Hyperparathyroid Crisis

Parathyroid crisis (hypercalcemic crisis from primary hyperparathyroidism) is a rare but life-threatening emergency with corrected calcium typically > 14 mg/dL caused by acute, massive PTH hypersecretion from a parathyroid adenoma (or less commonly carcinoma). The mechanisms of severe hypercalcemia mirror those of PHPT but are amplified: markedly elevated PTH drives aggressive osteoclast-mediated bone resorption, maximizes renal calcium reabsorption, and increases calcitriol production enhancing intestinal calcium absorption. At calcium levels > 14 mg/dL, patients develop severe neuromuscular dysfunction (weakness, confusion, coma), cardiovascular compromise (shortened QT, bradycardia, cardiac arrest), renal failure (nephrocalcinosis, calcium-induced vasoconstriction of afferent arterioles), and GI dysfunction (pancreatitis from calcium-activated trypsinogen, ileus, severe constipation). The precipitant is often dehydration or immobilization in a patient with previously undiagnosed PHPT, creating a vicious cycle: hypercalcemia → polyuria (nephrogenic DI effect) → dehydration → reduced renal calcium excretion → worsening hypercalcemia.