EFFECT OF POSTMENOPAUSAL HORMONE-THERAPY ON LIPOPROTEIN(A) CONCENTRATION

Background-Postmenopausal hormone therapy has been reported to decreas e levels of lipoprotein (Lp)(a) in cross-sectional studies and small o r short-term longitudinal studies. We report findings from a large, pr ospective, placebo-controlled clinical trial that allows a broad chara cterization of these effects for lour regimens of hormone therapy. Met hods and Results-The Postmenopausal Estrogen/Progestin Interventions s tudy was a 3-year, placebo-controlled, randomized clinical trial to as sess the effect of hormone regimens on cardiovascular disease risk fac tors in postmenopausal women 45 to 65 years of age, The active regimen s were conjugated equine estrogens therapy at 0.625 mg daily, alone or in combination with each of three regimens of progestational agents: medroxyprogesterone acetate (MPA) at 2.5 mg daily tie, continuous MPA) , MPA at 10 mg days 1 to 12 (ie, cyclical MPA), and micronized progest erone at 200 mg days 1 to 12. Plasma levels of Lp(a) were measured at baseline (n=366), 12 months (n=354), and 36 months (n=342). Assignment to hormone therapy resulted in a 17% to 23% average drop in Lp(a) con centrations relative to placebo (P<.0001), which was maintained across 3 years of follow-up. No significant differences were observed among the four active arms. Changes in Lp(a) associated with hormone therapy were positively correlated with changes in LDL cholesterol, total cho lesterol, apolipoprotein B, and fibrinogen levels and were similar acr oss subgroups defined by age, weight, ethnicity, and prior hormone use . Conclusions-Postmenopausal estrogen therapy, with Or without concomi tant progestin regimens, produces consistent and sustained reductions in plasma Lp(a) concentrations.