Quantitative and qualitative changes in lipids, lipoproteins, apolipoprotein A-I, and sex hormone-binding globulin due to two doses of conjugated equine estrogen with and without a progestin.

OBJECTIVE

To determine whether the quantitative and qualitative effects on lipoproteins differ between two doses of conjugated equine estrogen before and after progestin administration.

METHODS

We randomized 103 postmenopausal women into a control group and into two groups receiving either 0.625 mg or 1.25 mg of conjugated equine estrogen for 4 months and then the same estrogen dose plus cyclic medroxyprogesterone acetate for 8 months.

RESULTS

Both estrogen doses similarly lowered (P < .01) low-density lipoprotein (LDL) cholesterol and raised (P < .01) high-density lipoprotein (HDL) cholesterol, apolipoprotein A-I, triglyceride levels of all lipoproteins, and sex hormone-binding globulin capacity. Cyclic addition of the progestin reduced HDL cholesterol (P < .01) and apolipoprotein A-I (P < .05), but not LDL cholesterol in either estrogen group. A greater lowering of HDL cholesterol (P < .05) in response to the progestin was seen with the 0.625-mg dose of estrogen. Estrogen-induced triglyceride enrichment of HDL and LDL was not reversed by the progestin.

CONCLUSION

The only significant quantitative difference in lipoprotein levels between the doses of conjugated equine estrogen before or after administration of medroxyprogesterone acetate was a greater decline in HDL cholesterol levels with the lower dose after 4 months of the progestin. This difference was not sustained over time. There were no differences between doses in the estrogen-induced triglyceride enrichment of lipoproteins, and these qualitative changes were not affected by the progestin.