Also known as facteur thymique sérique, serum thymic factor · Wikipedia
Thymulin, originally called Facteur Thymique Serique (FTS) or serum thymic factor, is a zinc-bound nonapeptide (Glu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn) secreted by thymic epithelial cells and characterized historically by the Bach group. It is biologically active only when bound to zinc in an equimolar Zn-FTS complex. Endogenous circulating thymulin declines progressively with thymic involution after puberty. It is studied in immune regulation, T-cell differentiation, neuroendocrine-immune interactions, and inflammation, and is offered in the research-chemical channel for immune balance. There are no completed late-phase clinical trials.
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Browse all vendorsMechanism of action
Thymulin is a zinc-dependent nonapeptide (Glu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn) secreted by thymic epithelial cells; the zinc-bound conformation (Zn-FTS) is essential for biological activity, with one zinc ion per nonapeptide (Cung et al., PubMed 3356698; Reggiani et al.
Pharmacokinetic properties
Half-life
very short - minutes in plasma; activity dependent on continuous zinc availability
Routes
subcutaneous · intramuscular · intranasal
Bioavailability
Must be co-administered (or endogenously co-available) with zinc to be active. Not orally bioavailable. Several gene-therapy delivery approaches studied preclinically.
Amino-acid sequence
Glu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn
Use & research dosing
No human regulatory dose is established. Self-experimentation protocols in the research-chemical channel commonly report 100-500 mcg subcutaneously daily in short cycles, typically with zinc co-supplementation given the strict zinc-dependence of biological activity. Most published work is preclinical rodent at microgram per kilogram doses. Without zinc co-availability the molecule is effectively inactive, so any protocol that omits zinc should be considered incomplete. Research framing only.
Research-use framing only. SavePeptides sells nothing for human consumption. Doses above reflect reported research / self-experimentation ranges, not clinical recommendations.
Distinct from thymopoietin and the thymosin family. The zinc dependence is mechanistically central - biological activity requires the Zn-bound conformation, so co-availability of zinc matters for both endogenous activity (declines with zinc deficiency) and for any exogenous research protocol. Most evidence is preclinical or small immunology / endocrinology studies from the original Bach group and successors; no late-phase clinical trials have been completed.
— SavePeptides editorial desk · last updated 2026-05-25
Cautions & contraindications
Research foundation
Facts verified
2026-05-25
Confidence
low
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