This article reviews the physiology and pathophysiology of selected endocrine glands. The common presenting clinical signs and symptoms are reviewed, and the initial laboratory tests that may establish the diagnosis are recommended. Diagnosis and management of hypothyroidism, hyperthyroidism, hyperparathyroidism, hypoparathyroidism, pituitary disorders, diabetes mellitus (types I and II), hypoglycemia, and disorders of the adrenal cortex are discussed. The clinical management of the most commonly encountered endocrine disorders seen in the primary care setting is described, and pharmacologic considerations are underscored.