Toxic Multinodular Goiter

Toxic multinodular goiter (TMNG), also called Plummer disease, is hyperthyroidism caused by several thyroid nodules that secrete hormone autonomously. They no longer depend on pituitary TSH stimulation. Activating somatic mutations in the TSH-receptor pathway account for many autonomous nodules; other nodules have Gs-alpha pathway mutations or no identifiable mutation. The process usually evolves over years from a long-standing nontoxic multinodular goiter. The clinical course is therefore gradual, and the biochemical abnormality may be mild or initially subclinical. TMNG is the second most common cause of hyperthyroidism after Graves disease and is seen most often after age 50, particularly in women and in people with a history of iodine deficiency or longstanding nodular thyroid disease. The experienced clinician does not wait for a dramatic adrenergic presentation. An older adult may have unexplained weight loss, fatigue, proximal muscle weakness, atrial fibrillation or heart failure with little tremor or anxiety. This apathetic presentation occurs because cardiac and systemic effects may dominate while the excess hormone remains modest. Assess the pulse and rhythm, blood pressure, weight trend, exercise tolerance and signs of heart failure....