MK-677 and erectile dysfunction: how to use it correctly

MK-677 erectile dysfunction – Are you trading erections for looking bigger and more ripped?

Have you gotten erectile dysfunction from MK-677?

In this article, I’m going to show you why MK-677 might cause ED, and how it can actually help with erections as well.


What is MK-677 (Ibutamoren mesylate)

Ibutamoren is an oral medication, non-peptide agonist of the ghrelin receptor. MK 677 half-life is about 24 hours, so you only need to take it once per day.

Activation of the ghrelin receptor promotes the release of growth hormone levels (GH) from the pituitary gland. Thus MK-677 mimics the growth hormone-stimulating action of ghrelin.

MK-677 was designed to boost growth hormone production in people with a medical condition of growth hormone deficiency. This deficiency limits growth during youth.

Additionally, many elderly adults tend to have low growth hormone, thus boosting GH can help retain muscle, get rid of body fat and improve sleep quality.

Other common GH secretagogues include pralmorelin (GHRP-2), GHRP-6, examorelin (hexarelin) & ipamorelin.

Since MK-677 is a ghrelin receptor agonist, it will likely have many similar actions to ghrelin itself.

Ghrelin receptors are widely expressed in:

  • Many brain regions
  • Pituitary
  • Intestine
  • Kidney
  • Thyroid gland
  • Lung
  • Heart
  • Pancreatic islets
  • Ovaries
  • Testis
  • Sebaceous glands

Thus, MK-677 can have effects on all those tissues.

Let’s look at what effects ghrelin has.

Ghrelin is important for:

  • Learning
  • Memory
  • Cognitive function
  • Reward
  • Sleep
  • Taste sensation
  • Smell, and sniffing

Ghrelin has the following effects:

  • sympatholytic (stimulates the sympathetic nervous system)
  • analgesic (blunts pain)
  • antimicrobial
  • antifibrotic
  • osteogenic (improves bone mineral density)


  • Makes the skeletal muscle more excitable
  • Stimulates muscle regeneration following injury and promotes wound healing
  • Delays puberty
  • Promotes fetal lung development
  • Decreases thyroid hormone and testosterone levels
  • Stimulates the release of growth hormone, prolactin, glucagon, adrenocorticotropic hormone, cortisol, vasopressin, and oxytocin
  • Inhibits insulin release
  • Protects the body by different mechanisms including inhibition of unwanted inflammation and induction of autophagy. 

Quite a comprehensive list.

Ghrelin is released mostly during fasting. So using MK-677 can artificially signal a state of fasting.

Thus, providing a fasting signal and then eating at the same time, could have some undesirable effects. More on that later.

MK-677 erectile dysfunction

Can MK-677 cause erectile dysfunction?

There are no clinical studies showing that MK-677 can cause erectile dysfunction, nor was this side effect ever mentioned in the trials looking at MK-677.

However, let’s look at a few of the possible mechanisms for how someone might get ED when taking MK-677.

#1 MK-677 increases prolactin

This is by far the most common theory of why MK-677 might cause ED. and also why people might ask: “does MK 677 cause gyno”?

Prolactin has been shown to inhibit penile erection, particularly at the penile base. This becomes more obvious when the erection time lasts longer than 10 min (R).

Prolactin can inhibit erections by (R):

  • Lowering testosterone production.
  • Inhibiting dopamine release.
  • Inhibiting 5-alpha reductase and DHT production, which can also contribute to ED.
  • Inhibition of smooth muscle relaxation of the penile corpus cavernosum.

However, the increase in prolactin-induced by MK-677 seems to be small. Here are 2 studies showing a slight increase.

#1 After 8 weeks on 25mg MK-677, prolactin increased by 23%, from 7 to 8.6ug/L (R). Not a big jump and unlikely to contribute to ED.

#2 25mg MK-677 increased prolactin to 34.6ng/mL right after starting, which then dropped to 16.8 and 17.5ng/mL at weeks 2 and 8 respectively (R). Prolactin levels in the placebo group were 10.5 at the start, which then increased to 13.6 and 13.3ng/ml after 2 and 8 weeks respectively. It’s likely that these men had slightly elevated prolactin even before starting MK-677.

MK-677 erectile dysfunction prolactin

However, these three studies found no increase in prolactin on MK-677 (R, R, R).

In summary, is the MK-677-induced prolactin causing ED? Unlikely, unless someone already has high prolactin or is unhealthy to the point that a small increase in prolactin will send them over the top.

The most common recommendation for MK-677-induced ED is 100mg of vitamin B6. B6 helps lower prolactin by promoting dopamine production. It’s likely that people who benefit from B6 supplementation are low, to begin with.

Instead, optimize your diet as well, while using MK-677. Then you’ll have no need for supps.

#2 MK-677 lowers testosterone

The only study looking at the effects of MK-677 on testosterone found that it slightly lowered testosterone.

25mg MK-677 decreased testosterone from 22.4 (646ng/dl) to 19.7 to 20.7 (597ng/dl) after 2 and 8 weeks respectively. That’s a small 49ng/dl decline. Their testosterone was just under 600, which is more than enough for proper erections (R).

There aren’t any studies looking at MK-677 and aromatase and estradiol production, but ghrelin has been shown to lower aromatase (R). This would mean that activation of the ghrelin receptor (by MK-677 for example) is likely to lower estradiol.

The reason I bring this up is because a high estradiol-to-testosterone ratio contributes to ED. If MK-677 increased estradiol, it might have contributed to ED via this mechanism, but it seems unlikely.

#3 MK-677 stimulates the sympathetic nervous system

The sympathetic nervous system helps with arousal and getting an erection. However, too much stimulation will kill libido and contribute to premature ejaculation.

Sympathetic stimulation is responsible for vascular smooth muscle contraction of the penis as well as the promotion of the release of noradrenaline, adrenaline and cortisol. In high amounts that are unfavorable.

Contraction of the smooth muscle tissue of the penis inhibits the ability to get erections.

Ghrelin increases muscle sympathetic nervous system (R). So it’s possible that MK-677, by activating the ghrelin receptor, might be able to do the same.

Interestingly, MK-677 has been shown to lower blood pressure.

#4 MK-677 might worsen insulin sensitivity

Studies show that MK-677 can increase fasting glucose and insulin. This is a sign of insulin resistance. This is what should happen when you fast. However, on MK-677, people aren’t fasting. So you’re sending fasting signals while eating, which then creates insulin resistance and impaired glucose handling.

The prevalence of ED is approximately 3.5‐fold higher in men with diabetes than in those without diabetes (R).

If you already have high fasting glucose and then go on MK-677, it might likely make it worse. High blood sugar can contribute to vascular inflammation, which can worsen erectile function over time.

A lot of people use MK-677 to lose fat and insulin resistance is commonly found in overweight individuals.

Plus, if you’re already insulin resistant, and then eat a ton of food because you’re super hungry on MK-677, that will worsen glucose handling even more.

#5 MK-677 might cause performance anxiety-induced ED

There is evidence showing that MK-677 can worsen anxiety in predisposed individuals. Many users report the same thing. If MK-677 makes you nervous, this might be a boner killer.

How MK-677 can help with erections

More likely than not, MK-677 will boost your libido instead of lower it. High libido is more likely to help with erections.

Here are a few ways how MK-677 can help with erections.

#1 MK-677 boosts growth hormone

Growth hormone spikes when you get an erection.

Men with organic ED (of vascular origin) have lower baseline growth hormone and a blunted rise in growth hormone during erections (R). In the first graph, you can see how GH spikes as you get an erection. In the graph on the right, you can see that GH is much lower in men with ED and that they have a blunted spike in GH.

MK-677 erectile dysfunction growth hormone

By boosting GH, MK-677 is likely to help with erections.

MK-677 might also be able to keep your GH normal for a long time.

25mg MK-677 increased GH to normal levels and kept it there for at least 12 months. GH levels increased by 1.8 fold and IGF-1 levels also increased by 1.5 fold in the treatment groups (R).

MK-677 erectile dysfunction GH and IGF-1

#2 MK-677 boosts insulin-like growth factor-1 (IGF-1)

25 mg/day MK-677 increased mean serum IGF-I concentrations from 141microg/L at baseline to 219 and 265microg/L at week 2 and 4 (R).

MK-677 erectile dysfunction IGF-1

High GH will lead to higher IGF-1.

IGF-1 is positively correlated with sexual function (R) and promotes DHT and nitric oxide (NO) production.

If you’re not getting a decent boost in sexual function from MK-677, it might be that your GH and IGF-1 aren’t spiking high enough.

#3 MK-677 might increase dopamine

Ghrelin agonists promote motivation by boosting dopamine in mice (R). Dopamine helps to promote sexual desire and sexual function (R).

On the flip side, ghrelin decreases sexual behavior in rats (R).

Since we are neither mice or rats, it’s hard to say what will happen to your libido on MK-677. According to online anecdotal evidence, some people do report a boost in libido, whereas others don’t.

As an aside, ghrelin increases during fasting. During fasting, testosterone and T3 drop to slow the basal metabolic rate. Sexual function also goes down. Ghrelin agonists might do the same.

Other benefits of MK-677

MK 677 muscle gain

MK-677 has a strong muscle-sparing effect during a deficit and can even boost lean body mass and muscle growth.

During a caloric deficit without MK-677, nitrogen loss was 2.67g/day. On MK-677, the nitrogen balance was 0.31g/day (R). It went from a minus to a positive. Building muscle in a deficit.

Due to its muscle-sparing effect, it can also be very helpful against muscle wasting.

No PCT required

No side effects when stopping. Once you stop, GH and IGF-1 will likely go back to where they were before you started. Since MK-677 doesn’t suppress natural testosterone production, you don’t have to PCT or anything. It’s also not a selective androgen receptor modulator (SARM), so it does mess with your androgenic system at all.

Might improve thyroid hormone levels

This study found that 25mg MK-677 increased free T3 from 5.66 to 6.04pmol/L after 8 weeks (R).

Unlike ghrelin which suppresses thyroid function, MK-677 doesn’t seem to do the same.

Might help with hair regrowth

IGF-1 promotes hair growth, so restoring IGF-1 to normal might help (R).

Improves sleep quality

In young subjects, 25mg MK-677 increased deep sleep (stage 4) by 50% and REM (rapid eye movement) sleep by 20%. It also corrected a lot of deviations from normal sleep.

In older adults, treatment with MK-677 increased REM sleep by 50% and decreased the frequency of deviations from normal sleep (R).

Most people using MK-677 report improvements in sleep quality.

Adverse side effects of MK-677

MK-677 might worsen insulin resistance and glucose handling

Increases fasting blood sugar levels and contributes to insulin resistance. 25mg increased fasting glucose from 5.4 to 6.8nmol/L after 4 weeks (R).

Since ghrelin increases during fasting to promote lipolysis and gluconeogenesis (production of glucose), you can expect to become a little more insulin resistant. It’s supposed to happen when you fast.

MK-677 might cause heart problems

This trial was terminated early due to a safety signal of congestive heart failure in a limited number of patients (R).

MK-677 massively increases appetite

Since ghrelin is the hunger hormone, activating its receptor with MK-677 does the same.

It might be helpful for someone with low appetite, but most people can do with less appetite.

This review cracked me up:

I forgot about the hunger thing when i went fishing the otherday and took a decent dose before i left… BROOOO… IN the middle of fishing i told the people i was with im hungry and they offered me their cookies and i said it wasnt enough.. Man i fuckin left Speeding to the store @90mph almost in tears because i was SO FUCKIN HUNGRY I ate like 3hunnybuns+ 2cupcakes+ fuckin m&ms and a big ass bag of chips 😂😂😂. That shit was brutal as fuck. 😂😂😂.” (R)

MK-677 might make you more anxious

Ghrelin receptor agonists enhance fear memory (R). It might mean that MK-677 might make someone more anxious/fearful.

Quite a few people report that MK-677 significantly worsened their pre-existing anxiety (R). If you don’t have anxiety, MK-677 will likely not cause it.

But if you have anxiety, or are pre-disposed to it, it might definitely worsen your anxiety.

Does MK-677 cause brain damage?

Long-term use of Ibutamoren (MK-677) can lead to continuous activation of ghrelin receptors, which some researchers believe may have potential risks to brain health. This is why it’s recommended to cycle MK-677.

Neutral effects of MK-677


  • Doesn’t affect cortisol levels (R).
  • Likely doesn’t affect the metabolic rate long-term (R).


What Happens When You Stop Taking MK-677?

When you decide to stop taking MK-677, there are a few things that may occur as your body adjusts to the absence of the compound:

  1. Potential Decrease in GH Levels: Since MK-677 is a GH secretagogue, which means it stimulates GH release, stopping its use may lead to a reduction in GH levels. This decrease in GH can impact muscle growth, recovery, and overall body composition. It’s important to note that the extent and duration of this decrease depend on various factors, such as individual physiology, dosage, and duration of use.
  2. Loss of Water Retention: MK-677 can cause water retention in some individuals, leading to a slightly bloated appearance. When you stop taking it, this water retention may gradually subside, resulting in a leaner and more defined physique.
  3. Possible Decrease in Appetite: MK-677 is known to increase appetite, which can contribute to muscle gains and overall body weight. When you cease taking it, you may experience a decrease in appetite as your body adjusts. However, appetite levels should return to normal over time.
  4. Rebound Effects on Sleep Quality: MK-677 has been reported to improve sleep quality for some users. When discontinuing its use, you might notice a temporary alteration in your sleep pattern as your body readjusts to its natural sleep cycle.

It’s worth noting that individual experiences may vary, and not everyone will encounter significant changes when stopping MK-677. To minimize any potential side effects and ensure a smooth transition, it’s always advisable to consult with a healthcare professional before starting or discontinuing any supplement or medication.

What does MK 677 do and how does it work?

MK 677, also known as Ibutamoren or Nutrobal, is classified as a selective agonist of the ghrelin receptor and acts as a growth hormone secretagogue, meaning it stimulates the production and release of growth hormone.

One of the main benefits of MK 677 is its ability to increase growth hormone levels in the body. Growth hormone is essential for various bodily functions, including muscle growth, bone density, metabolism, and overall tissue repair. By increasing growth hormone levels, MK 677 may promote muscle growth and improve recovery after intense workouts.

Additionally, MK 677 has been shown to increase insulin-like growth factor 1 (IGF-1) levels. IGF-1 is a hormone that plays a crucial role in promoting cell growth and development. By increasing IGF-1 levels, MK 677 may further enhance muscle growth and recovery.

Another interesting aspect of MK 677 is its potential to improve sleep quality. Many users report experiencing deeper and more restful sleep while taking this compound. Adequate sleep is essential for muscle recovery and overall well-being, so this is an added benefit for those using MK 677.

It is important to note that MK 677 is not a steroid and does not suppress natural hormone production. However, like any compound, it may have side effects, and it is always recommended to consult with a healthcare professional before using any new substance.

How long should you take MK 677?

In general, most users tend to take MK 677 for a period of 8 to 12 weeks. This timeframe allows sufficient time for the compound to exert its effects and for you to assess how it impacts your body. It is important to note that these timelines are not set in stone.

Long-term usage of MK 677 is generally not recommended due to limited research available on the effects of prolonged use. As with any supplement, it is crucial to prioritize your safety and well-being, and to use MK 677 responsibly.

How much MK 677 should I take?

Generally, the suggested dose ranges between 10mg to 25mg per day. Some users start with a lower dose and gradually increase it to assess their tolerance and response.

Additionally, considering the long half-life of MK 677, taking it once a day is sufficient. Most people prefer to take it in the evening due to its potential to cause mild drowsiness, which can help promote better sleep.

Remember, consistency is key when it comes to achieving desired results. Your best results will likely come after 4-6 weeks.

Can MK 677 make you taller?

While MK 677 is known to promote muscle growth, improve bone density, and enhance recovery, the notion that it can make you taller is not entirely accurate. Growth hormone plays a crucial role in the development and growth of bones during adolescence, but once a person reaches their full adult height, it is unlikely that any further height increase can be achieved, regardless of supplementation.

While MK 677 may help optimize your body’s natural growth hormone production, it is not a magical solution to making you taller beyond your genetic potential.

For someone with short stature during development, MK-677 might help boost growth to normal levels.

How long does mk677 take to work?

Typically, users may start to notice some effects of MK677 within the first few weeks of consistent use. These effects can include improved sleep quality, increased appetite, and a general sense of well-being. An increase in appetite and improvement in sleep might happen right away. Physique benefits will likely come later.

The full effects of MK677 can take several weeks or even months to fully manifest. As with most supplements, patience and consistency are key. It is important to adhere to the recommended dosage and allow your body enough time to adjust to the compound.

How long to cycle MK 677?

Most MK-677 cycles last 8 to 12 weeks. After that, stop for 6-8 weeks before using it again if desired.

When should I take mk677?

Mk677 has a half-life of approximately 24 hours, meaning it remains active in your system for an extended period. As a result, most individuals will take mk677 once a day to maintain stable blood concentrations.

The best time to take mk677 is typically in the evening or before bed. This timing is preferred because the compound can increase growth hormone levels and promote better sleep quality. Taking it before bed allows for sufficient time for the compound to metabolize and exert its effects while you sleep, aiding in muscle recovery and regeneration.

However, it is worth noting that individual responses to mk677 may vary. Some people may find that taking it in the morning or at other times of the day suits them better.

Taking it in the morning could give your workout a boost and increase your appetite if that’s what you desire.

Is MK-677 a SARM?

MK-677 is wrongly mislabeled as a SARM (selective androgen receptor modulator) since it doesn’t interact with androgen receptors.

Unlike SARMs, which directly bind to and activate androgen receptors in specific tissues, MK-677 stimulates the secretion of growth hormone and insulin-like growth factor 1 (IGF-1). This leads to increased levels of both hormones, resulting in enhanced muscle growth, improved bone density, and increased metabolism.

Does mk677 suppress testosterone?

Preliminary studies have suggested that mk677 may not directly suppress testosterone production. In fact, some research indicates that it may even have a positive impact on testosterone levels. One study conducted on healthy young men found that mk677 increased growth hormone and insulin-like growth factor 1 (IGF-1) levels without significantly affecting testosterone levels.

However, it’s important to note that the long-term effects and potential interactions of mk677 on testosterone production are still not fully understood.

MK-677 before and after

Here are a few MK-677 impressive before and afters. Keep in mind that these guys also stuck to a good diet (tracked calories and macros) and trained hard!

MK-677 before and after
MK-677 before and after
MK-677 before and after
MK-677 before and after

Best MK-677 sources

Summary – MK-677 erectile dysfunction

It’s possible that MK-677 might contribute to ED by 1) increasing prolactin 2) lowering testosterone 3) worsening insulin resistance and 4) causing anxiety. However, these effects are likely too small to cause any real issues, unless they were already suboptimal before starting MK-677.

However, MK-677 is more likely to improve erections by 1) improving libido, 2) increasing GH, 3) increasing IGF-1 and 4) increasing dopamine.

Is MK-677 worth it?

MK-677 can speed up fat loss and help retain muscle mass during a deficit. We all want fast results. But if it lowers your quality of life, it’s not worth it.

Stick to good dietary and lifestyle habits that will ensure that you lose fat and build muscle over the long run. Hopefully, you’re in this for the long run which will be a couple of decades. If that’s the case, diet, exercise, sleep, sunlight, etc., will be the best bang for your buck.

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>1000ng/dl Testosterone: My Step-by-Step Guide on How I Do It Naturally!

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