. 2026 Jan 1:578:120578.
doi: 10.1016/j.cca.2025.120578. Epub 2025 Aug 27.
Affiliations
PMID: 40882886 DOI: 10.1016/j.cca.2025.120578
Knowing the minimal detectable dose can facilitate the interpretation of a hair test result: II. Case example with ibutamoren (MK-677), a growth hormone secretagogue
Pascal Kintz et al. Clin Chim Acta. 2026.
Abstract
Background and aims: On numerous occasions during hearings at the Court of Arbitration for Sport (CAS), it has been advocated by the anti-doping authorities that the results of hair tests should be interpreted with utmost precautions. This was due to the lack of data for the interpretation of the results. In particular, the knowledge of the expected concentrations after a single exposure and after a doping regimen can be missing.
Material and method: A single 10 mg dose of ibutamoren, a growth hormone secretagogue, was administered to a male volunteer and his hair was collected 4 weeks after exposure. In addition, the hair specimen of a subject who took 60 capsules of 10 mg ibutamoren over 90 days was collected 4 weeks after drug discontinuation. After addition of bicalutamide-D4 used as internal standard and incubation in phosphate buffer pH = 9.5, 25 mg of hair samples were extracted and purified by liquid/liquid extraction.
Results: Linearity was verified from 0.5 to 250 pg/mg (R2 = 0.9961). The limit of detection was 0.1 pg/mg. After a single exposure to 10 mg, ibutamoren tested positive at 1.3 pg/mg (segment 0 to 1 cm). After consumption of 60 capsules at 10 mg (whole vial), the 0 to 4 cm hair segment of a user for enhancement of athletic performances tested positive at 224 pg/mg, highlighting for the first time the incorporation in hair of this molecule.
Conclusion: The interpretation of the findings of ibutamoren in human hair can be established in the light of these new data as the minimal detectable dose has been established, as well as the range of concentrations after a regimen of 60 days for performance enhancement.
Keywords: Contamination; Doping; Hair; Ibutamoren; MK-677.
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Conflict of interest statement
Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.