Effects of Norplant contraceptive subdermal implants on serum lipids and lipoproteins

A longitudinal, short-term study of women using NORPLANT (levonorgestrel implants) was conducted. Cholesterol content of the major lipoproteins along with total cholesterol and triglycerides were measured in fasting blood samples from 32 women volunteers. Results for lipids and lipoproteins determined 6 and 12 months post-NORPLANT insertion were compared with values obtained for samples taken just before implantation. Total serum triglycerides was significantly reduced (p < 0.01) from 1.14 +/- 0.44mmol/l (mean +/- SD) to 0.89 +/- 0.25mmol/l at six and to 0.89 +/- 0.34mmol/l at twelve months post-insertion. Serum total cholesterol was 3.97 +/- 0.53mmol/l at the time of insertion while at six and twelve months post-insertion, they were 3.65 +/- 0.49mmol/l and 3.56 +/- 0.71mmol/l, respectively. These changes in values from the time of insertion to twelve months, were statistically significant (P < 0.02). As regards lipoprotein fractions, high density lipoprotein-cholesterol (HDL-chol) exhibited statistically significant reduction (P < 0.001) from 1.38 +/- 0.34 mmol/l to 0.71 +/- 0.30 mmol/l (mean +/- SD) six months post-insertion. Although the value had improved to 1.14 +/- 0.38mmol/l by twelve months, the value was still significantly different from the pre-insertion value. The low density lipoprotein-cholesterol (LDL-chol) had a mean value (+/- SD) of 2.08 +/- 0.45 mmol/l at the time of insertion. This was significantly elevated (P < 0.001) at six months to 2.54 +/- 0.48mmol/l (mean +/- SD). The twelve-month post-insertion value of LDL-chol (2.02 +/- 0.79) was similar to the pre-insertion value. The shift in HDL-cholesterol and LDL-cholesterol within six months followed by a virtual return to the pre-insertion values may represent only a transient change in metabolism of lipids and lipoproteins consequent upon NORPLANT contraception.