Thymulin
Zinc-dependent nonapeptide secreted by thymic epithelial cells — the only known circulating thymic hormone. Levels decline dramatically with thymic involution after puberty.
🔬 Mechanism of Action
Thymulin (Facteur Thymique Sérique, FTS) is a zinc-dependent nonapeptide (Glu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn) secreted exclusively by thymic epithelial cells. Discovered in 1977 by Bach and colleagues, it is the only known circulating thymic hormone — all other thymic factors (thymosin, thymopoietin) are paracrine.
Thymulin requires zinc binding to be biologically active; the Zn²⁺-thymulin complex has a completely different conformation from the apoprotein. This zinc dependency means that zinc deficiency (common in aging) directly causes functional thymulin deficiency even if secretion is normal.
Active Zn-thymulin promotes: T-cell precursor differentiation and maturation, NK cell cytotoxicity enhancement, suppressor T-cell modulation, and cytokine production balance. Serum thymulin levels peak in childhood and decline to undetectable levels by age 60 — paralleling thymic involution.
Source: PMID: 3299395
📜Background & History
Thymulin (FTS) was discovered by Jean-François Bach and Mireille Dardenne at Hôpital Necker in Paris (1977). It was the first — and remains the only — thymic hormone found in circulating blood. This makes it the immune system's equivalent of insulin or thyroxine: a measurable hormone that declines with age and whose deficiency has demonstrated clinical consequences. The discovery that thymulin requires zinc for biological activity (1980) was a landmark finding linking trace mineral nutrition to immune function.
🎯 Research Use Cases
- ✓Immune reconstitution after thymic involution
- ✓Zinc-thymulin immunotherapy research
- ✓Immunosenescence biomarker (serum levels indicate thymic function)
- ✓Anti-aging immune protocols targeting thymic restoration
💉 Dosing Protocol
| Typical Dose | 1-5 mg/day |
| Frequency | 1× daily for 10-30 day cycles |
| Half-Life | ~30 minutes (estimated) |
| Common Vial Sizes | 5 mg, 10 mg |
🧪 Reconstitution Example
⚠️Safety & Considerations
Well-characterized safety profile across decades of immunological research. Requires concurrent zinc supplementation for biological activity. Overstimulation of immune system possible in autoimmune conditions — use under medical supervision. Not to be combined with immunosuppressive drugs without careful monitoring.
⚡Interactions & Contraindications
REQUIRES zinc supplementation for biological activity — Zn-thymulin complex is the active form. May overstimulate immune system in autoimmune conditions. Not to be combined with immunosuppressive drugs without supervision. Well-characterized safety across decades of research.
🔗Synergies & Common Stacks
Thymulin (circulating thymic hormone) + Thymalin (thymic polypeptide extract) provide complementary thymic support through different mechanisms — Thymulin acts systemically, Thymalin acts directly on thymic tissue.
Thymulin (immune hormone) + Vilon (synthetic thymic dipeptide bioregulator) target immune function through different molecular pathways — circulating hormone vs. epigenetic gene regulation.