To compare the effects of estrogen and estrogen plus progestin on levels of C-reactive protein (CRP) and interleukin-6 (IL-6), and to examine the relationship between these changes and progression of angiographically defined coronary disease.

Baseline and follow-up (year 1 and year 3) plasma levels of IL-6 and CRP were measured in a subset of 232 patients from the Estrogen Replacement in Atherosclerosis (ERA) trial.

Serial angiograms were also available at baseline and closeout. Estrogen alone increased CRP by 40% (P = .01) at 1 year and 38% P = .002) at closeout. Estrogen plus medroxyprogesterone acetate increased CRP by 44.7% P = .001) at 1 year and 54.7% P = .0001) at closeout as compared with baseline levels. There were no significant changes in IL-6 with either treatment. In women in the active treatment arm, change in CRP during the first year was not associated with progression of coronary disease P = .2).

Estrogen and estrogen plus medroxyprogesterone significantly raise CRP levels in women with established coronary disease. In contrast, IL-6 levels are not affected by estrogen or estrogen plus progestin. Estrogen-induced changes in CRP are not associated with progression of atherosclerosis.