Effect of long-acting progestagen-only injectable contraceptives on carbohydrate metabolism and its hormonal profile

Two groups, each composed of 20 women, who used depomedroxyprogesterone acetate (DMPA) or norethisterone enanthate (NET-EN) injectable contraceptives were investigated for changes in 75-g OGTT and in the fasting and two-hour post oral glucose load (2-hours) levels of serum insulin, growth hormone, glucagon, cortisol and blood pyruvate. Samples were taken before and 3, 6 and 12 months after use of injectables. DMPA and NET-EN caused significant changes in mean blood glucose and pyruvate and in mean serum insulin, growth hormone and glucagon, but not in mean fasting cortisol. Changes with NET-EN started after 3 months, became maximal after 6 months and reverted to normal after 12 months of use, due to more frequent administration during the first 6 months of use (every 60 +/- 5 days) and to more spacing of the injections (every 84 +/- 5 days) after that. Changes with DMPA started after 3 months, and increased with the duration of use to become maximal after 12 months. Maximal changes were similar with DMPA and NET-EN and consisted of: a significant increase in fasting blood glucose and pyruvate and serum insulin; a significant increase in 2-hour blood glucose and pyruvate, serum insulin, growth hormone and glucagon. Although significant changes in blood glucose levels occurred with both DMPA and NET-EN, yet they did not reach the lower cut-off levels for impaired glucose tolerance in any user. With the same spacing of injections, i.e. every 84 +/- 5 days for NET-EN and every 90 +/- 5 days for DMPA, the effects on various parameters studied were less with NET-EN.