The most common type of neonatal hypercalcemia is which of the following?

• A. Disorders of parathyroid function
• B. Idiopathic infantile hypercalcemia
• C. Vitamin D intoxication
• D. Iatrogenic

Answer: (D)

The most common cause of neonatal hypercalcemia in the NICU setting is iatrogenic. In newborns, especially preterms or ill infants, calcium and vitamin D are frequently given through IV fluids or parenteral nutrition to support bone mineralization and growth. When these supplements are provided in excess, serum calcium rises, often with suppressed PTH as a result of the high calcium level. This makes iatrogenic hypercalcemia the typical scenario in newborns who develop high calcium levels.

Other causes, such as disorders of parathyroid function, idiopathic infantile hypercalcemia due to genetic defects in vitamin D metabolism, or vitamin D intoxication, do occur but are far less common in the neonatal period. Management focuses on removing or reducing the excess calcium/vitamin D source, ensuring adequate hydration, and monitoring calcium and related labs.