Thymulin
A nine-amino-acid thymic hormone that works only with a zinc ion bound to it, measured in people far more often than it is given to them
Thymulin is a natural thymic peptide whose activity depends on a zinc ion. Its literature is large, but almost all of it measures the hormone as a marker of thymic function and zinc status; the studies that give it to people are few, small and old.
What is it?
Thymulin has an unusual dependency. Stripped of metal by a chelating agent the peptide is inert; add zinc back at one ion per molecule and activity returns. That 1982 finding renamed the serum thymic factor thymulin, and it is why the literature treats it as a readout of zinc status rather than a therapy.
That use is well supported. Serum thymulin fell in people with mild zinc deficiency and rose again with zinc, at a point where plasma zinc itself looked normal. It was low in anorexia nervosa, and in children who died of severe malnutrition the thymus was nearly empty of it.
A 2021 rat study put numbers on that use: on a low-zinc diet, thymulin activity fell 61% while serum zinc fell 31%, making it the most responsive of five measures tested.
Direct administration is thinner. Lymphocytes from people with rheumatoid arthritis regained normal T-cell ratios when incubated with it, and four patients given it intravenously showed natural-killer activity moving towards the middle. Both studies are from the 1980s.
The modern work is in animals, and it has two strands. One is inflammation: thymulin or its analogue reduced fever and cytokines in septic mice, protected mice in diabetes and multiple sclerosis models, and relieved inflammatory pain in rats through the α7-nicotinic receptor. The other is delivery, since the peptide is short-lived: nanoparticle gene therapy carrying thymulin reversed established asthma pathology in mice, and a switchable adenovector raised thymulin in rats until doxycycline turned it off.
The newest result is the broadest. A 2026 mouse study identified thymulin as a thymus-derived factor that declines with age and restrains inflammatory myeloid cells by blocking NF-κB; giving it improved tumour control and made tumours respond better to anti-PD-L1 therapy, but only in older animals. None of that has been tested in a person.
Mechanism of Action
Thymulin is a thymic peptide that is active only when bound to a single zinc ion, which is why it is treated as a readout of zinc status.
Zinc dependence
Stripped of zinc it is inert; adding one zinc ion per molecule restores activity.
Anti-inflammatory
In animals it lowers cytokines by inhibiting NF-κB, and its analogue acts through the α7-nicotinic receptor in pain models.
Short-lived
Its brief life has pushed researchers toward gene therapy and nanoparticle delivery in animal studies.
Published Research
These are the studies that describe thymulin, read from their PubMed abstracts: four in people and one in mice.
Why it is called thymulin
Chelating the metal out of the serum thymic factor destroyed its activity; zinc restored it, best at one ion per peptide. The authors proposed the name thymulin for the zinc-bound form.
Mild zinc deficiency in humans
In three groups of mildly zinc-deficient adults, serum thymulin fell while plasma zinc stayed normal, and rose again with zinc given by mouth or added in the laboratory.
290 children in rural Nepal
Thymulin measured at ages 9 to 13 in 290 children averaged 1.37 ng/mL, and was higher with gestational age at delivery and with every body measurement taken.
Given to four patients
Added to blood cells, low concentrations raised natural-killer activity and higher ones lowered it. Four people with cancer given 10 µg/kg intravenously every three days showed the same pattern: activity rose in the two who started low and fell in the two who started high.
Ageing, inflammation and cancer immunotherapy
Thymulin was identified as a thymus-derived factor that falls with age and suppresses inflammatory cytokine production by inhibiting NF-κB; in mice it improved antitumour T-cell immunity and sensitised tumours to anti-PD-L1 therapy in an age-dependent way.
What thymulin does
A review of the thymulin-neuroendocrine axis and the peptide's anti-inflammatory properties, including work in congenitally athymic mice as a model of neuroendocrine and reproductive ageing.
Against other zinc measures
In rats fed low zinc, serum thymulin activity fell 61% against adequately fed animals, a larger drop than serum zinc (31%), superoxide dismutase (18%) or 5'-nucleotidase (26%).
Gene therapy in chronic asthma
In mice with established allergic asthma, nanoparticle-delivered thymulin gene therapy normalised inflammation, lung fibrosis and lung mechanics.
Preventing airway remodelling
A single dose of DNA nanoparticles carrying a thymulin analogue gene prevented lung inflammation, collagen deposition and smooth-muscle thickening in asthmatic mice, with plasmid still detectable at 27 days.
A switchable gene vector
A two-adenovector system raised thymulin in rat cerebrospinal fluid after brain injection and in serum after intramuscular injection, and doxycycline in the drinking water switched it off.
Septic inflammation in mice
Thymulin, free or on nanoparticles, reduced fever, apoptosis and cytokine production in mice given bacterial lipopolysaccharide and partly restored brain serotonin and melatonin.
Type 1 diabetes model
In mice with streptozotocin-induced diabetes, thymulin and the antioxidant enzyme peroxiredoxin 6 each reduced physiological damage, by different mechanisms.
How its analogue relieves pain
In rats, a thymulin-related peptide reversed inflammatory and cold and touch hypersensitivity, an effect largely blocked by an α7-nicotinic receptor antagonist, and it potentiated that receptor in oocytes.
Multiple sclerosis model
Thymulin loaded on nanoparticles protected mice against the relapsing-remitting form of experimental autoimmune encephalomyelitis.
Dosing Data
Not approved anywhere. The only human administration, in 1983, gave 10 µg/kg intravenously to four cancer patients.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
Side Effects & Contraindications
Reported Side Effects
Almost nothing is published: the human studies measured the hormone rather than gave it.
Contraindications & Cautions
A research peptide with no approval and no human safety data.
Legal Status
Thymulin is not approved as a medicine anywhere.
Frequently Asked Questions
?What is thymulin?
A nine-amino-acid hormone made by the epithelial cells of the thymus, inactive without a bound zinc ion.
?Why is it measured so often?
Serum thymulin falls with mild zinc deficiency before plasma zinc does, which makes it a sensitive marker of zinc and thymic status.
?Has it been given to people?
Barely. The record has four cancer patients given it intravenously in 1983, and laboratory work on cells from patients. Everything since is animal or cell work.
?What about the ageing and cancer result?
A 2026 study found thymulin declines with age and restrains inflammatory myeloid cells, improving tumour control in aged mice. It is a mouse finding.
?Why is thymulin a good zinc marker?
It only works when bound to zinc. In rats on a low-zinc diet, thymulin activity fell 61% while serum zinc fell 31%, making it the most responsive of five measures tested.
?What is the newest thymulin finding?
A 2026 mouse study found thymulin falls with age and restrains inflammatory myeloid cells by blocking NF-κB; giving it improved tumour control and response to anti-PD-L1 therapy in older mice only.
References
- [pubmed] 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;79(17):5370-3. PMID: 6957870.
- [pubmed] Prasad AS, et al. "Serum thymulin in human zinc deficiency." J Clin Invest, 1988;82(4):1202-10. PMID: 3262625.
- [pubmed] Palmer AC, et al. "Prenatal and childhood exposures are associated with thymulin concentrations in young adolescent children in rural Nepal." J Dev Orig Health Dis, 2020;11(2):127-135. PMID: 31475652.
- [pubmed] Dokhelar MC, et al. "Effect of a synthetic thymic factor (facteur thymique serique) on natural killer cell activity in humans." Int J Immunopharmacol, 1983;5(4):277-82. PMID: 6195118.
- [pubmed] Kanemaru H, et al. "Thymulin restrains age-associated myeloid inflammation and enhances cancer immunotherapy." Nat Commun, 2026;17(1). PMID: 42481458.
- [other] US FDA, Drugs@FDA (openFDA): no application for thymulin. Read September 30, 2026.
- [pubmed] Nasseri B, et al. "Thymulin treatment attenuates inflammatory pain by modulating spinal cellular and molecular signaling pathways." Int Immunopharmacol, 2019;70:225-234. PMID: 30851702.
- [pubmed] Wade S, et al. "Thymulin (Zn-facteur thymique serique) activity in anorexia nervosa patients." Am J Clin Nutr, 1985;42(2):275-80. PMID: 3927699.
- [pubmed] Davis SL, et al. "Concentrations of thymulin in unextracted serum from pigs, sheep and cattle as measured by ELISA." J Immunoassay, 1994;15(2):191-211. PMID: 8040352.
- [pubmed] Reggiani PC, et al. "Physiology and therapeutic potential of the thymic peptide thymulin." Curr Pharm Des, 2014;20(29):4690-6. PMID: 24588820.
- [pubmed] DiSilvestro RA, et al. "Comparison of Thymulin Activity with Other Measures of Marginal Zinc Deficiency." Biol Trace Elem Res, 2021;199(2):585-587. PMID: 32363520.
- [pubmed] da Silva AL, et al. "Nanoparticle-based thymulin gene therapy therapeutically reverses key pathology of experimental allergic asthma." Sci Adv, 2020;6(24):eaay7973. PMID: 32577505.
- [pubmed] da Silva AL, et al. "DNA nanoparticle-mediated thymulin gene therapy prevents airway remodeling in experimental allergic asthma." J Control Release, 2014;180:125-33. PMID: 24556417.
- [pubmed] Zappa-Villar MF, et al. "A new adenovector system for implementing thymulin gene therapy for inflammatory disorders." Mol Immunol, 2017;87:180-187. PMID: 28501652.
- [pubmed] Novoselova EG, et al. "Thymulin, free or bound to PBCA nanoparticles, protects mice against chronic septic inflammation." PLoS One, 2018;13(5):e0197601. PMID: 29795607.
- [pubmed] Novoselova EG, et al. "Thymulin and peroxiredoxin 6 have protective effects against streptozotocin-induced type 1 diabetes in mice." Int J Immunopathol Pharmacol, 2021;35:20587384211005645. PMID: 33779346.
- [pubmed] Safieh-Garabedian B, et al. "Involvement of the α7-nicotinic acetylcholine receptors in the anti-inflammatory action of the thymulin-related peptide (PAT)." Neuroscience, 2013;250:455-66. PMID: 23880090.
- [pubmed] Lunin SM, et al. "Protective Effect of PBCA Nanoparticles Loaded with Thymulin Against the Relapsing-Remitting Form of Experimental Autoimmune Encephalomyelitis in Mice." Int J Mol Sci, 2019;20(21). PMID: 31671728.
Sources & Citations
Studies were read from their PubMed abstracts; homeopathic-dilution papers that appeared in the searches were not cited. Read October 7, 2026.
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