VPT 311: General and Systemic Veterinary Pharmacology (2+1)

THYROID HORMONE

• The thyroid gland secretes three main hormones: thyroxine, triiodothyronine and calcitonin.
• Thyroxine and triiodothyronine produced in the thyroid follicles are critically important for the normal growth and development and for the energy metabolism.
• Calcitonin produced in the interfollicular cells is involved in the control of plasma calcium.
• The steps in thyroid hormone synthesis, storage and secretion include:
  • uptake of iodine by the follicle cells
  • oxidation of iodine and iodination of tyrosine residues of thyroglobulin
  • secretion of thyroid hormone
• Thyroid hormone is essential for the normal growth and development.
• Deficiency results in cretinism.
• They have a marked effect on the lipid, carbohydrate and protein metabolism.
• Both T₃ and T₄ are used to treat thyroid hormone deficiency
• L thyroxine sodium is used for oral administration.
• Its absorption is influenced by the presence of food in the stomach, suralfate, iron and calcium.
• Enzyme inducers like phenytoin, rifampin, carbamazepine increase the metabolism