Effects of combined oral contraceptive ethinylestradiol (30 microg) and dienogest (2 mg) on carbohydrate metabolism during 1 year of conventional or extended-cycle use.

The effects of extended regimens of combined oral contraceptives (COCs) on carbohydrate metabolism are largely unknown. The present study compared the effects of a COC containing 30 microg ethinylestradiol and 2 mg dienogest (EE/DNG) in conventional and extended-cycle regimen over 1 year. Parameters of carbohydrate metabolism were measured in 59 women treated with EE/DNG either conventionally (13 cycles of 21+7 days) or in extended-cycle regimen (4 cycles of 84+7 days). Blood samples were taken in a control cycle, and at 3 and 12 months of treatment. The mean levels of HbA1c and fasting glucose levels remained stable in both conventional and extended-regimen of EE/DNG. The mean levels of fasting insulin and C-peptide underwent comparable increases in both regimens, suggesting a similar readjustment of glucose metabolism via slightly increased insulin secretion. For both regimens, the response to the oral glucose tolerance test (OGTT) showed a slightly impaired glucose tolerance and insulin resistance at 3 months. These changes improved or returned to baseline at 12 months. Accordingly, the mean index for insulin resistance (homeostasis model assessment of insulin resistance, HOMA-IR) increased and the mean insulin sensitivity index [ISI (composite)] decreased modestly in both groups. The present study demonstrates that there are no statistically significant differences between the effects of conventional and extended-cycle treatment on carbohydrate metabolism over 1 year of treatment. In general, the effects of both regimens were moderate and mostly transient.