Research Article| Volume 55, ISSUE 2, P187-194, September 20, 2006

Low dose estrogens inhibit coronary artery atherosclerosis in postmenopausal monkeys



      To determine if low dose conjugated equine estrogens (CEE) result in a reduction of coronary artery atherosclerosis progression, and to relate these findings to previous studies using the traditional dose.


      Adult female monkeys (Macaca fascicularis) were fed an atherogenic diet for 10 months, to induce fatty streaks and small plaques comparable to those present in early postmenopausal women, and then ovariectomized and treated orally with: CEE (0.30 mg/day women's equivalent dose, n = 28) or placebo (n = 25) daily for 24 months. Body weight and estradiol were measured at 3, 6, 12 and 18 months and plasma lipids were measured at baseline and every 6 months.


      Despite the lack of effect on plasma lipid profiles, monkeys treated with low dose CEE had marked reductions in coronary artery atherosclerosis plaque extent (intimal area) in all three main coronary arteries: left anterior descending artery (52% less, 0.044 mm2 versus 0.091 mm2, p = 0.04); left circumflex artery (62% less, 0.045 mm2 versus 0.119 mm2, p = 0.006) and right circumflex artery (42% less, 0.018 mm2 versus 0.031 mm2, p = 0.20). The overall mean coronary atherosclerosis extent was 52% lower in CEE treated animals (0.042 mm2 versus 0.088 mm2, p = 0.02).


      Low dose CEE (0.30 mg/woman/day equivalent) was effective in reducing coronary atherosclerosis and the magnitude of the protection was comparable to previously reported studies using doses equivalent to 0.625 mg/woman/day. This study provides an experimental basis for the assumption that low dose CEE may be as effective as the traditional dose in inhibiting coronary atherosclerosis progression in early postmenopausal subjects.


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