Congenital Hypothyroidism

Congenital hypothyroidism Etiology The etiology of congenital hypothyroidism can be classified into two main categories: 1. Primary Hypothyroidism: Primary CH results from intrinsic abnormalities affecting the thyroid gland's development, structure, or function. Causes include thyroid dysgenesis (agenesis, ectopic thyroid tissue), thyroid dyshormonogenesis (defects in thyroid hormone synthesis), or inborn errors of metabolism affecting thyroid hormone transport or utilization. 2. Central Hypothyroidism: Central or secondary CH occurs due to defects in hypothalamic-pituitary-thyroid axis regulation, leading to insufficient stimulation of the thyroid gland by thyroid-stimulating hormone (TSH). Causes include congenital hypopituitarism, hypothalamic dysfunction, or pituitary gland abnormalities. Clinical Manifestations 1. Neonatal Features: Infants with congenital hypothyroidism may present with nonspecific signs and symptoms in the newborn period, such as lethargy, poor feeding, hypotonia, constipation, hoarse cry, jaundice, macroglossia, and umbilical hernia. These features may be subtle and easily overlooked without routine screening. 2. Growth and Developmental Delays: Untreated congenital hypothyroidism can lead to significant growth failure and developmental delays, including cognitive impairment, speech and language delays, motor delays, and behavioral abnormalities. Early detection and treatment are crucial to prevent permanent intellectual disability. 3. Physical Features: Infants with congenital hypothyroidism may exhibit characteristic physical features such as coarse facial features, puffy facies, macroglossia (enlarged tongue), short stature, delayed bone age, and umbilical hernia. These features may become more pronounced with prolonged untreated hypothyroidism. Diagnosis 1. Newborn Screening: Diagnosis of congenital hypothyroidism typically begins with newborn screening, which involves the measurement of TSH levels from a blood sample obtained via heel prick shortly after birth. Elevated TSH levels in the newborn period indicate hypothyroidism and prompt further evaluation. 2. Confirmation Testing: Confirmatory testing involves obtaining additional blood samples for measurement of serum thyroxine (T4) and triiodothyronine (T3) levels. Low T4 levels with elevated TSH levels confirm the diagnosis of congenital hypothyroidism. 3. Thyroid Imaging: Thyroid imaging studies such as thyroid ultrasound or thyroid scintigraphy may be performed to assess the size, location, and morphology of the thyroid gland. Thyroid imaging helps differentiate between thyroid dysgenesis (absent or ectopic thyroid gland) and thyroid dyshormonogenesis (normal or enlarged thyroid gland). Management 1. Thyroid Hormone Replacement Therapy: The cornerstone of treatment for congenital hypothyroidism is lifelong thyroid hormone replacement therapy with levothyroxine (T4). Oral administration of levothyroxine in appropriate doses restores thyroid hormone levels, promotes normal growth and development, and prevents long-term complications. 2. Monitoring and Follow-up: Infants with congenital hypothyroidism require regular monitoring of thyroid function, growth parameters, developmental milestones, and treatment adherence. Thyroid function tests should be performed periodically to adjust levothyroxine dosage and ensure optimal thyroid hormone levels. 3. Education and Support: Parents and caregivers of infants with congenital hypothyroidism should receive education about the importance of thyroid hormone replacement therapy, adherence to treatment, monitoring of thyroid function, and recognition of signs and symptoms of hypothyroidism or hyperthyroidism. Psychosocial support and counseling may be beneficial for coping with the diagnosis and managing the child's care. Prognosis The prognosis for infants with congenital hypothyroidism is generally favorable with early detection and appropriate treatment. Thyroid hormone replacement therapy initiated soon after birth can prevent the development of intellectual disability and promote normal growth and development. However, delayed diagnosis and treatment or inadequate thyroid hormone replacement therapy can result in permanent cognitive impairment, growth failure, and developmental delays. Long-term follow-up and monitoring are necessary to ensure optimal thyroid function, growth, and development throughout childhood and adolescence. With proper management and support, most children with congenital hypothyroidism can lead healthy, productive lives and achieve their full potential.