Neuroendocrine mechanism of anovulation in users of contraceptive subdermal implant of nomegestrol acetate (Uniplant)

Abstract

To evaluate a nomegestrol acetate subdermal contraceptive implant's (Uniplant; Thermex, Monaco) effect on the hypothalamus-pituitary-ovarian axis. A prospective clinical trial. San Borja-Arriarán Clinical Hospital, University of Chile, School of Medicine. Normally cycling healthy women. Insertion of Uniplant. Luteinizing hormone pulse and endocrine profiles were assessed before, 48 hours after insertion, and after prolonged use of the implant. Anovulation was noted in 100% of users in the first month. Seventy percent of subjects demonstrated follicular development with the absence of ovulation and an endocrine profile similar to the follicular phase: (LH pulse/8 hours 6.85 +/- 0.67, LH amplitude 3.54 +/- 0.65 mIU/mL (conversion factor to SI unit, 1.00), and E2 193 +/- 29.4 pg/mL (conversion factor to SI unit, 3.67), whereas 30% demonstrated no follicular activity with an endocrine profile similar to the luteal phase: (LH pulse/8 hours; 3.66 +/- 0.66, LH amplitude 5.76 +/- 1.73 mIU/mL, and E2 67.5 +/- 4 pg/mL. Clinical characteristics, serum gonadotropin concentration, and LH pulse characteristics failed to predict which subjects would initiate or remain devoid of follicular activity. Uniplant results in anovulation via two mechanisms: hypothalamic suppression in subjects who lack follicular development, and likely suppression of the pituitary LH surge in subjects who initiate follicular activity.