MK-677 (Ibutamoren) + GHK-Cu Stack: When to Pick One Over the Stack

What each one actually is

MK-677 (ibutamoren mesylate) is an oral, non-peptide small molecule that stimulates growth hormone release by acting on the ghrelin receptor and raises IGF-1. Merck first synthesized it in 1995 and stopped development in 1999 [5]. It is not a peptide and not a SARM, even though it is often sold alongside SARMs [5]. Ibutamoren is also under study as LUM-201 for pediatric growth hormone deficiency: in a randomized placebo-controlled trial of 68 prepubertal children given oral LUM-201 for 6 months, FDA's review says it was generally well tolerated, with increased appetite the most common drug-related event at 2.5 to 3 times the placebo rate [12][5].

GHK-Cu is the copper(II) complex of GHK, a tripeptide found in human plasma, saliva and urine, with levels reported to decline with age [6]. FDA knows of no approved drug that contains GHK-Cu. It should not be confused with copper histidinate (Zycubo), a different FDA-approved drug for Menkes disease [8][13]. GHK-Cu's proposed collagen, proteoglycan, metalloproteinase and wound-healing actions come from laboratory and animal work, not from proven human effects [6].

The MK-677 trial record

A 2-year, double-blind trial in 65 healthy adults aged 60 to 81 found that 25 mg daily raised fat-free mass by 1.1 kg after 12 months, against a 0.5 kg fall on placebo, while body weight rose 2.7 kg versus 0.8 kg [14]. Strength and function did not improve. Fasting glucose rose about 5 mg/dL (P=0.015), insulin sensitivity fell, and LDL dropped about 5 mg/dL; the most frequent side effects were increased appetite, transient mild leg edema and muscle pain [14][5].

In a 24-week hip-fracture trial of 123 patients given 25 mg daily, the trial was stopped early for a safety signal of congestive heart failure: per FDA's summary, 4 patients (6.5%) on MK-677 versus 1 (1.7%) on placebo [2][5]. IGF-1 rose 51.4 ng/mL more than placebo and gait speed improved, but most other functional measures did not, and the authors concluded MK-0677 has an unfavorable safety profile in that population [2].

The other large trials point the same way. In 161 hip-fracture patients treated for 6 months, IGF-1 rose 84% versus 17% but function did not significantly improve; serious adverse events occurred in 24% versus 18%, thrombosis in 4 versus 0, and HbA1c rose 0.7% versus 0.3% [15][5]. In 563 people with mild to moderate Alzheimer disease treated for 12 months, IGF-1 rose 72.9% with no effect on disease progression; drug-related adverse events were 35.5% versus 23.9%, and blood glucose increases occurred in 15.4% versus 4.6% [16][5]. In 24 obese men given 25 mg daily for 8 weeks, IGF-1 rose about 40% and fat-free mass increased, but total and visceral fat did not change and an oral glucose tolerance test showed impaired glucose handling at 2 and 8 weeks [17].

Shorter studies add hormone responses and a bone-drug interaction. In 32 healthy adults aged 64 to 81, 25 mg daily raised mean 24-hour GH concentration 97 plus or minus 23% after 2 weeks and IGF-1 from 141 to 265 micrograms per liter at 4 weeks, with fasting glucose rising from 5.4 to 6.8 mmol/L [18]. In 292 postmenopausal women with osteoporosis, adding MK-677 to alendronate raised femoral neck bone density 4.2% versus 2.5% with alendronate alone, with no extra gain at the spine, total hip or total body; 8.6% of women across all four arms stopped for adverse events judged treatment-related [19]. FDA's review of MK-677 reports no formal drug-interaction studies [5].

There is no approved dose. Trials used fixed oral doses of 2 mg to 50 mg per day, 25 mg once daily in most adult trials, for up to 2 years [5].

The GHK-Cu trial record

Topical copper-peptide products are sold as cosmetics, which do not require FDA approval before sale; disease-treatment or structure/function claims can make a product a drug under the law [20].

Human evidence is limited. After circumoral CO2 laser resurfacing, 13 patients completed a randomized study of skin care with or without GHK-Cu; computer analysis and blinded evaluators found no significant difference in redness resolution, wrinkles or overall skin quality, while a patient questionnaire showed a significant difference in overall skin quality favoring GHK-Cu (P=.04) [3]. In a trial of 86 evaluable patients with venous stasis ulcers, a 0.4% tripeptide copper complex cream was no different from an inert vehicle, while silver sulfadiazine 1% reduced ulcer size [4].

A 2026 systematic review of GHK-Cu literature from 2005 to 2026 kept 64 records and concluded that, despite four decades of preclinical work, the human literature is thin and fragmented: most randomized trials are small, run on facial cosmetic creams, and microneedle delivery has not been tested in a single registered, adequately powered human randomized trial [9].

The proposed mechanisms come from laboratory and animal work summarized by the researchers who advanced them: GHK is reported to stimulate collagen and proteoglycan production, modulate metalloproteinases, attract immune and endothelial cells to injury sites, and speed wound healing in dogs, rats, mice and pigs [6].

Picking one over the stack

Systemic goal versus local goal. The trials of IGF-1, lean mass and bone density on this page are of MK-677; GHK-Cu was not tested on those endpoints [14][19]. For laser-resurfaced skin or a chronic wound, the randomized human trials are of GHK-Cu, and their objective results were negative [3][4].

What has to be watched. MK-677 carries the fluid retention, glucose, HbA1c and congestive heart failure signals described above, and FDA places it in category 2 for significant safety risks in compounding, citing the potential for congestive heart failure in certain patients [1][5]. For injectable GHK-Cu, FDA states there are limited human data to inform safety-related considerations and flags a risk of immunogenicity from aggregation and peptide-related impurities [1].

Legal and sport status

MK-677 has no FDA approval. FDA's December 12, 2025 warning letter states that ibutamoren is excluded from the dietary supplement definition and that products marketed with drug claims for it are unapproved new drugs [7][5]. For compounding, FDA lists ibutamoren mesylate in category 2 for significant safety risks [1]; its advisory committee voted 1 yes, 13 no against adding it to the pharmacy bulks list, with members citing fluid retention, congestive heart failure and hyperglycemia [21]. It is not one of the six peptides in HHS's October 2026 draft enforcement-discretion policy [22]. Compounded drugs are not FDA-approved, and FDA does not review their safety, effectiveness or quality before marketing [23]. The World Anti-Doping Agency names ibutamoren (MK-677) in class S2.2.4 and prohibits it at all times, in and out of competition [10][24].

GHK-Cu is not an approved medicine either [8]. Non-injectable GHK-Cu sits in category 1, the group under evaluation for the bulks list, and FDA has said it plans to consult its Pharmacy Compounding Advisory Committee about it before the end of February 2027 [8]. Injectable GHK-Cu appears in the 'nominated but withdrawn' table on FDA's page about bulk substances that may pose significant safety risks, with FDA noting limited human data and the immunogenicity concern [1]. GHK-Cu is not named on WADA's 2026 or 2027 Prohibited List, but WADA's S0 class covers substances with no approval from any governmental health authority, and the 2027 notes say peptides not specifically named may still be prohibited, so an anti-doping organization is the place to confirm an athlete's status [10][11].

What the answer comes down to

MK-677 is the option with systemic IGF-1 and lean-mass data, together with the metabolic, cardiac and sport-rule issues above. Topical GHK-Cu is the option with local skin and wound trials, which were small and did not show objective benefit over their comparison arms [14][3][4][9]. The choice rests on whether the goal is systemic or local, not on the combination.