Peripheral Circulatory and Metabolic Concequences of Thyrotoxicosis: IV. Blood Flow in Resting and Working Calf Muscle in Patients with Thyrotoxicosis before and after Treatment

Abstract

Frey, H. M. M. Peripheral Circulatory and Metabolic Consequences of Thyrotoxicosis. IV. Blood Flow in Resting and Working Calf Muscle in Patients with Thyrotoxicosis before and after Treatment. Scand. J. din. Lab. Invest. 19, 143–148, 1967. Blood flow in the gastrocnemius muscle was studied by the ¹³³xenon clearance technique in patients with thyrotoxicosis before and after treatment. Before treatment, muscle blood flow at rest was 57 per cent higher than after a euthyroid state had been re-established. In the thyrotoxic state, the maximal force of plantar flexion in the ankle was reduced to 72 per cent of the value after treatment. This reduction in muscle power is relatively greater than the reduction of calf volume that usually takes place in thyrotoxicosis.

For a given work load, blood flow was considerably greater in thyrotoxic than in normal muscle. This difference in muscle blood flow between the thyrotoxic and euthyroid subject increased with heavier work load.

Three factors probably determine the vascular response in resting and working skeletal muscle in thyrotoxicosis: high oxygen consumption, low muscular contraction force, and low mechanical efficiency.