Exemestane vs MK-677
FDA Approved vs Well Studied
avoid Mechanism-based · 64% Both Exemestane and MK-677 carry hepatotoxic risk. Combining hepatotoxic compounds significantly increases liver damage potential. If unavoidable, include liver support (TUDCA/NAC) and monitor ALT/AST frequently.
Molecular Data
Exemestane MK-677
Weight 296.40 Da 624.77 Da
Half-life ~24 hours ~24 hours
Type Steroidal aromatase inhibitor (irreversible, suicide inhibitor) Non-peptide ghrelin receptor agonist
Key Benefits
Exemestane
01 Irreversible aromatase inactivation eliminates estrogen rebound upon discontinuation
02 Steroidal structure with mild androgenic activity may offset some low-estrogen side effects
03 Potent estrogen suppression (85-95% reduction in estradiol at full dose)
04 Compatible with tamoxifen (unlike anastrozole, no pharmacokinetic interference)
05 Prevents gynecomastia during testosterone or aromatizable steroid cycles
06 Reduces estrogen-driven water retention, bloating, and blood pressure elevation
07 Oral dosing with once-daily or less frequent administration for cycle support
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)
Side Effects
Exemestane
Joint pain and stiffness (generally less severe than with anastrozole due to mild androgenic activity)
Fatigue and general malaise
Hot flashes or flushing
Mood changes (irritability, flat affect, low mood)
Headache
Increased sweating
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.
Contraindications
Known hypersensitivity to exemestane or any excipients
Premenopausal women (not indicated and potentially harmful to reproductive function)
Pregnancy or breastfeeding (teratogenic risk)
Severe hepatic impairment
Pre-existing severe osteoporosis or high fracture risk
Concurrent use with other aromatase inhibitors (anastrozole, letrozole)
Heart disease or congestive heart failure
Diabetes or pre-diabetes
Active cancer
Severe cardiovascular disease
Pregnancy or breastfeeding
Research Evidence
Exemestane MK-677
Status FDA Approved Well Studied
References 5 studies 7 studies
Latest — July 2024
FDA Approved Yes No
This comparison is for educational and research purposes only. Consult a healthcare professional before use.