Does progestogen reduction in oral contraception parallel reduced lipid metabolic effects?

Twelve young fertile women participated in a cross-over design study whose purpose was to evaluate the effect on lipid metabolism induced by two sequential contraceptive preparations. Sequilarum (50 micrograms of ethinylestradiol + levonorgestrel where the levonorgestrel dose is varied from 50 micrograms during the first 11 days up to 125 micrograms during the lst 10 days of the cycle) was compared with Ovanone (50 micrograms of ethinylestradiol for 22 days with the addition of 2.5 mg lynestrenol during the last 15 days of the cycle). Serum triglycerides, phospholipids, free and total cholesterol were determined, and also was the level of these lipid components in ultracentrifugally isolated lipoprotein lipids. The relative fatty acid composition of serum lecithin and serum cholesterol ester was assessed by gas-liquid chromatography. As expected, both of these preparations are predominantly estrogenic in their effects on lipoprotein metabolism, since both raise serum and VLDL triglyceride levels. The absence of any substantial influence on HDL cholesterol should probably be interpreted as a modifying effect of the progestogen component of both preparations. As to the relative fatty acid composition of serum lecithin the shift induced in palmitic and stearic acids was the same as found in earlier studies when 17C-alkylated exogenous sex steroids were administered, i.e. an increase in the palmitic acid concomitant with a decrease in the stearic.