What is thymulin?
Thymulin is a nine-residue peptide hormone made by thymic epithelial cells, and it is active only with bound zinc (Dardenne et al., 1985). J.-F. Bach, M. Dardenne and colleagues in Paris isolated it from pig serum as facteur thymique sérique (FTS) and sequenced it as pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn; a synthetic copy matched the natural factor's activity (Pleau et al., 1977). A 1982 paper from the group proposed the name thymulin for the zinc-bound form (Dardenne et al., 1982). It is not a St Petersburg peptide bioregulator, and it differs from thymalin, a calf thymus extract.
In a PubMed search of 12 October 2026, 572 records named thymulin, facteur thymique sérique, serum thymic factor or thymic serum factor in the title or abstract. Of these, 412 predate 2000, and 158 list Bach, Dardenne, J.-M. Pléau or W. Savino as an author. MEDLINE indexes 291 of them under animals without humans; many human studies measured blood thymulin activity.
Synthetic thymulin, nonathymulin, reached placebo-controlled trials in the 1980s, and it is not an approved drug in the United States (no Drugs@FDA record, October 2026). Disguised Alpha does not currently list thymulin; this page is a literature reference for laboratory researchers. Nothing on this page is guidance for use in people.
Thymulin reference data
| Property | Value |
|---|---|
| Name | Thymulin |
| Also called | Facteur thymique sérique (FTS; also written facteur thymique serique), serum thymic factor, FTS-Zn (the zinc-bound form), nonathymulin (INN of the synthetic nonapeptide) |
| Sequence | pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn, with an N-terminal pyroglutamic acid and a free carboxyl terminus; active as a zinc complex, best at one zinc ion per peptide |
| Compound class | Thymic nonapeptide hormone; a zinc-dependent metallopeptide |
| Molecular formula | C₃₃H₅₄N₁₂O₁₅ (peptide without zinc) |
| Molecular weight | 858.9 g/mol (peptide without zinc; monoisotopic mass 858.38 Da) |
| PubChem | CID 3085284, titled Nonathymulin (all-L); CID 71300623, titled Thymulin, has one stereocenter undefined; no record for the zinc complex |
Values are from PubChem CID 3085284, whose synonyms include the INN nonathymulin (also listed for UNII 9H198D04WL); CID 71300623 carries the names thymulin and facteur thymique sérique. CID 3085284 also lists "Thymalin", a different material (see our thymalin research guide).
What the research covers
Six research areas follow, each with its model.
Sequence, zinc and the active form
Synthetic or natural FTS lost its activity in a rosette bioassay after exposure to the chelating resin Chelex 100. Zinc salts restored it, best at one metal ion per peptide molecule (Dardenne et al., 1982). Monoclonal antibodies that blocked the hormone recognized only the zinc-bound molecule, while antibodies screened by RIA or ELISA on a zinc-free substrate bound a zinc-independent site (Dardenne et al., 1985). Models: bioassay, antibodies and thymus tissue.
Where thymulin is made and what controls it
In young and old mice, daily prolactin reversibly raised the number of thymulin-producing thymic cells and blood thymulin. Bromocriptine lowered secretion, and prolactin also stimulated cultured human and mouse thymic epithelial cells (Dardenne et al., 1989). A La Plata review co-authored by Dardenne summarizes evidence that thymulin acts on the pituitary and describes vectors expressing a synthetic analog, metFTS, in athymic nude mice (Reggiani et al., 2014). Models: mice and cell cultures.
Blood thymulin as a zinc marker in people
A Detroit study, with Bach and Dardenne as co-authors, assayed serum thymulin activity in two volunteers made mildly zinc deficient by diet and in twelve mildly zinc-deficient adults, six of them with sickle cell anemia. Activity fell with zinc deficiency and was corrected by zinc supplementation and by zinc added in vitro, and the authors proposed it as a sensitive indicator of zinc deficiency (Prasad et al., 1988). Model: small human studies.
Inflammation and pain models in rodents
The La Plata review summarizes work pointing to thymulin and a synthetic analog as anti-inflammatory and analgesic peptides (Reggiani et al., 2014), but not every finding points one way. In rats, low intraperitoneal amounts of 20 to 150 ng doubled liver IL-1β and lowered pain thresholds, an effect a Beirut group linked partly to prostaglandin E2 (Safieh-Garabedian et al., 1997).
In mice given rising amounts of bacterial lipopolysaccharide, a Pushchino group reported less apoptosis and plasma cytokine production and lower NF-κB, MAPK and PKC-θ activity with free or nanoparticle-bound thymulin (Novoselova et al., 2018). A 2009 rat study of thymulin and NF-κB in the hippocampus was retracted in 2010 and is not used here (Haddad, 2009). Models: rats and mice.
Myeloid inflammation and tumors in aged mice
A University of Southern California group identified thymulin, which it describes as declining with age, as a circulating factor that suppressed IL-1α, IL-1β, IL-6 and TNF-α production by myeloid cells through NF-κB inhibition. Tumor-bearing mice received thymulin acetate with equimolar zinc chloride, 1.5 mg/kg intraperitoneally each day, or a zinc chloride vehicle. In aged mice it delayed AT-3 and E0771 breast tumor growth, prolonged survival and made tumors responsive to anti-PD-L1 antibody, with minimal effect in young mice (Kanemaru et al., 2026). Models: mice and human blood cells ex vivo.
Trials of synthetic thymulin in people
Two randomized, double-blind, placebo-controlled trials in rheumatoid arthritis compared placebo with three daily amounts of nonathymulin. The middle amount was reported as the most effective, with clinical improvement on global assessment in 56 percent against 17 percent on placebo and no clear change in immunological parameters (Amor et al., 1987).
In a double-blind pilot trial, 40 matched people with multiple sclerosis and moderate disability received nonathymulin or placebo for six months. Disability scores did not differ significantly, and the authors judged it not effective (Roullet et al., 1989). We found no later trial of the peptide in PubMed.
Key studies
- Pleau JM, et al. "Structural study of circulating thymic factor: a peptide isolated from pig serum. II. Amino acid sequence." J Biol Chem. 1977. PMID 914862.
- Dardenne M, et al. "Contribution of zinc and other metals to the biological activity of the serum thymic factor." Proc Natl Acad Sci U S A. 1982. PMID 6957870. DOI 10.1073/pnas.79.17.5370.
- Amor B, et al. "Nonathymulin in rheumatoid arthritis: two double blind, placebo controlled trials." Ann Rheum Dis. 1987. PMID 3310925. DOI 10.1136/ard.46.7.549.
- Prasad AS, et al. "Serum thymulin in human zinc deficiency." J Clin Invest. 1988. PMID 3262625. DOI 10.1172/JCI113717.
- Kanemaru H, et al. "Thymulin restrains age-associated myeloid inflammation and enhances cancer immunotherapy." Nat Commun. 2026. PMID 42481458. DOI 10.1038/s41467-026-75383-0.
Handling and storage of lyophilized thymulin
General laboratory practice for a lyophilized nonapeptide, in line with the site's peptide storage guide and reconstitution guide:
- Keep the sealed powder dry, at -20°C and protected from light, and let a cold vial reach room temperature before opening.
- Record whether the material is the peptide alone or the zinc complex, and any zinc added. A chelating resin removed activity in the founding assays, so note any EDTA or other chelator in buffers.
- Test a small portion in water first, and dissolve before adding salt or buffer. Keep solutions as single-use aliquots at 2 to 8°C, protected from light, without freeze-thaw cycles.
- Name the assay: activity assays read the zinc-bound hormone, while some immunoassays also detect the peptide without zinc (Dardenne et al., 1985).
Frequently asked questions
What is thymulin?
A nine-residue thymic peptide hormone, pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn, that is active as a zinc complex (Dardenne et al., 1982), studied in animals, cell cultures and human studies.
What does facteur thymique sérique mean?
French for serum thymic factor (FTS): the Paris group's name for the factor it isolated from pig serum (Pleau et al., 1977). The zinc-bound form became thymulin, or FTS-Zn (Dardenne et al., 1982).
Is the thymulin peptide the same as thymalin, thymogen or a thymosin?
No. Thymalin, a calf thymus extract, and thymogen, the dipeptide Glu-Trp, come from the St Petersburg bioregulator program, and the thymosins from a calf thymus fraction; see our thymalin and thymogen guides and the thymic peptides explainer. Thymulin came from pig serum (Pleau et al., 1977).
Why does thymulin need zinc?
Without zinc the peptide was inactive in the founding bioassay, and zinc restored activity, best at one ion per peptide (Dardenne et al., 1982). The zinc-bound form also has its own shape, recognized by specific antibodies (Dardenne et al., 1985).
Has thymulin been tested in people?
Yes, as research history: two placebo-controlled rheumatoid arthritis trials (Amor et al., 1987) and a 40-person multiple sclerosis pilot trial that found no significant difference (Roullet et al., 1989). Other human studies measured blood thymulin (Prasad et al., 1988).
Does Disguised Alpha sell thymulin?
Not currently. Thymus research materials in the catalog include Thymalin and Thymosin Alpha-1.
Related compounds and guides
- Thymic peptides explained
- Thymalin research guide
- Thymosin alpha-1 research guide
- Thymogen research guide
Literature reference for laboratory research only. Not for human consumption.