Comparison of the metabolic effects of two hormonal contraceptive methods: an oral formulation and a vaginal ring. I. Carbohydrate metabolism and liver function.

A prospective, long-term study was undertaken to compare the metabolic effects of a contraceptive vaginal ring releasing levonorgestrel (about 290 microgram per day) and estradiol (about 180 microgram per day) and a combined oral contraceptive containing 30 microgram ethinylestradiol and 150 microgram levonorgestrel in two groups of women (n = 22 and 20, respectively). An intravenous glucose tolerance test, including determination of the insulin response to glucose, and liver function tests were performed. Both the glucose tolerance and fasting values of glucose were unaltered. The early insulin response to glucose increased by 50 percent in the contraceptive ring roup after one year of treatment, but not in the oral contraceptive group. All other insulin values were unchanged. All liver function values remained within the normal range in all subjects. There was a small significant decrease in alkaline phosphatases in both groups, which is in contrast to the effects of the early combined pills, which could cause an elevation. It is concluded that neither of these two contraceptive methods, the effects of which are predominantly gestagenic, seems to cause impairment of glucose tolerance or hepatic function.