To describe a rare case of late-onset neonatal hypocalcemia in a very preterm infant caused by maternal adenoma-related hyperparathyroidism (HyperPT) and to discuss diagnostic and therapeutic implications.

Case report of a preterm infant born at 29 weeks of gestation with very low birth weight. Clinical course, laboratory findings, maternal history, and management were reviewed to identify the etiology and guide treatment.

The infant developed transient, asymptomatic hypocalcemia during the neonatal period. Maternal evaluation revealed primary HyperPT due to a parathyroid adenoma as the underlying cause. The newborn responded to calcium supplementation and optimized vitamin D therapy.

Maternal HyperPT can cause delayed neonatal hypocalcemia even in preterm infants. Early recognition through coordinated maternal–neonatal evaluation is crucial. Optimal vitamin D administration and close interdisciplinary communication between obstetrics and neonatology are essential for prevention and management.

Patient and caregiver consent were obtained.

Received: 12 December 2025

Accepted: 18 March 2026

Article published online:
14 April 2026

© 2026. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/).

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