LabMed

Thyroid Storm

At a Glance

Thyroid storm is an acute and severe hypermetabolic episode that can include fever, tachycardia, hypertension, diarrhea, neurologic abnormalities, and death. Profound and rapid thyroid hormone release leads to severe hypermetabolism with these clinical manifestations.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

Thyroid storm represents an extreme and acute form of hyperthyroidism, and, because of the nature of this rapid onset thyrotoxicosis, thyroid storm is a clinical, rather than a laboratory diagnosis. However, because thyroid storm is usually associated with a patient's ongoing hyperthyroidism and very frequently associated with Grave’s disease, the relevant laboratory values include those used to diagnose hyperthyroidism and Grave’s disease. Generally, a diagnosis of hyperthyroidism is made when a pattern of low TSH and elevated free T4 is seen. (Table 1)

Table 1

Test Results Indicative of the Disorder
TSH Free T4 Total T3
<0.1 mclUnits/mL >1.8 ng/dL >181 ng/dL

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications - OTC drugs or Herbals - that might affect the lab results?

Hospitalized patients may have transiently low or high TSH. Most frequently, TSH levels are suppressed during the acute phase of illness or during treatment on glucocorticoid or dopamine therapy. Other drugs like amiodarone can increase TSH levels. Critically ill euthyroid patients may be differentiated from hyperthyroid ill patients, because the latter show profoundly low TSH values less than 0.01 mU/L. Increases in T3 and T4 may occur with the ingestion of large quantities of exogenous thyroid hormone.

What Lab Results Are Absolutely Confirmatory?

Although no lab test is absolutely confirmatory for thyroid storm, the pattern of low TSH and elevated T3/T4 suggests hyperthyroidism and compliments the clinical manifestations of thyroid storm described. The presence of antithyroid peroxidase (TPO) and thyrotropin-binding inhibitory immunoglobulins (TBII) antibodies confirms an autoimmune etiology.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

Thyroid storm represents an extreme and acute form of hyperthyroidism. Generally, a diagnosis of hyperthyroidism is made when a pattern of low TSH and elevated free T4 is seen. Because thyroid storm is usually associated with a patient's ongoing hyperthyroidism and very frequently is associated with Grave’s disease, the relevant laboratory values include those used to diagnose hyperthyroidism and Grave’s disease.

Antimicrosomal antibodies are directed against thyroid cell microsomes with reactivity approaching 100% in adults and 85% of patients with Grave’s disease. Low titers can be seen in healthy individuals. Thyroid peroxidase is the primary autoantigen of microsomes, and testing for anti-TPO antibodies may provide greater sensitivity and specificity over assays for microsomal antibodies in detecting autoimmune thyroiditis. Like antimicrosomal antibodies, anti-TPO antibodies are found in the majority of individuals with Grave’s disease. Low levels may still be detected in healthy individuals and are seen increasingly in elderly patients.

Anti-thyrotropin-receptor antibodies (TRAbs) bind thyroid cell membranes near the TSH receptor site. Like anti-TPO antibodies, the presence of these immunoglobulins is indicative of one of a number of thyroid autoimmune disorders, including Grave’s disease.

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications - OTC drugs or Herbals - that might affect the lab results?

The clinical setting must be considered when interpreting laboratory tests for hyperthyroidism. As mentioned, suppression of TSH may occur in ill, hospitalized patients, and pharmacotherapeutics can inflate TSH levels. Amiodarone can increase TSH levels. Critically ill euthyroid patients may be differentiated from hyperthyroid ill patients, because the latter show profoundly low TSH values less than 0.01 mU/L. Increases in T3 and T4 may occur with the ingestion of large quantities of exogenous thyroid hormone.

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