Side-by-side · Research reference
MK-677vsThymalin
Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.
APhase 2Reviewed13/45 cited
BHuman-MechanisticDraft12/40 cited
MK-677
Oral GHS · Ibutamoren
Oral capsule · 1×/day
Thymalin
Immune restorer · Russian peptide bioregulator
IM · Daily for 5–10 days · 1-2×/year
01Mechanism of Action
Parameter
MK-677
Thymalin
Primary target
Ghrelin receptor (GHS-R1a)Murphy 1998
T-cell precursors + thymus-axis maturation pathwayKhavinson 2002
Pathway
GHS-R1a → Gαq → Ca²⁺ → sustained GH pulses across 24 hrNass 2008
Modulation of T-cell differentiation + thymic hormone restoration in age-involuted thymusKhavinson 2002
Downstream effect
Sustained GH + IGF-1 elevation; appetite stimulation; lean mass preservationNass 2008
Restored T-cell populations, improved immune surveillance, reduced infection rates in elderlyKhavinson 2002
Origin
Non-peptide spiroindane-piperidine small molecule designed at MerckMurphy 1998
Polypeptide fraction isolated from calf thymus extractKhavinson 2002
Antibody development
—
—
02Dosage Protocols
Parameter
MK-677
Thymalin
Standard dose
10–25 mg / day oralNass 2008
25 mg used in Nass 2008 elderly trial; 10–15 mg common community dose.
5–10 mg / day IM × 5–10 daysKhavinson 2002
Frequency
Once daily, oral
Once daily during cycle
Lower / starter dose
5 mg / day
2.5 mg / day
Evidence basis
Phase 2 trials (Nass 2008, Murphy 1998)Nass 2008Murphy 1998
Russian clinical + in vitroKhavinson 2002
Duration
8–16 weeks per cycle (off-cycle to reset receptor sensitivity)
5–10 day cycles, 1–2× per year
Reconstitution
Oral, no reconstitution
Saline or bacteriostatic water
Timing
Pre-sleep preferred for natural GH pulse alignment
Morning preferred
04Side Effects & Safety
Parameter
MK-677
Thymalin
Increased appetite
Strong appetite increase via ghrelin agonism
—
Water retention
Mild edema, paresthesias
—
Cancer risk
Contraindicated in active malignancy (GH/IGF-1 axis)
—
Cardiovascular
No clear adverse signal in trials; congestive heart failure caution
—
Drowsiness
Common, especially during initial weeks
—
Pregnancy / OB
Avoid
Avoid
Injection site reaction
—
Mild erythema at IM site
Allergic reaction
—
Rare hypersensitivity to bovine-derived polypeptide
Autoimmune flare
—
Theoretical risk in active autoimmune disease
Long-term safety
—
Limited Western data
Absolute Contraindications
MK-677
- ·Active malignancy
- ·Pregnancy / breastfeeding
- ·Disrupted hypothalamic-pituitary axis
- ·Congestive heart failure (caution)
Thymalin
- ·Pregnancy / breastfeeding
- ·Bovine protein hypersensitivity
Relative Contraindications
MK-677
- ·Untreated diabetes
- ·Pre-diabetes
- ·Severe insulin resistance
Thymalin
- ·Active autoimmune disease
- ·Concurrent immunosuppressant therapy
05Administration Protocol
Parameter
MK-677
Thymalin
1. Form
Capsule or oral solution. No injection.
Add 1–2 mL saline or bacteriostatic water per 10 mg vial.
2. Site
Oral. Take with or without food.
Intramuscular — deltoid or gluteal. Rotate sites.
3. Timing
Pre-sleep preferred — aligns with natural GH pulse.
Morning preferred during cycle.
4. Storage
Capsule: room temp ≤25 °C, dry place.
Lyophilised: refrigerate, light-protected. Reconstituted: use immediately.
5. Caveat
Monitor HbA1c every 8–12 weeks during chronic use.
23–25G, 25–38 mm IM needle.
06Stack Synergy
MK-677
— no documented stacks
Thymalin
+ Thymosin α-1
ModerateThymalin is a polypeptide complex; Thymosin α-1 is a single purified peptide. Both target the thymus-axis but at different levels — Thymalin restores broad thymic signaling; Tα-1 provides a specific molecular activator. Anecdotally combined for elderly immune support.
- Thymalin
- 5–10 mg IM · daily × 7 days
- Thymosin α-1
- 1.6 mg SQ · 2× weekly during the cycle
- Primary benefit
- Broad thymic restoration + targeted immune activation