Which of the following is seen in cold temperature: March 2011

Ans. A: Increased Thyroxine release Endocrine mechanisms which causes heat production (thermogenesis) are epinephrine, norepinephrine and thyroxine Thermoregulatory response activated by exposure to cold ( posterior hypothalamus) Increased heat production - Shivering Hunger - Increased voluntary activity - Increased TSH secretion - Increased catecholamines Decreased heat loss - Cutaneous vasoconstriction - Curling up - Horripilation T3 and T4 regulation The 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.