EFFECT OF THYROIDECTOMY ON RESISTANCE TO LOW ENVIRONMENTAL TEMPERATURE1

Abstract

The role of the thyroid hormone in the resistance to cold is confirmed by the observation that adult rats thyro-parathyroidectomized 2 wks. previously die within a wk. at 0 to 2[degree]C while normal, parathyroidectomized, and thy-roxine-treated thyroidectomized rats survive for several wks. at the same temps. However, the death of thyroidectomized animals in the cold occurs only after an initial period of one to several days during which the general appearance and food consumption of the animals are comparable to those of normal controls. Hence, in contrast with the adrenals, the thyroid gland plays a small role if any in the first reactions following exposure to cold (such as the increase in metabolism, in food consumption and in adrenal wt.). The resistance of thyroidectomized rats on exposure to cold is affected by: the time interval between operation and exposure to cold, as the sooner the animals are placed at 0 to 2[degree]C after operation the longer they survive; the body wt., as larger animals are more resistant, and the environmental temp. of the surroundings before exposure to cold, as a previous exposure at 33 to 34[degree]C shortens, and a previous adaptation to cold lengthens the survival of thyroidectomized rats at 0 to 2[degree]C (fig. 2 and 3).