Diagnostic Testing for Thyroid Storm in a 34-Year-Old Male
Immediate Core Laboratory Tests (Do Not Delay Treatment)
Order serum-free T3 (FT3), free T4 (FT4), and TSH immediately to confirm thyrotoxicosis, but initiate treatment without waiting for results. 1 Thyroid storm is primarily a clinical diagnosis—laboratory confirmation supports but should never delay management. 2, 3
Essential Initial Panel
Thyroid function tests: FT3, FT4, and TSH are essential to confirm the diagnosis, though you will typically find markedly elevated FT3 and FT4 with suppressed or undetectable TSH. 1, 4 No single laboratory value establishes thyroid storm—the diagnosis rests on clinical criteria combined with biochemical thyrotoxicosis. 2, 3
Complete blood count (CBC): Critical for detecting agranulocytosis (a life-threatening complication of antithyroid drugs if previously treated) and identifying infection as a potential precipitating trigger. 1 Infection is one of the most common triggers for thyroid storm. 2
Comprehensive metabolic panel: Assess for hepatic dysfunction (elevated transaminases, bilirubin), acute kidney injury (elevated creatinine), and electrolyte abnormalities—all common manifestations of multiorgan decompensation in thyroid storm. 5 Severe lactic acidosis may be present in cases with multiorgan failure. 5
Liver function tests: Monitor for hepatitis, which can occur both as a complication of thyroid storm itself and as a side effect of thionamide therapy. 1, 5
Additional Diagnostic Studies
Thyroid peroxidase (TPO) antibodies: Helps distinguish autoimmune causes (Graves' disease) from other etiologies of thyrotoxicosis such as painless thyroiditis or toxic nodular disease. 1, 6 This is particularly important because painless destructive thyroiditis can rarely cause thyroid storm and requires different management than Graves' disease. 6
TSH receptor antibodies (TRAb): If TPO antibodies are ordered, consider TRAb to confirm Graves' disease, though absence does not exclude thyroid storm from other causes. 6
Coagulation studies (PT/INR, PTT, fibrinogen, D-dimer): Screen for disseminated intravascular coagulation (DIC), which can complicate severe thyroid storm with multiorgan dysfunction. 5
Arterial blood gas: Evaluate for severe lactic acidosis and respiratory status in critically ill patients. 5
Troponin and BNP: Assess for cardiac injury and heart failure, as thyroid storm commonly causes cardiovascular decompensation including acute pulmonary edema and heart failure. 2, 5
Blood cultures: If infection is suspected as the precipitating trigger, obtain before initiating antibiotics. 2
Ongoing Monitoring During Treatment
Serial thyroid function tests: Monitor response to antithyroid therapy, though clinical improvement precedes normalization of thyroid hormones. 1
Serial CBC: Continue monitoring for agranulocytosis development during thionamide therapy. 1
Platelet count: Monitor for thrombocytopenia, another potential complication of thionamide therapy. 1
Repeat liver function tests: Track hepatic function during treatment with thionamides. 1
Critical Pitfalls to Avoid
Never delay treatment while waiting for laboratory confirmation. 1, 2 Thyroid storm carries 10% mortality even with treatment, and any delay worsens outcomes. 3 The diagnosis is clinical—use the Burch-Wartofsky point scale (≥45 points highly suggestive, ≥25 points suggestive) or Japan Thyroid Association criteria to guide your clinical assessment. 2
Do not assume Graves' disease is the only cause. 6 Painless thyroiditis, toxic multinodular goiter, and even iodine-induced thyrotoxicosis (Jod-Basedow phenomenon) can precipitate thyroid storm. 4, 6 If findings are inconsistent with Graves' disease (negative TRAb, no radioiodine uptake), consider alternative etiologies. 6
Recognize that multiorgan dysfunction indicates severe disease. 5 The presence of acute liver failure, acute kidney injury, DIC, or heart failure signals life-threatening thyroid storm requiring intensive care management. 5 These patients need aggressive supportive care alongside definitive antithyroid treatment.