[Congestive heart failure caused by the thyroid stimulating hormone(TSH) secreting pituitary adenoma: report of two cases].

A 42-year-old man and a 31-year-old man with congestive heart failure caused by the thyroid stimulating hormone(TSH) secreting pituitary adenoma were reported. Heart failure was improved after transsphenoidal resection of the pituitary adenoma in each patient. The syndrome of inappropriate secretion of TSH causes hyperthyroidism. Thyroid hormone acts directly on cardiac muscle to increase the stroke volume. Hyperthyroidism itself reduces the peripheral vascular resistance and an elevated basal metabolism which is the basic physiologic change in hyperthyroidism dilates small vessels and reduces vascular resistance. The reduced vascular resistance contributes to increase stroke volume. Thyroid hormone also acts directly on the cardiac pacemakers to be apt to cause tachycardiac atrial fibrillation. These mechanical changes in hyperthyroidism increase not only the cardiac output but also the venous return. The increased blood volume and the shortened ventricular filling time due to tachycardia result in congestive heart failure. TSH secreting pituitary adenoma is a rare tumor, however heart failure is common disease. TSH secreting pituitary adenoma should be taken into consideration in patients with heart failure. The presented cases were very enlightening to understand the relation between brain tumor and heart disease.