This study was designed to elucidate the relationship between the age of the patients presenting with autoimmune thyroiditis and subclinical hypothyroidism and the changes in their cardiovascular system. The following characteristics were estimated: the structure of the left ventricle, its overall and segmental diastolic function (by tissue Doppler echocadiography), and rigidity of the arterial walls (from the Young's modulus of elasticity, by ultrasonography). The patients were 95 women at the age of 20 to 50 years of whom 47 presented with autoimmune thyroiditis and subclinical hypothyroidism and 48 with euthyroidism (controls). They were divided into 3 age groups to be compared in the «subclinical hypothyroidism vs control» mode. Group 1 comprised 12 ad 13 women respectively aged 20-30 years, Group 2 contained 12 and 10 patients (31-40 years), group 3 included 23 and 25 patients (41-50 years). Young women with subclinical hypothyroidism were characterized by high values of Young's modulus and a large number of dysfunctional left ventricular segments (p<0.05). In the patients of the intermediate age, subclinical hypothyroidism also tended to have high values of Young's modulus in the absence of diastolic dysfunction. The oldest patients showed no signs of left ventricular dysfunction or arterial wall rigidity compared with controls (p<0.05). The results of the study indicate that the patient's age influences manifestations of changes in the cardiovascular system characteristic of subclinical hypothyroidism. In young women, this condition is associated with more pronounced disturbances of both overall and segmental diastolic functions and arterial elasticity than in control subjects. The women of older age groups show less apparent cardiovascular and metabolic abnormalities while the role of subclinical hypothyroidism as a cardiovascular risk factor is relatively insignificant.