Regulation Of Thyroid Hormone Secretion Research Articles

Sympathetic regulation of thyroid hormone secretion

Publisher Summary This chapter discusses the sympathetic regulation of thyroid hormone secretion. The finding of sympathetic nerve terminals very close to thyroid follicle cells signifies that there is a morphologic basis for a direct, nonvascular, influence of sympathetic stimuli on thyroid hormone secretion. There is also evidence that such an influence is exerted. In mice, whose TSH secretion has been eliminated, sympathetic stimulation or administration of norepinephrine (NE) or other arylmethylamines induces secretion of thyroid hormone, as reflected by signs of endocytosis of thyroglobulin followed by release of thyroidal radioiodine into the blood. The secretory response to sympathetic stimulation is restricted to the thyroid regions supplied by the stimulated nerve, indicating that the effect results from an action of NE released within the gland. The thyroid activation is probably induced by the amine as such the effect is augmented after pretreatment with a monoamine oxidase inhibitor, and the catecholamine precursor DOPA exerts a thyroid-stimulating effect only after its decarboxylation to dopamine. It is found that although catecholamines certainly affect thyroid blood flow, their stimulatory effect on the thyroid hormone secretion cannot entirely be explained by their influence on thyroid vessels, and it is rather the result of a direct action on the follicle cells.

Studies on the regulation of thyroid hormone secretion, with special emphasis on the effect of acute reduction of thyroid hormones in the blood

Studies on the regulation of thyroid hormone secretion, with special emphasis on the effect of acute reduction of thyroid hormones in the blood

Effect of stimulation of the vagus nerve on the thyroidal release of 131I-labeled hormones.

Effects of electrical stimulation of the vagus nerve on the content of PB131I in thyroid venous blood were studied in dogs. After stimulating the nodose ganglion on either side, the concentration of the PB131I in thyroid venous blood and the PB131I output from the thyroid increased in all 14 cases. Unilateral nodose ganglion stimulation facilitated the secretion of PB131I bilaterally, the increase on the stimulated side being always more pronounced than the other. The PB13lI response to nervous stimulation was characterized by a prompt increase within 15 min. Effects of stimulation of the vago-accessory myelencephalic rootlets of the vagus nerve were also investigated to ascertain the pathway through which the nervous stimulus was transmitted to the thyroid for secretion of its hormone.The results indicate that regulation of thyroid hormone secretion by the vagus nerve depends mainly on fibers passing through the main stem of the vagus among its original rootlets. A significant increase in thyroid blood f...

Studies on the neurohumoral regulation of thyroid hormone secretion. Effect of electrical stimulation of the hypothalamus on the secretion of I-131-labeled thyroid hormone

Using a stereotaxic apparatus, electrode was implanted into the hypothalamus of the dogs before experiments and the influence of the electrical stimulation on various areas of hypothalamus on the content of PBI131 in thyroid venous blood was studied. The dogs received intramuscular injection of about 100-500 microcuries of I131 5 or 6 days before experiments. Thyroid venous blood was obtained by inserting the polyethylene catheter into the thyroid vein.When the anterior hypothalamus and the median eminence was stimulated, definite increase of PBI131 was observed, while in hypophysectomized dogs, the stimulation of these areas did not promote the thyroid hormone secretion.This would indicate that the increase of thyroid hormone secretion by the stimulation of the anterior hypothalamic area and median eminence is due to the increased secretion of thyrotropin from the pituitary gland.