Hypocalcemia

Low PTH

• Hypoparathyroidism

  • DiGeorge syndrome

• Hypomagnesemia (impairs secretion, action of PTH)

• Renal PO₄³⁻ wasting with hypercalciuria (hereditary hypophosphatemic rickets with hypercalciuria)

• Autoimmune polyendocrinopathy, candidiasis, ectodermal dystrophy (APECED) syndrome

  • Destroys multiple endocrine glands, including parathyroid

High PTH

• Vitamin D deficiency/resistance

  • Nutritional

  • Kidney disease

  • Liver disease

• Pseudohypoparathyroidism

• Hungry bone syndrome

• Inadequate intake

Neonatal hypocalcemia

• Prematurity

• Intrauterine growth restriction

• Infant of diabetic mother

Artifact

• Hypoalbuminemia

  • For each 1 g/dL below normal albumin level, add 0.8 mg/dL to the serum calcium

• Ionized calcium (iCa) is more reliable

  • No albumin correction

• Calcium is bound by citrate

  • Citrate-bound calcium is included in total serum calcium level but will result in a lower iCa level

  • If iCa low, ensure not being drawn from line with blood products running in the line (e.g., in secondary lumen)

• Lab error, specimen handling issues

• Weakness

• Paresthesias

• Carpopedal spasms

• Tetany

• Seizures

• Steatorrhea

• Prolonged QT interval

• Rickets

• Poor nail growth

• Papilledema

• Calcifications of basal ganglia

• Labs:

  • Albumin

  • Ionized calcium (iCa)

  • Parathyroid hormone (PTH)

  • Phosphorus

  • Magnesium

  • 25-OH vitamin D

  • 1,25-OH₂ vitamin D

  • Urine calcium/creatinine (UCa/Cr) ratio

• Treat underlying cause

• Give calcium

  • Mild-moderate hypocalcemia: oral calcium repletion

  • Severe hypocalcemia: IV calcium

    • Can cause cardiac arrest if administered too rapidly

    • Ideally administered centrally as extravasation can cause tissue necrosis

      • Calcium gluconate safer than calcium chloride for peripheral IV infusion

• Give vitamin D if indicated

• Replace magnesium if hypomagnesemic

• Be aware that calcium and/or vitamin D can cause hypercalciuria