Comparison of serum cortisol measurement by immunoassay and liquid chromatography-tandem mass spectrometry in patients receiving the 11β-hydroxylase inhibitor metyrapone.

Abstract

The accurate measurement of cortisol by immunoassay is compromised by the potential for cross-reactivity of reagent antibodies with structurally related steroids present in serum. This susceptibility is potentiated when normal steroid metabolism is altered pharmaceutically by antisteroidogenic drugs utilized in the management of Cushing's syndrome to moderate cortisol production. The clinical implications of falsely elevated cortisol results include over-treatment and unrecognized hypoadrenalism. To investigate the effect of the 11β-hydroxylase inhibitor metyrapone on serum cortisol assay, a comparison of measurement by immunoassay versus liquid chromatography-tandem mass spectrometry (LC-MS/MS) was conducted.