MK-677 and Erectile Dysfunction: Is There a Link?

MK-677, a common growth hormone secretagogue, is popular among bodybuilding communities due to its effects on muscle growth and tissue recovery. As an anabolic hormone, there are case reports and rumours that MK-677 could cause erectile dysfunction. This article discusses the science behind the rumours.
Klara Hatinova

Klara Hatinova

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

A blue image with text saying "Can MK-677 Cause Erectile Dysfunction?"

Can MK-677 cause erectile dysfunction?

There are case reports where men have taken MK-677 for performance enhancement and experienced difficulty getting an erection. One explanation is that MK-677 may increase prolactin levels. However, the exact link between MK-677 and erection dysfunction is still a little unclear.

MK-677 and Erectile Dysfunction

MK-677 is a growth hormone secretagogue, meaning it can act on the pituitary master gland in the brain to increase the release of Growth Hormone (GH). Due to this, the non-peptide supplement MK-677 has been used for muscle growth, preventing weight-loss sarcopenia, improving tendon repair, increasing bone density and other anabolic benefits.

Nonetheless, the FDA has not approved MK-677 for this use. The FDA, or Food and Drug Administration governs medical drugs, which do not include health supplements. Therefore, the evidence for MK-677's safety and efficacy comes only from small studies, rarely done in a controlled and systematic way. This makes it challenging to establish the side effects of taking MK-677, such as its link with cancer or brain damage.

Erectile dysfunction is a common side effect of androgen-enhancing drugs, especially after withdrawal from these drugs [1]. Androgen-enhancing drugs increase levels of steroid hormones, including testosterone and are similar to MK-677. Androgen-enhancing drugs have a common target of increasing growth hormone.

This begs the question – does MK-677 cause erectile dysfunction?

Prolactin, Growth Hormone, MK-677 and Erectile Dysfunction

Prolactin and Erectile Dysfunction

Prolactin is a hormone pituitary gland produces, just like Growth Hormone. Although it is commonly linked to breastfeeding, its function in men is equally essential to regulating sexual function. Hyperprolactinemia, or high levels of prolactin in the blood, is known to induce erectile dysfunction [2].

Elevated prolactin levels have been shown to inhibit penile erection, particularly at the penile base. This was established based on a study that found that base erection time was correlated with prolactin levels, meaning higher prolactin levels led to longer base erection times [3].

Hyperprolactinemia can lead to erectile dysfunction through several mechanisms. One of the plausible mechanisms is a reduction in testosterone production, a crucial hormone for sexual function in men. However, this is by no means the only mechanism since many males with high prolactin levels also have regular testosterone levels. Alternative mechanisms may involve cortisol and neurotransmitter regulation of the link between prolactin and testosterone [4].

In some cases, hyperprolactinemia can be a side effect of certain medications, which is why men are worried about taking growth hormone secretagogues.

Prolactin and MK-677

Growth hormone secretagogues, such as MK-677, have been linked to increased prolactin levels [5].

MK-677 acts on the pituitary gland, which releases both GH and prolactin, which may explain why MK-677 can also increase prolactin levels. GH and prolactin are similar in chemical structure, meaning their synthesis process is similar. This means that prolactin may be equally affected if there is a deficit in producing GH [6].

So Can MK-677 Cause Erectile Dysfunction?

There are case reports where men have taken MK-677 for performance enhancement and experienced difficulty getting an erection. Therefore, erectile dysfunction is a symptom you should look out for if supplementing with MK-677, and weigh out the benefits of taking MK-677 against its side effects.

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.