Abstract: Objective To investigate the clinical characteristics of patients with acute myocardial infarction (AMI) combined with hypothyroidism, and to explore the correlation between thyroid function and AMI. Methods The clinical data of 511 patients with AMI combined with hypothyroidism were retrospectively analyzed. According to thyroid function,patients were divided into hypothyroidism group (n=40), subclinical hypothyroidism group (n=67), low T3 syndrome group (n=52) and normal thyroid function group (the normal group, n=352). The general situation, biochemical indexes, coronary lesions and echocardiographic indexes were compared between the four groups. Multivariate Logistic regression analysis of the influencing factors of hypothyroidism were analysed in patients with myocardial infarction. Results Compared with the control group, patients showed higher age, increased proportion of hypertension, Gensini score and lower level of highdensity lipoprotein cholesterol (HDL-C) in the hypothyroidism group and the low T3 group (P < 0.05). Compared with the control group, the level of low-density lipoprotein cholesterol (LDL-C) was significantly elevated, left atrial diameter (LAD) increased, and left ventricular ejection fraction (LVEF) decreased in hypothyroidism group (P < 0.05). Logistic regression analysis showed that advanced age (OR=1.038), hypertension (OR=1.992) and high level of LDL-C (OR=1.649) were the risk factors for the occurrence of hypothyroidism in patients with myocardial infarction, and the high level of HDL-C (OR=0.172),free triiodothyronine (FT3, OR=0.550) and LVEF (OR=0.953) may be protective factors. Conclusion Patients with AMI and hypothyroidism show dyslipidemia, increased coronary stenosis, cardiac insufficiency, and the lower level of FT3. In the early clinical stage, the development of myocardial infarction can be predicted from the thyroid function in patients,especially the level of FT3.

Key words: myocardial infarction, hypothyroidism, subclinical hypothyroidism, low T3 syndrome, coronary artery disease, heart failure