Laboratory Studies
See the list below:
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Thyroid function studies confirm the diagnosis in the appropriate clinical setting.
Elevation of free T4 and low to undetectable TSH levels are diagnostic of thyrotoxicosis; in earlier stages, T3 rise precedes T4 rise.
Excessive TSH levels in the setting of elevated free T4 indicate hyperthyroidism of pituitary origin.
There is little utility in obtaining total T4 levels, as variations in serum thyroid-binding proteins alter the ability to interpret results.
Particularly in thyroid storm, the diagnosis must be made on the basis of the clinical examination as rapid assays are not universally available.
Thyroid function studies do not distinguish thyrotoxicosis from thyroid storm; however, several laboratory abnormalities may be encountered in thyroid storm.
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Hyperglycemia
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Hepatic function abnormalities
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Low serum cortisol
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Leukocytosis
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Hypokalemia (in thyrotoxic periodic paralysis)
Imaging Studies
See the list below:
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Chest radiography may identify congestive heart failure or pulmonary infections, often associated with progression to thyroid storm.
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Nuclear thyroid scan
Diffuse uptake in Graves disease
Focal uptake in toxic nodular thyroiditis
Other Tests
See the list below:
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Electrocardiogram
Sinus tachycardia most common
Atrial fibrillation (often in elderly patients)
Complete heart block (rare)
