THE IMPORTANCE OF ENDOGENOUS FEEDBACK FOR MONOFOLLICULAR GROWTH IN LOW-DOSE STEP-UP OVULATION INDUCTION WITH FOLLICLE-STIMULATING-HORMONE IN POLYCYSTIC-OVARY-SYNDROME - A RANDOMIZED STUDY

Objective: To evaluate the role of endogenous feedback in monofollicul ar growth during low-dose gonadotrophin therapy in polycystic ovary sy ndrome (PCOS) by measuring FSH levels in a group of patients cotreated with a GnRH agonist (GnRH-a) (group B) compared with patients not cot reated with an agonist (group A). Design: Prospective randomized study . Setting: University tertiary care Reproductive Endocrinology Unit. P atients: Women with clomiphene citrate-resistant PCOS. Main Outcome Me asures: Follicle-stimulating hormone, E(2), and inhibin levels, follic ular growth. Results: In group A, FSH levels decreased significantly f rom 7.3 mIU/mL (conversion factor to SI unit, 1.00) at day -5 to 5.9 m IU/mL at day 0 (day that hCG was administered) despite a constant dose , whereas they remained at a level of 7.4 mIU/mL in group B. The rate of monofollicular growth was significantly higher in group A (80%) tha n in group B (22%). No significant differences in E(2) levels or inhib in levels were found between the groups. Conclusions: The absence of a decrease of FSH during GnRH-a treatment in association with a lower r ate of monofollicular growth suggests that endogenous feedback during low-dose step-up ovulation induction in PCOS plays an important role. The absence of this feedback mechanism in the presence of normal inhib in levels suggests that negative feedback control by inhibin during fo llicular stimulation is minimal.