Snapshot A 35-year-old man presents to his surgeon for 1-week follow-up of his thyroidectomy for thyroid neoplasm. He reports that his post-operative recovery is going well and denies any symptoms except some muscle cramping. His past medical history includes hypertension. On physical exam, there are spasms of his triceps with blood pressure cuff inflation and facial muscle contractions with tapping of the cheeks. Introduction Clinical definition acquired or genetic condition of ↓ parathyroid hormone (PTH) characterized by ↓ calcium normal or ↑ phosphate Etiology Surgical excision or injury (most common) Autoimmune destruction Pathogenesis actions of PTH ↑ bone resorption of calcium and phosphate ↑ kidney reabsorption of calcium ↓ kidney reabsorption of phosphate ↑ kidney calcitriol production causes ↑ serum calcium and ↓ serum phosphate deficiency of PTH causes ↓ serum calcium ↑ serum phosphate Presentation Symptoms symptoms of hypocalcemia tetany Chvostek sign contraction of facial muscles with percussion of the facial nerve Contraction of Cheek = Chvostek Trousseau sign carpal spasm with occlusion of brachial artery with a blood pressure Tricep spasm = Trousseau sign Studies Diagnostic testing studies ↓ calcium remember to correct with albumin ↑ phosphate ↓ or undetectable PTH level ECG prolonged QT interval Differential Pseudohypoparathyroidism distinguishing factors same symptoms of hypocalcemia and hyperphosphatemia ↑ serum PTH DIAGNOSIS Diagnostic criteria ↓ serum calcium on 2+ occasions separated by 2+ weeks ↓ or undetectable PTH level Treatment First-line intravenous calcium gluconate indication symptomatic hypocalcemia asymptomatic hypocalcemia < 7.6 mg/dL oral calcium carbonate indication asymptomatic hypocalcemia >7.6 mg/dL oral calcitriol indication asymptomatic hypocalcemia >7.6 mg/dL