In patients with thyroid carcinoma who after thyroid elimination took thyroxine and triiodothyronine both hormones were discontinued and after 7 days a complex of peripheral and laboratory parameters was evaluated. Discontinuation of thyroid hormones led to a drop of their serum level and concurrent rise of the TSH level and serum cholesterol. The duration of the pre-ejection period of the systole, the Q-Kd interval and Achilles tendon reflex was protracted. The value of the index of the preejection time increased and that of the index of the expulsion time declined. The heart rate and systolic pressure declined and the body eight increased. Seven-day discontinuation of thyroid hormones did not affect the plasma level of noradrenaline, adrenaline and cyclic adenosine monophosphate. The diastolic pressure and index of electromechanical systole did not change.