Preterm heart failure and refractory lactic acidosis caused by congenital hypothyroidism: A case report and review of literature.

BACKGROUND: Congenital hypothyroidism (CH) is a common condition in both preterm and term infants characterized by either thyroid gland absence or hypofunctionality. The clinical association of refractory lactic acidosis and heart failure has rarely been observed in cases of pediatric patients with CH pathology. Here, we explored the etiological relationship between CH, heart failure, and refractory lactic acidosis to reflect the importance of thyroid function screening in neonates with heart disease. CASE SUMMARY: A 33-day-old extremely premature female infant presented with tachypnea, respiratory distress, recurrent infections, and abdominal distension postnatal. On admission to our facility, she had cardiomegaly, hepatomegaly, and lactic acidosis (revealed on blood gas analysis), with lactate progressively rising to 25 mmol/L. Chest radiographs showed pulmonary congestion, while echocardiography revealed cardiac enlargement, left ventricular wall thickening, and pericardial effusion. Initial management aimed at correcting acidosis and treating heart failure proved ineffective. After reassessment, thyroid function tests showed significantly decreased triiodothyronine, free triiodothyronine, thyroxine, and free thyroxine levels, with a significantly increased thyroid-stimulating hormone level, confirming a CH diagnosis. Levothyroxine was administered, resulting in rapid correction of lactic acidosis and gradual improvement of thyroid function and systemic symptoms, culminating in full recovery and discharge. We also reviewed the relevant literature on thyroid and cardiac dysfunctions in order to explore their deeper association. CONCLUSION: This case links CH-induced heart failure with refractory lactic acidosis, urging prompt thyroid screening in affected neonates to reduce mortality.