The effect of Norplant on glucose metabolism under hyperglycemic hyperinsulinemic conditions

To assess the impact of a levonorgestrel-releasing implant contraceptive (Norplant; Wyeth-Ayerst Laboratories, Philadelphia, PA) on glucose metabolism.

Prospective evaluation of insulin action and secretion in women under hyperglycemic hyperinsulinemic clamp conditions in the midfollicular phase before and 8 weeks after Norplant placement.

Yale University Clinical Research Center.

Seven previously normally cycling, nonobese, nondiabetic women participated in the study.

Norplant insertion.

Basal levels of glucose and insulin, as well as glucose-mediated insulin secretion, glucose uptake, and tissue sensitivity to insulin were assessed using the hyperglycemic hyperinsulinemic clamp technique before and after Norplant insertion.

Norplant placement did not alter the fasting glucose or insulin levels. However, it was associated with a significant 37% increase in the first phase insulin response from a control level of 51 +/- 8 to 70 +/- 10 microU/mL (conversion factor to SI unit, 7.175), and a significant 48% increase in the second phase insulin response from 60 +/- 5 to 89 +/- 8 microU/mL. In association with this increase in insulin levels after Norplant insertion, total mean body glucose uptake (M) increased from 8.08 +/- 0.91 to 9.53 +/- 0.95 mg/kg per minute. However, when expressed as the total body glucose uptake per unit of insulin, the M:I ratio (a measure of tissue sensitivity to insulin) decreased significantly from a mean of 0.12 +/- 0.02 to 0.10 +/- 0.01 mg/kg per minute per microU/mL.

Although Norplant insertion does not alter basal glucose and insulin levels, tissue sensitivity to insulin under hyperglycemic hyperinsulinemic conditions is decreased after Norplant insertion.