Triphasic Randomized Clinical Trial: Comparison of effects on carbohydrate metabolism

One hundred thirty women were randomly assigned to treatment with one of three triphasic oral contraceptives and 43 women using nonhormonal methods served as controls for a 6-month study of the metabolic effects of these formulations. One of the oral contraceptives contained ethinyl estradiol and levonorgestrel, and the other two contained ethinyl estradiol and norethindrone. Compared with pretreatment assessment, all three triphasic oral contraceptives produced small increases in the mean plasma glucose levels that were statistically significant but clinically unimportant. No subjects had abnormal glucose response curves in glucose tolerance test results. Compared with pretreatment assessment, all of the oral contraceptive preparations produced small increases in the mean insulin levels at 3 months but not at 6 months. Overall there were no statistically significant differences among the three formulations in their effects on carbohydrate metabolism as measured by glucose or insulin levels after 6 months of treatment.