Effects of oral combined hormone replacement therapy on plasma lipids and lipoproteins

Hormone replacement therapy has been shown to decrease the risk of coronary heart disease (CHD) in menopausal women. In this cross-sectional study, we addressed the following question: What effects would combined oral hormone replacement therapy have on plasma lipid and lipoprotein profiles independent of the other known CHD risk factors? We analyzed the plasma lipoproteins of two groups of menopausal women who were randomly selected from a large database of individuals. One group (n = 10) was not taking any hormone replacement therapy (NO HRT), while the second group (n = 8) was taking a daily dose of 0.625 mg conjugated estrogen and 2.5 mg medroxyprogesterone orally (PremPro, Wyeth-Ayerst, Philadelphia, PA) for at least 6 months (HRT). The two groups were not different in age, body weight, percent body fat, body mass index (BMI), waist to hip ratio, blood pressure, or insulin and glucose levels. High-density lipoprotein (HDL)-cholesterol was significantly higher (P < .05) in the HRT group. The total cholesterol (TC) to HDL-cholesterol ratio was significantly lower for HRT versus NO HRT (P < .05). Apolipoprotein (apo) A-1, the apo A-1/B ratio, and lecithin:cholesterol acyltransferase (LCAT) activity were significantly higher in HRT (P < .05). Lipoprotein subclass profiles measured by nuclear magnetic resonance (NMR) spectroscopy showed an increase in larger HDL subpopulations (H3 and H4) in HRT (P < .05), which are considered antiatherogenic. No differences were seen in the cholesterol concentration or size of low-density lipoprotein (LDL) subpopulations in HRT compared with NO HRT. These results indicate that the combined estrogen and progesterone treatment leads to beneficial effects on plasma lipoproteins. The beneficial effects include (1) increases in HDL-cholesterol and predominance of HDL2, (2) no adverse effects on LDL subpopulation distribution, and (3) increases in apo A-1 levels and LCAT activity, which indicate an improvement in reverse cholesterol transport.