Effect of KI upon Basal Metabolism and Respiratory Quotient in Thyroidectomized Guinea Pigs. ∗

Abstract

Loeb, 1 Gray and Rabinovitch, 2 McCordock, 3 and others have found that the administration of potassium iodide causes a marked stimulation of the thyroid gland in guinea pigs, as shown by a great increase in the number of mitotic figures, a slight softening of the colloid and an increase in the height of the acinar epithelial cells. Cordonnier 4 and the author 5 found that the basal metabolism was only very slightly affected after administration of KI in guinea pigs. In the latter experiments, the majority of the determinations as well as the average for all the animals was at the upper limit of the variations obtained in normal animals. Loeb 1 suggested the following possibilities to explain this discrepancy which exists between the marked degree of stimulation of the thyroid gland and the very slight effect upon basal metabolism after administration of KI. (1) Although KI stimulates the thyroid gland at certain periods of its action at the same time it prevents an excess of thyroxin thus produced from leaving the acini, and instead it is at least partly retained in the gland. (2) The stimulation of the acini does not necessarily lead to an excess production of thyroxin. (3) Peripheral effects counteract the stimulating effect of the thyroid hormone upon the basal metabolism.

The following experiments were carried out to investigate the peripheral action of KI. Twelve male guinea pigs, weighing between 400 and 450 gm., were as completely thyroidectomized as was possible, and 3 weeks after the operation, 8 were given 0.05 gm. of KI by mouth daily and biweekly metabolism tests were made. The remaining 4 guinea pigs served as controls. These were similarly thyroidectomized but were not given KI.