MK-677 (lbutamoren Mesylate)


MK-677 (lbutamoren Mesylate)

  • First described in 1995.
  • It is a growth hormone secretagogue which essentially means it stimulates growth hormone secretion.
  • It is part of a class of drugs called it belongs to the GHRP (Growth Hormone Releasing Peptides).
  • MK-677 is a third generation GHRP because it can be taken orally.
  • MK-677 mimics ghrelin (the hunger hormone).
  • In many studies on children and the elderly it has shown to increase growth hormone and IGF-1 (Insulin like growth factor 1 – more on this to come) significantly. Furthermore, it was shown to increase lean body tissue, increase energy expenditure (metabolic rates increase) and improved sleep quality.
  • MK-677 closely resembles GHRP-6.
  • The issue with MK-677 is that it is not selective for growth hormone stimulation. It increases prolactin serum levels, cortisol and ACTH (adrenocorticotropic hormone).
  • The postulated theory behind this is the fact that MK-677 works in the anterior pituitary gland Growth Hormone Cells and there is spill over onto other closely related cells like prolactin and ACTH cells.
  • The above spill over effects are unlikely to be significant.
  • It is banned by WADA.

Side Effects

  • Increased appetite. This appetite might be of benefit to those looking to gain weight.
  • Fatigue, although MK-677 does improve sleep, day time sleepiness is a common side effect.
  • Increased fasted blood sugar levels are common and this must be looked out for by self-testing or visiting your doctor/pharmacy/clinic. This is secondary to impaired insulin sensitivity. The damaging effects of raised blood sugar levels will be discussed in a separate post.
  • Oral Hypoglycaemics may be necessary (e.g., Metformin 500mg taken in the evening after dinner).
  • Water retention is very common which may result in high blood pressure. Possible ways to avoid this involve the use of anti-hypertensives (specifically low dose diuretics – you must consult with your doctor first).
  • Joint pain and carpal tunnel syndrome do occur, possibly secondary to the oedema or overgrowth of connective tissue.
  • Paraesthesia (pins and needles) have also been reported. Could be secondary to nerve compression by the oedema or uncontrolled/elevated blood sugar levels.
  • The side effects noted above are not as commonly seen as they are in though using pure Growth Hormone since MK-677 alone does not increase growth hormone above the normal range.


  • The half life of this drug in dogs is 4 to 6 hours.
  • 10 mg daily has been compared to 25mg daily in a multitude of studies. 25 mg in elderly patients seemed to greatly increase growth hormone and IGF-1 levels to that of young adults.
  • Therefore, doses range from 10 to 25 mg orally daily.
  • Individuals prefer to take the drug in the evening in order to avoid the hunger and fatigue that may occur if taken in the morning.
  • This drug is used by bodybuilders to increase appetite.
  • This drug also can aid in fat loss if calories are controlled.
  • Cycles tend to range from 3 to 6 months in duration.
  • Combination cycles are popular. CJC-1295 or Sermorelin are used to compliment actions of MK-677 and enhances release of growth hormone.

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