hypoparathyroidism
Hypoparathyroidism is the condition of too little parathyroid hormone. With the calcium alarm silenced, the body cannot pull calcium up when it falls, so blood calcium drops while phosphate climbs, leaving nerves and muscles dangerously over-excitable.
By far the most common cause is accidental damage to or removal of the parathyroid glands during neck surgery, especially thyroid operations. Less often it stems from autoimmune destruction, genetic syndromes, or low magnesium. Whatever the cause, the result is the same: without PTH the kidney wastes calcium and retains phosphate, and the kidney cannot fully activate vitamin D, so calcium absorption from food also suffers.
Symptoms are those of hypocalcemia: tingling, muscle cramps, and tetany, with seizures or heart-rhythm problems if severe. Unusually among hormone deficiencies, the standard treatment is not simply replacing the missing hormone but giving calcium and active vitamin D, since recombinant PTH is costly and reserved for hard cases. Long-term, the disease and its treatment both need careful monitoring to avoid swinging into high urine calcium and kidney damage.
After a total thyroidectomy removed or starved all four parathyroids, a patient needs lifelong calcium and active vitamin D to keep blood calcium normal.
Surgical loss of all parathyroids can mean lifelong replacement.
It is one of the few hormone deficiencies not routinely treated by replacing the hormone itself; calcium plus active vitamin D usually suffices, with recombinant PTH kept for difficult cases.