E03.1

Clinical Causes: Aplasia of the thyroid gland, meaning the gland did not develop properly during fetal growth Congenital atrophy of the thyroid, where the gland was initially formed but later diminishes in size and function Genetic mutations affecting thyroid development Certain environmental factors during pregnancy that interfere with thyroid gland formation Unknown causes in some cases where the exact reason for gland absence or underdevelopment is not identified

Key Symptoms: Languidness and fatigue Poor feeding and weight gain in infants Jaundice or yellowing of the skin Constipation Dry skin and hair Hypotonia (baby sounds 'floppy') Coarse facial features in older children Delayed developmental milestones Hearing difficulties Slow growth and short stature

Diagnosis Path: Diagnosis often involves newborn screening tests measuring levels of TSH (thyroid-stimulating hormone) and T4 (thyroxine). Confirmatory tests include blood tests to assess hormone levels and imaging studies such as ultrasound or scintigraphy to evaluate the presence and size of the thyroid gland. Given that no goiter is present, the absence or underdevelopment of the gland is key in diagnosis. Early diagnosis, ideally in the newborn period, is essential for preventing developmental delays.

Treatment Protocols: Treatment typically involves lifelong thyroid hormone replacement therapy with synthetic levothyroxine. This approach aims to normalize hormone levels, support normal growth, and prevent intellectual disabilities. Regular monitoring through blood tests helps to adjust medication doses as needed. Early initiation of treatment usually results in a favorable outcome with normal development. In some cases, ongoing medical follow-up is required to manage the condition effectively.