Excess triiodothyronine as a risk factor of coronary events

Background: Abnormalities in cardiac function, eg, arrhythmias and congesti ve heart failure, often accompany thyrotoxicosis. A relationship between th yroid hormone excess and the cardiac complications of angina pectoris and m yocardial infarction (MI) remains largely speculative. Methods: The results of thyroid function studies on blood samples drawn fro m a total of 1049 patients (aged 40 years or older) immediately on emergenc y medical admission were related to frequencies of angina pectoris and myoc ardial infarction as determined according to current diagnostic algorithms. After 3 years, those patients who had initially presented with angina pect oris or acute MI were observed for subsequent coronary events; of these (n= 185), 98% of the subjects (n=181) could be reevaluated. Results: On hospital admission, the relative rate of angina pectoris and MI was markedly high (odds ratio, 2.6; 95% confidence interval, 1.3-5.2; P=.0 07) in patients with elevated serum free and total triiodothyronine (T-3) l evels. An initially elevated free Tg level was a risk factor for subsequent coronary events during the 3-year follow-up (adjusted odds ratio, 4.8; 95% confidence interval, 1.3-17.4; P=.02). Conclusions: An elevation of serum free T-3 levels at hospital admission is associated with a 2.6-fold greater likelihood of the presence of a coronar y event. Moreover, an initially elevated T-3 level is associated with a 3-f old higher risk of developing a subsequent coronary event during the next 3 years. Excess Tg Seemed to be a factor associated with the development and progression of acute myocardial ischemia.