Parathyroid Gland & Its Disorders MCQ - Practice Questions with Answers

In humans, four parathyroid glands are present on the backside of the thyroid gland, one pair each in the two lobes of the thyroid gland.
The cells of the parathyroid glands are arranged in a compact mass and are of two types: small chief cells or principal cells and large oxyphil cells (or eosinophil cells).
The chief cells of the parathyroid secrete a hormone called parathy­roid hormone (PTH) or parathormone or also called Collip’s hormone.
This hormone regulates the calcium and phosphate balance between the blood and other tissues. 
It mobilises the release of calcium into the blood from the bones. 
PTH increases calcium absorption from the intestines. 
It increases calcium resorption from the nephrons (and inhibits phosphate reabsorption) of the kidneys.
Parathyroids are under the feeding back control of blood calcium level. 
A fall in blood calcium stimulates them to secrete parathormone, a rise in blood calcium inhibits parathor­mone secretion from them. 
Thus PTH has an effect that opposes the effect of calcitonin.

Parathyroid Disorders:

• Hypoparathyroidism (deficiency of PTH):
  • It causes the lowering of blood cal­cium level. 
  • This increases the excitability of nerves and muscles, causing cramps and convulsions. 
  • Sustained con­tractions of the muscles of the larynx, face, hands and feet are produced. 
  • This disorder is called parathyroid tetany or hypocalcemic tetany.
• Hyperparathyroidism (excess of PTH):
  • Excess of PTH draws more calcium from the bones. 
  • It causes demineralisation, resulting in softening and bending of the bones. 
  • Some of the bone substance is replaced by cavities that are filled with fibrous tissues. 
  • This condition leads to osteoporosis.
  • An excess of parathormone also causes calcium to be deposited in the kidneys.