<prompt> Which of the following is seen in cold temperature:March 2011Increased Thyroxine releaseDecreased Thyroxine releaseUnaltered Thyroxine releaseNone of the above  <response>: Ans. A: Increased Thyroxine releaseEndocrine mechanisms which causes heat production thermogenesis are epinephrine, norepinephrine and thyroxine Thermoregulatory response activated by exposure to cold posterior hypothalamusIncreased heat production- ShiveringHunger- Increased voluntary activity- Increased TSH secretion- Increased catecholaminesDecreased heat loss- Cutaneous vasoconstriction- Curling up- HorripilationT3 and T4 regulationThe production of thyroxine and triiodothyronine is regulated by thyroid-stimulating hormone TSH, released by the anterior pituitary.The thyroid and thyrotropes form a negative feedback loop: TSH production is suppressed when the T4 levels are high.The TSH production itself is modulated by thyrotropin-releasing hormone TRH, which is produced by the hypothalamus and secreted at an increased rate in situations such as cold exposure to stimulate thermogenesis.TSH production is blunted by somatostatin SRIH, rising levels of glucocoicoids and sex hormones estrogen and testosterone, and excessively high blood iodide concentration. 