Leptin concentrations in hirsute women with polycystic ovary syndrome or idiopathic hirsutism: influence on LH and relationship with hormonal, metabolic, and anthropometric measurements

BACKGROUND: The known association between leptin, obesity and insulin action suggests that leptin may have a role in polycystic ovarian syndrome (PCOS) but this has only been addressed peripherally. METHODS: We assessed the influence of leptin on LH and investigated the relationship between leptin and body mass index (BMI), waist:hip ratio (WHR), androgen concentrations, fasting insulin and insulin:glucose ratio (IGR) in 27 women with PCOS and in 20 age- and weight-matched women with regular, ovulatory menstrual cycles and idiopathic hirsutism (IH), RESULTS: Leptin concentrations were significantly higher in obese PCOS women than in normal weight women with either PCOS or IH (P = 0.0028), but did not differ between obese women with PCOS and IH, WHR, insulin: concentrations and IGR were significantly higher in obese PCOS patients in comparison with the three other groups. In IH patients, the association between leptin concentrations and WHR was lost after adjustment for BMI, In PCOS patients, a significant correlation was observed between leptin and fasting insulin concentrations, IGR, WHR and LH. After adjustment for BMI, only the correlation with LH remained significant. A stepwise regression model was set up with LH as the dependent variable to test the hypothesis that the concentrations of leptin might be modulating the concentrations of LH in PCOS patients, The relationship of LH concentrations with IGR was found to be BMI dependent. In contrast, leptin concentrations contributed negatively and significantly to LH concentrations, independently of either BMI or IGR, CONCLUSIONS: We speculate that the known attenuation in basal or stimulated response of LH in obese PCOS patients might be related to leptin resistance, which could influence LH hypersecretion, In IH ovulatory patients, normal LH concentrations suggest the presence of preserved regulatory mechanisms of GnRH pulsatility, Further studies are needed to specifically investigate the proposed correlation between leptin and GnRH modulation in PCOS.