Hyperthyroidism in early infancy: pathogenesis, clinical features and diagnosis with a focus on neonatal...

Area of Science:

• Neonatal endocrinology
• Pediatric immunology
• Molecular genetics

Background:

• Neonatal hyperthyroidism is primarily linked to maternal Graves' disease, affecting about 1% of infants born to affected mothers.
• The condition typically results from maternal antibodies crossing the placenta and stimulating the fetal thyroid via the thyrotropin (TSH) receptor.
• Persistent, nonimmune forms can arise from TSH receptor molecular abnormalities, often presenting with prematurity and hypotrophia.

Purpose of the Study:

• To review the causes, clinical signs, and diagnostic approaches for neonatal hyperthyroidism.
• To differentiate between immune-mediated and nonimmune causes of the disorder.
• To highlight the role of TSH receptor mutations in persistent neonatal hyperthyroidism.

Main Methods:

• Review of existing literature on neonatal hyperthyroidism.
• Analysis of diagnostic criteria including thyroid hormone levels (T4, T3, TSH) and thyroid-stimulating immunoglobulins (TSI).
• Discussion of molecular studies for identifying TSH receptor mutations.

Main Results:

• Common clinical signs include tachycardia, goiter, hyperexcitability, poor weight gain, and hepatosplenomegaly.
• Diagnosis requires serial thyroid function tests and TSI determination to distinguish immune from nonimmune causes.
• TSH receptor mutations are identified in nonimmune cases, leading to constitutive receptor activation.

Conclusions:

• Neonatal hyperthyroidism requires careful diagnosis, distinguishing transient immune forms from persistent nonimmune forms.
• TSH receptor mutations are a key cause of nonimmune congenital hyperthyroidism.
• Early diagnosis and appropriate management are crucial for affected neonates.