A randomized double-blind study of the effects of two low-dose combined oral contraceptives on biochemical aspects. Report from a seven-centred study. WHO Special Programme of Research, Development and Research Training in Human Reproduction. Task force on Oral Contraceptives.

A comparative study of the metabolic effects of two combined oral contraceptive preparations was undertaken in seven WHO Collaborating Centres for Research in Human Reproduction. A total of 847 subjects were randomly allocated to one of two pill groups - norethisterone lmg/ethinyl estradiol 35 micrograms (NET/EE) or levonorgestrel 150 micrograms/ethinyl estradiol 30 micrograms (LNG/EE). An additional 195 women using an IUD served as a comparison group. Blood samples were taken on admission, and at 3 and 12 months thereafter. Both pills induced changes in fasting and 2-hour glucose, triglycerides, total cholesterol, HDL-cholesterol, bilirubin, alkaline phosphatase, albumin, and total protein, but not aspartate aminotransferase. The most dramatic and probably most clinically important changes were an increase in triglycerides and a decrease in HDL-cholesterol. The NET/EE preparation appeared to induce a greater increase in triglycerides, but no significant difference was found between the two pill preparations with respect to HDL-cholesterol changes.