Hypothyroidism and Thyrotoxicosis

Thyroid disorders are the most common endocrine conditions encountered in clinical practice and can range from clinically obvious to clinically silent. This review provides the definition and epidemiology of the conditions of hypothyroidism and hyperthyroidism. Hypothyroidism can be congenital or acquired, and its pathogenesis, diagnosis, and management are presented. The three most common disorders of thyrotoxicosis (diffuse toxic goiter [Graves disease], toxic nodular goiter, and iatrogenic thyrotoxicosis in thyroid hormone–treated patients are addressed, as well as the many diseases in each of these categories. This review also discusses thyroiditis, goiter, thyroid nodules, and thyroid cancer. Tables list the causes of elevated serum thyroid-stimulating hormone (TSH) levels, the etiologic classification of thyrotoxicosis, characteristic features of thyroiditis, and causes of elevated serum total thyroxine levels. Figures show the prevalence of abnormalities in thyroid function tests in different populations, certain forms of hyperthyroidism that result from pathophysiologic activation of the TSH receptor, and inflammation of thyroid tissue in acute thyroiditis.   This review contains 3 figures, 12 tables, and 61 references. Key Words: Hypothyroidism, Thyrotoxicosis, Thyrotropin, celiac disease, vitiligo, pernicious anemia, Sjögren syndrome, Graves disease, Munchausen syndrome