Halotestin vs MK-677
Well Studied vs Well Studied
avoid Mechanism-based · 64% Both Halotestin 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
Halotestin MK-677
Weight 336.44 Da 624.77 Da
Half-life ~9.5 hours ~24 hours
Type 9-fluoro-11-beta-hydroxy-17-alpha-methyltestosterone (C20H29FO3) Non-peptide ghrelin receptor agonist
Key Benefits
Halotestin
01 Dramatic increase in strength and power output without water retention
02 Pronounced increase in aggression and competitive drive
03 Does not aromatize to estrogen, producing a hard and dry appearance
04 Enhances red blood cell production and oxygen-carrying capacity
05 Rapid onset of effects, typically noticeable within days
06 Uniquely suited for pre-competition or pre-meet peaking protocols
07 Short cycle duration limits cumulative exposure
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
Halotestin
Severe hepatic stress (elevated ALT, AST, GGT, bilirubin)
Pronounced aggression and irritability
HDL cholesterol suppression and LDL elevation
Elevated blood pressure
Headaches (frequently reported, may be related to blood pressure changes)
Suppression of endogenous testosterone production
Oily skin and acne
Decreased appetite (potentially related to liver stress)
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 or suspected prostate cancer
Breast cancer in males
Pregnancy (Category X - causes fetal harm)
Active liver disease or existing hepatic impairment
Severe cardiovascular disease or uncontrolled hypertension
Hypercalcemia
Nephrosis or nephrotic phase of nephritis
History of cholestatic jaundice or hepatic dysfunction from prior anabolic steroid use
Hypersensitivity to fluoxymesterone or any formulation component
Heart disease or congestive heart failure
Diabetes or pre-diabetes
Active cancer
Severe cardiovascular disease
Pregnancy or breastfeeding
Research Evidence
Halotestin MK-677
Status Well Studied Well Studied
References 5 studies 7 studies
Latest October 2023 July 2024
FDA Approved Yes No
This comparison is for educational and research purposes only. Consult a healthcare professional before use.