Laboratory Tests Necessary in the Management of Thyroid Storm
In thyroid storm, essential laboratory tests include serum-free triiodothyronine (FT3), free thyroxine (FT4), and thyroid stimulating hormone (TSH) levels to confirm the diagnosis, though treatment should not be delayed waiting for results. 1
Core Laboratory Tests for Diagnosis
- Thyroid Function Tests: Low to undetectable TSH (<0.01 mU/L) with elevated FT4 and/or FT3 levels are the hallmark laboratory findings in thyroid storm 2
- Complete Blood Count: Essential to evaluate for potential agranulocytosis (a side effect of thioamide therapy) and to assess for infection as a potential trigger 1
- Liver Function Tests: Important to assess hepatic dysfunction, which can be a feature of thyroid storm 3
- Basic Metabolic Panel: To evaluate electrolyte abnormalities and renal function 4
Additional Laboratory Tests
- Thyroid Receptor Antibody (TRAb): Particularly if Graves' disease is suspected as the underlying etiology 2
- Thyroid Peroxidase (TPO) Antibody: Can help distinguish between different causes of thyrotoxicosis 1
- Blood Cultures: Important when infection is suspected as a triggering factor for thyroid storm 4
- Cardiac Biomarkers: To assess for cardiac involvement, as cardiogenic shock within 48 hours of ICU admission is independently associated with mortality 4
Laboratory Monitoring During Treatment
- Serial Thyroid Function Tests: To monitor response to therapy 1
- Complete Blood Count: Regular monitoring for potential agranulocytosis, which typically presents with sore throat and fever in patients on thioamide therapy 1
- Liver Function Tests: To monitor for hepatitis, a potential side effect of thioamide therapy 1
- Platelet Count: To monitor for thrombocytopenia, another potential side effect of thioamide therapy 1
Special Considerations
- Pregnancy: In pregnant women with thyroid storm, the same laboratory tests apply, with additional monitoring of fetal status through ultrasound examination, nonstress testing, or biophysical profile 1
- Therapeutic Plasma Exchange: For refractory cases, monitoring of thyroid hormone levels before and after plasma exchange sessions may be necessary 5
Common Pitfalls
- Delaying Treatment: Laboratory confirmation is important but treatment should never be delayed while waiting for test results in suspected thyroid storm 1, 3
- Missing Precipitating Factors: Laboratory tests should also target potential triggers such as infection, which is a common precipitant of thyroid storm 3
- Overlooking Mimics: Several conditions can mimic thyroid storm, including sepsis, sympathomimetic overdose, and serotonin syndrome; appropriate laboratory tests should be ordered to rule out these conditions 3
Remember that thyroid storm is a clinical diagnosis based on a combination of signs, symptoms, and laboratory findings. No single laboratory value definitively establishes the diagnosis, making clinical judgment crucial 3.