Ibutamoren (MK-677) Effects and Reviews

By Dr. Dimitar Marinov

medical reviewed by Best HGH Doctors and Clinics dedicated team.

Evidence basedThis article is reviewed by medical professionals for the relevancy and accuracy of the content. Every article is evidence-based and contains references to peer-reviewed studies and academic research.

The growth hormone market is full of products claiming to be as effective as the FDA-approved therapy with human growth hormone (HGH).

One of these products is a growth hormone secretagogue (GHS) called Ibutamoren (code names MK-677 and L-163,191). Sellers present it as a newer, safer, more convenient, and much more affordable therapy for low HGH.

Its popularity stems from the fact that there is no need for daily injections like other GHS or HGH. It’s an oral non-peptide HGH stimulant.

Yet, MK-677 is not FDA-approved, and research about its safety and effectiveness is scarce. You can buy the product only illegally and without any guarantee about its contents or possible risks.

In this article, we will break down the evidence so far and weigh in on all pros and cons of MK-677.

What does MK-677 do?

MK-677 belongs to a class of drugs that stimulate the pituitary gland into producing more growth hormone.

What is Ibutamoren (MK-677)?

It is a GHS that mimics the hunger hormone (ghrelin). Ghrelin spikes when you are hungry and triggers the ghrelin receptors in the brain called growth hormone secretagogue receptors (GHS-R).

According to research, activating these receptors will increase your appetite, but also stimulate the pituitary gland to produce HGH which helps counteract low blood sugar while fasting.

Thus, MK-677 triggers the GHS-R by mimicking ghrelin and stimulates natural HGH production. Animal studies report that GH levels rise 30-40 minutes after oral administration of Ibutamoren and the effect continues for several hours.

The half-life of MK-677 is 4-6 hours which is significantly longer than most GHS. It’s orally active due to its non-peptide structure.

Ibutamoren leads to increased frequency in growth hormone pulses and an increase in the normal levels of insulin-like growth factor-1 (IGF-1). IGF-1 is the mediator of HGH’s anabolic effects.

For example, a trial with 65 elderly people (aged 60-81) showed that 25mg of MK-677 taken by mouth increases mean HGH and IGF-1 levels up to those of healthy young adults. The study also revealed that long-term Ipamorelin intake (up to 2 years) can successfully maintain high HGH and IGF-1 levels.

However, there is a lack of large studies investigating the effects of MK-677 in more diverse population groups.

MK-677 is still a drug under investigation that’s not approved for marketing in the US. Thus, any forms of Ibutamoren available on the market are illegal and unregulated.

Are the benefits of MK-677 so great?

MK-677 is mainly investigated for the treatment of growth hormone deficiency (GHD) and muscle wasting. According to a trial in 32 healthy elderly people, ibutamoren leads to a 55% increase in IGF-1 levels at 2 weeks and 88% by 4 weeks.

Increase in IGF-1 and HGH levels from Ibutamoren

However, only one study has investigated its effectiveness in patients with GHD. Young adults with childhood-onset GHD took 50mg of MK-677 for 4 days. The participants achieved IGF-1 levels comparable to the reference values for healthy elderly individuals.

Currently, we lack studies on Ibutamoren’s effects on children. One study reports that a week of MK-677 leads to an increase in HGH and IGF-1 levels but the exact effects on long-term growth remain unknown.

A study in younger obese individuals found that 2 months of oral treatment with the GH secretagogue MK-677 resulted in an increase in muscle mass of approximately 3 kg and a transient increase in basal metabolic rate. The scientists reported no significant changes in fat mass in the initial study or the follow-up.

The previously mentioned 2-years long trial with 65 elderly people reported 5-7 lbs. of weight gain for the whole period of the study. There were no changes in fat mass or muscle strength despite the increase in HGH secretion.

There are currently no studies investigating the effect of MK-677 on muscle wasting and cachexia

MK-677 also led to a slight reduction in LDL levels and an increase in bone mineral density. However, no significant functional improvements have been reported in patients with bone fractures.

In addition, some healthy people who took MK-677 reported improved deep sleep and decreased sleep latency.

What are the most common side effects of Ibutamoren?

The most commonly reported side effect of MK-677 is an increase in appetite, which is a result of triggering the ghrelin receptors. However, the effect appears to be transient and decreases with prolonged use.

Ibutamoren also leads to transient elevation of cortisol, prolactin, and leptin levels, while thyroid hormones increase after 1-2 months of therapy. Furthermore, it may lead to decreased total testosterone (T) without affecting free T levels.

According to the long-term trial in healthy older adults potential side effects of MK-677 include:

  • muscle pain
  • water retention
  • increased blood sugar
  • increased insulin resistance


Also, one study of MK-677 was terminated early due to a safety signal of congestive heart failure in a limited number of patients.

Due to its illegal status, there is also a high chance of counterfeit, diluted, and contaminated products. In fact, most illegal sellers wrongly label it as a SARM (selective androgen receptor modulator) – a class of drugs with similar anabolic properties to anabolic steroids, and many mistakenly consider HGH to be a steroid (which they are not).

How do users review MK-677?

MK-677 users share that they have experienced benefits such as improved recovery from training, improved muscle pump, and better sleep.

User reviews about MK-677

Many of them also took it in an attempt to heal sports traumas. Some users suggest that it helped them recover their joints and tendons after training injuries.

Most of the MK-677 users report variable results in muscle gain, fat gain, and water retention. That might be due to the illegal status of the medication and the lack of quality regulation.

Manufacturers can dilute it or add various substances, so you never know what effects to expect

The main negative effects reported were:

  • headaches
  • hunger
  • sugar cravings
  • sleepiness
  • water retention


Most users recommend taking Ibutamoren in the evening, due to the sleep-promoting effects as well as in an attempt to avoid extra hunger and weight gain.

On the other hand, when you start legal HGH therapy, you will be monitored by a medical doctor. An experienced endocrinologist will assess your results and the risk of side effects on every checkup.

If there are any concerns, your physician can make the necessary changes to ensure the safety and effectiveness of your treatment.