PARATHYROID DISORDERS -

(i) 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 larynx, face, hands and feet are produced. This disorder is called parathyroid tetany or hypocalcaemic tetany.

(ii) Hyperparathyroidism (excess of PTH). Excess of PTH draws more calcium from the bones.

• It causes demineralisation, resulting in softing and bending of the bones. Some of the bone substance is replaced by cavities that are filled with fibrous tissues.
• Osteoporosis is common in women who have reached menopause (cessation of menstruation). An excess of parathormone also causes calcium to be deposited in the kidneys. Analysis of the content of kidney stones sometimes suggests the presence of a parathyroid tumour.