MK-677 vs YK-11
Well Studied vs Limited Research
synergistic Researched · 95% MK-677 (Ibutamoren) is frequently combined with YK-11. MK-677 increases growth hormone and IGF-1 through ghrelin receptor agonism, which complements YK-11's AR-mediated and follistatin-mediated anabolic mechanisms through a completely independent pathway. MK-677 does not suppress testosterone and is not hepatotoxic, making it one of the safer adjuncts to a YK-11 cycle. The combination may enhance lean mass gains, recovery, and joint comfort (via GH-mediated collagen synthesis), potentially offsetting YK-11's reported joint dryness.
Molecular Data
MK-677 YK-11
Weight 624.77 Da 430.54 Da
Half-life ~24 hours ~6-10 hours
Type Non-peptide ghrelin receptor agonist Steroidal selective androgen receptor modulator with myostatin-inhibiting properties (C25H34O6)
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)
YK-11
01 Dual mechanism combining partial AR agonism with myostatin inhibition via follistatin upregulation
02 May theoretically promote muscle growth beyond what AR activation alone can achieve by removing myostatin-mediated growth limits
03 Steroidal structure providing oral bioavailability without requiring injection
04 Partial AR agonist activity may confer tissue selectivity with reduced androgenic side effects compared to full agonists (theoretical, not demonstrated in vivo)
05 Short half-life allows for relatively rapid clearance if side effects necessitate discontinuation
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.
YK-11
Liver stress and enzyme elevation (ALT, AST) due to 17-alpha alkylated steroidal structure
Testosterone suppression (dose- and duration-dependent, expected in all users)
Joint dryness and discomfort (related to reduced estrogenic activity and potential drying effect)
Hair shedding (consistent with androgenic activity from the DHT-derived structure; may or may not be reversible)
Lipid disruption (HDL suppression, LDL elevation)
Reduced libido and mood changes secondary to hormonal suppression
Mild headaches, particularly during the first week
Contraindications
Heart disease or congestive heart failure
Diabetes or pre-diabetes
Active cancer
Severe cardiovascular disease
Pregnancy or breastfeeding
Pre-existing liver disease or elevated liver enzymes at baseline (17-alpha alkylated compounds are contraindicated in hepatic impairment)
Hormone-sensitive cancers (prostate cancer or other androgen-responsive malignancies)
Pregnancy or potential pregnancy (teratogenic risk from androgen receptor agonism and hormonal disruption)
Breastfeeding
Age under 25 (incomplete endocrine system maturation and higher risk of lasting HPG axis disruption)
Concurrent use of other hepatotoxic compounds or medications (oral steroids, certain NSAIDs, statins, etc.)
Known cardiovascular disease (insufficient safety data)
Research Evidence
MK-677 YK-11
Status Well Studied Limited Research
References 7 studies 4 studies
Latest July 2024 2013
FDA Approved No No
This comparison is for educational and research purposes only. Consult a healthcare professional before use.