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Hormones & growth

MK-677 (Ibutamoren)

The oral ghrelin mimetic - activates the body's own growth hormone axis with one tablet per day.

2 min read 9 sources

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White tablet bottle with a black TPD label for MK-677 (ibutamoren) on a white podium, next to it a large blue 3D molecule in a bright lab
Phase 3 · not approved

Summary

At a glance

Sources checked on 26 Oct 2026

Fat-free mass in 12 months
+1.1 kg

healthy older adults, placebo -0.5 kg, strength and function unchanged1

IGF-1 after 12 months
+72.9 %

563 people with Alzheimer's, progression was not slowed4

Deviations from normal sleep
8 %

young adults, highest study dose, on placebo 42 percent6

Fasting blood sugar
+0.3 mmol/l

on average over 12 months, insulin sensitivity fell1

Phase 3 in the registry
2 trials

as LUM-201 in childhood growth hormone deficiency, one recruiting, as of 26 Oct 20268

  • Ibutamoren is an agonist at the ghrelin receptor GHSR that works as a tablet. It amplifies the natural pulses of growth hormone.93
  • In healthy older adults growth hormone and IGF-1 rose to the levels of young adults. Fat-free mass rose by 1.1 kg in 12 months, strength and function did not change.1
  • Several trials showed no clinical benefit despite higher IGF-1: neither in Alzheimer's nor in most measures after a hip fracture.42
  • Common were more appetite, mild fluid retention and muscle pain. Blood sugar rose. The hip fracture trial ended early because of heart failure in a few patients.132
  • Ibutamoren is not approved (as of October 2026). Everything here is the state of research, not a recommendation.89
Profile

Updated June 2026

How long does it stay in the body?

Share left after one dose, calculated with a half-life of ~24 hours

Half-life ~24 hours
After 48 hours: 25 %
Hour 24 · 50 %Hour 48 · 25 %Hour 72 · 12.5 %Hour 120 · 3.1 %

Simplified model without an absorption phase, half-life from the TPD lexicon.

Class
Ghrelin receptor agonist

GHSR, orally active

Use
Oral

1 tablet per day

Half-life
about 24 hours
Status
Research

phase 2 in trials, not approved

Sizes
10 to 15 mg

2 sizes in the shop

Contents 13 sections
  1. At a glance
  2. What is MK-677?
  3. How it works
  4. How to take it
  5. Dosing
  6. What the research shows
  7. Research status
  8. Side effects
  9. Storage
  10. Related compounds
  11. FAQ
  12. Glossary
  13. Sources

What is MK-677?

MK-677 (also Ibutamoren or MK-0677) is an oral non-peptide ghrelin receptor agonist (GHSR). It mimics the action of ghrelin - the body's hunger hormone - and triggers growth hormone (GH) release from the pituitary.

Unlike injectable GH releasers (CJC-1295, Ipamorelin), MK-677 is orally active and has a long half-life. One tablet per day is enough for stable GH pulses over 24 hours.

Comparison

Three points on the growth hormone axis

Ibutamoren acts at the ghrelin receptor, GHRH analogues at the GHRH receptor, growth hormone itself at the GH receptor. Tap a card to open its entry.

Ghrelin agonist, tablet MK-677 (Ibutamoren) GHSR GHRH-R GH-R 1 of 3 targets
GHRH analogue Sermorelin GHSR GHRH-R GH-R 1 of 3 targets GHRH analogue Tesamorelin GHSR GHRH-R GH-R 1 of 3 targets Growth hormone itself HGH 191AA (Somatropin) GHSR GHRH-R GH-R 1 of 3 targets

Simplified from the targets in ChEMBL. Ibutamoren and the GHRH analogues stimulate the body's own release, growth hormone replaces it. 9

How it works

MK-677 activates the GHSR (Growth Hormone Secretagogue Receptor) in the hypothalamus and pituitary. That produces two main effects:

  • Stronger GH pulses: the pituitary releases more growth hormone, which prompts the liver to produce IGF-1.
  • Appetite increase: ghrelin is the body's hunger hormone - more appetite is the direct consequence.

Both effects together make MK-677 the classic bulking tool: more growth hormone plus more hunger plus deeper sleep.

Where it acts

Where ibutamoren acted in studies

Tap a point or a card. Colour = ghrelin receptor, grey = observed in studies.

  1. Pituitary and brain

    Growth hormone pulses amplified, more deep and REM sleep3

    GHSR
  2. Liver

    IGF-1 rose to the levels of young adults1

    Observed in trials
  3. Muscle and body

    Fat-free mass +1.1 kg in 12 months, strength unchanged1

    Observed in trials
  4. Blood sugar

    Fasting blood sugar rose, insulin sensitivity fell1

    Observed in trials
  5. Heart

    After hip fracture heart failure in a few patients, trial stopped2

    Observed in trials

Targets in the ChEMBL database9

Compound CHEMBL2105872: one recorded mechanism, agonist with direct binding to the human receptor.

Ghrelin receptor (GHSR)
Gene
GHSR
UniProt
Q92847
ChEMBL
CHEMBL4616
Action
Agonist, direct binding
Blue molecules docking onto glassy receptors connected to a glowing glass gland
Ibutamoren activates the ghrelin receptor and the pituitary releases more growth hormone. Symbolic image.

How to take it

Oral tablet, once per day. Ideally in the evening before bed.

  • 1 tablet with some water.
  • Before bed makes sense - GH pulses occur naturally at night and MK-677 amplifies them.
  • Plus: mildly sedating, improves sleep quality.

With evening dosing the noticeable hunger comes in the morning and during the day - exactly where it's useful for bulking.

White tablet bottle with a black TPD label for MK-677, next to it three tablets and a glass of water
Tablet with some water. Symbolic image.

Dosing

Dosing

Dosing, titration and syringe

Loading the dosing information …

  • Getting started and stepping up, drawn as a staircase
  • Units on the U-100 syringe for every step
  • How long one vial lasts
MK-677 bottle with three tablets in a small dish next to a glass of water and a closed notebook
Symbolic image.

What the research shows

MK-677 is well researched in mid-size human studies:

  • Nass et al. 2008: 25mg per day over 2 years sustainably elevated GH and IGF-1, plus moderate gains in lean mass.
  • Adunsky et al. 2011: after hip fracture, 25mg per day raised IGF-1, but most functional measures did not improve. The trial was stopped early over a safety signal (congestive heart failure in a limited number of patients).

Phase-3 trials for sarcopenia and growth disorders ran but didn't lead to approval. Currently MK-677 runs as a research compound and in off-label use.

Study results

What the trials measured

Interactive: switch tabs, tap points, show or hide arms. Arms are named relative to each other, no dosing advice.

Body composition after 12 months1

65 healthy adults aged 60 to 81, change in kg

Fat-free mass1
Placebo -0.5 kg
Ibutamoren (25 mg, highest study dose) +1.1 kg
Cell mass (intracellular water)1
Placebo -1.0 kg
Ibutamoren (25 mg, highest study dose) +0.8 kg
Limb fat1
Placebo +0.2 kg
Ibutamoren (25 mg, highest study dose) +1.1 kg
Body weight1
Placebo +0.8 kg
Ibutamoren (25 mg, highest study dose) +2.7 kg

Values from the abstract (limb fat on placebo 0.24 kg). Visceral and total fat did not change significantly. More fat-free mass did not bring better strength or function.

IGF-1 in healthy older adults3

Mean in µg/l, highest study dose, 32 participants aged 64 to 81 years

0 Week 0Week 2Week 4 +265.0 µg/l

Ibutamoren (25 mg, highest study dose): Week 0 +141.0 µg/l, Week 2 +219.0 µg/l, Week 4 +265.0 µg/l.

After 4 weeks IGF-1 was in the range of young adults. Mean 24-hour growth hormone rose by 97 percent after 2 weeks, the number of pulses stayed the same.

Rise in IGF-1 per trial45

Change in percent, highest study dose

Alzheimer's, 6 weeks4
Ibutamoren (25 mg, highest study dose) +60.1%
Alzheimer's, 12 months4
Ibutamoren (25 mg, highest study dose) +72.9%
Obese men, 8 weeks5 about 40 percent in the abstract
Ibutamoren (25 mg, highest study dose) +40.0%

IGF-1 rose clearly in all trials. In Alzheimer's this brought no benefit, in obesity fat-free mass rose while fat did not fall.

Deviations from normal sleep6

Young adults, 7 days each, share of nights with deviations

Sleep deviations6
Placebo 42%
Ibutamoren (25 mg, highest study dose) 8%

At the highest study dose deep sleep (stage IV) lengthened by about 50 percent and REM sleep by more than 20 percent. In older adults REM sleep rose by almost 50 percent.

Nitrogen balance during calorie restriction7

8 healthy adults, second diet week, grams per day

Nitrogen balance7
Placebo -1.48 g
Ibutamoren (25 mg, highest study dose) +0.31 g

On placebo the body kept losing protein, with ibutamoren the balance was even. IGF-1 was 264 instead of 188 ng/ml.

Stainless steel lab cart with a glass stomach model and a bone, a glowing crescent moon behind it
Studies on body, bone, sleep and IGF-1. Symbolic image.

Research status

Where the research stands

From the first trials in the 1990s to the phase 3 trials as LUM-201 in children with growth hormone deficiency: every registered trial with status and participants. As of 26 Oct 2026. 8

  1. Preclinical Early studies: growth hormone pulses amplified
  2. Phase 1 no registered trial
  3. Phase 2 10 trials, 6 completed, 1 stopped early
  4. Phase 3 2 trials, 0 completed
  5. Approval not yet
300 participants in phase 3 Planned figures for running trials Not approved yet. ChEMBL lists ibutamoren with phase 2 as the highest phase, the registry has listed two phase 3 trials under the name LUM-201 since 2026.8
Show all 13 trials on a timelineHide timeline 7 completed 5 running 1 stopped early 0 with results
Phase 2
Phase 3
Without phase

Bar: start to primary endpoint (planned for running trials). Green = completed, blue = progress until 26 Oct 2026, grey = stopped early.

Side effects

  • Appetite increase: wanted for bulking, unwanted in a cut.
  • Water retention: classic GH symptom, especially in hands and face.
  • Sleep depth: usually improved, some report vivid dreams in the first weeks.
  • Blood sugar: can rise slightly because GH causes insulin resistance. Caution with diabetes or prediabetes.

Storage

Dry and cool, out of reach of children. Keep original container closed.

Three white capsule bottles on a bright shelf next to a folded light blue towel
Store dry and cool, out of reach of children. Symbolic image.
Level · MK-677 (Ibutamoren)

How the level builds up

One dose per day: each dose adds to what is left of the previous one.

Lexicon: Oral, 1 tablet per day
Peak 2×Trough 1×
Day 4 · 5. dose
1.94× of the first dose
Plateau
from Day 4

97 % of the plateau after dose 5

Peak
2×

of the first dose

Trough
1×

before the next dose

Simplified model, values relative to the first dose, no dosing information. Dashed: the first dose alone, green: the plateau.

Related

Related compounds

Same receptors or a different path: all in the TPD lexicon.

MK-677 (Ibutamoren)
Ipamorelin Also at the ghrelin receptor, as an injection GHRP-6 Also at the ghrelin receptor, as an injection GHRP-2 Also at the ghrelin receptor, as an injection Sermorelin Different path: GHRH receptor Tesamorelin Different path: GHRH receptor HGH 191AA (Somatropin) Growth hormone itself

FAQ

Common questions about MK-677 (Ibutamoren)

Short answers, each backed by the sources below.

Is ibutamoren approved?

No, as of 26 October 2026 there is no approval. ChEMBL lists phase 2 as the highest phase. The registry lists two phase 3 trials under the name LUM-201 in children with growth hormone deficiency, one recruiting, the other not yet.89

How does ibutamoren work?

According to ChEMBL it binds directly to the ghrelin receptor GHSR and activates it. In older adults mean 24-hour growth hormone rose by 97 percent because existing pulses got higher, not more frequent. IGF-1 was in the range of young adults after 4 weeks.93

Does ibutamoren build muscle?

Fat-free mass rose in trials: by 1.1 kg in 12 months in healthy older adults (placebo -0.5 kg). In obese men it rose within 8 weeks as well. Strength and function did not improve in the older adults, though. Part of the gain can be water.15

What happens to sleep?

In a small trial with young adults the highest study dose lengthened deep sleep by about 50 percent and REM sleep by more than 20 percent. Deviations from normal sleep fell from 42 to 8 percent. In older adults REM sleep rose by almost 50 percent.6

Why was there no benefit despite higher IGF-1?

In Alzheimer's IGF-1 rose by 72.9 percent while disease progression did not change. After a hip fracture IGF-1 also rose, but most function measures did not improve. The trial was stopped early because of heart failure in a few patients.42

Which side effects were seen?

Most often more appetite that eased after a few months, plus mild fluid retention in the legs and muscle pain. Fasting blood sugar rose and insulin sensitivity fell. Cortisol rose slightly in the long-term trial.13

How long has ibutamoren been studied in humans?

The longest trial ran 2 years in healthy older adults and confirmed the 12-month results. The Alzheimer's trial ran 12 months with 563 participants.14

Glossary

Terms explained briefly

Dotted words in the text open these explanations directly.

Fat-free mass
Body weight without fat: muscle, bone, organs and water. Water can make up part of the gain.
GH secretagogue
Substance that stimulates the body's own growth hormone release instead of replacing it.
Ghrelin
Hormone from the stomach that triggers hunger and stimulates growth hormone release.
Ghrelin receptor (GHSR)
Receptor in the pituitary and brain that the hunger hormone ghrelin binds to. Activating it releases growth hormone.
Growth hormone (GH)
Pituitary hormone released in pulses, mainly at night. It stimulates IGF-1 production in the liver.
Half-life
Time after which only half of a substance is left in the blood.
Hypothalamus
Control centre in the brain that directs the pituitary.
IGF-1
Insulin-like growth factor 1, mediates many effects of growth hormone. Used as a marker of the GH axis.
Insulin resistance
Cells respond less to insulin and blood sugar rises more easily.
Pituitary gland
Gland at the base of the brain that produces growth hormone among other hormones.
Placebo
Dummy preparation without active substance. Comparing against it shows what is due to the substance itself.

Evidence

Sources

Show all 9 sourcesHide sources 7 Studies1 Trial registry1 Database checked 26 Oct 2026

Studies

  1. Two years of ibutamoren in healthy older adults

    Nass et al., Annals of Internal Medicine, 2008

    DOI 10.7326/0003-4819-149-9-200811040-00003 PMID 18981485
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  2. Phase 2b trial after hip fracture, stopped early

    Adunsky et al., Archives of Gerontology and Geriatrics, 2011

    DOI 10.1016/j.archger.2010.10.004 PMID 21067829
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  3. Growth hormone and IGF-1 in healthy older adults over 4 weeks

    Chapman et al., Journal of Clinical Endocrinology and Metabolism, 1996

    DOI 10.1210/jcem.81.12.8954023 PMID 8954023
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  4. No effect on Alzheimer's progression

    Sevigny et al., Neurology, 2008

    DOI 10.1212/01.wnl.0000335163.88054.e7 PMID 19015485
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  5. Eight weeks in obese men

    Svensson et al., Journal of Clinical Endocrinology and Metabolism, 1998

    DOI 10.1210/jcem.83.2.4539 PMID 9467542
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  6. Sleep quality on ibutamoren

    Copinschi et al., Neuroendocrinology, 1997

    DOI 10.1159/000127249 PMID 9349662
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  7. Protein loss during calorie restriction reversed

    Murphy et al., Journal of Clinical Endocrinology and Metabolism, 1998

    DOI 10.1210/jcem.83.2.4551 PMID 9467534
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed

Trial registry

  1. All trials on ClinicalTrials.gov

    ClinicalTrials.gov, U.S. National Library of Medicine

    Checked 26 Oct 2026 via ClinicalTrials.gov API v2

Database

  1. Ibutamoren and GH axis compounds in ChEMBL

    ChEMBL, EMBL-EBI (CHEMBL2105872, CHEMBL13817, CHEMBL1201490, CHEMBL2111290, CHEMBL1201621)

    Checked 26 Oct 2026 via ChEMBL

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