Objective: To determine the metabolic mechanisms underlying hypercholesterolemia in postmenopausal women and to determine whether a low dose of lovastatin will correct this abnormality.
Design: In the first part of the study, turnover rates of autologous low-density lipoprotein (LDL) were measured in hypercholesterolemic and control women. In the second part, hypercholesterolemic women participated in a placed-controlled, randomized, double-blind study using lovastatin as the therapeutic agent.
Setting: The General Clinical Research Center of the University of Texas Southwestern Medical Center, Dallas, utilizing inpatient and outpatient facilities, and the Veterans Affairs Medical Center, Dallas, Tex.
Patients: For the LDL turnover study, 26 postmenopausal women with moderate hypercholesterolemia (mean +/- SD LDL cholesterol, 4.78 +/- 0.59 mmol/L [185 +/- 23 mg/dL]) and 13 postmenopausal women with normal levels of plasma lipids and lipoproteins (mean +/- SD LDL cholesterol, 3.31 +/- 0.39 mmol/L [128 +/- 15 mg/dL]) were studied. Sixteen postmenopausal women participated in the drug study.
Interventions: In the drug study, patients received blindly both lovastatin (10 mg/d) and placebo.
Main outcome measures: In the first study, kinetic parameters of LDL metabolism; in the second study, response in lipids and lipoproteins to lovastatin therapy.
Results: In the LDL turnover study, mean (+/- SD) input (production) rates for LDL apolipoprotein B (apo B) were similar for hypercholesterolemic women and control women (12.4 [+/- 3.2] mg/kg per day and 11.1 [+/- 2.2] mg/kg per day, respectively). In contrast, mean (+/- SD) fractional catabolic rates for LDL apo B in hypercholesterolemic women (0.29 [+/- 0.04] pools per day) were significantly lower than those in normolipidemic women (0.35 [+/- 0.03] pools per day). In the drug trial, lovastatin therapy reduced mean (+/- SD) total cholesterol and LDL cholesterol from 7.03 (+/- 1.16) mmol/L (272 [+/- 45] mg/dL) and 4.42 (+/- 0.80) mmol/L (171 [+/- 31] mg/dL, respectively, to 5.70 (+/- 1.03) mmol/L (221 [+/- 40] mg/dL) and 3.46 (+/- 0.85) mmol/L (134 [+/- 33] mg/dL).
Conclusions: The turnover data suggest that hypercholesterolemia in post-menopausal women is primarily attributable to a reduced activity of LDL receptors. In accord, the hypercholesterolemia in these women was effectively lowered by low doses of lovastatin. Thus, a low dose of lovastatin appears highly effective for treatment of moderate hypercholesterolemia in most postmenopausal women, presumably because it reverses the reduction in LDL receptor activity associated with menopause.