Disorders of the Thyroid Gland in Infancy, Childhood and Adolescence

Thyroid disorders in infancy, childhood and adolescence represent common and usually treatable endocrine disorders. Thyroid hormones are essential for normal development and growth of many target tissues, including the brain and the skeleton. Thyroid hormone action on critical genes for neurodevelopment is limited to specific time window, and even a short period of deficiency of TH can cause irreversible brain damage. During the first trimester of pregnancy fetal brain development is totally dependent on maternal thyroid function. Congenital hypothyroidism is one of the most preventable causes of mental retardation, but early diagnosis is needed in order to prevent irreversible SNC damage. Today more than 70% of the babies worldwide are born in areas without an organized screening program. New insights about genetic causes, screening strategies and treatment of congenital hypothyroidism are reported. Hyperthyroidism in newborns is usually a transient consequence of transplacental passage of TSH receptor stimulating antibodies. Hypothyroidism can be detected in infants born to hyperthyroid mothers, due to transplacental passage of TSH receptor antibodies or hypothalamic-pituitary suppression. In childhood and adolescence autoimmune thyroid disease (AITD) as chronic lymphocytic thyroiditis and Graves’ disease account for the main cause of hypothyroidism and hyperthyroidism, respectively. Incidence of AITD increase from infancy to adolescence. Other autoimmune disorders are frequently associated. An increased risk of thyroid nodules and cancer is suggested. Differentiated thyroid cancer and medullary thyroid carcinoma in childhood and adolescence require specific expertise. Follow up programs are advised for high risk patients as long term survivors of childhood cancer. For complete coverage of this and related areas of Endocrinology, please visit our free online textbook, WWW.ENDOTEXT.ORG.