2 Hyperthyroidism

This chapter reviews the pathophysiology, clinical manifestations, diagnosis and treatment of hyperthyroidism. Hyperthyroidism has multiple and often dramatic clinical manifestations because thyroid hormones control the basal metabolic rate, affect cardiovascular function by increasing the sensitivity of beta-receptors to catecholamines, and profoundly influence growth, sexual maturation, and neurological and cognitive development [1, 2]. “Hyperthyroidism” refers to excessive activity of the thyroid gland resulting in overproduction of thyroid hormones while “thyrotoxicosis” describes the clinical features of the hypermetabolic state associated with excess levels of circulating free thyroid hormones. In practice, the two terms are often used less precisely and interchangeably. There are several challenges in the diagnosis and management of hyperthyroidism in children including biological, psychosocial, and environmental issues [3, 4]. However, despite these challenges the vast majority of pediatric patients with hyperthyroidism have an excellent prognosis.