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.
This study investigated the detection of ibutamoren (MK-677), a growth hormone secretagogue, in human hair samples to aid forensic interpretation of anti-doping hair test results. Two scenarios were examined: (1) a single 10 mg oral dose administered to a male volunteer, with hair collected 4 weeks later; and (2) hair collected from an individual who had consumed 60 capsules of 10 mg ibutamoren over 90 days, also sampled 4 weeks after discontinuation. Researchers developed a liquid/liquid extraction method using bicalutamide-D4 as an internal standard, with a validated linear range of 0.5–250 pg/mg and a limit of detection of 0.1 pg/mg. The study found that a single 10 mg dose produced a positive hair result at 1.3 pg/mg in the 0–1 cm segment, while the prolonged-use scenario yielded 224 pg/mg in the 0–4 cm segment. The authors conclude that these findings establish, for the first time, ibutamoren's incorporation into human hair and provide reference concentration ranges to support interpretation of hair test results in anti-doping proceedings. Key limitations include the very small sample size (essentially two subjects) and the non-controlled nature of the second case.
Why this grade: The study involves only two human subjects with no control group or randomization, making findings preliminary and insufficient to draw broad clinical or forensic conclusions beyond establishing proof-of-concept detection thresholds.
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-D 4 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 (R 2 = 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.
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