A case of severe neonatal hypercalcaemia secondary to neonatal thyrotoxicosis

Hypercalcaemia is a recognised complication of thyrotoxicosis. Evidence in the paediatric population is limited, and this is the first reported case of hypercalcaemia noted to occur secondary to neonatal thyrotoxicosis. Signs and symptoms of both hypercalcaemia and thyrotoxicosis can be non-specific and subtle. An awareness of the condition and a high index of suspicion are required in order to make the diagnosis. While asymptomatic neonatal hypercalcaemia may be transient and self-limiting, symptomatic patients require treatment with hyperhydration. Serum calcium levels in combination with parathyroid hormone, vitamin D, and urine calcium-creatinine ratios can help narrow the differential diagnoses, but it is important that the underlying cause is carefully investigated.