Hypothyroidism develops in case of inadequate hormone production by the thyroid gland or in case of an inadequate response of the thyroid gland to thyrotropin. In thyroid hormone deficiency sometimes a disorder of the cardiovascular system may dominate. The authors described in two case-histories the clinical picture of two girls with severe hypothyroidism where cardiovascular symptoms predominated in the clinical picture. They paid special attention to the diagnosis and causal treatment of the disease. In the conclusion the authors discuss the causes of development of hypothyroidism in childhood and draw attention to the import ance of collaboration of the child endocrinologist and cardiologist in the diagnosis and treatment of this disease.

        Key words: hypothyroidism, pericardial exudate, echocardiography