endocrine and metabolic disorders
Hyperthyroidism
Key Points
Hyperthyroidism has many causes; the most common etiology is Graves disease, caused by excessive hormone synthesis by an abnormal thyroid. Other causes of hyperthyroidism include excessive stimulation of a normal thyroid gland (eg, by thyroid-stimulating hormone [TSH], human chorionic gonadotrophin [hCG], ingestion of iodine or iodine-containing drugs), excessive hormone synthesis by an abnormal thyroid (eg, toxic nodular goiter), excessive release of thyroid hormones (eg, due to thyroiditis), or ingestion of excessive quantities of thyroid hormone. Symptoms and signs are many but include tachycardia, fatigue, weight loss, nervousness, and tremor; patients with Graves disease may also have exophthalmos and infiltrative dermopathy. Free thyroxine (T4), and/or free or total triiodothyronine (T3) are elevated, and TSH is suppressed (except in rarer cases of pituitary causes of hyperthyroidism). Hormone synthesis can be suppressed withmethimazole(or in certain cases,propylthiouracil) and adrenergic symptoms relieved with beta-blockers; long-term treatment may require thyroid ablation with radioactive iodine or surgery. Thyroid storm—resulting from untreated or inadequately treated severe hyperthyroidism—is a life-threatening emergency that presents with severe symptoms of hyperthyroidism and may result in cardiovascular collapse or shock; it is treated with a regimen of antithyroid drugs, iodine, and hemodynamic support. 