Serum concentrations of estradiol, progesterone, and levonorgestrel are not determinants of endometrial histology or abnormal bleeding in long-term Norplant implant users.

The objective of this study was to determine the relevance of serum estradiol, progesterone and levonorgestrel concentrations to endometrial histology and uterine bleeding associated with long-term Norplant implants use. Eighteen five-year users of Norplant implants had endometrial biopsies and determinations of serum estradiol, progesterone and levonorgestrel concentrations. Correlations among these factors and uterine bleeding were calculated. Proliferative endometrium (but not sex steroid levels) was associated with abnormal bleeding. Neither ovarian steroid nor levonorgestrel concentrations was a predictor of abnormal bleeding. Hyperplastic changes were not seen even with high estradiol and low levonorgestrel levels.