ABOUT THIS PROJECT
About Thymulin Source
Thymulin Source is an independent editorial project that publishes summaries of the peer-reviewed research literature on Thymulin — the zinc-dependent nonapeptide thymic hormone also known as serum thymic factor (FTS).
What This Site Is
Thymulin Source is an independent editorial project that publishes summaries of the peer-reviewed research literature on Thymulin. We are not a clinic. We do not employ clinicians and we do not provide medical advice. We do not manufacture, sell, or distribute any product. Our work is editorial commentary on publicly available science.
The site exists to make the primary research literature on Thymulin accessible to researchers, science writers, and informed general readers. Every quantitative claim is cited. Every cited source is verified against PubMed, PMC, or the original journal. We do not publish claims not supported by the reviewed literature.
The Compound
Thymulin (serum thymic factor, FTS) is a 9-amino-acid nonapeptide hormone — sequence pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn, MW 858.86 Da, CAS 63958-90-7 — produced exclusively by thymic epithelial cells. It is the only known thymic hormone requiring a zinc cofactor for biological activity. The foundational biochemistry was characterized beginning in the 1970s by Jean-François Bach and Mireille Dardenne at the Institut National de la Santé et de la Recherche Médicale (INSERM), Paris.
Thymulin is not to be confused with: thymalin (a bovine polypeptide extract and Khavinson bioregulator, entirely different compound), thymosin alpha-1 (a distinct 28-amino-acid peptide), thymopentin (a 5-amino-acid synthetic fragment), or thymosin beta-4 (a 44-amino-acid peptide). These are four separate research literatures. This site covers Thymulin (FTS) only.
Molecular Structure and Zinc Binding
Thymulin's nine amino acids form a compact peptide that adopts a distinct three-dimensional conformation only when zinc is coordinately bound. The zinc-free form — apothymulin — circulates in serum but cannot bind the thymulin receptor on T-lymphocyte precursors. Zinc binding creates a specific epitope; monoclonal antibodies raised against Zn-thymulin inhibit its biological activity. This structure-function relationship — documented by PNAS publications in 1982 and 1985 — is the foundation of everything else the research record measures.
When zinc is deficient (whether from dietary insufficiency, aging-related metallothionein upregulation, or alpha-2-macroglobulin competition), circulating thymulin is predominantly in the inactive apothymulin form. The serum zinc level alone does not predict Zn-thymulin bioactivity.
Editorial Standards
Every page on this site cites primary literature. The references page lists complete citations with DOI and PubMed or PMC URLs for every source used. Findings are attributed to named studies, named species, and named doses — not presented as established human effects.
Thymulin Source does not make medical claims. Language on this site describes what was measured in research models. "Reduced thermal hyperalgesia in a CFA rat model" is accurate; "reduces pain" is not a claim this site makes. When the research record contains a gap — such as the absence of human exogenous thymulin administration trials — that gap is named, not papered over.
The disclaimer that governs this site: the peer-reviewed thymulin record, cited at the source — not a clinic, not a vendor.