Effect of postmenopausal estrogen replacement on plasma Lp(a) lipoprotein concentrations

Women who receive postmenopausal estrogen replacement experience a lower rate of coronary heart disease than women who do not receive these hormones. Evidence suggests that mechanisms in addition to decreases in plasma low-density lipoprotein levels and increases in high-density lipoprotein concentrations are responsible for the apparent beneficial effect of estrogens. Therefore, we studied the effect of estrogen on plasma Lp(a) lipoprotein, newly suggested to be a risk factor for coronary heart disease in postmenopausal women.

The 31 healthy, normolipidemic subjects received placebo and conjugated equine estrogens (0.625 and 1.25 mg/d) for 3-month periods in a randomized, double-blind, crossover trial.

The mean Lp(a) lipoprotein concentration was 20.4 +/- 14.6 mg/dL during placebo treatment; it decreased by 14% (P < .01) with 0.625 mg of conjugated estrogens and by 16% (P < .005) with 1.25 mg. The Lp(a) lipoprotein concentration during placebo treatment was not significantly correlated with the responses to either dose of estrogen. There was no effect of estrogen on the plasma concentration of cholesterol ester transfer protein, suggesting that this protein is not involved in estrogen-induced changes in very-low-density lipoprotein or high-density lipoprotein concentrations and composition.

Estrogen decreases the plasma Lp(a) lipoprotein concentration, which could explain some of the protective effect of estrogen replacement therapy on coronary heart disease.