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    Also known as

    Other names:

    • MK 677, MK-677 and MK677
    • LUM-201

    Brand names:

    • Nutrobal

     

    Therapeutic Goods Administration (TGA) approval

    Ibutamoren (MK 677) is not listed on the Australian Register of Therapeutic Goods (ARTG).1

     

    World Anti-Doping Code Prohibited List 2025

    Ibutamoren is listed under S2.2.4 Peptide Hormones, Growth factors, Related Substances and Mimetics (prohibited at all times).2

    This substance meets at least two of the following three criteria, as determined by the World Anti-Doping Agency (WADA);

    • It has the potential to enhance or does enhance sports performance
    • It poses an actual or potential health risk to the athlete
    • It violates the spirit of sport (as defined in The Code).

    The Prohibited List is updated yearly after consultation with scientific, medical, and anti-doping experts to ensure that it aligns with the latest medical and scientific evidence and doping trends.

     

    What is it?

    Ibutamoren (MK 677) is an orally active growth hormone secretagogue (GHS)3 that has a long biological effect. 

    Ibutamoren is technically considered a poison.

     

    Uses

    Ibutamoren has not been approved for human use.4 

    This means that there is no toxicity data, and the extent of potential side effects remain unknown. 

     

    How does it work?

    Ibutamoren stimulates secretion of growth hormone (GH) and insulin-like growth factor 1 (IGF-1)5, which increase protein synthesis for muscle growth and increase metabolic rate, to increase fat loss.

    MK 677 is marketed online as a substance to ‘build muscle’.  

     

    Adverse Health Effects and Risk

    Side effects of Ibutamoren vary in severity based on several factors. 

    Some anecdotal negative effects that may occur include;

    • increased appetite
    • water retention
    • muscle cramps
    • headaches
    • fatigue and;
    • mood changes (manifest as anxiety or mood swings).

    Ibutamoren may also have the potential to negatively affect your body’s physiological responses.6 

    Results of a few clinical safety studies were stopped due to concerns that Ibutamoren increases the risk of;

    • congestive heart failure
    • insulin sensitivity
    • glucose tolerance and;
    • bone mineral density.

     

    What if an athlete has been prescribed Ibutamoren for a medical condition?

    A Therapeutic Use Exemption (TUE) would not be granted for the use of Ibutamoren.

    References

    1. Australian Register of Therapeutic Goods (ARTG). [online] Therapeutic Goods Administration (TGA)
      Available at: https://www.tga.gov.au/resources/artg?keywords=ibutamoren
    2. WADA (2025). The Prohibited List. [online] World Anti-Doping Agency
      Available at: https://www.wada-ama.org/en/prohibited-list 
    3. Codner E, Cassorla F, Tiulpakov AN, Mericq MV, Avila A, Pescovitz OH, Svensson J, Cerchio K, Krupa D, Gertz BJ, Murphy G. Effects of oral administration of ibutamoren mesylate, a nonpeptide growth hormone secretagogue, on the growth hormone–insulin‐like growth factor I axis in growth hormone–deficient children. Clinical Pharmacology & Therapeutics. 2001 Jul;70(1):91-8
    4. 1.4. Ibutamoren | Therapeutic Goods Administration (TGA)
    5. Sigalos JT, Pastuszak AW. The safety and efficacy of growth hormone secretagogues. Sexual medicine reviews. 2018 Jan;6(1):45-53
    6. Smith RG, Thorner MO. Growth hormone secretagogues as potential therapeutic agents to restore growth hormone secretion in older subjects to those observed in young adults. The Journals of Gerontology: Series A. 2023 Jun 1;78(Supplement_1):38-43

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