Objective: to evaluate the features of structural and functional remodeling of the left heart during hospitalization in patients with ST-segment elevation myocardial infarction (STEMI) and concomitant newly diagnosed hypothyroidism. Materials and methods: the study included 133 patients with STEMI aged 40 to 88 years admitted to the Rostov Regional Clinical Hospital. All patients were divided into 3 groups depending on the newly diagnosed hypothyroidism: Group 1 (control) included patients with STEMI without hypothyroidism syndrome (n=57), Group 2A — patients with STEMI and subclinical hypothyroidism (n=42) and Group 2B — patients with STEMI and manifest hypothyroidism (n=34). Patient data, clinical symptoms, information on complications in the acute period of myocardial infarction, echocardiographic examination results were entered into a specially developed questionnaire. Results: patients with STEMI of all groups were found to have increased values of indexed LV ESV and LVM, decreased values of indicators characterizing myocardial contractility, as well as the presence of stage I LVDD. Patients with subclinical hypothyroidism were found to have statistically significantly higher values of the indexed LA volume than patients without hypothyroidism. The peculiarities of structural and functional remodeling of the heart in the presence of overt hypothyroidism include significantly higher linear and volumetric parameters of the LA (ILP and IOLP), a greater decrease in the contractility of the LV myocardium (lower values of SV, SI and IOC), a more pronounced impairment of diastolic properties of the myocardium (lower DT value) compared to the control group. Conclusion: in patients with STEMI and concomitant overt hypothyroidism, more pronounced remodeling of the left heart in conditions of acute myocardial injury (larger size and volume of the LA, more pronounced impairment of systolic and diastolic function of the LV).