Case Report: Diagnosis of Hyperthyroidism in a Preterm Infant With Concurrent Respiratory Distress Syndrome.

Background/Objective: Neonatal hyperthyroidism in preterm infants is often misdiagnosed due to significant symptom overlap with respiratory distress syndrome (RDS), leading to frequent diagnostic delays. This case highlights the critical need for early suspicion in infants born to mothers with Graves' disease, particularly when clinical symptoms such as unexplained tachycardia are present, even in the absence of maternal thyroid-stimulating hormone receptor autoantibody (TRAb) testing. Case Description: A preterm male infant presented with severe RDS. Unexplained tachycardia prompted thyroid function testing, which revealed thyrotoxicosis. Following the diagnosis of hyperthyroidism by thyroid function tests, neonatal Graves' disease was confirmed by detecting elevated TRAb levels in both the neonate and his mother. Through a multidisciplinary approach, the infant was successfully treated with methimazole and propranolol, resulting in normalized thyroid function and complete resolution of respiratory distress. Discussion: The hypermetabolic state induced by thyrotoxicosis can exacerbate RDS severity in preterm neonates. This case demonstrates that persistent or atypical respiratory symptoms in infants, particularly with a maternal history of autoimmune thyroid disease, should prompt immediate endocrine evaluation. Conclusion: Preterm infants with RDS are at risk for delayed diagnosis of concurrent hyperthyroidism. Systematic prenatal TRAb screening and targeted postnatal thyroid testing are essential. Early diagnosis and collaborative management are key to preventing complications and optimizing outcomes.