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mechanism involving the interaction of stimulatory and inhibitory factors. Thyrotropin-releasing hormone (TRH) from the hypothalamus stimulates the pituitary to release TSH.In Graves' disease, a circulating autoantibody against the thyrotropin receptor provides continuous stimulation of the thyroid gland. This stimulatory immunoglobulin has been called long-acting thyroid stimulator (LATS), thyroid-stimulating immunoglobulin (TSI), thyroid-stimulating antibody (TSab), and TSH-receptor antibody (TRab). These antibodies stimulate the production and release of thyroid hormones and thyroglobulin.20. Thyroid storm is a rare but severe and potentially life-threatening complication of hyperthyroidism or Graves disease. The patient developed the thyroid storm because she did not take her antithyroid medication, which resulted in thyrotoxic crises. This hypermetabolic state was caused by the excessive release of thyroid hormones. Symptoms must be rapidly treated in order to prevent life-threatening complications such as high output heart failure, hyperthermia, delirium, and hypovolemia from excessive vomiting. Individuals may be undiagnosed or undertreated when they develop the symptoms. The symptoms are caused by the build-up and sudden release and action of thyroxine (T4) and triiodothyronine (T3) that exceeds metabolic demands.What causes hypothyroidism?21.The function of the thyroid gland is to take iodine, found in many foods, and convert it into thyroid hormones: thyroxine (T4) and triiodothyronine (T3). Thyroid cells are the only cells in the body that can absorb iodine. These cells combine iodine and the amino acid tyrosineto makeT3 and T4. T3 and T4 are then released into the bloodstream and are transported throughout the body where they control metabolism (conversion of oxygen and calories to energy).Hypothyroidism is an underactive thyroid gland. Hypothyroidism means that the thyroid gland can't make enough thyroid hormones to keep the body running normally. People are hypothyroid if they have too little thyroid hormone in the blood. Common causes are autoimmune diseases, such as Hashimoto's thyroiditis, surgical removal of the thyroid, and radiation treatment. In a person with the primary hypothyroidism (underactive thyroid gland), the blood levelof T4 (the primary thyroid hormone) will be low, while the TSH levelwill be high (usually 4.5-10.0 mlU/L). What causes myxedema coma?22.Myxedema is a term used to denote hypothyroidism, in which patients exhibit multiple organ abnormalities and progressive mental deterioration. In the patient with underlying hypothyroidism, a number of physiologic alterations occur to compensate for the lack of thyroid hormone. If these homeostatic mechanisms are overwhelmed by factors such as infection, or medications such as sedatives and anesthetics, the patient may decompensate into myxedema coma. Patients with hypothyroidism typically have a history of fatigue, weight gain, constipation,
and cold intolerance. A common misconception is that a patient must be comatose to be diagnosed with myxedema coma; however, they are at risk for significant cardiovascular and pulmonary complications. Patients will exhibit