Differential Effects of Oral Estrone Versus 170-Estradiol on Lipoproteins in Postmenopausal Women*

Abstract

Toward the definition of optimal postmenopausal estrogen replacement we compared the effects of three graduated doses of two oral estrogens, estrone sulfate and 17 beta-estradiol, on the lipid profiles of two groups of six postmenopausal women. Because of metabolic interconversions equivalent serum concentrations of estrone and estradiol were produced with these regimens. However, differential effects were noted in lipoproteins. 17 beta-Estradiol caused an increase in total plasma cholesterol (from 5.71 +/- 0.36 to 5.99 +/- 0.57 mmol/L, baseline to high dose; P less than 0.02), high density lipoprotein (HDL) cholesterol (from 1.45 +/- 0.15 to 1.78 +/- 0.36 mmol/L; P less than 0.02), HDL2 cholesterol concentration (from 0.41 +/- 0.08 to 0.62 +/- 0.26 mmol/L; P less than 0.01), and triglyceride concentration (from 1.09 +/- 0.29 to 1.24 +/- 0.30 mmol/L; P less than 0.01) without affecting low density lipoprotein (LDL) cholesterol concentration. By contrast, estrone sulfate caused a decrease in total plasma cholesterol (from 6.51 +/- 0.85 to 5.87 +/- 0.41 mmol/L; P less than 0.05) and LDL cholesterol concentration (from 4.34 +/- 0.57 to 3.67 +/- 0.44 mmol/L; P less than 0.01) and an increase in HDL cholesterol (from 1.37 +/- 0.20 to 1.50 +/- 0.26 mmol/L; P less than 0.05) and HDL2 cholesterol concentration (from 0.34 +/- 0.18 to 0.49 +/- 0.18 mmol/L; P less than 0.01), but no change in total triglyceride concentration. We deduce that the differential effect of orally administered estrogens on lipoprotein metabolism in postmenopausal women may be attributed to a first pass effect on hepatic metabolism.