Lesson 2: Signs and Symptoms of Hyperthyroidism
Thyroid Storm
Thyroid storm lies at the opposite end of the spectrum. Thyroid storm is a rare, life-threatening condition of extreme thyrotoxicosis. Thyroid storm occurs in one to two percent of all hyperthyroidism, and it was once thought to be related to thyroid surgery. Today, it’s known that other circumstances besides surgery can trigger thyroid storm, including radioiodine ablation, serious infection, particularly pneumonia, toxemia of pregnancy, the use of iodine contrast dyes, the heart medication amiodarone because of its high iodine content, extreme emotional stress, abrupt withdrawal of anti-thyroid medications, excess thyroid hormone ingestion, diabetic ketoacidosis, pulmonary embolism, and strokes.
Thyroid storm is not related to unusually high thyroid hormone levels, but to a change in the way the body responds to thyroid hormone. Thyroid storm can be triggered by any of the conditions listed above. Using beta blockers and anti-thyroid drugs, for instance, before thyroid surgery can prevent thyroid storm, when suspected or anticipated. Thyroid storm causes warning signs that suggest it may be developing. These include significant weight loss, usually forty pounds or more within a short period, a very high body temperature, profuse sweating and occasionally mental changes.
According to one theory, although not unusually high, thyroid hormone levels rise at a higher rate than usual. For instance an FT4 of 1.8 ng/dl might rise to 3.0 ng/dl within a few days in impending thyroid storm. Another theory is that levels do not rise at a faster rate, but that the body’s tissues become intolerant of doses of thyroid hormone they were previously tolerant of. Because patients in thyroid storm respond quickly to beta adrenergic blocking agents like propranolol, it’s also suspected that a change in adrenergic receptors makes the patient more susceptible to thyroid hormone.
The diagnosis of thyroid storm is based on a clinical impression contributed to by physical findings, such as body temperature elevated higher than 100 degrees F or tachycardia, and increased thyroid hormone levels. Core temperatures exceeding 106 degrees Fahrenheit have been reported in thyroid storm. Patients with ophthalmopathy, goiter and weight loss may be suspected of having thyroid storm.
Other symptoms seen in thyroid storm are exaggerated symptoms of tachycardia out of proportion to fever, mania, confusion, tremor, diarrhea, hyperdefecation, nausea, vomiting, diaphoresis, emotional lability, altered mental status, lethargy, agitation, muscle weakness of large proximal muscles particularly the shoulders and thighs, arrhythmias, congestive heart failure, abdominal pain or jaundice. Approximately 50 percent of patients with thyroid storm will have cardiovascular symptoms, such as widened pulse pressure, increased systolic blood pressure, premature ventricular contractions, atrial arrhythmias, premature ventricular contractions and malignant ventricular tachyarrhythmias.
Untreated, thyroid storm can progressively worsen, potentially causing congestive heart failure, refractory pulmonary edema, circulatory collapse, and coma. Death may occur within 72 hours. Mortality in thyroid storm is reported to be as high as 20 percent, although it’s more likely to occur in the elderly, and other causes frequently contribute to death. In one study in the Chicago area, thyroid storm was most likely to be seen in heat waves and occur in elderly people who hadn’t previously been diagnosed with or treated for hyperthyroidism.
Early treatment is important. Before treatment is started, blood for thyroid hormone levels should be drawn and also blood for a metabolic profile and CBC. Treatment consists of supportive care, correcting the hyperthyroid state and managing the precipitating event that triggered the storm.
Intravenous fluids are generally used to treat dehydration, and antipyretics are given to lower the temperature. Aspirin should be avoided since it decreases protein binding, thereby increasing free T4 and free T3 levels. A bolus of 900-1200 mg PTU is generally given followed by 30-60 mg daily for 3-6 weeks. Potassium iodide in the form of SSKI or Lugol’s solution is administered after the PTU to help reduce the production of new thyroid hormone and to reduce the release of thyroid hormone from the thyroid gland. Beta blockers are administered at low doses intravenously. Treatment for the precipitating cause should also be started. If infection is not determined, cultures of blood, sputum and urine should be performed to help detect an infectious process. A chest radiograph is also performed to help determine if pneumonia is present. Thyroid storm generally lasts for three days although the event may persist for one week.
