MK-677 vs HGH: An Unapproved Pill and a Restricted Prescription Hormone

MK-677 and HGH are compared because both raise growth hormone, but they are different kinds of product with very different legal standing. HGH is somatropin, recombinant human growth hormone, an FDA-approved biologic for specific conditions such as growth hormone deficiency in children and adults.^[6] MK-677, also called ibutamoren, is a small-molecule pill that mimics ghrelin and makes the pituitary release more of its own growth hormone. It was never approved.^[15][10] Distributing HGH for an unapproved use, such as anti-aging or bodybuilding, is a federal crime, while FDA lists MK-677 as a substance that raises significant safety risks in compounding.^[9][10]

MK-677 vs HGH at a glance

What each one is

Somatropin is growth hormone made by recombinant DNA technology. Genotropin, one of several brands, is approved for children with growth failure from growth hormone deficiency, Prader-Willi syndrome, being born small for gestational age, Turner syndrome or idiopathic short stature, and for adults with growth hormone deficiency that began in adulthood or childhood.^[6] Somatropin products were approved as drugs and became licensed biologics on March 23, 2020.^[12]

MK-677 was developed in the 1990s as an oral, non-peptide mimic of the growth hormone-releasing peptides.^[15] It acts on the ghrelin receptor, and taken once a day by mouth it raised growth hormone and IGF-1 in older adults to levels seen in healthy young adults.^[1] It is now sold as a performance-enhancing supplement,^[5] and FDA’s drug database lists no approved application for it.

The human evidence for each

MK-677: real trials, mixed results

MK-677 has more randomized human trials than most products sold beside it, and they show what it does and does not do. In the longest, 65 healthy adults aged 60 to 81 took 25 mg or placebo daily in a two-year trial. After a year, lean mass had risen by 1.1 kg on MK-677 and fallen by 0.5 kg on placebo, but visceral fat and total fat did not change, and the extra lean mass brought no measurable gain in strength or function. People on MK-677 gained 2.7 kg of body weight (0.8 kg on placebo), their average fasting glucose climbed 5 mg/dL, and their insulin sensitivity fell.^[1]

• Obese young men (1998). In 24 obese men treated for eight weeks, IGF-1 rose about 40% and lean mass rose, while total and visceral fat did not change and a glucose tolerance test worsened.^[2]
• Hip fracture (2011). In 123 older adults recovering from hip fracture, IGF-1 rose but most measures of function did not improve, and it was stopped early over a heart failure safety signal in a small number of patients.^[3]
• Alzheimer disease (2008). In 563 people with mild to moderate Alzheimer disease, a year of MK-677 raised IGF-1 by 72.9% but did not slow the disease on any of four measures.^[4]

HGH: proven in deficiency, small gains in healthy adults

In the conditions on its labels, somatropin is an established treatment.^[6] In healthy adults the picture is different. A systematic review of randomized trials in healthy older people (220 people given growth hormone, average age 69) found fat mass fell by 2.1 kg and lean mass rose by 2.1 kg, with no change in weight. People on growth hormone were more likely to have swelling, joint pain, carpal tunnel syndrome and breast enlargement in men, and somewhat more likely to develop diabetes or impaired fasting glucose. On that evidence, the authors said growth hormone should not be recommended for anti-aging.^[7]

A second review, of 303 young, fit people given growth hormone in trials, found lean mass rose by 2.1 kg but strength and exercise capacity did not seem to improve, and swelling and fatigue were more common.^[8]

Both raise lean mass a little in healthy adults. Neither has been shown to make them stronger, and both worsen blood sugar.

Regulatory and legal status

HGH: approved, and restricted by statute

Growth hormone has its own federal crime. Under 21 U.S.C. 333(e), knowingly distributing human growth hormone, or holding it to distribute, is punishable by up to five years in prison unless the use is treatment of a disease or recognized condition that FDA has authorized and a physician has ordered. If a minor is involved, the maximum is ten years. The term covers somatropin and its analogs.^[9] A 2007 review noted that distributing growth hormone as an anti-aging agent is illegal in the United States.^[7]

Because somatropin is a licensed biologic, it also cannot be compounded. FDA’s guidance states that for purposes of sections 503A and 503B, “a drug does not include any biological product that is subject to licensure.”^[13] HGH sold outside a pharmacy filling a prescription for an approved product is outside the legal supply chain.

MK-677: unapproved and flagged by FDA

FDA placed ibutamoren mesylate in its active Category 2, its safety-concern group of bulk substances, for 503B outsourcing facilities on December 29, 2022 and for 503A pharmacies on September 29, 2023. The agency names a possible risk of congestive heart failure in some patients and points to the hip fracture trial that was stopped early.^[10] It appears on FDA’s May 2026 list of 503A Category 2 substances.^[11] MK-677 is not among the six peptides in the October 28, 2026 HHS enforcement-discretion policy, which in any case covers only peptides.

Both are banned in sport at all times. WADA lists growth hormone under S2.2.3 and names “ibutamoren (MK-677)” under S2.2.4 among growth hormone secretagogues.^[14]

Safety: what is known about each

• MK-677. In the trials: increased appetite that faded over a few months, mild leg swelling and muscle pain, higher fasting glucose, lower insulin sensitivity and a rise in cortisol.^[1] A heart failure signal ended the hip fracture trial.^[3] A 2025 case report described liver inflammation in a man in his early thirties after two months of MK-677, which resolved when he stopped.^[5]
• HGH. In healthy older adults: swelling, joint pain, carpal tunnel syndrome, breast enlargement in men and a higher chance of diabetes.^[7] Its label warns about use in acute critical illness, tumor growth, impaired glucose tolerance and raised pressure inside the skull, and it is contraindicated in active cancer.^[6]
• Both. Each raises IGF-1. Products bought online have unknown contents: a pill sold as MK-677 or a vial sold as HGH outside a pharmacy has no FDA review behind it.

Why people combine them

Some users take MK-677 with HGH or with injectable growth hormone peptides, on the idea that more signals mean more growth hormone. No published study has tested MK-677 with HGH. Stacking them adds the known effects of each on blood sugar and fluid retention.^[1][7] A combined product would also mix an approved biologic, which may not be compounded, with a substance FDA lists for safety risk.^[10][13] For the injectable peptides that also raise growth hormone, see CJC-1295 vs ipamorelin and sermorelin vs tesamorelin.

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