Thymulin
Immune / Thymic Peptide HormoneresearchAlso known as: Facteur Thymique Sérique, FTS, Serum Thymic Factor, FTS-Zn
A zinc-dependent nonapeptide hormone produced by thymic epithelial cells that plays an essential role in T-cell differentiation and immune regulation, declining significantly with age.
Overview
Thymulin (formerly known as Facteur Thymique Sérique or FTS) is a 9-amino acid peptide hormone exclusively produced by the thymic epithelial cells. It is unique among thymic hormones in that it requires a zinc ion (Zn²⁺) for biological activity — the metallopeptide complex FTS-Zn is the active form. Thymulin is essential for T-cell differentiation, promoting the maturation of thymocytes into functional T-lymphocyte subsets. Its serum levels decline dramatically with age, paralleling thymic involution, and this decline is associated with immunosenescence. Research has explored thymulin for immune restoration in elderly and immunocompromised individuals, as well as for anti-inflammatory effects in conditions like rheumatoid arthritis and allergic diseases. More recent research has investigated intranasal thymulin gene therapy and thymulin analogs for neuroinflammatory conditions.
Mechanism of Action
Thymulin acts through immune regulatory pathways: (1) Binds to high-affinity receptors on immature T-cells, promoting differentiation into CD4+ and CD8+ subsets; (2) Requires zinc as a cofactor — forms a biologically active FTS-Zn complex; (3) Modulates cytokine production by T-cells, promoting balanced Th1/Th2 responses; (4) Enhances IL-2 production and IL-2 receptor expression on T-cells; (5) Promotes natural killer (NK) cell activity; (6) Exerts anti-inflammatory effects by reducing pro-inflammatory cytokine production; (7) Crosses the blood-brain barrier and modulates neuroinflammation.
Molecular Formula
C33H54N10O15Zn
Molecular Weight
878.22 g/mol (with Zn)
Sequence
pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn
Dosage Protocols
Dose Range
1mg – 5mg
Frequency
Once daily
Route
subcutaneous
Cycle Length
10-30 days
Must be supplemented with adequate zinc (15-30mg/day) for biological activity. Experimental dosing — no established human protocols outside of research settings.
Source: Research literature extrapolation
Side Effects
| Effect | Severity |
|---|---|
| Injection site reaction | mild |
| Mild immune activation symptoms | mild |
| Zinc-related GI effects | mild |
Pros & Cons
Endogenous human hormone with well-characterized physiological role in immunity
Directly addresses immunosenescence by restoring thymic hormone levels
Anti-inflammatory effects extend to CNS, with potential neuroprotective applications
Synergistic with zinc supplementation for enhanced immune function
Very limited human clinical data outside of early immunological studies
Requires adequate zinc status for activity — ineffective in zinc-depleted individuals unless supplemented
Not commercially available as a pharmaceutical — research use only
Less studied and less accessible than other immune peptides like Thymosin Alpha-1
Research Studies
Legal Status
Not FDA-approved. Available as a research chemical. Endogenous human hormone. No specific regulatory restrictions for research use.
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