Leptin and leptin binding activity in the preovulatory follicle of polycystic ovary syndrome patients.

To investigate the clinical importance of leptin's intraovarian effects, we studied the concentration of leptin and leptin binding activity in the plasma and in the follicular fluid of PCOS patients (n=20; median BMI: 27.1 kg/m2, range 19.7- 36.3) undergoing controlled ovarian stimulation with long-term GnRH agonist, recombinant FSH, and in vitro fertilization. Follicular fluid and blood samples were collected during follicle aspiration for IVF. Total leptin concentration was measured by radioimmunoassay, and specific leptin binding activity was accessed by a gel filtration column assay. Follicular fluid and plasma leptin levels were similar (median 1135 pmol/l vs. 1409 pmol/l; p=0.81). Follicular fluid to plasma leptin ratio was independently associated with cumulative FSH dose (r=0.63; p=0.006) and insulin resistance index (r=- 0.45; p=0.04). Specific leptin binding activity was higher in the plasma than in the follicular fluid [median 7.94% vs. 3.49%; p<0.001]. When multivariate analysis was used to...