EFFECTS OF ADDING C-19 VERSUS C-21 PROGESTIN TO CONJUGATED ESTROGEN IN MODERATELY HYPERCHOLESTEROLEMIC POSTMENOPAUSAL WOMEN

OBJECTIVE: Our purpose was to compare the effects on fasting plasma li poprotein lipids of adding low dosage C-19 continuous progestin (dl-no rgestrel) versus conventional low-dosage continuous C-21 progestin (me droxyprogesterone acetate) to cyclic conjugated estrogen therapy. STUD Y DESIGN: Nine hypercholesterolemic postmenopausal women with intact u teri were randomly assigned in a prospective, double-blind, two-period crossover study of conjugated estrogen plus either(1) dl-norgestrel ( 0.05 mg/day) or (2) medroxyprogesterone acetate (2.5 mg/day) for 1 yea r and after an appropriate washout period were switched to the alterna tive regimen for another year. Four subjects received conjugated estro gen only. RESULTS: Compared with baselines, each of the C-19 and C-21 progestin regimens significantly increased plasma high-density lipopro tein cholesterol (15% vs 12%) and reduced the ratio of total cholester ol/high-density lipoprotein cholesterol (20% vs 15%, respectively), bu t only the former significantly reduced plasma triglycerides (24% vs 0 .3%, p < 0.05). CONCLUSIONS: Low dosages of either dl-norgestrel (C-19 ) or medroxyprogesterone acetate (C-21) when combined with conjugated estrogen significantly improve plasma lipoprotein lipids of postmenopa usal women.