Falsely undetectable TSH in a euthyroid patient.

BACKGROUND: Measuring thyroid hormone levels is essential and helpful in the diagnosis of thyroid diseases. CASE PRESENTATION: We had a patient with undetectable serum TSH level by the Siemens immunoassay, whereas by ELISA and Roche-Abott immunoassay, serum level of TSH was in the normal range. CONCLUSION: If the result of TSH level revealed very low or undetectable through one specific method, it should not be considered necessarily as a symptom of hyperthyroidism. It is to be requested to measure by the other methods with other devices too.