MK-677 (Ibutamoren)

What it is

MK-677, also called ibutamoren or MK-0677, is commonly grouped with “peptides” in wellness and bodybuilding discourse, but chemically it is not a peptide^{[6 ,13 ]}. It is an orally active small-molecule agonist of the ghrelin/growth hormone secretagogue receptor that increases pulsatile growth hormone secretion and downstream IGF-1 levels^{[6 ,13 ]}.

MK-677 was developed as part of a pharmaceutical search for growth hormone secretagogues that could stimulate endogenous GH rather than replace GH directly^{[6 ]}. It was studied in catabolic states, older adults, Alzheimer disease, hip-fracture recovery, and kidney-disease populations^{[6 –12 ]}. Despite this clinical research program, it has no FDA-approved indication.

At the receptor level, ibutamoren activates the ghrelin receptor, which is involved in growth hormone release, appetite, energy balance, and metabolic regulation^{[13 ]}. Structural work has shown how ghrelin and ibutamoren signal through the human ghrelin receptor^{[13 ]}. This biology helps explain both its research interest and its adverse-effect concerns.

In clinical studies, ibutamoren has generally been administered orally^{[6 –12 ]}. This page describes published studies and regulatory status only and does not provide dosing guidance.

Regulatory status

Ibutamoren is not FDA-approved for growth hormone deficiency, sarcopenia, bodybuilding, anti-aging, appetite stimulation, recovery from fracture, Alzheimer disease, dialysis, or any other indication. No FDA-approved ibutamoren product label was identified during this review.

503A Category 2

FDA’s 503A framework allows compounding from a bulk drug substance only when the substance satisfies a USP/NF monograph pathway, is a component of an FDA-approved drug when no monograph exists, or appears on FDA’s 503A bulks list^{[1 ]}. FDA’s April 22, 2026 category document lists Ibutamoren Mesylate in 503A Category 2, the category for bulk substances that raise significant safety concerns^{[2 ]}.

503B Category 2 and the heart-failure signal

FDA’s safety-risk page lists ibutamoren mesylate in both 503A and 503B Category 2. FDA states that ibutamoren poses significant safety risks due to potential congestive heart failure in certain patients and notes a randomized placebo-controlled hip-fracture trial that was terminated early because of a potential congestive-heart-failure safety signal^{[4 ]}.

October 2024 PCAC vote

The October 29, 2024 PCAC minutes state that FDA reviewed ibutamoren mesylate for growth hormone deficiency, osteoporosis, hip fracture, sarcopenia, obesity, and Alzheimer disease^{[5 ]}. The committee voted 1 yes and 13 no on whether ibutamoren mesylate should be placed on the 503A bulks list, with concerns including fluid retention, congestive heart failure, and hyperglycemia^{[5 ]}.

For 503B outsourcing facilities, FDA states that bulk drug substances must be on the 503B bulks list or used for a drug on the shortage list at the relevant time^{[3 ]}. FDA’s safety-risk page also identifies ibutamoren mesylate as 503B Category 2^{[4 ]}. MK-677/ibutamoren is not listed in federal controlled-substance schedules in 21 CFR Part 1308 as reviewed on May 7, 2026^{[14 ]}.

Research summary

Early human studies established endocrine activity. Murphy and colleagues reported that MK-677 reversed diet-induced catabolism and increased GH/IGF-1-related markers in a controlled clinical setting^{[6 ]}. Svensson and colleagues studied obese young males and found increased markers of bone formation and resorption^{[7 ]}. These studies show biological activity but do not establish clinical benefit for athletic performance or anti-aging.

Older-adult body composition: Nass 2008

The most cited older-adult trial was a randomized study by Nass and colleagues. In healthy older adults, oral ghrelin mimetic MK-677 increased GH and IGF-1 and changed body composition, including increased fat-free mass, but it did not meaningfully improve functional outcomes^{[8 ]}. The study also reported adverse effects such as increased appetite, transient edema, and changes relevant to glucose metabolism^{[8 ]}.

Alzheimer disease: negative trial

The Alzheimer disease program was negative. Sevigny and colleagues conducted a randomized trial of MK-677 in Alzheimer disease and reported no clinical effect on Alzheimer disease progression^{[9 ]}. This is important because neurodegenerative and “brain health” claims sometimes appear in online discussion despite a published negative clinical trial.

Hip-fracture recovery: heart-failure signal

The hip-fracture recovery program raised safety concerns. Adunsky and colleagues conducted a multicenter randomized placebo-controlled phase 2b study in patients recovering from hip fracture^{[10 ]}. FDA later cited this trial in its safety-risk page and PCAC discussion because the trial was terminated early due to a potential congestive-heart-failure signal^{[4 –5 ,10 ]}.

Hemodialysis IGF-1 study

Other clinical research has explored special populations. Campbell and colleagues studied MK-0677 in hemodialysis patients and found increased serum IGF-1 in a randomized blinded study^{[11 ]}. Such physiologic findings do not prove benefit on hard outcomes such as hospitalization, mortality, frailty, or quality of life.

Marketplace quality and hepatotoxicity

Quality and marketplace concerns are also documented. Van Wagoner and colleagues analyzed products marketed as SARMs and sold online; ibutamoren appeared in this broader internet-product quality context^{[12 ]}. A 2025 case report described hepatotoxicity induced by MK-677^{[15 ]}. Overall, ibutamoren has meaningful human trial evidence, but the evidence includes negative efficacy trials and safety signals rather than an approved therapeutic profile.

Calibration

Older-adult body-composition data are frequently overinterpreted. In the Nass trial, increased fat-free mass did not clearly translate into improved strength or function^{[8 ]}. For a patient-facing reference page, the clinically meaningful endpoint is not whether IGF-1 rises, but whether people move better, fracture less, live longer, recover faster, or experience better quality of life without unacceptable harm. That has not been established for routine use.

There is also a category problem for this site. Ibutamoren is included because it appears in peptide-clinic discourse, but it should not be described as a peptide. Calling it a peptide may confuse readers about chemistry, regulatory treatment, and product-quality risks.

Regulatory and evidence assessments point in the same direction. FDA and PCAC materials identify specific safety concerns and a committee vote against 503A list inclusion^{[4 –5 ]}. A balanced page should include both the endocrine activity and the heart-failure, fluid-retention, and hyperglycemia concerns^{[4 –5 ,8 ,10 ]}.

The Alzheimer and hip-fracture studies are particularly important for editorial calibration. They show that a biologically active GH secretagogue can fail to improve a disease outcome or create safety concerns in vulnerable populations^{[9 –10 ]}. For readers, this is a useful lesson: changing a hormone marker is not the same as proving a treatment effect.

The most accurate editorial summary is that ibutamoren is a discontinued investigational drug candidate with real human data, not a validated wellness compound.

Public discourse

No qualifying public-discourse entries were identified for this page. Search results included bodybuilding videos, clinic pages, and anonymous forum discussions, but no accessible named-source podcast, article, or transcript with a verifiable quote meeting this site’s citation standard.

Public discourse reflects the views of the speakers cited and does not represent medical advice or the editorial position of ProPeptideGuide.

Side effects and safety

Ibutamoren’s known and theoretical adverse effects follow from ghrelin receptor and GH/IGF-1 activation. Published studies and FDA materials raise concerns about increased appetite, edema/fluid retention, hyperglycemia or glucose-metabolism effects, and congestive heart failure in susceptible patients^{[4 –5 ,8 ,10 ]}.

FDA’s explicit safety statement

FDA’s concern is explicit. The agency identifies ibutamoren mesylate as a significant-safety-risk bulk substance and cites a hip-fracture randomized trial terminated early because of a potential congestive-heart-failure signal^{[4 ]}. PCAC minutes also record committee concerns about fluid retention, congestive heart failure, and hyperglycemia^{[5 ]}.

Long-term safety not established

Long-term safety is not established for anti-aging, bodybuilding, or wellness use. GH/IGF-1 axis stimulation may be clinically relevant in people with diabetes, prediabetes, active malignancy, edema, heart failure, sleep apnea, or conditions affected by growth-factor signaling. No FDA-approved label exists to define contraindications, monitoring, or drug interactions.

Grey-market product risks

Grey-market product risks include inaccurate labeling, contamination, variable dose, and undisclosed ingredients. The internet-marketplace literature for performance-enhancing products supports caution about assuming that a product labeled MK-677 contains only the stated ingredient^{[12 ]}.

The 2025 hepatotoxicity case report adds a separate caution signal^{[15 ]}. A case report cannot establish incidence or prove that all MK-677 exposures cause liver injury, but it is relevant to claims that ibutamoren is a benign supplement-like compound. Liver injury, edema, hyperglycemia, and heart-failure concerns should be discussed before any public-facing provider listing is considered.

Available through

Ibutamoren is not currently available through FDA-compliant prescription or compounding channels in the United States as of 2026-05-07^{[1 –5 ]}. ProPeptideGuide does not link to or endorse grey-market vendors.