Some effects of altitude on thyroid function.

Abstract

Experiments have been performed to assess the effects of altitude on thyroid function and thyroxine (T4) metabolism. Sprague—Dawley rats were exposed in a hypobaric chamber to a reduced atmospheric pressure equivalent to an altitude of 18,000 feet, for either 3 or 30 days. Thyroid function was determined by measuring the rate of uptake of iodine (127I) by the gland with a double isotope technique, the concentration of T4 in the gland, and the rate of secretion of 125I from the gland prelabeled with the isotope. Peripheral turnover of T4 was measured in animals equilibrated with 131I—T4 by administration of a daily dose of known specific activity; thyroidal accumulation of 131I was prevented with KC104. The results indicate that the activity of the thyroid gland was greatly decreased in both groups of exposed rats; decreases in the rate of uptake of iodine by the gland, the concentration of T4 in the gland and the rate of secretion of iodine by the gland were observed. The rate of deiodination was greatly ...