Hypocalcemia is a condition of low serum calcium concentration and, specifically, low levels of ionized (nonprotein-bound) calcium. Causes can be differentiated by low parathyroid hormone (PTH) levels or high PTH levels.

Hypocalcemia with elevated PTH can be caused by vitamin D deficiency (rickets) or resistance, postrenal transplant or parathyroid surgery, medullary thyroid carcinoma, pancreatitis, alcohol use disorder, a need for massive blood transfusion (due to citrate chelation), or rhabdomyolysis. Hypocalcemia can be drug-induced by medications including anticonvulsants, corticosteroids, barbiturates (in elderly patients), bisphosphonates, calcitonin, methicillin, mithramycin, colchicine, estrogens, and glutethimide. Ethylene glycol poisoning, fluoride poisoning, and vitamin A intoxication are other possible causes. In pregnant patients, tetracycline can contribute to hypocalcemia.

Hypocalcemia with decreased PTH can be caused by genetic disorders, hemosiderosis, Wilson disease, DiGeorge syndrome, hungry bone syndrome, thyroid or parathyroid surgery, parathyroid radiation therapy, HIV, or autoimmune hypoparathyroidism.

The presentation of acute hypocalcemia ranges from asymptomatic to life-threatening. Severe hypocalcemia is characterized by neuromuscular irritability (tetany). Other symptoms include seizure, paresthesia, facial muscle tics (Chvostek sign), laryngospasm, bronchospasm, and/or carpopedal spasm (Trousseau sign). Other signs and symptoms include papilledema and cardiac irregularities including arrhythmias, hypotension, prolonged QT interval, or heart failure.

Chronic hypocalcemia findings range from ectopic calcification (basal ganglia), dry skin, cataracts, and dental anomalies to neurological findings of dementia, parkinsonism, or extrapyramidal signs.

Infants with hypocalcemia are mostly asymptomatic. Some may present with neuromuscular irritability with muscle twitching or may have clonic seizures. Rarely laryngospasm, bronchospasm, or pylorospasm may be present, and there may be findings of inspiratory stridor, wheezing, or vomiting.

Management primarily involves supplementation with oral or intravenous (IV) formulations of calcium. Choice of formulation and route of administration depends on clinical severity and types of access available.