hypoparathyroidism
Acquired Hypoparathyroidism
Causes:
Acquired chronic hypoparathyroidism is usually secondary to surgical removal of parathyroid. Some of the remaining may undergo vascular compromise secondary to fibrotic changes in the neck.
Post thyroidectomy
Post subtotal parathyroidectomy for hyperparathyroidism.
Radiation-induced damage
Glandular damage with hemochromatosis or hemosiderosis after repeated blood transfusions
Transient hypoparathyroidism is frequent following surgery for hyperparathyroidism. Period of recovery to euparathyroid state is variable.
Treatment:
Replacement with vitamin D or 1,25(OH)2D3 a.k.a. calcitriol combined with high oral calcium intake.
Some patients vacillate between hypocalcemia and hypercalcemia.
Vitamin D in doses of 40,000 - 120,000 units/day (1 - 3 mg/d) combined with >1 g elemental calcium is satisfactory. Calcitriol 0.5 - 1 mcg daily can be used if they are difficult to control
There is lowered urinary calcium reabsorption typical of hypoparathyroidism. Therefore, care must be taken to avoid excessive urinary calcium excretion after vitamin D and calcium replacement therapy, otherwise kidney stones develop.
Thiazide diuretics lower urinary calcium by as much as 100 mg/d in hypoparathyroid patients on vitamin D, provided they adhere to low sodium diet. Use of THZ diuretics is recommended in such patients.