Apparent Hyperandrogenemia Due to Immunoassay Interference Resolved by Liquid Chromatography-Tandem Mass Spectrometry.

Testosterone is commonly measured using immunoassays in clinical practice; however, these methods are subject to analytical interference in both men and women. In women, due to physiologically lower testosterone levels, even modest elevations may appear pathologic and complicate the diagnostic process. We report a case of a 43-year-old female patient with persistently elevated serum testosterone levels documented across multiple institutions. Despite comprehensive endocrine evaluations and imaging studies, no underlying cause could be identified. Ultimately, liquid chromatography-tandem mass spectrometry (LC-MS/MS) confirmed normal testosterone levels, indicating that the falsely elevated testosterone was due to assay interference. Further analysis using a protein precipitation assay revealed the presence of heterophilic antibodies, which were responsible for the assay interference. This case highlights the importance of considering immunoassay artifacts in the differential diagnosis of unexplained biochemical hyperandrogenism, particularly in the absence of clinical signs of androgen excess.