Metabolic and temperature responses to physical exercise in thyroidectomized dogs

Abstract

The purpose of the present work was to further elucidate the role of thyroid hormones in the control of body temperature and metabolism during physical exercise. Changes in rectal temperature (Tre), some parameters of exercise-metabolism and in the plasma noradrenaline (NA) levels were examined in eight dogs performing submaximal treadmill exercise to exhaustion before and after thyroidectomy (THY). The metabolic 'responses to adrenaline (A) infusion were also compared in intact and THY dogs. During the exercise performed by THY dogs Tre increases were markedly attenuated, plasma FFA level increases were reduced and the pattern of plasma NA changes was modified in comparison with control runs. The reduced exercise-induced FFA mobilization in THY dogs might be attributed to a lower activation of the adrenergic system in the later stage of exercise and to the weaker lipolytic action of catecholamines. The attenuated Tre increases during exercise performed by THY dogs and the exercise-hyperthermia described previously in dogs treated with thyroid ormones suggest that an optimum level of thyroid hormones is necessary to induce typical changes in body temperature during physical exercise.

Effects of racing and training on serum thyroid hormone concentrations in racing Greyhounds

“…Furthermore, the measured increase in body temperature and severity of lactic acidosis after exercise was not blunted, as would be expected if the dogs had been hypothyroid. 43 If TSH concentrations, metabolic responses to exercise, and clinical signs are considered together, these Greyhounds should be classified as euthyroid despite low total and free T 4 concentrations.…”