Last Updated October 20, 2023

 October 20, 2023

Searching for a detailed comparison of MK-677 vs. ipamorelin for muscle growth research?

While MK-677 and ipamorelin differ in their structure and route of administration, both have been shown to boost growth hormone levels in test subjects.

This comprehensive guide delves into the latest clinical data on the potential of ipamorelin and MK-677 for a wide range of benefits, including:

  • Increasing lean body mass
  • Improving muscle strength
  • Boosting bone mineralization

We’ll also shed light on how these compounds are dosed and their potential side effects. In addition, we’ll present a trusted vendor for sourcing research-grade ipamorelin and MK-677.

Buy research peptides from our top-rated vendor...

Disclaimer: contains information about products that are intended for laboratory and research use only, unless otherwise explicitly stated. This information, including any referenced scientific or clinical research, is made available for educational purposes only. Likewise, any published information relative to the dosing and administration of reference materials is made available strictly for reference and shall not be construed to encourage the self-administration or any human use of said reference materials. makes every effort to ensure that any information it shares complies with national and international standards for clinical trial information and is committed to the timely disclosure of the design and results of all interventional clinical studies for innovative treatments publicly available or that may be made available. However, research is not considered conclusive. makes no claims that any products referenced can cure, treat or prevent any conditions, including any conditions referenced on its website or in print materials.

What is Ipamorelin?

Ipamorelin, also known as NNC 26-0161, is a synthetic pentapeptide derived from a met-enkephalin analog called growth hormone releasing peptide-1 (GHRP-1). However, unlike endogenous enkephalins that target opioid receptors, GHRPs activate the receptors for the hunger hormone ghrelin.

Activating these receptors in the pituitary gland (“growth hormone secretagogue receptors”) promotes the release of growth hormone (GH).

Thus, compounds like ipamorelin that trigger the ghrelin receptors in the pituitary gland are termed growth hormone secretagogues (GHSs). GHS may also trigger the synthesis of other pituitary hormones, such as prolactin or ACTH. Yet, ipamorelin is highly selective, stimulating only the GH production in the anterior pituitary [1].

Developed and patented by Novo Nordisk and Helsinn Therapeutics in 1994, ipamorelin was designed to emulate ghrelin's role in the digestive system, enhancing peristalsis [2]. Thus, the peptide was investigated for its potential benefits in patients with post-surgical ileus, a type of intestinal paralysis that may occur following gastrointestinal surgery.

While phase-2 trials showed some promise of ipamorelin for this condition, the improvements over a 7-10-day treatment were not deemed sufficiently significant, leading to discontinuation of its clinical development [3, 4].

In addition, preclinical studies have suggested that the peptide may have benefits related to its ability to boost both GH and its anabolic mediator insulin-like growth factor-1 (IGF-1). These purported benefits include [5]:

  • Increased appetite and weight gain
  • Increased muscle mass and strength
  • Increased bone mass

The United States Food and Drug Administration (FDA) has not approved ipamorelin for any indication. However, ipamorelin remains accessible to qualified researchers for scientific research.

Ipamorelin in the UK

What is MK-677?

MK-677 is a non-peptide compound also known as ibutamoren. It is structurally classified as both a spiroindoline and spiropiperidine, and it works similarly to a peptide-based GHS called growth hormone-releasing peptide-6 (GHRP-6) [6].

Like GHRP-6 and ipamorelin, MK-677 can cross the blood-brain barrier to activate the pituitary gland's ghrelin receptors, leading to GH release. Yet, unlike other GH secretagogues, MK-677 boasts an oral bioavailability of over 60% and may be taken in capsule form rather than as an injection [7].

Merck & Co developed MK-677 in the 1990s, aiming to produce an orally active GHS that could treat growth hormone deficiency (GHD) [8]. Currently, Lumos Pharma, a company specializing in treatments for rare diseases, is researching MK-677. The compound is in phase-2 clinical trials as a potential therapy for children with GHD [9].

MK-677 has been shown to cause significant increases in GH and IGF-1 levels, with only a transient effect on cortisol and prolactin. In addition, the GHS has been reported to have the following potential benefits in adults when given orally [5, 7]:

  • Increased muscle mass without increases in adiposity
  • Reduction of cholesterol levels
  • Improved sleep

It's important to note that MK-677 is still under investigation and has not received FDA approval for any indication. As such, it's classified as an Investigational New Drug, however available for purchase by qualified professionals for educational or experimental purposes [10].

MK-677 vs. Ipamorelin | Comprehensive Comparison

Both MK-677 and ipamorelin significantly increase GH and IGF-1 levels in test subjects.

For example, here is a timeline of GH-related effects following a single ipamorelin administration in healthy adults [11]:

  • Subcutaneous application of ipamorelin significantly elevates GH levels within 40 minutes.
  • With a half-life under 2 hours, it was noted that ipamorelin’s GH-boosting effect persists for 2-3 hours following subcutaneous injection.
  • Study authors reported that ipamorelin doses at both 60mcg/kg and 100mcg/kg of body weight can lead to similar GH increases: about 26.6ng/ml (80mIU/l) peak GH.

In addition, studies in laboratory animals report a 54% increase in IGF-I following ipamorelin application [12].

On the other hand, studies report that MK-677 has a considerably longer half-life of 4-6 hours, and daily oral intake can significantly increase GH and IGF-1 levels [5, 7].

A trial in 32 healthy older adults reported the following findings [13]:

  • When taken as 10mg or 25mg/daily capsules, MK-677 increased mean 24-h GH concentration by 57% and 97%, respectively.
  • Pulsatile GH-release increased 1.7-fold over 24 hours.
  • Daily administration led to a 55% increase in IGF-1 levels at 2 weeks and 88% at 4 weeks.

In addition, MK-677 was reported to cause a dramatic 55.6ng/ml peak in GH levels after a single 25mg dose when combined with caloric restriction [14].

Based on these findings, both ipamorelin and MK-677 appear to increase GH levels significantly, although the GH peak with MK-677 appears to be greater.

Benefits of MK-677

Clinical studies have investigated the effects of MK-677, showing that its ability to significantly increase GH is associated with muscle mass growth alongside other benefits.

Below, we outline some of the more notable findings related to this orally active GHS:

  • Increased lean mass and muscle growth: A study in 24 young, obese volunteers revealed that 8 weeks of 25mg/daily MK-677 resulted in a +6.6lb increase in lean body mass, without any effect on fat mass compared to placebo [15]. Other trials have also reported a significant reduction in nitrogen losses during low-calorie dieting [14].
  • Reduced LDL (bad) cholesterol levels: The longest published MK-677 trial, which lasted 2 years, reported that 25mg/day of the GHS significantly reduced LDL cholesterol. The researchers noted that LDL increased by 0.12mmol/l with placebo but decreased by 0.14mmol/l with MK-677 within the first 12 months [16].
  • Improved sleep: A study in eight young subjects reported that a 14-day course at 25mg/daily taken before bedtime resulted in an approximately 50% increase in the duration of deep sleep (slow-wave sleep) and a 20%+ increase in rapid-eye movement (REM) sleep [17].

Benefits of Ipamorelin

Clinical research on ipamorelin is limited, with existing studies shorter than one week in duration. Despite the peptide's apparent potency, the short-term nature of these studies has been insufficient for researchers to observe the effects of elevated GH levels, such as enhanced muscle growth or lean mass development.

Conversely, numerous preclinical tests have delved into the ipamorelin’s influence on muscle mass, appetite, body weight, and bone density. Here are the most notable findings:

  • Weight and muscle gains: Ipamorelin may promote weight gain that is tied to both lean and fat mass augmentation. One experiment in healthy mice reported a 16.9% surge in body weight within two weeks of treatment. This weight gain was suggested to be due to the appetite-boosting effects of ghrelin receptor activation [18].
  • Preserving muscle strength: Another experiment in mice revealed that ipamorelin mitigated the loss of muscle strength, which can occur in catabolic conditions induced by corticosteroids. This indicates that the peptide may counteract muscle wasting in certain conditions [12].
  • Increased bone mineralization: The aforementioned study also reported that ipamorelin therapy increased bone mineralization in mice given a combination of ipamorelin and corticosteroids, in contrast to the control animals receiving only corticosteroids [12]. Experiments on female rats also suggest that ipamorelin treatment can elevate bone mineral content, promoting denser and more robust bones [19].

MK-677 Side Effects

While MK-677 is yet to be approved for any indication, available clinical trials report that the peptide is safe and well-tolerated when taken for up to two years at a daily dose of 25mg.

According to the longest available trial on the compound, the most commonly experienced side effects include [16]:

  • Increase in appetite (67%)
  • Joint pain (58%)
  • Mild lower extremity edema (44%)
  • Mild muscle pain (33%)

The researchers reported that all of these complaints subsided within a few months of discontinuing MK-677 therapy [16].

Trials with higher doses (50mg/daily) taken for just a few days report diarrhea and dry skin as side effects potentially related to MK-677 use [20].

MK-677 is contraindicated in subjects with a history of cancer or active malignancies, as increased GH and IGF-1 levels can stimulate the proliferation of cancer cells and disease progression.

Ipamorelin Side Effects

Unfortunately, there is a lack of long-term safety data outlining all potential side effects of ipamorelin in test subjects. Available trials have lasted up to one week and report that the peptide may cause mild gastrointestinal issues, including nausea [3].

Based on available laboratory animal research, ipamorelin is likely to result in increased appetite over longer periods of administration, potentially leading to weight gain [21].

In contrast to MK-677, ipamorelin is applied subcutaneously, which is also associated with potential side effects at the injection site, such as:

  • Pain
  • Redness
  • Bleeding
  • Hardening at the injection site
  • Numbness

Ipamorelin is not recommended in subjects with oncological conditions. This is due to concerns that the peptide’s proliferative effects could accelerate disease progression.

MK-677 vs. Ipamorelin | Dosing and Administration

MK-677 and ipamorelin are research chemicals with no established “safe” dose.

To the extent that both compounds have been used in clinical settings, the available data indicate vastly different dosage recommendations, frequency of use, and routes of administration:

  • MK-677 is taken as oral capsules, usually once daily, thanks to its relatively long half-life.
  • Ipamorelin must be administered via subcutaneous injections, and it's usually applied two to three times daily due to its short half-life.

Below, we outline the most frequently used dosing protocols for MK-677 and ipamorelin based on the available clinical data.

Reference MK-677 Dosing Protocol

MK-677 studies have applied the compound in doses of up to 25mg/daily for up to two years, while considerably shorter studies have also administered 50mg/daily [16, 20].

The capsules are best taken in the evening to mimic physiological GH release and minimize increases in appetite.

Based on the available data, experts recommend initiating studies at MK-677 doses no higher than 25mg/daily. Here is a sample dosing protocol rooted in the research:

  • Daily MK-677 Dosage: 25mg taken as an oral capsule.
  • Administration Frequency: Once daily, taken in the evening on an empty stomach (two hours after a meal).
  • Research Study Duration: 3-12 months, with or without cycling
  • Notes: A bottle of 60 MK-677 12.5mg capsules will be sufficient for a month of research per subject.

Reference Ipamorelin Dosing Protocol

There are no clinical reports of long-term ipamorelin use in humans. The available data stem from a week-long clinical trial involving ipamorelin doses of roughly 0.03mg per kilogram of body weight, twice daily. This translates to 2.4mg per administration, totaling 4.8mg daily [3].

However, researchers aiming to achieve changes in body composition or other GH-related benefits in their test subjects must apply the peptide for longer periods. Hence, some researchers have recommended lower doses given over extended cycles of 8-12 weeks.

The following experimental dosing regimen is for reference only, and is subject to change when more quality data become available:

  • Daily Ipamorelin Dosage: 200-300 mcg.
  • Administration Frequency: 2-3 daily subcutaneous injections of 100mcg each.
  • Research Cycle Duration: 8-12 weeks.
  • Recommendation: Alternate injection sites with each use.

MK-677 vs. Ipamorelin

Where to Buy Research Peptides Online? | 2024 Edition

When seeking a trustworthy source of MK-677 and ipamorelin as reference materials, it's essential to thoroughly assess multiple suppliers before finalizing a purchase.

It’s important to look for aspects such as quality, affordability, shipping, and feedback from previous customers.

Based on our extensive experience and knowledge of the research chemicals, we recommend two excellent options for researchers:

Chemyo for MK-677

Chemyo has consistently demonstrated their reliability as a supplier of high-purity MK-677 and other research chemicals, offering several benefits:

  • Lab-Tested MK-677 with Over 99% Purity: Through high-performance liquid chromatography and mass spectrometry (HPLC-MS) analysis, Chemyo guarantees the premium quality of its MK-677 for research.
  • USA Made Compounds: Every research compound from Chemyo is produced in the USA at laboratories adhering to stringent guidelines.
  • Free Shipping & Newsletter Discount: The vendor extends free U.S. shipping for orders exceeding $100. Additionally, new subscribers to Chemyo’s newsletter receive 10% off their first order.

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Core Peptides for Ipamorelin

Core Peptides is our go to vendor of ipamorelin and other GH secretagogue peptides, having earned our loyalty for the following reasons:

  • Lab-Verified Ipamorelin: Core Peptides submits each batch of ipamorelin to a third-party laboratory for state-of-the-art quality testing.
  • Perks & Discounts: US orders over $200 ship free, while the vendor offers attractive bulk discounts for purchases of five ipamorelin vials or more.
  • Customer Support: Core Peptides’ friendly support staff is available to answer any product- or order-related queries and undertakes to respond to within one business day.

Buy research peptides from Core Peptides today...

Bacteriostatic Water For Research Peptides

Researchers interested in investigating the potential effects of ipamorelin in test subjects should note that the peptide is available as a lyophilized powder, which must be reconstituted with a suitable diluent such as bacteriostatic water.

In addition, researchers must obtain other materials essential for successful reconstitution, such as vials and alcohol prep pads.

At, we understand the hassle of searching for high-quality materials online and sourcing each from a different vendor. This is why we recommend sourcing all essential tools for reconstitution, including bacteriostatic water, from our trusted supplier:

Ipamorelin vs. MK-677 | Overall

Ipamorelin and MK-677 are two potent GH secretagogues with notable research potential. Ipamorelin is a peptide with a short half-life and requires subcutaneous injections for administration. In contrast, MK-677 is a non-peptide compound with a longer half-life and excellent oral bioavailability.

Of the two, MK-677 has undergone more extensive testing. Evidence suggests it prompts a more substantial increase in serum GH levels. Its oral capsule form also makes it more convenient for administration in research settings.

Yet, ipamorelin is more selective in its GH-stimulating effects and does not influence other pituitary hormone levels.

Researchers looking to include either compound in their research can purchase MK-677 and ipamorelin from a reliable online vendor.


  1. Raun, K., Hansen, B. S., Johansen, N. L., Thøgersen, H., Madsen, K., Ankersen, M., & Andersen, P. H. (1998). Ipamorelin, the first selective growth hormone secretagogue. European journal of endocrinology, 139(5), 552–561.
  2. Johansen, N. L., Lau, J., Madsen, K., Lundt, B. F., Hansen, B. S., & Peschke, B. (1998). US Patent No. 5,767,085. Washington, DC: US Patent and Trademark Office.
  3. Beck, D. E., Sweeney, W. B., McCarter, M. D., & Ipamorelin 201 Study Group (2014). Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. International journal of colorectal disease, 29(12), 1527–1534.
  4. National Library of Medicine (US). (January 20, 2011 – April 13, 2017). Safety and Efficacy of Ipamorelin Compared to Placebo for the Recovery of Gastrointestinal Function. Identifier NCT01280344.
  5. Sinha, D. K., Balasubramanian, A., Tatem, A. J., Rivera-Mirabal, J., Yu, J., Kovac, J., Pastuszak, A. W., & Lipshultz, L. I. (2020). Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males. Translational andrology and urology, 9(Suppl 2), S149–S159.
  6. Lee, J., Kwon, A., Chae, H. W., Lee, W. J., Kim, T. H., & Kim, H. S. (2018). Effect of the Orally Active Growth Hormone Secretagogue MK-677 on Somatic Growth in Rats. Yonsei medical journal, 59(10), 1174–1180.
  7. Sigalos, J. T., & Pastuszak, A. W. (2018). The Safety and Efficacy of Growth Hormone Secretagogues. Sexual medicine reviews, 6(1), 45–53.
  8. Patchett, A. A., Nargund, R. P., Tata, J. R., Chen, M. H., Barakat, K. J., Johnston, D. B., Cheng, K., Chan, W. W., Butler, B., & Hickey, G. (1995). Design and biological activities of L-163,191 (MK-0677): a potent, orally active growth hormone secretagogue. Proceedings of the National Academy of Sciences of the United States of America, 92(15), 7001–7005.
  9. National Library of Medicine (US). (Novermber 4, 2020 – ). Phase 2 Study of LUM-201 in Children With Growth Hormone Deficiency (OraGrowtH210 Trial) (OraGrowtH210). Identifier NCT04614337.
  10. Liu, H., Sun, D., Myasnikov, A., Damian, M., Baneres, J. L., Sun, J., & Zhang, C. (2021). Structural basis of human ghrelin receptor signaling by ghrelin and the synthetic agonist ibutamoren. Nature communications, 12(1), 6410.
  11. Gobburu, J. V., Agersø, H., Jusko, W. J., & Ynddal, L. (1999). Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharmaceutical research, 16(9), 1412–1416.
  12. Andersen, N. B., Malmlöf, K., Johansen, P. B., Andreassen, T. T., Ørtoft, G., & Oxlund, H. (2001). The growth hormone secretagogue ipamorelin counteracts glucocorticoid-induced decrease in bone formation of adult rats. Growth hormone & IGF research : official journal of the Growth Hormone Research Society and the International IGF Research Society, 11(5), 266–272.
  13. Chapman, I. M., Bach, M. A., Van Cauter, E., Farmer, M., Krupa, D., Taylor, A. M., Schilling, L. M., Cole, K. Y., Skiles, E. H., Pezzoli, S. S., Hartman, M. L., Veldhuis, J. D., Gormley, G. J., & Thorner, M. O. (1996). Stimulation of the growth hormone (GH)-insulin-like growth factor I axis by daily oral administration of a GH secretogogue (MK-677) in healthy elderly subjects. The Journal of clinical endocrinology and metabolism, 81(12), 4249–4257.
  14. Murphy, M. G., Plunkett, L. M., Gertz, B. J., He, W., Wittreich, J., Polvino, W. M., & Clemmons, D. R. (1998). MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism. The Journal of clinical endocrinology and metabolism, 83(2), 320–325.
  15. Svensson, J., Lönn, L., Jansson, J. O., Murphy, G., Wyss, D., Krupa, D., Cerchio, K., Polvino, W., Gertz, B., Boseaus, I., Sjöström, L., & Bengtsson, B. A. (1998). Two-month treatment of obese subjects with the oral growth hormone (GH) secretagogue MK-677 increases GH secretion, fat-free mass, and energy expenditure. The Journal of clinical endocrinology and metabolism, 83(2), 362–369.
  16. Nass, R., Pezzoli, S. S., Oliveri, M. C., Patrie, J. T., Harrell, F. E., Jr, Clasey, J. L., Heymsfield, S. B., Bach, M. A., Vance, M. L., & Thorner, M. O. (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.
  17. Copinschi, G., Leproult, R., Van Onderbergen, A., Caufriez, A., Cole, K. Y., Schilling, L. M., Mendel, C. M., De Lepeleire, I., Bolognese, J. A., & Van Cauter, E. (1997). Prolonged oral treatment with MK-677, a novel growth hormone secretagogue, improves sleep quality in man. Neuroendocrinology, 66(4), 278–286.
  18. Lall, S., Tung, L. Y., Ohlsson, C., Jansson, J. O., & Dickson, S. L. (2001). Growth hormone (GH)-independent stimulation of adiposity by GH secretagogues. Biochemical and biophysical research communications, 280(1), 132–138.
  19. Svensson, J., Lall, S., Dickson, S. L., Bengtsson, B. A., Rømer, J., Ahnfelt-Rønne, I., Ohlsson, C., & Jansson, J. O. (2000). The GH secretagogues ipamorelin and GH-releasing peptide-6 increase bone mineral content in adult female rats. The Journal of endocrinology, 165(3), 569–577.
  20. Chapman, I. M., Pescovitz, O. H., Murphy, G., Treep, T., Cerchio, K. A., Krupa, D., Gertz, B., Polvino, W. J., Skiles, E. H., Pezzoli, S. S., & Thorner, M. O. (1997). Oral administration of growth hormone (GH) releasing peptide-mimetic MK-677 stimulates the GH/insulin-like growth factor-I axis in selected GH-deficient adults. The Journal of clinical endocrinology and metabolism, 82(10), 3455–3463.
  21. Venkova, K., Mann, W., Nelson, R., & Greenwood-Van Meerveld, B. (2009). Efficacy of ipamorelin, a novel ghrelin mimetic, in a rodent model of postoperative ileus. The Journal of pharmacology and experimental therapeutics, 329(3), 1110–1116.

Scientifically Fact Checked by:

David Warmflash, M.D.

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