Levonorgestrel plasma concentrations and hormone profiles after insertion and after one year of treatment with a levonorgestrel-IUD

Abstract

Plasma concentrations of levonorgestrel, progesterone, estradiol, FSH and LH were measured in seven volunteers who had a levonorgestrel-releasing IUD inserted postmenstrually. Blood samples were collected twice weekly during a mean of 93 days immediately postmenstrually and during a mean of 41 days over the twelfth to fifteenth month of treatment. Patterns of bleeding were studied during the first year of treatment. The IUDs used were designed to release 25 micrograms/day of levonorgestrel. The mean +/- SD plasma concentration of levonorgestrel for all subjects during the first three months was 260 +/- 68 pg/ml, and 129 +/- 28 pg/ml after one year of treatment. During the initial period of blood sampling only two of the subjects ovulated, while only two did not ovulate after one year of treatment. Intermenstrual spotting occurred during the first sixty days of treatment. Three subjects developed amenorrhea at the end of the first year. All the subjects continued the use of the IUD and no pregnancies occurred.

PIP: Steroid profiles of women wearing levonorgestrel-containing IUDs during the first 3 months of treatment were compared with those from the same subject after 1 year of treatment. Bleeding patterns were also studied in the 7 volunteers in this study. Plasma concentrations of levonorgestrel, progesterone, estradiol, follicle stimulating hormone, and luteinizing hormone were assayed in blood samples collected 2 times/week during a mean of 93 days immediately postmenstrually and during a mean of 41 days over the 12th-15th month of treatment. The medicated IUDs were designed to release 25 mcg of steroid per day. Steroid profiles showed that during the initial period of blood sampling only 2 subjects ovulated, but by 1 year only 2 of 7 had not ovulated. Levonorgestrel concentrations (mean) were 260+ or -68 pg/ml during the first 3 months and 129+ or -28 pg/ml at the end of 1 year of treatment. After the 1-year trial, all subjects continued using the medicated IUD and no pregnancies have occurred. Bleeding side effects were mostly spotting and intermenstual bleeding during the first 60 days of treatment; however, 3 subjects had developed amenorrhea by the end of the first year of treatment.