Prospective evaluation of endometrial thickness as a predictor of pituitary down-regulation after gonadotropin-releasing hormone analogue administration in an in vitro fertilization program

Objective: To determine whether pituitary down-regulation after gonadotropin-releasing hormone analogue (GnRH-a) administration can be accurately predicted by transvaginal ultrasonographic measurement of endometrial thickness. Design: Prospective study. Setting: An IVF unit of an academic medical center. Patient(s): One hundred eighty-one patients undergoing 265 NF-ET treatment cycles using GnRH-a in the long protocol. Main Outcome Measure(s): Serum concentrations of E-2 were determined, and endometrial thickness was measured by transvaginal sonography. The accuracy of endometrial thickness for predicting pituitary down-regulation was calculated. Result(s): Pituitary down-regulation, defined as a serum E-2 concentration of less than or equal to 55 pg/mL, was achieved in 77% (204 of 265) of the cycles. An endometrial thickness of less than or equal to 6 mm was found in 92.2% (188 of 204) of cycles in which down-regulation was achieved. An estradiol level of less than or equal to 55 pg/mL was present in 95.9% (188 of 196) of cycles with endometrial thickness of less than or equal to 6 mm. Conclusion(s): A state of relative hypoestrogenism after GnRH-a administration, indicative of pituitary down-regulation, can be predicted with a high degree of accuracy by ultrasonographic measurement of endometrial thickness. Thus, routine testing for serum E-2 concentration may be safely omitted. This may allow further simplification of IVF protocols and increase both cost-effectiveness and patients' convenience. (C) 1998 by American Society for Reproductive Medicine.