Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Head-to-head comparison of MK-677 and Tesamorelin — mechanism, side effects, legal status, and pricing.
MK-677 (ibutamoren, MK-0677, L-163,191) is an orally active, non-peptide small-molecule growth hormone secretagogue developed by Merck in the 1990s. It is a spiropiperidine ghrelin-receptor (GHSR-1a) agonist — not a peptide and not a SARM, though it is commonly misclassified as both in grey-market retail. Merck discontinued development after mixed efficacy and adverse metabolic / cardiovascular findings; it is not FDA-approved.
Tesamorelin (Egrifta / Egrifta SV) is a stabilized analog of human GHRH(1-44) with a trans-3-hexenoic acid moiety at the N-terminus that protects against protease degradation. FDA-approved in November 2010 for the reduction of excess abdominal fat in HIV-infected patients with lipodystrophy, it is the only FDA-approved GHRH analog for this indication. Off-label use for general body composition and visceral fat reduction in non-HIV populations is common but outside the approved label.
MK-677
Tesamorelin
Category
Legal Status
Mechanism
Half-life
Side Effects
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MK-677
No pricing data yet.
Check MK-677 prices →Tesamorelin
COA corpus from Disclosed Labs — independently tested batches only.
MK-677
5
COAs
98.3%
Avg purity
3
Labs
Tesamorelin
175
COAs
99.5%
Avg purity
14
Labs
Tesamorelin is among peptides under FDA review for the Category 1 (503A) list; if added, it would require a prescription to be compounded by registered 503A/503B pharmacies — not yet authorized. MK-677 remains research-only. In April 2026 the FDA removed 12 peptides from Category 2, which does not place them on the Category 1 list or authorize compounding. The FDA's Pharmacy Compounding Advisory Committee is advisory and meets July 23–24, 2026 to review nominations and make recommendations to the FDA.
MK-677 has meaningful human data from Merck-sponsored Phase I/II trials. Murphy et al. (JCEM 1998, PMID 9467534) showed 25 mg MK-677 reversed nitrogen wasting during caloric restriction in healthy adults. Svensson et al. (JCEM 1998, PMID 9467542) reported ~40% IGF-1 elevation, increased fat-free mass, and higher energy expenditure over 8 weeks in obese men. Copinschi et al. (Neuroendocrinology 1997, PMID 9349662) documented improved slow-wave and REM sleep in young and older adults. Nass et al. (Ann Intern Med 2008, PMID 18981485) — the pivotal 2-year randomized trial in 65 healthy older adults — restored GH and IGF-1 to young-adult levels and increased fat-free mass, but produced modest fasting glucose elevation and insulin resistance. The Adunsky et al. Phase IIb hip-fracture trial (Arch Gerontol Geriatr 2011, PMID 21067829) was stopped early after a congestive-heart-failure safety signal (4/62 ibutamoren vs 1/60 placebo). Merck discontinued development. MK-677 is commonly mislabeled as a 'SARM' in grey-market retail — it is not; it is a ghrelin-receptor agonist and oral GH secretagogue. It has never been FDA-approved.
Key references
FDA approval (NDA 022505) was based on two Phase 3 trials reported by Falutz et al. (NEJM, 2007; PMID 18057338) and the pooled 52-week safety extension, showing ~15-18% reduction in visceral adipose tissue with improved triglycerides in HIV patients with abdominal fat accumulation. Stanley et al. (JAMA, 2014; PMID 25038357) demonstrated concurrent reductions in visceral and liver fat (NAFLD). Baker et al. (Arch Neurol, 2012; PMID 22869065) reported favorable effects on executive function in older adults with and without mild cognitive impairment at 1 mg/day for 20 weeks — note this cognition signal was in MCI / healthy older adults, not specifically APOE4-positive individuals. Current label dose is 1.4 mg SubQ daily (Egrifta SV); legacy Egrifta used 2 mg/day. Off-label use for general body composition in non-HIV populations is common but outside the FDA label.
MK-677 and Tesamorelin are both in the Performance category and may have overlapping mechanisms. Researchers should review both profiles carefully, understand the mechanisms of action, and monitor the relevant biomarkers when combining compounds in the same class. As always, consult a licensed healthcare provider before making any decisions about combining research compounds.
This platform provides informational tools only, not medical advice. This comparison is for educational purposes only. Consult a licensed provider.
Contraindications
Lab Testing
Key references
Disclosed Labs