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Estradiol (E2) plasma levels were assessed in forty-seven women treated for one through seven years with the same set of NorplantR implants. Each woman was subjected to one (n = 34), two (n = 11) or three (n = 2) sampling runs. At each sampling run, blood samples were drawn every third or fourth day during 5 or 6 consecutive weeks. Sampling runs were classified as ovulatory (n = 11), anovulatory (n = 49) or uncertain (n = 1) according to progesterone levels. Controls were Copper T users (n = 8), all classified as ovulatory.
No significant differences were found for the mean E2 levels between NorplantR users and Copper T users and between ovulatory and anovulatory cases. The mean of the peak E2 value found in each sampling run was significantly higher in anovulatory NorplantR subjects than in the control group. The mean of the minimum E2 level observed was significantly lower in NorplantR cases than in Copper T users. A single woman from the NorplantR group and none from the Copper T group had all E2 values below 370 pmol/l.
The inhibition of the reproductive function induced by NorplantR implants is associated with a wider range of E2 circulating levels. None of the values observed at the extremes should cause serious concerns. High peaks are transitory and opposed by the antiestrogenic effect of levonorgestreJ. Persistent low levels which could be associated with a hypoestrogenic state were observed in a single case.
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Accepted: July 21, 1988
Received: April 25, 1988
© 1988 Published by Elsevier Inc.