Relative fatty acid composition of lecithin during postmenopausal replacement therapy--a comparison between ethinyl estradiol and estradiol valerate.

The relative fatty acid composition of serum lecithin was followed in groups of women during postmenopausal replacement therapy. The effects of estradiol valerate and ethinyl estradiol in two different doses, and the modulating influence of various progestogens and antiestrogens were compared. Unopposed estrogen treatment enhanced liver lecithin synthesis along pathway I, i.e. reduced the amount of stearic acid and increased the amount of palmitic acid. The effect was clearly dose-dependent and even the low dose of 10 micrograms of ethinyl estradiol was more potent than 2 mg of estradiol valerate. No qualitative difference between the two estrogens was recorded. The sequential addition of the antiestrogen tamoxifen significantly reduced the influence of ethinyl estradiol. Liver lecithin synthesis along pathway I may be stimulated by all estrogens and not only by 17C-alkylated compounds. The prostaglandin precursors, dihomogammalinolenic and arachidonic acid, showed a seemingly dose-dependent increase during estrogen treatment. The comparatively weaker effects of estradiol valerate on lipid metabolism should make this non-alkylated estrogen the first choice in clinical practice.