Hypocalcemia

Hypocalcemia is a condition characterized by low serum calcium levels, typically <8.5 mg/dL (2.12 mmol/L). It can result from inadequate calcium intake, vitamin D deficiency, hypoparathyroidism, or disorders affecting calcium metabolism.

Definition

Hypocalcemia is a condition characterized by low serum calcium levels, typically <8.5 mg/dL (2.12 mmol/L). It can result from inadequate calcium intake, vitamin D deficiency, hypoparathyroidism, or disorders affecting calcium metabolism.

Epidemiology

Common electrolyte disturbance in hospitalized patients
Can occur at any age; congenital forms are rare
Post-surgical hypocalcemia is common after thyroid or parathyroid surgery
Prevalence higher in patients with chronic kidney disease or malabsorption

Etiology

Hypoparathyroidism: surgical, autoimmune, genetic (DiGeorge syndrome)
Vitamin D deficiency or resistance
Chronic kidney disease → phosphate retention and secondary hyperparathyroidism
Magnesium deficiency (impairs PTH secretion and action)
Acute pancreatitis, sepsis, critical illness
Medications: bisphosphonates, loop diuretics, cisplatin

Pathophysiology

Low calcium → increased neuromuscular excitability → tetany, cramps, paresthesia
Hypocalcemia may prolong QT interval → cardiac arrhythmias
Hypoparathyroidism: insufficient PTH → decreased bone resorption, renal calcium reabsorption, and vitamin D activation
Vitamin D deficiency → reduced intestinal calcium absorption
Renal failure → phosphate retention → secondary hypocalcemia