circuits are involved in the pathophysiology of polycystic ovary syndrome (PCOS). The progesterone metabolite allopregnanolone is a potent GABA(A)-receptor-modulating steroid, and patients may have increased concentrations of allopregnanolone or altered GABA(A) receptor sensitivity. We investigated both of these possibilities in this study. PatientsWe enrolled 9 women with PCOS and 24 age-matched eumenorrhoeic controls, who were divided into two groups by body mass index (BMI) (16 normal weight and 8 overweight). MeasurementsWe investigated the effects of allopregnanolone injection on GABA(A) receptor sensitivity in both groups of women. All women received a single intravenous dose of allopregnanolone (0050mg/kg). GABA(A) receptor sensitivity was assessed with the saccadic eye velocity (SEV) over 30 degrees (SEV30 degrees), the SEV30 degrees/allopregnanolone concentration ([Allo]) ratio, and sedation, which were measured together with serum allopregnanolone at intervals for 180min after injection. The controls were tested in the follicular phase of the menstrual cycle. ResultsBaseline allopregnanolone concentrations were higher in the PCOS women than in the normal-weight (P=0034) and overweight controls (P=0004). The allopregnanolone concentrations after injection were higher in the PCOS women (P=0006) and overweight controls (P=0037) than in the normal-weight controls. All groups showed a decline in the SEV30 degrees/[Allo] ratio after injection. Allopregnanolone had a smaller effect on the SEV30 degrees/[Allo] ratio in the overweight women (PCOS, P=0032; controls, P=0007) than in the normal-weight controls. The sedation score after allopregnanolone injection was lower in the PCOS patients than in the controls, but was not different between the two control groups. ConclusionsPCOS women had elevated baseline allopregnanolone concentrations compared with follicular-phase controls. All overweight women (PCOS and controls) were less sensitive to allopregnanolone than normal-weight controls.