Ibutamoren MK-677

What Is MK-677 (Ibutamoren)?

MK-677, also known as Ibutamoren or Nutrobal, is not a SARM. It’s frequently mislabelled as one, but Ibutamoren is actually a growth hormone secretagogue (GHS): an orally active compound that stimulates the pituitary gland to release growth hormone (GH) and insulin-like growth factor 1 (IGF-1).

If you’re looking to buy MK-677 in the UK, sarms.co.uk supplies research-grade Ibutamoren capsules with 99%+ HPLC-verified purity and full Certificates of Analysis. Every batch is manufactured in GMP-certified UK facilities and independently tested, with free next-day UK delivery on all MK-677 orders. Whether you’re searching for MK-677 for sale UK, Ibutamoren capsules, Nutrobal for sale, or the best MK-677 UK supplier, our HPLC-tested Ibutamoren meets the highest quality standard available.

Originally developed by Merck, MK-677 mimics the action of ghrelin, the “hunger hormone,” by binding to the ghrelin receptor (GHSR). This triggers a cascade of GH pulses that closely mimic the body’s natural secretion pattern, unlike exogenous GH injection, which delivers a single bolus dose.

MK-677 has been studied in multiple human clinical trials, including investigations for growth hormone deficiency, sarcopenia, sleep quality, and bone density. It has some of the most robust human data of any compound sold in this category.

Compound Profile

Chemical Name	2-amino-2-methyl-N-[1-(1-methylsulfonylspiro[2H-indene-1,4′-piperidine]-6-yl)but-3-en-1-yl]propanamide
Other Names	Nutrobal, Oratrope, L-163,191
CAS Number	159752-10-0
Molecular Formula	C₂₇H₃₆N₄O₅S
Molecular Weight	528.66 g/mol
Half-Life	~24 hours (confirmed in human pharmacokinetic studies)
Solubility	PEG-300 / DMSO
Classification	Growth Hormone Secretagogue (GHS), NOT a SARM
Developer	Merck & Co.
PubChem CID	9939050

How Does MK-677 (Ibutamoren) Work?

MK-677 works by mimicking ghrelin at the growth hormone secretagogue receptor (GHSR) in the pituitary gland and hypothalamus. This is a completely different mechanism to SARMs. There is zero androgen receptor involvement.

1. Growth Hormone Pulsatility

MK-677 stimulates the pituitary to release GH in natural pulsatile patterns, maintaining the body’s feedback loops. This is distinct from exogenous GH injection, which can suppress natural production. Copinschi et al. (1997) demonstrated that MK-677 increased 24-hour GH secretion by approximately 97% in young healthy males (PMID: 9467534).

2. IGF-1 Elevation

Multiple clinical trials have shown sustained IGF-1 increases with MK-677 administration. Nass et al. (2008) demonstrated that 25 mg/day for 2 years increased IGF-1 levels to those of healthy young adults in elderly subjects, without significant adverse effects on glucose metabolism at the study endpoint (PMID: 18981485).

3. Appetite Stimulation

Because MK-677 activates the ghrelin receptor, it increases appetite. This is a feature for some research applications (e.g., cachexia, muscle wasting) and a consideration for others. The appetite effect is most pronounced in the first few weeks and typically moderates over time.

4. Sleep Quality

Copinschi et al. (1997) also observed significant improvements in sleep quality, specifically increased duration of REM sleep and Stage IV (deep) sleep. GH secretion is naturally highest during deep sleep, and MK-677 appears to amplify this pattern.

5. No Androgen Receptor Activity

MK-677 does not bind to androgen receptors, does not suppress testosterone, and does not require post-cycle therapy. Its effects are mediated entirely through the GH/IGF-1 axis.

What Does the Research Say?

MK-677 has more published human clinical data than most compounds in this category. Here’s what the evidence shows:

Growth Hormone & IGF-1 (Human Trial)

Copinschi et al. (1997) conducted a study in healthy young males showing that MK-677 at 25 mg/day increased 24-hour GH secretion by ~97% and IGF-1 levels significantly. The compound maintained pulsatile GH release patterns and improved sleep architecture (PMID: 9467534).

Long-Term IGF-1 in Elderly (2-Year Human Trial)

Nass et al. (2008) published results from a landmark 2-year study in healthy elderly subjects. MK-677 at 25 mg/day restored IGF-1 levels to those of young adults. Lean body mass increased and fat mass showed trends toward reduction. Fasting glucose increased modestly but remained within normal limits for most subjects (PMID: 18981485).

Nitrogen Balance & Catabolic States

Murphy et al. (1998) demonstrated that MK-677 reversed diet-induced nitrogen wasting (a marker of muscle protein breakdown) in healthy volunteers placed on a calorie-restricted diet. This suggests potential applications in catabolic conditions and muscle preservation during energy deficit (PMID: 9753023).

Bone Mineral Density

Several studies have demonstrated that MK-677 improves markers of bone turnover. In the Nass et al. (2008) 2-year study, osteocalcin (a bone formation marker) increased significantly, suggesting sustained anabolic effects on bone tissue.

Important Considerations

MK-677 can increase fasting blood glucose and insulin levels due to GH’s counter-regulatory effects on insulin sensitivity. The Nass et al. (2008) study reported modest glucose elevations. Additionally, water retention and increased appetite are commonly reported effects. These are pharmacological consequences of GH elevation and should be factored into any research protocol.

⚠️ Important: Despite extensive clinical research, MK-677 has NOT received regulatory approval from the FDA or MHRA. It remains an investigational compound sold for research purposes only.

MK-677 (Ibutamoren) vs. SARMs: Key Differences

Since MK-677 is commonly sold alongside SARMs, here’s how it actually compares:

Factor	MK-677 (Ibutamoren)	Typical SARMs (e.g. RAD-140, Ostarine)
Mechanism	Ghrelin receptor agonist (GHS)	Androgen receptor modulator
Primary effect	GH/IGF-1 elevation	Lean mass, strength
Androgen receptor binding	None	Yes (selective)
Testosterone suppression	None	Dose-dependent
PCT required	No	Commonly recommended
Appetite effects	Significant increase	Minimal
Sleep effects	Improved REM/deep sleep	No direct effect
Human clinical trials	Multiple, including 2-year study	Varies by compound
Glucose effects	May increase fasting glucose	Minimal

The honest take: MK-677 isn’t a SARM , it’s a growth hormone secretagogue that works through the ghrelin/GH/IGF-1 axis. It’s one of the most clinically studied compounds in the performance research space, with a 2-year human trial. Its effects on sleep, recovery, and bone density make it unique. The appetite increase and glucose effects are real considerations, not something to brush past.

MK-677 Dosage & Cycle Length (Research Use Only)

Based on published clinical trial data and commonly referenced research protocols:

• Clinical trial dosage: 25 mg per day (used across multiple published studies)
• Commonly referenced research dosages: 10–25 mg per day
• Half-life: ~24 hours (confirmed in human PK studies), supporting once-daily administration
• Typical research cycle length: 8–16 weeks (studies have run up to 2 years)
• Administration: Oral capsule
• Timing note: Often administered before bed to align with the natural GH release pattern during sleep

A note on dosing: The clinical trials consistently used 25 mg/day with significant GH and IGF-1 elevations. Lower doses (10–15 mg) are sometimes referenced for research protocols aimed at sleep and recovery benefits with reduced appetite stimulation.

Who’s Researching MK-677 (Ibutamoren) and Why?

• Growth hormone deficiency: MK-677 as a non-injectable alternative to recombinant GH therapy
• Sarcopenia and age-related muscle loss: the Nass et al. 2-year study demonstrated sustained lean mass and GH elevation in elderly subjects
• Bone density and osteoporosis: Murphy et al. (2001) showed increased bone mineral density markers in postmenopausal women
• Sleep quality research: MK-677 significantly improved REM and deep sleep in clinical studies
• Body recomposition: exploring MK-677’s effects on lean mass, fat distribution, and IGF-1 elevation
• MK-677 stacking protocols: commonly studied alongside RAD-140 (Testolone) and Ostarine (MK-2866) for synergistic research
• Appetite and metabolism research: MK-677’s ghrelin-mimetic action makes it relevant to cachexia and metabolic studies

Why Buy MK-677 (Ibutamoren) in the UK from sarms.co.uk?

Purity You Can Verify

Every batch is independently tested via High-Performance Liquid Chromatography (HPLC) by third-party laboratories. We publish full Certificates of Analysis. Download the PDF directly from this page and verify with the testing lab if you want.

Proper Concentration

10 mg per capsule, 90 capsules per bottle. No underdosed products, no proprietary blends. You know exactly what you’re getting.

UK Manufactured

Compounded in GMP-certified facilities. Not imported from unregulated overseas labs.

Transparent Supply Chain

We test raw materials before compounding. We test the finished product after compounding. Two tests, two stages, full documentation.

Storage & Handling

• Store at room temperature (15–25°C) in a cool, dry place
• Keep away from direct sunlight and moisture
• Keep the container tightly sealed after each use
• Keep out of reach of children
• Do not use past the expiry date printed on the label
• Shelf life: 24 months when stored correctly

MK-677 (Ibutamoren): Frequently Asked Questions

Is MK-677 a SARM?

No. MK-677 (Ibutamoren) is a growth hormone secretagogue. It works by activating the ghrelin receptor to stimulate GH and IGF-1 release. It does not bind to androgen receptors and has no direct anabolic mechanism.

Does MK-677 suppress testosterone?

No. MK-677 works through the GH/IGF-1 axis, not the androgen receptor pathway. It does not cause testosterone suppression and does not require post-cycle therapy.

Does MK-677 increase appetite?

Yes. Because MK-677 activates the ghrelin receptor (“hunger hormone”), appetite stimulation is a well-documented effect. This is most pronounced during the first few weeks and typically moderates with continued use.

Can MK-677 affect blood sugar?

Clinical trials have shown that MK-677 can modestly increase fasting blood glucose and insulin levels. This is a pharmacological effect of elevated GH, which acts as a counter-regulatory hormone to insulin. Researchers should be aware of this interaction.

Does MK-677 improve sleep?

Yes. Copinschi et al. (1997) demonstrated that MK-677 significantly increased both REM sleep and Stage IV (deep) sleep duration. GH secretion is naturally concentrated during deep sleep phases.

Can I stack MK-677 with SARMs?

Researchers commonly study MK-677 alongside SARMs like Ostarine (MK-2866) or RAD-140, combining MK-677’s GH/IGF-1 elevation and sleep benefits with the androgen receptor-mediated lean mass effects of SARMs.

How long has MK-677 been studied in humans?

The longest published human trial is the Nass et al. (2008) 2-year study in elderly subjects. This is one of the most extensive human datasets available for any compound in this category.

Where can I buy MK-677 (Ibutamoren) in the UK?

You can buy MK-677 directly from sarms.co.uk. We are a UK-based supplier offering HPLC-tested, research-grade Ibutamoren with free next-day delivery. Every batch includes a downloadable Certificate of Analysis.

What is the MK-677 price in the UK?

MK-677 (Ibutamoren) pricing varies by concentration and volume. At sarms.co.uk, we offer competitive UK pricing with no hidden fees. Check the product options above for current pricing. All orders include free next-day UK delivery.

MK-677 vs MK-2866 (Ostarine): what’s the difference?

MK-677 (Ibutamoren) is a growth hormone secretagogue that works via the ghrelin receptor. It is not a SARM. MK-2866 (Ostarine) is an actual SARM that binds to androgen receptors. They work through completely different mechanisms and are frequently studied together in stacking protocols.

Is MK-677 the same as Ibutamoren?

Yes. MK-677 and Ibutamoren are the same compound. MK-677 is the research designation, while Ibutamoren is the international nonproprietary name (INN). It’s also sometimes called Nutrobal or by its earlier code L-163,191.

Is MK-677 (Ibutamoren) legal in the UK?

MK-677 is legal to purchase in the UK for research purposes. It is not approved for human consumption by the MHRA and is not a licensed medicine. It is listed on WADA’s prohibited substances list for competitive athletes.

What is the best MK-677 brand in the UK?

The best MK-677 brand is one that provides independent HPLC testing with published Certificates of Analysis. At sarms.co.uk, every batch is third-party tested and we publish full COAs. Download them directly from this page and verify with the testing lab yourself.

References & Further Reading

1. Copinschi G, et al. (1997). “Effects of a 7-day treatment with a novel, orally active, growth hormone (GH) secretagogue, MK-677, on 24-hour GH profiles, insulin-like growth factor I, and adrenocortical function in normal young men.” The Journal of Clinical Endocrinology & Metabolism, 82(5), 1572–1577. PMID: 9467534
2. Nass R, et al. (2008). “Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial.” Annals of Internal Medicine, 149(9), 601–611. PMID: 18981485
3. Murphy MG, et al. (1998). “Effect of alendronate and MK-677 (a growth hormone secretagogue), individually and in combination, on markers of bone turnover and bone mineral density in postmenopausal osteoporotic women.” The Journal of Clinical Endocrinology & Metabolism, 86(3), 1116–1125. PMID: 9753023
4. Chapman IM, et al. (1996). “Stimulation of the growth hormone (GH)-insulin-like growth factor I axis by daily oral administration of a GH secretagogue (MK-677) in healthy elderly subjects.” The Journal of Clinical Endocrinology & Metabolism, 81(12), 4249–4257. PMID: 8954023

Related Research Compounds

Exploring other research compounds? Browse our full range:

• RAD-140 (Testolone): the most potent SARM by anabolic ratio, commonly stacked with MK-677 in research protocols
• Ostarine (MK-2866): the most studied SARM, frequently combined with Ibutamoren for lean tissue research
• Cardarine (GW-501516): a PPARδ agonist studied for endurance and fat oxidation
• Ligandrol (LGD-4033): a popular SARM for lean mass and bone density research
• Stenabolic (SR-9009): a Rev-Erb agonist studied for metabolic regulation
• RAD-150 (TLB-150): the esterified variant of RAD-140
• Research Stacks: pre-configured stacks for bulking, cutting, and recomposition studies

All products are HPLC-tested with published COAs. View our full catalogue.

Disclaimers

• Ibutamoren (MK-677) is sold strictly for laboratory and research purposes only
• This product is not intended for human consumption
• MK-677 is not a medicine, supplement, or food product
• MK-677 may affect blood glucose and insulin levels. Researchers should consider metabolic interactions
• Not suitable for individuals under 18 years of age
• Pregnant or breastfeeding women must not handle this compound
• Researchers should consult qualified professionals and adhere to all applicable regulations
• sarms.co.uk does not provide medical advice and makes no claims regarding therapeutic outcomes
• We are not responsible for any adverse effects resulting from misuse of this product
• The content on this page does not constitute medical advice

Content last reviewed: 17 February 2026