HORMONE REPLACEMENT THERAPY PREVENTS CORONARY-ARTERY DISEASE IN OVARIECTOMIZED CHOLESTEROL-FED RABBITS

The prevention of coronary artery disease in women is of considerable importance. We have therefore investigated the influence of oestrogen monotherapy and oestrogen-progestogen replacement therapy on coronary artery disease using a simple morphometric method. We studied sixty-three cholesterolfed rabbits for nineteen weeks. They were randomized to either ovariectomy (51 rabbits) or a sham operation (12 rabbits). The ovariectomized rabbits were randomized to receive either 17-beta-estradiol, 17-beta-estradiol plus norethisterone acetate, 17-beta-estradiol plus levonorgestrel, or placebo. The rabbits with the sham operation received placebo. The hormone therapies reduced the development of coronary artery disease compared to placebo (p < 0.0001). Furthermore, the coronary artery disease was attended by atherosclerosis in the more distal parts of the coronary arteries (p < 0.0001), the thoracic aorta (p < 0.0001) and the abdominal aorta (p < 0.0001), and by a reduced relative heart weight (p < 0.05). We conclude that coronary atherosclerosis can be determined quantitatively by morphometry in rabbit arteries. Estradiol monotherapy reduces coronary atherosclerosis in cholesterol-fed rabbits and the addition of norethisterone acetate or levonorgestrel does not attenuate this beneficial effect.