INTRODUCTION
Hypothyroidism is the most common disturbance of thyroid function in children; acquired hypothyroidism is most often caused by autoimmune thyroiditis [1]. As in adults, acquired hypothyroidism can be caused by both thyroid disease (primary hypothyroidism) and hypothalamic-pituitary disease (central hypothyroidism); furthermore, primary hypothyroidism may be either subclinical (elevated serum thyroid-stimulating hormone [TSH] and normal serum free thyroxine [T4] concentrations) or overt (elevated serum TSH and low serum free T4 concentrations). Whatever its cause, hypothyroidism in children can have deleterious effects on growth, pubertal development, and school performance.An overview of the clinical manifestations, causes, diagnosis, and treatment of acquired hypothyroidism in children is discussed below. Details about each of the causes are available in linked topics. Evaluation and management of congenital hypothyroidism are discussed separately. Information in this topic pertains to primary hypothyroidism; information on secondary (central) hypothyroidism is presented only when helpful to separate this entity from primary hypothyroidism. (See "Clinical features and detection of congenital hypothyroidism" and "Treatment and prognosis of congenital hypothyroidism" and "Thyroid physiology and screening in preterm infants".)
TERMINOLOGY
●Autoimmune thyroiditis – Autoimmune thyroiditis is the most common cause of acquired hypothyroidism [1]. Synonymous terms include chronic lymphocytic thyroiditis and Hashimoto thyroiditis; for the sake of consistency, this topic will use autoimmune thyroiditis.
●Autoimmune thyroid disease – This is a somewhat broader term, encompassing disorders with autoimmune mechanisms that have a risk of both hypothyroidism (Hashimoto disease) and hyperthyroidism (Graves disease).
CLINICAL MANIFESTATIONS
●Clinical presentation – Presenting features of acquired hypothyroidism in children may include: