Objective: To study the endocrinologic profile of regularly menstruating users of levonorgestrel subdermal implants.
Design: Observational, prospective, case-controlled comparative study.
Setting: The Family Planning Clinic of PROFAMILIA, in Santo Domingo, Dominican Republic.
Patients, participants: Thirty one regularly cycling Norplant users and 12 nonhormonal contraceptors who volunteered to participate.
Interventions: Norplant contraceptive implants were inserted in 31 subjects between 13 and 77 months before this study.
Main outcome measures: Follicle-stimulating hormone, luteinizing hormone, estradiol (E2), and progesterone (P) were serially assayed for one menstrual cycle.
Results: Almost half of the cycles among Norplant users were anovulatory; all the rest (55%) had some form of dysfunction: diminished gonadotropin surge, luteal phase insufficiency (low P levels and shortened luteal phase), and E2 profiles different from normal controls.
Conclusions: Anovulation is clearly one of the main mechanisms of action of Norplant, but even in presumptive ovulatory cycles, the dysfunctions described possibly contribute to the high contraceptive effectiveness of Norplant.
PIP: The study sought to examine the endocrinologic profile of regularly menstruating users of levonorgestrel subdermal implants. This observational, prospective, case-controlled, comparative study occurred at the Family Planning Clinic of PROFAMILIA in Santo Domingo, Dominican Republic. 31 subjects agreed to receive Norplant contraceptive implants between 13-77 months prior to this study and there were 12 nonhormonal contraceptors who also volunteered to participate. Follicle stimulating hormone, luteinizing hormone, estradiol (E2), and progesterone (P) were serially assayed for 1 menstrual cycle, and almost 1/2 of the cycles of norplant acceptors were anovulatory: the remainder (55%) had some form of dysfunction such as diminished gonadotropin surge, luteal phase insufficiency (low P levels and shortened luteal phase), and E2 profiles different from controls. Anovulation is clearly 1 of the main mechanisms of Norplant action, but even in presumptive ovulatory cycles, the dysfunctions described could have contributed to the high contraceptive effectiveness of Norplant.