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Reminder of important clinical lesson
First case report of testosterone assay-interference in a female taking maca (Lepidium meyenii)
  1. L Srikugan1,
  2. A Sankaralingam2,
  3. B McGowan3
  1. 1Department of Diabetes & Endocrinology, Guy’s & St Thomas NHS Trust, London, UK
  2. 2Department of Chemical Pathology, Guy’s & St Thomas NHS Trust, London, UK
  3. 3Department of Endocrinology, Guy’s & St Thomas NHS Trust, London, UK
  1. Correspondence to L Srikugan, shil0611{at}


A young female with prolonged intermenstrual bleeding was found to have raised total plasma testosterone of 25.8 nmol/l (NR<2.9 nmol/l) using the Roche Elecsys Testosterone I immunoassay without clinical features of virulisation. Few months ago investigations for lethargy and low libido had shown normal total testosterone of 0.8 nmol/l. Further history revealed that she was using maca extract to improve her lethargy and low libido. Maca is traditionally used for its aphrodisiac and fertility-enhancing properties. Maca use has not been shown to affect serum testosterone in mice and human studies.

Immunoassay interference with maca was suspected. Testosterone immunoassays use monoclonal antibodies specifically directed against testosterone. They are prone to interference from androgenic compounds. Reanalysis of the original serum sample using Elecsys Testosterone II assay, a higher affinity assay, revealed a total testosterone level of 2.9 nmol/l. It is important to exclude assay interference when testosterone level is greater than 5 nmol/l without supportive clinical signs.

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  • Competing interests None.

  • Patient consent Obtained.