Insulin sensitivity is unaltered by the use of the Norplant subdermal implant contraceptive

Prior evaluations of carbohydrate metabolism in Norplant implant users, using the oral glucose tolerance test, have shown mild but clinically insignificant deterioration of insulin sensitivity. Using the more sensitive insulin tolerance test, the effects of the Norplant implant system on insulin sensitivity was studied in normal women. Insulin tolerance tests were performed before Norplant implant insertion in ten ovulatory female volunteers and repeated after 12 weeks of use. Both fasting glucose and fasting insulin values were similar before and after the use of Norplant implants. There was no significant difference in either the Kitt glucose value or the Kitt insulin value at baseline and at 3 months of use. Furthermore, the insulin-to-glucose ratio did not differ before and after the use of Norplant implants. There was a significant correlation with BMI and Kitt glucose value (r = -0.45, p < .05), as well as between fasting insulin and BMI (r = 0.6, p = 0.006). In the first three months of use, the levonorgestrel-containing implant system, Norplant, does not affect sensitivity to insulin or glucose in normal, nondiabetic women.