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Excerpt from Hyperthyroidism, Thyroid Storm, and Graves DiseaseSynonyms, Key Words, and Related Terms: thyroid hormone, thyroxine, T4, triiodothyronine, T3, elevated levels of thyroid hormone, diffuse toxic goiter, goiter, exophthalmos, pretibial myxedema, thyrotoxicosis, toxic multinodular goiter, congestive heart failure, thyromegaly, atrial fibrillation, myopathy, periodic paralysis, thyroid bruit, infrequent blinking, lid lag, pulmonary infection, diabetic ketoacidosis, hyperosmolar coma, insulin-induced hypoglycemia, withdrawal of antithyroid medication, vigorous palpation of thyroid gland, thyroid hormone overdose, toxemia of pregnancy Please click here to view the full topic text: Hyperthyroidism, Thyroid Storm, and Graves DiseaseBackground: Hyperthyroidism, thyroid storm, and Graves disease are conditions of excess thyroid hormone. The elevated level of thyroid hormones can result in clinical manifestations ranging from mild to severely toxic with resultant morbidity and mortality for affected patients.Hyperthyroidism Hyperthyroidism presents as a constellation of symptoms due to elevated levels of circulating thyroid hormones. Because of the many actions of thyroid hormone on various organ systems in the body, the spectrum of clinical signs produced by the condition is broad. The presenting symptoms can be subtle and nonspecific, making hyperthyroidism difficult to diagnose in its early stages without the aid of laboratory data. The term hyperthyroidism refers to inappropriately elevated thyroid function. Though often used interchangeably, the term thyrotoxicosis, which is an excessive amount of circulating thyroid hormone, is not synonymous with hyperthyroidism. Increased levels of hormone can occur despite normal thyroid function, such as in instances of inappropriate exogenous thyroid hormone or excessive release of stored hormone from an inflamed thyroid gland. Graves disease Graves disease (diffuse toxic goiter), the most common form of overt hyperthyroidism, is an autoimmune condition in which autoantibodies are directed against the thyroid-stimulating hormone (TSH) receptor. As a result, the thyroid gland is inappropriately stimulated with ensuing gland enlargement and increase of thyroid hormone production. Risk factors for Graves disease include family history of hyperthyroidism or various other autoimmune disorders, high iodine intake, stress, use of sex steroids, and smoking. The disease is classically characterized by the triad of goiter, exophthalmos, and pretibial myxedema. Thyroid storm Thyroid storm is a rare and potentially fatal complication of hyperthyroidism. It typically occurs in patients with untreated or partially treated thyrotoxicosis who experience a precipitating event such as surgery, infection, or trauma. Thyroid storm must be recognized and treated on clinical grounds alone, as laboratory confirmation often cannot be obtained in a timely manner. Patients typically appear markedly hypermetabolic with high fevers, tachycardia, nausea and vomiting, tremulousness, agitation, and psychosis. Late in the progression of disease patients may become stuporous or comatose with hypotension.
Pathophysiology: In healthy patients, the hypothalamus produces thyrotropin-releasing hormone (TRH), which stimulates the anterior pituitary gland to secrete thyroid-stimulating hormone (TSH); this in turn triggers the thyroid gland to release thyroid hormone. Thyroid hormone concentration is regulated by negative feedback by circulating free hormone primarily on the anterior pituitary gland and to a lesser extent on the hypothalamus. The secretion of TRH is also partially regulated by higher cortical centers. The thyroid gland produces the prohormone thyroxine (T4), which is deiodinated primarily by the liver and kidneys to its active form, triiodothyronine (T3). The thyroid gland also produces a small amount of T3 directly. T4 and T3 exist in 2 forms: a free, unbound portion that is biologically active and a portion that is protein bound to thyroid-binding globulin (TBG). Despite consisting of less than 0.5% of total circulating hormone, free or unbound T4 and T3 levels best correlate with the patient's clinical status. Frequency:
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