Thyroid Hormone and Temperature Stress

One of the most important and essential environmental factors is the temperature that imposes the survival and distribution of different life forms on earth. Most plants and animals live within a relatively narrow range of temperature extending from about 10-150C. Temperature is considered to be the one of the most important rate limiting factors for almost all enzymes of physiological and biochemical reactions that control metabolic rate. Based on the temperature, the entire biomass is divided into two distinct groups: homeotherms, and poikilotherms specifying the relation of body temperature with that of the environment. Homeotherms, with a complete homeostatic mechanism are able to maintain their body temperature at an optimum physiological range despite fluctuations in environmental temperatures, thereby exhibiting thermal independence with respect to the environment. On the contrary, poikilotherms without a complete homeostatic mechanism are largely affected by fluctuations in environmental temperatures. Each species lives in a much narrower zone of tolerance where its life processes are not damaged by temperature fluctuations.