Summary Hypoparathyroidism is the decreased production of parathyroid hormone by chief cells of the parathyroid gland most commonly caused by a thyroidectomy that results in decreased plasma calcium levels, increased plasma phosphate levels, and decreased active Vitamin D levels. Diagnosis is made by obtaining serum calcium, phosphate, PTH, and 1,25(OH)2 Vitamin D levels. Treatment is aimed at supplementing vitamin D and calcium levels. There is no current hormone replacement therapy available. Etiology Findings decreased plasma calcium levels increased plasma phosphate levels decreased 1,25(OH)2 Vitamin D levels Etiology iatrogenic thyroidectomy most common cause Pathophysiology decreased PTH levels cause decreased urinary excretion of phosphate at kidneys login to view 1 more bullet decreased conversion of inactive form of vitamin D to active form login to view 1 more bullet Presentation Symptoms hypocalcemia more common in hypoparathyroidism login to view 10 more bullets Imaging Radiographs skull basal ganglia calcification Evaluation Labs decreased PTH calcium 1,25-Vit D urinary calcium increased serum phosphate normal alkaline phosphatase pH alkalosis increases albumin binding to ionized calcium leads to hypocalcemia EKG prolonged QT interval Labs associated with various PTH, and Vitamin D anomalies Serum Ca Serum Phos PTH Common Cause Hyperparathyroidism Increased Decreased Increased Adenoma Hypoparathyroidism Decreased Increased Decreased Thyroidectomy (including parathyroid) Ectopic PTH Increased Decreased Decreased Malignancy Vitamin D malabsorption Decreased Decreased Increased Celiac disease, other GI disease Hypo Vit D with no phosphate excretion from the kidney Decreased Increased Increased Renal failure, pseudo hypoparathyroidism Treatment Nonoperative calcium and vitamin D supplementation indications login to view 2 more bullets outcomes login to view 1 more bullet Prognosis No current hormone replacement therapy available Treatment is aimed at supplementing vitamin D and calcium levels