Principal effects on the body of thyroid hormones:

  1. Regulation of organic metabolism and energy balance:  All protein, fat and carbohydrate metabolism is influenced by thyroxine. Since the overall effect is to increase catabolism, they increase the basal metabolic rate (BMR). The energy produced raises the body temperature.
  2. Regulation of growth and development: They regulates tissue (especially nervous tissue) growth, particularly in children.
  3. Increase the reactivity of the nervous system.
  4. Mineral metabolism(calcitonin): It regulates the calcium and phosphate levels in the blood.Calcium levels in the blood need to be maintained to ensure normal muscle contractions.