Impact of MK-677 on Gut Microbiome

In this article, we will take a close look at MK-677, also known as ibutamoren, and its potential impact on the gut microbiome. We will understand the role of growth hormones, which are stimulated by MK-677, in influencing the composition and diversity of gut microbiota. Furthermore, we will discuss the implications of these interactions for human health.
Klara Hatinova

Klara Hatinova

Klara is postgraduate researcher in experimental psychology at the
University of Oxford.

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Impact of MK-677 on Gut Microbiome

The current scientific literature does not provide any direct evidence linking the intake of MK-677 to changes in the gut microbiome. However, growth hormone, the anabolic hormone released in response to MK-677, has a demonstrated impact on the gut microbiota composition, diversity and gut barrier permeability.

What is MK-677?

MK-677, also known as ibutamoren, is a non-peptide growth hormone secretagogue. This means it stimulates growth hormone (GH) secretion within your body rather than directly supplying growth hormone. MK-677 was better at increasing GH levels than a previously used agent [1].

In addition to increasing GH levels, MK-677 also increases insulin-like growth factor (IGF-1) levels. This is because increases in GH levels trigger increases in IGF-1 levels [2]. IGF-1 has an anabolic effect and is important for growth in children [3, 4]

MK-677 has been evaluated for treating various clinical conditions, but it is not currently available therapeutically. Despite this, it is widely available online as a 'supplement' product [5].

In sports, MK-677 is considered a potential performance-enhancing compound due to its ability to stimulate the secretion of growth hormones. This increases one's ability to form lean body mass and muscle mass and improve body composition. This makes it a banned doping substance in human and equine sports [6].


As a supplement, MK-677 is not regulated by the FDA.

What is the Microbiome?

The microbiome refers to all the microbes that inhabit the human body - the human microbiota. This includes bacteria, viruses, and fungi. The largest community is the gut microbiome, but there are also microbes on your skin, hair, mouth, nose, vagina and other areas. The microbiome is highly dynamic and is influenced by factors such as diet, lifestyle, and the external environment [7, 8, 9].

These microorganisms are crucial in maintaining health and can influence the development and treatment of many health conditions. The roles of the microbiome include the following:

  • digestion
  • detoxification
  • immunity
  • protection against pathogens
  • metabolism of food and production of short-chain fatty acids

The diseases the microbiome has been linked to include:

The microbes generate short chain fatty acids, consequently impacting one's health.

MK-677 and the Microbiome

The gut microbiome, a complex ecosystem of bacteria in our intestines, plays a crucial role in our overall health and can be influenced by hormone levels such as GH. Supplementing MK-677, which increases GH levels, would also impact the human gut microbiome.

What Exactly Does Growth Hormone Do?

Growth hormone (GH), or somatotropin, is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals. It acts via the ghrelin receptor and is crucial for maintaining healthy human tissue, including the brain and other vital organs.

How does Growth Hormone Interact with the Microbiome?

There is sufficient evidence to say that without Growth Hormone, our microbiome composition would be different [12, 13].

In several studies, mice unable to produce GH had different levels of Lactobacillus, Lachnospiraceae, Bifidobacterium, and Faecalibaculum gut microbes [13]. This was age-dependent, meaning that the growth hormone levels reduced with age, as did the microbiome's composition. This was not the case in mice that could not produce growth hormone. Therefore, growth hormone levels could mediate between age and gut microbiota composition.

IGF-1, a peptide released downstream of GH, is also important in modulating the microbiome. In combination, GH and IGF-1 can impact the gut barrier's permeability, translocating bacteria throughout the body and multiplication of cells throughout the gastrointestinal tract [14]. Increasing movement of microbes can also impact the nervous system, as there is a clearly defined gut-brain axis.

Growth Hormone and the Microbiome

Growth hormone can impact the microbiome by changing the permeability of the gut barrier, cell proliferation, immunity and altering the microbial species in the microbiome

MK-677 and the Microbiome

In the section above, we have discussed how growth hormone and IGF-1 impact the gut microbiome. But what about MK-677? It is fair to assume that since MK-677 stimulates the release of growth hormone and IGF-1, its effect on the gut microbiome will be similar.

Nonetheless, there may be a subtle change in the impact of MK-677 vs endogenous growth hormone on the gut microbiome. This is because MK-677 is taken in tablet form. The synthetic tablet itself contains additional agents to improve the absorption of the active substance ibutamoren. Therefore, these chemicals can also impact the gut microbiome. A direct investigation of the microbiome species and gut permeability would be required to determine these additional effects.

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Klara Hatinova

Klara Hatinova

Klara is a postgraduate researcher in experimental psychology at the University of Oxford. She has worked across a spectrum of hot topics in neuroscience, including her current project measuring reinforcement learning strategies in Parkinson’s disease. Previously, she studied the efficacy of psilocybin as a therapy for critical mental health conditions and examined molecular circadian rhythms of migraine disorders. She completed her undergraduate degree in Neuroscience at the University of Glasgow and participated in a year abroad at the University of California, where she worked on a clinical trial for spinal cord injury.