MK-677 (Ibutamoren) vs Thymulin
A detailed comparison to help you understand the differences and choose the right peptide for your research goals.
MK-677 (Ibutamoren)
MK-677, also known as Ibutamoren, is an orally active growth hormone secretagogue. Unlike peptides, it can be taken orally and has a long half-life, providing 24-hour GH elevation.
Full details →Thymulin
Thymulin (Facteur Thymique Sérique) is a zinc-dependent nonapeptide hormone produced by thymic epithelial cells. It plays important roles in T-cell differentiation and immune system maturation.
Full details →Side-by-Side Comparison
| Aspect | MK-677 (Ibutamoren) | Thymulin |
|---|---|---|
| Dose Range | 10 mg–25 mg | 100 mcg–400 mcg |
| Frequency | 1x daily | 1x daily |
| Cycle Length | 8–24 weeks | 4–8 weeks |
| Route | oral | subcutaneous |
| Mechanism | Acts as a potent, selective agonist of the ghrelin receptor (GHS-R1a). Increases GH and IGF-1 levels without affecting cortisol. Mimics ghrelin's GH-releasing effects. | Requires zinc for biological activity. Promotes T-cell differentiation, modulates cytokine production, and influences neuroendocrine function. Levels decline significantly with age. |
| Typical Dosage | Typical dosing: 10-25mg taken orally once daily. Often taken at night due to sleep benefits and appetite increase. | Research protocols vary. Often studied alongside zinc supplementation. Typical research doses in the microgram range. |
| Administration | Oral administration (capsule or liquid). Can be taken with or without food. Long half-life allows once-daily dosing. | Subcutaneous or intramuscular injection in research settings. Requires adequate zinc status for activity. |
| Side Effects | Increased appetite and water retention are most common. May cause lethargy, vivid dreams, and mild numbness. Can affect blood glucose and insulin sensitivity. | Limited data on exogenous administration. Theoretical effects on immune function require monitoring. |
| Best For |
Key Differences
Unique to MK-677 (Ibutamoren):
Unique to Thymulin:
Key Studies
MK-677 (Ibutamoren)
- Knowing the minimal detectable dose can facilitate the interpretation of a hair test result: II. Case example with ibutamoren (MK-677), a growth hormone secretagogue.
Clinica chimica acta; international journal of clinical chemistry, 2026
- Hepatotoxicity induced by MK-677.
BMJ case reports, 2025
- Investigating the P53-dependent anti-cancer effect of ibutamoren in human cancer cell lines.
Basic & clinical pharmacology & toxicology, 2025
Thymulin
- Thymulin restrains age-associated myeloid inflammation and enhances cancer immunotherapy.
Nature communications, 2026
- Thymulin and peroxiredoxin 6 have protective effects against streptozotocin-induced type 1 diabetes in mice.
International journal of immunopathology and pharmacology, 2021
- Nanoparticle-based thymulin gene therapy therapeutically reverses key pathology of experimental allergic asthma.
Science advances, 2020
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