THYROIDAL INFLUENCE ON ALTITUDE TOLERANCE

Ths investigation aimed at obtaining support for the concept that lesser amounts of cortisol are effective in prolonging the survival time of thyroidectomized rats exposed to altitude because of a decreased catabolism of the steroid in hypothyroid animals. The data indicate that hyperthyroid animals are more susceptible to altitude exposure than are normal animals, and a greater amount of cortisol is required to protect altitude-exposed adrenalectomized animals that have also been thyroidectomized. Increased thyroid function in altitude-exposed animals is indicated by measurements on the following parameters which were increased: thyroidal uptake of I131, release of thyroidal I131, erythrocyte uptake of I131-labeled triiodothyronine. (Author)