Falsely Elevated TSH

Can TSH be falsely elevated? Thyroid function tests (immunoassays) are subject to errors. As such, when there is a disagreement between clinical and biochemical assessment of a patient’s thyroid status, a laboratory error should be considered. It is worthy to note that some immunoassays use a biotin-steptavidin signaling system. Thus patients on supraphysiological doses of biotin (upwards of 10mg daily instead of the physiological dose range of 30-100mcg) are likely to present with discordant laboratory and clinical features.

Causes of falsely elevated TSH

  • Macro TSH
  • Anti-animal antibodies
  • Heterophilic antibodies

Falsely elevated free T4

  • Nonesterified free fatty acids
  • Heterophilic antibodies
  • Iodothyronine antibodies


Favresse J, Burlacu MC, Maiter D, Gruson D. Interferences With Thyroid Function Immunoassays: Clinical Implications and Detection Algorithm. Endocr Rev. 2018 Oct 1;39(5):830-850.

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