Effects of estropipate treatment on plasma lipids and lipoprotein lipid composition in postmenopausal women.

It is generally believed that the cardioprotective benefit of long term treatment of postmenopausal women with estrogen results in part from its capacity to increase high density lipoprotein (HDL) and lower low density lipoprotein (LDL) concentrations. The extent to which the various estrogens employed in replacement treatment affect the composition of lipoproteins, however, is not known. For this reason, we have examined the impact of one such preparation, the synthetic estrone estropipate (1.25 mg/day), on lipoprotein levels and composition in six postmenopausal women. After 6 months of treatment, whole plasma triglyceride (pretreatment, 135 +/- 63; posttreatment, 143 +/- 56 mg/dL), cholesterol (pretreatment, 232 +/- 14; posttreatment, 216 +/- 29 mg/dL), and HDL-C (pretreatment, 57.8 +/- 14.8; posttreatment, 55.6 +/- 13.2) were unchanged. However, plasma free (unesterified) cholesterol (FC) fell (pretreatment, 73.4 +/- 6.2; posttreatment, 53.7 +/- 9.3 mg/dL; P less than 0.05) and lecithin (L) rose significantly (pretreatment, 2.12 +/- 0.29; posttreatment, 2.47 +/- 0.34 mumol/mL; P less than 0.01). The consequence of these changes was a significant decline in the plasma FC/L ratio (pretreatment, 0.91 +/- 0.17; posttreatment, 0.68 +/- 0.12; P less than 0.01) to levels observed in healthy menstruating women. The calculated lipoprotein particle size was unchanged in very low density lipoproteins and increased significantly (P less than 0.05) in LDL after estropipate therapy. Since qualitatively altered lipoproteins enriched in FC and an increased FC/L ratio in plasma are both associated with increased coronary risk, the improvement noted in these parameters after estropipate therapy indicates that its use may be beneficial despite the lack of change in whole plasma lipids.