Thyroid gland: Hormones and functions
The gland is composed of two types of cells; follicular cell (secrete thyroid hormone) and para-follicular cell (secrete and store calcitonin hormone)
Location: in neck region on either side of trachea
Size: Each lobe is 4-6 cm long, and 1.5 cm thick
Hormones of Thyroid gland
Thyroxine (Tri-Iodothyronine and tetra-Iodothyronine)
- Increase basal metabolism rate by increasing O2 comsumption in most tissues except lungs, brain, testis and retina
- Essential for growth of skeletal
- Increase carbohydrate metabolism, promote gluconeogenesis
- Effect on lipid metabolism
- Stimulate NA-K ATPase.
- Influence water and electrolyte balance.
- It is regulated by TSH
- At first T4 is synthesized which is converted to T3. T3 is five times more potent than T4.
- Deficiency of thyroxine: Goiter, Hypothyroidism
- Excess of thyroxine: thyrotoxicosis, hyperthyroidism.
- It lowers calcium level in blood ( antagonistic to parathyroid hormone)