MK-677 (Ibutamoren) for Men Over 40: What the Trials Show About Growth Hormone, IGF-1, Muscle, Sleep, Blood Sugar and Appetite, and How It Compares to Ipamorelin
MK-677 is the only growth hormone secretagogue a man can swallow, which is most of the reason it outsells every injectable peptide in the grey market. It has more randomized trial data than ipamorelin, CJC-1295 and sermorelin combined, and that data is less flattering than the forums suggest. This guide lays out what the studies measured, what they found, where the blood sugar and heart failure signals came from, and how a man over 40 who is going to use it anyway should monitor it.
MK-677 (ibutamoren) is an oral, non-peptide compound that mimics ghrelin at the growth hormone secretagogue receptor and keeps growth hormone and IGF-1 elevated for a full day from one capsule. Randomized trials in older adults show a 40 to 90 percent rise in IGF-1, about 1.1 kg of extra fat-free mass over 12 months, deeper sleep in the first week, and no improvement in strength, alongside higher fasting glucose, reduced insulin sensitivity, water retention and a heart failure signal in a hip fracture trial. This guide separates what MK-677 reliably does from what it is sold as doing.
MK-677, sold under the names ibutamoren and Nutrobal, is a growth hormone secretagogue that a man takes as a capsule rather than an injection. Merck developed it in the 1990s as a treatment for frailty in older adults, ran it through more than a dozen randomized trials, and shelved it when the strength and function results did not match the blood test results. It resurfaced twenty years later as a research chemical sold alongside SARMs, and it now sits in the stacks of a large number of men over 40 who want the growth hormone effect without the needles.
This guide covers how MK-677 raises growth hormone, what the Nass 2008 trial in Annals of Internal Medicine found after a year of daily dosing in 65 older adults, what the compound does to muscle, sleep, blood sugar, appetite and the heart, whether it touches testosterone, how it compares to ipamorelin and the other secretagogues men over 40 are offered, its legal status and its unexpected second life as a pediatric drug, and a 12 week plan for a man who intends to use it with bloodwork rather than blind.
24 hours
Half-Life Of MK-677, Versus About 2 Hours For Ipamorelin
MK-677 is a small non-peptide molecule that survives the gut, reaches peak blood levels in about 30 to 60 minutes and stays active for a full day, so one oral dose of 10 to 25 mg raises growth hormone and IGF-1 around the clock. Injectable secretagogues like ipamorelin produce a single 2 to 3 hour pulse per injection
+40 to +90%
Rise In IGF-1 On MK-677 25 mg Daily Across Randomized Trials
Chapman 1996 recorded a 55 percent rise in IGF-1 at 25 mg in older adults within 2 to 4 weeks, Svensson 1998 about 40 percent in obese men at 2 months, Nass 2008 roughly 50 to 60 percent at 12 months, and the hip fracture trials over 80 percent. The rise appears within 2 weeks and holds for as long as the drug is taken
+1.1 kg
Extra Fat-Free Mass After 12 Months In The Nass 2008 Annals Trial
In 65 healthy adults aged 60 to 81 randomized to MK-677 25 mg or placebo, fat-free mass rose by 1.1 kg more on the drug and body cell mass by about 0.8 kg. Strength on leg press and grip, walking speed and stair climbing did not improve, and total fat mass did not fall significantly
+5 mg/dL
Increase In Fasting Glucose On MK-677 In The Same Trial
Fasting glucose rose by about 0.3 mmol/L (5 mg/dL) and insulin sensitivity fell measurably on MK-677 versus placebo over 12 months. HbA1c also drifted up. Every trial that measured glucose found the same direction, which is why MK-677 is a poor fit for a man with a fasting glucose already above 100 mg/dL
+50%
Increase In Stage IV Deep Sleep In Young Men After 7 Days Of MK-677 25 mg
Copinschi 1997 in Neuroendocrinology found MK-677 increased stage IV sleep by roughly half and REM sleep by about 20 percent in young men, and increased REM by around 50 percent in older adults. The deep sleep effect is the most consistently reported benefit in user accounts and is the one with the cleanest trial support
What Is MK-677 And How Does It Raise Growth Hormone?
MK-677 raises growth hormone by activating the ghrelin receptor in the pituitary and hypothalamus, the same receptor the stomach hormone ghrelin uses to signal hunger and to trigger growth hormone release. It is a spiropiperidine, a small synthetic molecule rather than a peptide, which is why it survives stomach acid and can be taken by mouth. Once absorbed, MK-677 increases the size of the natural growth hormone pulses the pituitary already makes, particularly the large overnight pulse, and it keeps doing so for about 24 hours because its half-life is roughly a full day. Growth hormone then tells the liver to make IGF-1, and IGF-1 is the hormone that actually does most of the tissue work and the one that shows up on a blood test.
The distinction from the injectable secretagogues matters for a man over 40 choosing between them. Ipamorelin and the other growth hormone releasing peptides hit the same ghrelin receptor but clear from the blood in about 2 hours, so each injection produces one pulse and the pituitary rests in between. Sermorelin, CJC-1295 and tesamorelin work on the separate GHRH receptor and are also short-acting unless the CJC-1295 carries the DAC modification. MK-677 is the only option that keeps the ghrelin receptor occupied continuously, which is what makes it convenient, and also what produces its distinctive side effects: the constant appetite signal, the sustained IGF-1 elevation and the insulin resistance that come with never letting the system return to baseline.
MK-677 Compared With The Injectable Growth Hormone Secretagogues Men Over 40 Are Offered
| Compound | Route And Half-Life | Receptor | Typical Use | Notes |
|---|---|---|---|---|
| MK-677 (ibutamoren) | Oral capsule; half-life about 24 hours | Ghrelin receptor (GHS-R1a) | 10 to 25 mg once daily, usually at night | Only oral option. Strongest appetite effect, most water retention, only one that reliably raises fasting glucose. Most randomized trial data of the group |
| Ipamorelin | Subcutaneous injection; half-life about 2 hours | Ghrelin receptor (GHS-R1a) | 200 to 300 mcg 1 to 3 times daily | Most selective of the peptides: minimal cortisol and prolactin release, little appetite effect. Pulsatile, so IGF-1 rise is smaller and glucose effect is minor |
| Sermorelin | Subcutaneous injection; half-life about 10 to 20 minutes | GHRH receptor | 200 to 500 mcg nightly | Oldest and cheapest. Short pulse, mild effect, historically FDA approved for pediatric use. Works better stacked with a ghrelin receptor agonist |
| CJC-1295 (no DAC) | Subcutaneous injection; half-life about 30 minutes | GHRH receptor | 100 to 300 mcg 1 to 3 times daily with ipamorelin | The usual injectable partner to ipamorelin. Together they mimic a natural pulse from both sides of the axis |
| Tesamorelin | Subcutaneous injection; half-life about 30 to 40 minutes | GHRH receptor | 1 to 2 mg nightly | The only one FDA approved for adults (HIV-related visceral fat). Best evidence for visceral fat loss of any secretagogue. Expensive |
What Did The Nass 2008 Trial Actually Find After A Year Of MK-677?
The Nass 2008 trial found that a year of MK-677 25 mg raised growth hormone and IGF-1 into the range of young adults, added about 1.1 kg of fat-free mass, and changed nothing that a man would notice in the mirror or the gym. Ralf Nass and colleagues at the University of Virginia randomized 65 healthy adults aged 60 to 81 to MK-677 or placebo for 12 months, with a second year of open-label follow-up, and published the results in Annals of Internal Medicine. The 24 hour growth hormone profile roughly doubled, IGF-1 rose by about half, and the study was the longest and most carefully measured trial of any growth hormone secretagogue ever run in healthy older people.
The body composition findings deserve a careful reading. Fat-free mass measured by DEXA rose by 1.1 kg more on MK-677 than placebo, and body cell mass by about 0.8 kg, which means most of the gain was real tissue rather than only fluid. Total fat mass and visceral fat did not fall significantly. Limb fat dropped slightly. Leg press strength, grip strength, walking speed and stair climbing did not improve. Fasting glucose rose by about 5 mg/dL and insulin sensitivity fell. LDL cholesterol dropped by a small amount. The authors concluded that the compound reversed the hormonal picture of aging without reversing the functional picture, which is the same conclusion Merck had reached a decade earlier. A man over 40 reading the forums would not guess that the flagship trial of MK-677 showed no strength gain.
Rise In IGF-1 From Baseline On MK-677 25 mg Daily Across Randomized Trials (Approximate Percent)
Does MK-677 Build Muscle, Or Mostly Water And Appetite?
MK-677 produces a modest, real gain in lean tissue over months, a larger and faster gain in water weight over days, and a sustained increase in appetite that accounts for much of the scale change men report. The 1.1 kg of fat-free mass in Nass 2008 took a year. Svensson 1998 in the Journal of Clinical Endocrinology and Metabolism gave 24 obese men 25 mg daily for 8 weeks and recorded a 3 kg rise in fat-free mass, but most of that came in the first two weeks, which is the signature of fluid retention rather than muscle, and visceral fat did not change. Murphy 1998 showed the mechanism that probably matters most: in healthy volunteers on a calorie-restricted diet, 7 days of MK-677 25 mg reversed the nitrogen loss that dieting causes and pushed nitrogen balance positive. That is a muscle-sparing effect during a deficit, not a muscle-building effect during a surplus.
The appetite effect is not a side effect in the usual sense; it is the ghrelin receptor doing its primary job. In Nass 2008 increased appetite was the most common complaint in the first months and faded for most participants after that. For a man over 40 in a lean bulk who is struggling to eat enough, the appetite signal is useful. For the far more common man over 40 who is carrying 15 kg he does not want, it is the single strongest argument against MK-677, because the compound raises hunger, raises fasting glucose and does not reduce fat mass, which is the exact opposite of what a GLP-1 drug does. Men on semaglutide or tirzepatide who add MK-677 often report the two cancelling each other out, and the trial data make that predictable.
The Blood Test Improves; The Function Test Does Not
Every MK-677 trial in older adults found the same split: growth hormone and IGF-1 rose to the levels of a man in his twenties, fat-free mass rose by a kilogram or so, and strength, walking speed and stair climbing did not change. Merck ran the frailty program specifically to find a functional benefit and stopped when it could not. A man over 40 who wants more muscle and strength will get more from 1.6 grams of protein per kilogram, progressive resistance training and, if his testosterone is low, testosterone therapy, than from any growth hormone secretagogue. MK-677 changes the number on the lab report far more reliably than it changes the number on the bar.
What Does MK-677 Do To Sleep?
MK-677 increases deep slow-wave sleep and REM sleep within the first week, and this is the effect with the cleanest trial evidence and the one men over 40 most often notice. Georges Copinschi and colleagues at the Free University of Brussels gave 8 young men MK-677 25 mg or placebo for 7 days each in a crossover design and recorded polysomnography. Stage IV sleep, the deepest stage, increased by about 50 percent, and REM sleep by about 20 percent. In a parallel group of older adults, REM sleep rose by roughly 50 percent and the time to reach REM shortened. The mechanism is straightforward: the largest growth hormone pulse of the day occurs during the first slow-wave episode of the night, and growth hormone secretagogues deepen that episode. Taking MK-677 in the evening puts the peak blood level over the first sleep cycle. The trade-off is that the same dose taken in the evening also puts the peak appetite signal over the hours a man is most likely to raid the fridge, and some men report vivid dreams and morning grogginess in the first two weeks.
Change In Sleep Architecture After 7 Days Of MK-677 25 mg (Copinschi 1997, Approximate Percent)
Does MK-677 Raise Blood Sugar, And Where Did The Heart Failure Signal Come From?
MK-677 raises fasting glucose and lowers insulin sensitivity in every trial that measured them, and it produced a heart failure signal in one trial of frail hip fracture patients that led to the study being stopped early. The glucose effect is a direct consequence of growth hormone, which opposes insulin at the liver and in muscle. In Nass 2008 fasting glucose rose by about 5 mg/dL and HbA1c drifted up over 12 months. Svensson 1998 recorded higher fasting insulin and glucose within 8 weeks in obese men. The rise is small in a man with normal glucose handling and larger in a man who is already insulin resistant, which describes a large share of men over 40 with a waist above 100 cm. A fasting glucose above 100 mg/dL, an HbA1c above 5.7 percent or a fasting insulin above 10 uIU/mL before starting is a reason not to start.
The heart signal comes from the hip fracture program. Bach 2004 in the Journal of the American Geriatrics Society randomized 161 patients recovering from hip fracture to MK-677 25 mg or placebo for 24 weeks and found IGF-1 rose 84 percent with modest improvements in stair climbing and gait speed. A larger follow-up, Adunsky 2011 in Archives of Gerontology and Geriatrics, enrolled 123 patients and was halted after a review found more congestive heart failure events in the MK-677 arm than placebo. The mechanism is almost certainly fluid retention: growth hormone increases sodium reabsorption in the kidney, and an extra litre or two of fluid is trivial in a healthy 45 year old and dangerous in an 82 year old with a stiff heart. No trial in healthy adults has shown a cardiac problem. Still, ankle swelling, a rapid weight gain of more than 2 kg in the first week, or breathlessness lying flat are reasons to stop, and any man with a known heart condition, uncontrolled blood pressure or reduced ejection fraction should leave the compound alone.
MK-677 Side Effects, Where They Come From And What To Do
| Effect | How Common And When | Mechanism | What To Do |
|---|---|---|---|
| Increased appetite | Most users; strongest in weeks 1 to 8, then fades in most | Direct ghrelin receptor activation | Dose in the evening, keep protein at 1.6 g/kg, do not run it during a fat loss phase or alongside a GLP-1 drug |
| Water retention, puffy hands and ankles | Common; first 1 to 3 weeks | Growth hormone increases renal sodium reabsorption | Cut sodium, start at 10 mg rather than 25 mg. Rapid gain over 2 kg in a week or swelling that persists past week 4 means stop |
| Higher fasting glucose and insulin | Consistent across all trials; measurable by week 4 to 8 | Growth hormone antagonises insulin at liver and muscle | Baseline and week 8 fasting glucose, insulin and HbA1c. Rising HbA1c or fasting glucose over 100 mg/dL ends the run |
| Numb or tingling hands, carpal tunnel | Uncommon at 10 mg, more at 25 mg | Fluid retention in the wrist tunnel | Dose reduction; resolves on stopping. Same effect as recombinant growth hormone |
| Lethargy, grogginess in the morning | Common in first 2 weeks with evening dosing | Deeper sleep plus transient rise in prolactin and cortisol on early doses | Usually resolves; if not, move the dose to morning or lower it |
| Muscle and joint aches | Occasional | Fluid shifts and rapid IGF-1 rise | Reduce dose; stop if persistent |
| Heart failure events | Only observed in frail elderly hip fracture patients (Adunsky 2011) | Sodium and fluid retention in an already compromised heart | Absolute reason to avoid in any man with heart failure, reduced ejection fraction or uncontrolled hypertension |
Does MK-677 Affect Testosterone, Cortisol Or Prolactin?
MK-677 does not change testosterone, LH or FSH, and it produces a small, transient rise in cortisol and prolactin that fades after the first few doses. The ghrelin receptor is not part of the testicular axis, and the trials that measured sex hormones in men found no difference from placebo. That makes MK-677 straightforward to combine with testosterone therapy, hCG or enclomiphene from a hormonal standpoint, and it is why the compound is not a post-cycle or fertility tool in either direction. The cortisol effect is real but minor: the first doses of any ghrelin receptor agonist trigger a cortisol and prolactin release along with the growth hormone, which is the reason ipamorelin was developed as a more selective alternative, and it is why some men feel unusually tired or flat in the first week. By week 2 the cortisol response is blunted and 24 hour cortisol output is no different from baseline. Men who are already running high cortisol from poor sleep or stress will not fix that with MK-677, and men with a history of gynecomastia or elevated prolactin should check prolactin at week 4 rather than assume.
How Does MK-677 Compare With Ipamorelin For A Man Over 40?
Ipamorelin is the safer of the two for a man over 40 who is not already lean and insulin sensitive, and MK-677 is the more convenient and the more potent. The two compounds hit the same receptor; the difference is entirely about duration. Ipamorelin produces a single growth hormone pulse per injection, typically 200 to 300 mcg once to three times a day, and its selectivity means very little cortisol, prolactin or hunger. Because it is pulsatile, the IGF-1 rise is modest, usually 15 to 30 percent, and the glucose effect is small. MK-677 keeps the receptor engaged for 24 hours, produces a 40 to 90 percent IGF-1 rise, more water, more hunger and a measurable blood sugar shift. A man who wants the deep sleep benefit and is lean, insulin sensitive and eating in a surplus can reasonably choose MK-677 at 10 to 15 mg. A man with a fasting glucose in the 90s, a waist above 100 cm, or a goal of fat loss should choose ipamorelin, usually with CJC-1295, or tesamorelin if visceral fat is the target, and should probably ask whether he needs a secretagogue at all before his testosterone, sleep and protein intake are in order.
Choosing Between MK-677, An Injectable Secretagogue Or Neither For A Man Over 40
Step 1
Baseline bloodwork first
Morning IGF-1, fasting glucose, fasting insulin, HbA1c, lipids, morning testosterone, prolactin and blood pressure. An IGF-1 already in the top third for age is a reason to stop here; the population data link high IGF-1 to higher, not lower, risk
Step 2
Fasting glucose over 100 or HbA1c over 5.7
MK-677 is off the table. If a secretagogue is still wanted after diet and training are fixed, ipamorelin with CJC-1295 or tesamorelin carries a much smaller glucose penalty
Step 3
Goal is fat loss
No MK-677. The appetite and glucose effects work against the goal and no trial has shown fat loss. Tesamorelin has the visceral fat evidence; a GLP-1 drug has far more
Step 4
Lean, insulin sensitive, in a surplus, wants sleep and recovery
MK-677 10 to 15 mg in the evening is a reasonable trial with week 8 bloodwork. 25 mg is the trial dose and carries proportionally more water, hunger and glucose shift for a modest extra IGF-1 gain
Step 5
Reassess at 12 weeks
IGF-1 within the reference range for age, fasting glucose and HbA1c unchanged, no swelling, sleep and recovery clearly better: continue in 12 week blocks with 4 week breaks. Any glucose drift or IGF-1 above range: stop, and it clears within days
Is MK-677 Legal, And Why Is It Being Trialled In Children?
MK-677 is not approved for any use in any country, it is prohibited in sport by the World Anti-Doping Agency under the S2 class of peptide hormones and growth factors, and it is sold in the United States as a research chemical in a legal grey zone that the FDA has warned about repeatedly. It is not a controlled substance, so possession is not a crime, but selling it for human consumption violates federal law, which is why every bottle says not for human use. Product quality is the practical problem: independent testing of grey market MK-677 has found underdosed and mislabelled products, and because the compound is potent at low milligram doses, a capsule that contains 40 mg instead of 10 mg is a real risk. The compound has a legitimate second life. Lumos Pharma licensed it from Merck as LUM-201 and is running phase 2 and 3 trials in children with growth hormone deficiency, where the oral route replaces daily injections and the early data show growth velocity comparable to injected growth hormone in children who still have a working pituitary. That program is the only route by which ibutamoren might one day become a prescription drug, and it says nothing about adult use.
What Does A Monitored 12 Week Trial Of MK-677 Look Like?
A 12 Week Monitored Plan For MK-677 In A Man Over 40
Week 0: Baseline and exclusion
- ✓Draw IGF-1, fasting glucose, fasting insulin, HbA1c, lipids with ApoB, morning total and free testosterone, prolactin and a metabolic panel. Record blood pressure and body weight on three mornings
- ✓Exclude on any of: fasting glucose over 100 mg/dL, HbA1c over 5.7 percent, IGF-1 in the top third of the age range, any heart failure or reduced ejection fraction, uncontrolled hypertension, active cancer or a cancer history within 5 years, sleep apnea that is not treated
- ✓Source from a vendor with a third-party certificate of analysis for the specific batch. Confirm the goal is a surplus or maintenance phase, not fat loss
Weeks 1 to 2: Start at 10 mg in the evening
- ✓Take 10 mg about an hour before bed on an empty stomach or a light protein meal. Expect deeper sleep within 3 to 5 nights, some morning grogginess, and 1 to 2 kg of water in the first week
- ✓Weigh daily. A gain above 2 kg in the first week, ankle swelling, or breathlessness lying flat means stop and do not restart
- ✓Plan meals in advance; the evening appetite surge is strongest in these two weeks. Keep protein at 1.6 to 2.2 g/kg so the extra intake goes somewhere useful
Weeks 3 to 4: Hold or step to 15 mg
- ✓If sleep is better, hands are not numb and weight has stabilised, hold at 10 mg or step to 15 mg. There is little reason for a man over 40 to go to 25 mg; the trial dose was chosen to maximise IGF-1, not to balance benefit against side effects
- ✓Check prolactin at week 4 if there is any history of gynecomastia or elevated prolactin, and blood pressure weekly
- ✓Morning grogginess that persists past week 3 usually means the dose should move to the morning or come down
Week 8: The decision bloodwork
- ✓Repeat IGF-1, fasting glucose, fasting insulin and HbA1c at the same lab. IGF-1 should be higher but within the reference range for age; above the range means reduce or stop
- ✓Fasting glucose up more than 5 mg/dL, fasting insulin up more than 3 uIU/mL or HbA1c up 0.2 or more means the compound is costing more metabolically than it is returning. Stop
- ✓Compare training log, sleep tracker and body weight against baseline. The honest question is whether anything other than the IGF-1 number has changed
Weeks 9 to 12: Complete and break
- ✓Finish the block, then take 4 weeks off. MK-677 clears within a few days and IGF-1 returns to baseline within 2 to 3 weeks, so the break resets the glucose effect and shows what the compound was actually doing
- ✓Repeat glucose and IGF-1 at the end of the break. If both are back to baseline and the sleep and recovery benefits were clear, a second 12 week block is reasonable. If glucose stays elevated, the compound has done something that needs a doctor
- ✓Many men find the 4 week break is when they notice the appetite was the main thing that changed, which is useful information
The Cheapest Secretagogue Is Also The Least Selective
MK-677 exists because Merck wanted an oral growth hormone drug for frail older adults, and it works exactly as designed: it raises growth hormone and IGF-1 around the clock from a single capsule. What it does not do is the thing a man over 40 usually wants, which is to add strength, lose fat or feel younger in any way a trial could measure. The deep sleep benefit is real and appears within a week. The appetite, water and glucose effects are equally real and appear in the same week. For a lean man in a surplus who wants to sleep harder and recover faster, a low dose with bloodwork is defensible. For everyone else, ipamorelin is safer, tesamorelin has better fat evidence, and fixing testosterone, protein and sleep comes before any of them.
Continue Reading
Related Articles
Ipamorelin vs CJC-1295: Which Growth Hormone Peptide Is the Better Choice After 45?
9 min read
IGF-1 for Men Over 40: What the Number Means, Why Both Low and High Shorten Life, and How Peptides, Protein and Fasting Move It
14 min read
Sermorelin vs. Ipamorelin: Which GH Peptide Is Right for You? (2026 Guide)
15 min read