THE EFFECT OF THYROID-HORMONE THERAPY ON ANGIOGRAPHIC CORONARY-ARTERYDISEASE PROGRESSION

OBJECTIVE: To study the effect of adequacy of thyroid hormone replacem ent therapy on coronary atherosclerosis. DESIGN: Retrospective cohort study of elderly hypothyroid patients with coexisting coronary artery disease. The association between the adequacy of thyroid replacement a nd the progression of angiographic coronary artery disease was investi gated. Fisher's exact test was used for statistical analysis. SETTING: Coronary angiographies were performed at the Cardiac Catheterization Laboratory of the Victoria General Hospital, Halifax, Nova Scotia, the only tertiary referral centre for Nova Scotia and Prince Edward Islan d. Information about the past and current thyroid status of the subjec ts was collected from their family physicians. PATIENTS: Of 4103 patie nts admitted for coronary angiography during 1992 and 1993, 25 were on thyroid replacement therapy to treat hypothyroidism. Ten patients who underwent more than one coronary arteriography were selected (seven f emales and three males, mean age 65+/-10 years). RESULTS: Of five pati ents inadequately treated for hypothyroidism, all demonstrated angiogr aphic evidence of coronary atherosclerosis progression. However, five of seven who were treated adequately did not show atherosclerosis prog ression (P=0.02, OR=0.72, 95% CI 1.36 to infinity). Decreasing or main taining the dose of L-thyroxine at 100 mu g or less resulted in corona ry atherosclerosis progression in six of six patients, whereas five of six patients taking fixed or increasing doses of L-thyroxine 150 mu g or higher were spared from disease progression (P=0.015, OR=0.41, 95% CI 2.4 to infinity). CONCLUSIONS: Angiographic coronary artery diseas e progression may be prevented by adequate thyroid replacement in hypo thyroidism. With the help of modem, sensitive thyroid stimulating horm one assays higher doses of L-thyroxine may be safer and more effective in the atherosclerosis management of this patient population. Thyroid hormones can protect against atherosclerosis, presumably due to their metabolic affects on plaque progression.