Parathyroid Gland

Parathyroid Gland

Tiny glands on posterior aspect of lobes of thyroid gland – usually two pairs of glands, but can vary – 3-8mm long and 2-5mm wide. Two types of cells – oxyphil cells (function unclear) and chief cells (secrete PTH).

Parathyroid hormone (PTH)/Parathormone:
• single chain polypeptide consisted of 84 amino acids
• controls calcium balance of blood. Release is stimulated by falling serum calcium levels and inhibited by high serum levels of calcium
• secretion responds to serum ionised calcium concentration

Effects of hormone:
increases osteoclast activity  release of ionic calcium
increases resorption of calcium by renal tubules
increases absorption of calcium by intestinal mucosal cells

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