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Ovulatory dysfunction during continuous administration of low-dose levonorgestrel by subdermal implants
A Faundes1, V Brache, A S Tejada
1PROFAMILIA, Santo Domingo, Dominican Republic.
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.