twice daily) or propylthiouracil (5 to 7 mg/kg/day dividedevery 8 hours). Both medications are equally effective, however, propylthiouracil is no longer a first-line therapy secondary to concerns of severe liver injury and acute liver failure.A beta blocker, such as propranolol or atenolol, is startedif symptoms are severe to control cardiac manifestations and is tapered as the methimazole takes effect. Antithyroidmedication is usually continued for 1 to 2 years because theremission rate is approximately 25% per year. In patientscomplying with the treatment regimen, the 2-year courseof treatment can be repeated. Medication should suppressthyroid function to normal, without the need to add thyroidhormone replacement to normalize serum free T4. Complications of methimazole are muscle pain, rash, granulocytopenia, and jaundice. The granulocytopenia is an idiosyncraticcomplication of rapid onset, which is observed only in theearly months after institution of antithyroid medication and requires monitoring the complete blood count. If asuppressed white blood cell count is observed, antithyroidtherapy must be discontinued. This potentially lethal rarecomplication affects 3 in 10,000 users a year. After resolution,the other of the two antithyroid medications can be startedbecause there is usually less than a 50% chance of a similarreaction from the other medication. Iodine administration, which may suppress thyroid function but becomes ineffectivein a few weeks, is sometimes used as a preparation for surgery but never for long-term therapy.
Radioiodine. Radioiodine (131I) is slower in exerting therapeutic effects, may require repeated dosing, and is likely to cause permanent hypothyroidism. Hypothyroidism is the desired outcome because it is easier and safer to treat than continued hyperthyroidism. Although studies reveal no longterm consequences, concern remains about possible sequelae in children. This method of treatment is entering the mainstream for children and adolescents. Radioiodine given to a pregnant teenager renders the fetus hypothyroid and is contraindicated.
Surgery. Surgical treatment consists of partial or completethyroidectomy. Risks associated with thyroidectomy includethe use of anesthesia and the possibility that the thyroidremoval will be excessive causing hypothyroidism or that itwill be inadequate resulting in persistent hyperthyroidism.In addition, keloid formation, recurrent laryngeal nervepalsy, and hypoparathyroidism (transient postoperative orpermanent) may occur. Thyroid storm caused by the releaseof large amounts of preformed hormone is a serious but rarecomplication. Even with optimal immediate postoperativeresults, patients may become hypothyroid within 10 years.
Thyroid storm (see Table 175-4) is a rare medical emergency consisting of tachycardia, disorientation, elevated blood pressure, and hyperthermia. Treatment includes reducing the hyperthermia with a cooling blanket and administering a beta blocker to control the tachycardia, hypertension, and autonomic hyperfunction symptoms. Iodine may be given to block thyroid hormone release after an antithyroid medication is started. Hydrocortisone may be indicated for relative adrenal insufficiency, and therapy for heart failure includes diuretics and digoxin.