Studies on the mechanism by which epinephrine stimulates glucose oxidation in the thyroid.

In previous communications we reported stimulation in uitro of glucose oxidation in the thyroid by thyroid-stimulating hormone and acetylcholine (1, 2). These observations have been extended to epinephrine and related compounds. Epinephrine is known to affect the physiology of the thyroid gland. Both epinephrine and norepinephrine modify thyroid blood flow and increase the release of thyroid hormone (3-5). In some of these studies, the effect of epinephrine on thyroid hormone release was felt to be independent of its action on blood flow (4, 5). In addition, administration of epinephrine in oil to dogs causes thyroid hyperplasia, although this effect may be mediated through the pituitary (6). A role of epinephrine in glucose metabolism is well established. It activates hepatic muscle and adrenal phosphorylase (7, 8) and in studies with rat epididymal fat pad it has been shown to stimulate glucose uptake and oxidation (9). However, in muscle epinephrine appears to inhibit glucose uptake (10). This report shows that epinephrine increases thyroidal glucose metabolism and offers evidence that this is due to increased oxidation of reduced forms of triand diphosphopyridine nucleotides.