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 serum phosphate levels increase decreased conversion of inactive form of vitamin D to active form 1,25(OH)2-vitamin levels decrease Presentation Symptoms hypocalcemia more common in hypoparathyroidism neuromuscular irritability Chvostek's sign seizures tetany cataracts fungal infections of the nail hair loss skin changes vitiligo blotchiness of skin 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 decreased serum calcium level decreased levels of vitamin D outcomes must monitor labs on a regular basis Prognosis No current hormone replacement therapy available Treatment is aimed at supplementing vitamin D and calcium levels