Description - Infants with congenital hypothyroidism are unable to produce adequate amounts of the thyroid hormone thyroxine. Thyroid hormone is important for normal function of all of the body's organs and is essential for normal brain development. The most common causes of primary hypothyroidism are total or partial failure of the thyroid gland to develop (aplasia or hypoplasia), or its development in an abnormal location (an ectopic gland). Less commonly, hypothyroidism is induced by medications (antithyroid drugs or excess iodine) in the mother or is due to a hereditary inability to manufacture thyroid hormones as a result of enzyme deficiencies. Secondary hypothyroidism results from failure of the pituitary to release thyrotropin (TSH). Tertiary hypothyroidism results from failure of the hypothalamus to secrete thyrotropin-releasing hormone.
Clinical Features – Symptoms can appear as early as 1-3 weeks of age although infants may appear clinically normal up to 6 months of age. Infants who are not identified and treated promptly suffer mental retardation and variable degrees of growth failure, deafness, and neurologic abnormalities as well as classical hypometabolic symptoms of hypothyroidism. When symptoms or clinical signs are present, they may include prolonged neonatal jaundice, constipation, lethargy and poor muscle tone, feeding problems, a large tongue, puffy face, distended abdomen and umbilical hernia.
Treatment - Caution should be used in instituting treatment before the diagnosis has been confirmed by a specialist. Treatment consists of synthetic thyroid hormone in pill form, prescribed on a daily basis. It is crushed, mixed with food and administered daily. The child's thyroxine concentration is maintained in the upper half of the normal range and re-evaluation of thyroid function tests and growth and development is done periodically. A pediatric endocrinology consultation should be obtained for diagnostic and follow-up purposes.