Thyroid and Parathyroid Conditions: Hyperthyroidism.

Hyperthyroidism is an excess in thyroid hormone production caused by such conditions as Graves disease, toxic multinodular goiter, and toxic adenoma. Overt hyperthyroidism is defined as a low or undetectable thyrotropin (TSH) level with elevated triiodothyronine (T3) or thyroxine (T4) values, whereas subclinical hyperthyroidism is defined as low or undetectable TSH with normal T3 and T4 levels. Symptoms of hyperthyroidism include nervousness, heat intolerance, weight loss, and fatigue. The long-term consequences of unmanaged or poorly managed hyperthyroidism include increased risk of all-cause mortality, cardiovascular events, atrial fibrillation, sexual dysfunction, and osteoporosis. Overt and subclinical hyperthyroidism can be managed effectively with antithyroid drugs (eg, propylthiouracil, methimazole) or with definitive therapies (eg, radioactive iodine ablation, thyroidectomy). Subclinical hyperthyroidism is not always treated, although close monitoring is needed to prevent disease complications or progression to overt hyperthyroidism. Treatment for subclinical hyperthyroidism is recommended for patients 65 years or older with TSH levels lower than 0.10 mIU/L. Treatment also is recommended for symptomatic patients or those with cardiac or osteoporotic risk factors. Thyroid storm is a life-threatening complication of unmanaged or inadequately managed hyperthyroidism that warrants urgent treatment in a hospital setting.