MK-677 vs TB-500 (Ac-LKKTETQ)
Well Studied vs Moderate Research
synergistic Mechanism-based · 47% MK-677 and TB-500 (Ac-LKKTETQ) work through complementary pathways. Growth hormone signaling supports tissue repair processes. A well-established combination in recovery protocols.
Molecular Data
MK-677 TB-500 (Ac-LKKTETQ)
Weight 624.77 Da 844 Da
Half-life ~24 hours Not precisely established; effects persist longer than 24 hours
Chain — 7 amino acids
Type Non-peptide ghrelin receptor agonist Acetylated heptapeptide
Key Benefits
MK-677
01 97% increase in 24-hour growth hormone secretion
02 40-72% elevation in IGF-1 levels
03 Enhanced sleep quality with improved REM patterns
04 Preferential lean tissue gains of 1.1-2.7kg over 8-12 months
05 15% basal metabolic rate increase within 2 weeks
06 Oral administration (no injections required)
TB-500 (Ac-LKKTETQ)
01 Promotes wound healing
02 Enhances cell migration
03 Supports angiogenesis (new blood vessel formation)
04 Reduces inflammation
05 Promotes keratinocyte migration
06 Supports collagen deposition
07 Enhances tissue repair
08 Active region of thymosin beta-4
Dosing Protocols
MK-677
Start 12.5mg daily, increase to 25mg based on tolerance / Once daily, preferably at bedtime on empty stomach
TB-500 (Ac-LKKTETQ)
2-2.5mg per injection / 2x weekly (e.g., Monday and Thursday)
Loading phase 2-2.5 mg 2x weekly for 4-6 weeks
Maintenance 2 mg Weekly or bi-weekly
Side Effects
MK-677
Appetite stimulation (>50% of users)
Water retention (30-40%)
Lethargy (20-30%)
Fasting glucose elevation (5-15mg/dL)
Note on testosterone suppression: at doses up to 20 mg daily, MK-677 is unlikely to cause significant testosterone suppression on its own. Above 20 mg daily, the likelihood of suppression and other side effects (insulin resistance, water retention, lethargy) increases. The case report documenting 85.7% testosterone suppression involved co-administration with LGD-4033, a SARM known to be profoundly suppressive, making the SARM the likely primary driver of that suppression.
TB-500 (Ac-LKKTETQ)
Injection site reactions
Mild fatigue
Head rush (reported)
Contraindications
Heart disease or congestive heart failure
Diabetes or pre-diabetes
Active cancer
Severe cardiovascular disease
Pregnancy or breastfeeding
Not authorized for medicinal use
Active cancer (theoretical concern)
Pregnancy or breastfeeding
Prohibited by WADA in sports
Research Evidence
MK-677 TB-500 (Ac-LKKTETQ)
Status Well Studied Moderate Research
References 7 studies 4 studies
Latest July 2024 —
FDA Approved No No
This comparison is for educational and research purposes only. Consult a healthcare professional before use.