Predicting the FSH threshold dose in women with WHO Group II anovulatory infertility failing to ovulate or conceive on clomiphene citrate

BACKGROUND: The objective of this investigation was to establish independent predictors of follicle-stimulating hormone (FSH) threshold dose in anovulatory women undergoing ovulation induction with FSH preparations. METHODS: One hundred and fifty-one patients with WHO Group II anovulatory infertility failing to ovulate or conceive on clomiphene citrate underwent ovarian stimulation with FSH-only preparations following a low-dose step-up protocol. The individual FSH threshold dose was defined as the FSH dose when meeting the human chorionic gonadotrophin criteria (one follicle ≥17 mm, or 2–3 follicles ≥15 mm). The influence of demographics, physical characteristics, obstetric and infertility and menstrual cycle history, ovarian ultrasonography, endocrine parameters and type of gonadotrophin preparation on the FSH threshold dose was assessed through multiple regression analysis. RESULTS: In the univariate analysis, age, body mass index (BMI), failure to ovulate with clomiphene citrate, menstrual cycle history (amenorrhea, oligomenorrhea or anovulatory cycles of 21–35 days), mean ovarian volume, LH/FSH ratio, testosterone and free androgen index were significant (P < 0.05) predictors of FSH threshold dose. In the multivariate analysis, menstrual cycle history, mean ovarian volume and BMI remained significant (P < 0.001). CONCLUSIONS: The individual FSH threshold dose for ovulation induction in anovulatory women can be predicted based on three variables easily determined in clinical practice: menstrual cycle history, mean ovarian volume and BMI. A FSH dosage nomogram was constructed based on these parameters.