What causes hypoparathyroidism?Causes of hypoparathyroidism include accidental removal of a parathyroid gland when the thyroid is removed, or when part of the parathyroid tissue is removed during surgery. Other causes include absent parathyroid glands from birth or the
sudden stop of functioning due to unknown reasons (idiopathic). It is often associated with cardiac defects, such as DiGeorge.
The accidental removal of the parathyroid glands during neck surgery is the most frequent cause of hypoparathyroidism. Complications of surgery on the parathyroid glands is another common cause of this disorder. There is the possibility of autoimmune genetic disorders causing hypoparathyroidism such as Hashimoto's thyroiditis, pernicious anemia, and Addison's disease. The destruction of the gland by radiation is a rare cause of hypoparathyroidism. Occasionally, the parathyroids are absent at birth causing low calcium levels and possible convulsions in the newborn. Symptoms in the advanced and continuous stages of hypoparathyroidism include splitting of the nails, inadequate tooth development and mental retardation in children, and seizures.
Abnormal low levels of calcium result in irritability of nerves, causing numbness and tingling of the hands and feet, with painful-cramp like muscle spasms known as tetany. Laryngeal spasms may also occur causing respiratory obstruction.
Hypoparathyroidism can result from congenital disorders, iatrogenic causes (eg, drugs, removal of the parathyroid glands during thyroid or parathyroid surgery, radiation), infiltration of the parathyroid glands (eg, metastatic carcinoma, Wilson disease, sarcoid), suppression of parathyroid function, or idiopathic mechanisms. Hypocalcemia is the most important consequence of hypoparathyroidism. Approximately half of serum calcium is ionized; the other half is bound to plasma proteins and other substances. The ionized calcium is physiologically active, and a significant reduction in ionized calcium level causes the signs and symptoms of hypocalcemia.