Sympathetic Activation of Thyroid Hormone Secretion in Mice

Abstract

The influence of the sympathetic nervous system on the secretion of thyroid hormone was studied in mice, in which TSH secretion had been blocked by exogenous thyroxine. Stimulation of the right cervical sympathetic trunk for 5–60 sec induced a formation of intracellular colloid droplets and an increase in blood 131I. The droplet formation was restricted to the thyroid regions supplied by this nerve, as judged from the distribution of catecholamine-containing nerve terminals in thyroids of animals with a left-side sympathectomy. Iv L-norepinephrine (NE) induced a symmetrical formation of colloid droplets and an increase in blood 131I. Phentolamine inhibited all these effects. Neither uni- nor bilateral occlusion of the carotid blood flow for 60 sec was followed by any colloid droplet formation or blood 131I increase. The results suggest that sympathetic stimulation induces endocytosis of thyroglobulin and release of thyroid hormone, through a direct action on alpha adrenergic receptors in thyroid follicle cells by NE released from intrathyroidal sympathetic nerve terminals. (Endocrinology90: 194, 1972)