Thymulin: uses, evidence and status

compound file

The answer, first. A zinc-dependent nonapeptide hormone secreted by thymic epithelial cells, described in the 1970s under the name facteur thymique serique. The strongest evidence is for rheumatoid arthritis, graded C — small or open-label human only.

Two double-blind placebo-controlled trials of the analogue nonathymulin reported global improvement in 56% of patients versus 17% on placebo at 5 mg daily ¹.

That was 1987. Nothing has replicated it. Every other use — age-related inflammation and tumour immunity, pain and inflammation, immune restoration and T-cell maturation, multiple sclerosis — grade D or E: animal or mechanism data only, or a claim the human trials have already tested and not supported.

What it is used for

Every use graded on its own evidence, not the compound as a whole. 5 outcomes, ranked by what the human record supports.

#outcome · human · animal · gradewhat the best evidence actually shows

01Rheumatoid arthritis2 RCTs of an analogue · limitedgrade CTwo double-blind placebo-controlled trials of the analogue nonathymulin reported global improvement in 56% of patients versus 17% on placebo at 5 mg daily ¹. That was 1987. Nothing has replicated it.

02Age-related inflammation and tumour immunityno trial · mousegrade DIn aged mice thymulin suppressed myeloid interleukin-1 and interleukin-6 output through NF-kappa-B, improved tumour control and sensitised tumours to anti-PD-L1 ⁴. Mice only, published 2026.

03Pain and inflammationno trial · ratgrade DA thymulin-related peptide cut endotoxin-induced hyperalgesia and inflammatory cytokines in rats ⁵. Rat only, and the molecule tested was an analogue, not thymulin.

04Immune restoration and T-cell maturationbiomarker only · mousegrade DSerum thymulin activity falls with mild zinc deficiency in humans and is restored by zinc, tracking T-cell subset shifts ³. That measures the body's own thymulin, not an injected dose.

05Multiple sclerosis1 RCT, n=40 · nonegrade EForty patients, six months of subcutaneous nonathymulin, six months of follow-up. No difference on Kurtzke disability score, ambulation index or functional scale ². The authors called it not effective.

gradewhat it means

ARegulatory approval, or multiple adequately-powered trials agreeing with each other

BAt least one well-powered human randomised trial, with the direction replicated

CSmall or open-label human trials only

DAnimal or mechanism data only, with no controlled human outcome

EA claim the human trials have already killed

How it works

The proposed mechanism, in three steps. A mechanism is a reason to run a trial, never a substitute for one.

1targetThe nonapeptide is biologically inactive until it binds a zinc ion. The zinc-peptide complex is the active hormone ⁹.

2signalIt acts on T-cell precursors and on the hypothalamic-pituitary axis, and in mice suppresses NF-kappa-B in myeloid cells ⁶⁴.

3effectIn mice, thymulin gene therapy restored pituitary function lost with age ⁸. No human dosing study has measured any of this.

What it does not do

Claims the current record does not support. Worth knowing before you set expectations.

not supported by the evidence

Regrows or restores the adult thymus. No human study has given thymulin and measured thymic output, T-cell counts or infection rates. Not one.
An immune peptide with human trials. The two human trials used nonathymulin, a synthetic analogue, in 1987 and 1989 ¹². Thymulin itself has none.
Slows ageing. The ageing evidence is mouse gene therapy and mouse parabiosis ⁸⁴. No human has been dosed and followed.

How it is used

What published protocols administered, and what the community reports doing. Descriptive on both counts, and never a recommendation.

routeNo route is established in humans. The 1980s trials injected the analogue nonathymulin subcutaneously ².

formatLyophilised powder sold for research use.

published dosesNo published human dose exists for thymulin itself. The analogue nonathymulin was trialled at 1, 5 and 10 mg daily, with 5 mg the best of the three ¹. Rodent work uses microgram doses given intraperitoneally ⁵. None of that transfers to a person.

human pharmacokineticsNo human pharmacokinetic data published.

reported conventionsAs reported on peptide forums and vendor protocol sheets, 2019-2026: microgram-range subcutaneous doses copied out of rodent papers, run in short blocks. No circulating convention has a human study behind it. Convention, not guidance.

commonly paired withThymosin Alpha-1

This site does not publish protocols to follow. The doses above are what studies administered or what users report, stated as facts about the literature and the market. How protocols are structured, mixing and storage and the reconstitution calculator cover the arithmetic.

What to expect

Where a trial measured it, the trial. Where only the community reports it, that is said out loud.

onsetNo trial has measured onset for thymulin in a human. The nonathymulin arthritis trials assessed response after weeks of daily dosing ¹. The multiple sclerosis trial found nothing at six months and nothing at twelve ².

most common reportAs reported: nothing perceptible. No felt effect is described consistently by anyone.

adverse effectsThe arthritis trials recorded minimal adverse effects ¹, and the multiple sclerosis trial recorded no significant side effects across 40 patients over 12 months ². Both used the analogue. Thymulin itself has no human safety record.

the stop signalNo stop signal appears in the literature and none is reported by users. The two trials ran fixed courses and ended on schedule ¹².

Approval and status

What regulators and sport bodies have actually said, separately from what the evidence shows.

approvalNot approved anywhere. Never reached a modern regulatory filing.

FDANo US approval. Not named on the FDA list of bulk substances flagged for compounding safety risks ¹⁰.

sport [WADA]Not named. Falls under S0, non-approved substances ¹¹.

sold asresearch chemical

Check the vial

The grade above describes a molecule studied under controlled conditions. It says nothing about the powder in a particular vial.

That gap is the one part of this market a reader can actually close. How to read a certificate of analysis covers the five measures in five minutes, and the 2026 audit grades vendors on the documents they publish against a rubric printed in full.

Questions we get

What is Thymulin used for?

Nothing with a human outcome behind it. Thymulin is bought as an immune and anti-ageing compound, and both claims rest on rodent work ⁴⁵⁸. The only controlled human trials tested nonathymulin, a synthetic analogue: positive in rheumatoid arthritis in 1987 ¹, negative in multiple sclerosis in 1989 ². Neither line was pursued.

How is Thymulin used?

Descriptively: there is no published human protocol for thymulin. The analogue nonathymulin was injected subcutaneously at 1, 5 or 10 mg daily in the 1980s trials ¹². Rodent studies dose in micrograms intraperitoneally ⁵. Whatever schedule circulates in the research market was worked out from animal papers, not from a human study.

How long does Thymulin take to work?

Unknown, because no one has measured it in a person. The nearest data point is the analogue. Response in rheumatoid arthritis was assessed after weeks of daily dosing ¹. Six months of treatment moved nothing in multiple sclerosis ². There is no pharmacokinetic study, so even the half-life in humans is unpublished.

Is Thymulin an approved drug?

No. Thymulin is sold as a research chemical, not as an approved medicine, and it has never held an approval in any country. On our index it is graded animal only on clinical evidence and niche on community adoption, and those two are rated separately on purpose.

Under the World Anti-Doping Code it falls in S0, non-approved substances, prohibited at all times ¹¹.

References

Amor B, et al. Nonathymulin in rheumatoid arthritis: two double blind, placebo controlled trials. Ann Rheum Dis. 1987. PMID 3310925
Roullet E, et al. Nonathymulin treatment of multiple sclerosis: double-blind pilot study. Acta Neurol Scand. 1989. PMID 2618585
Prasad AS, et al. Serum thymulin in human zinc deficiency. J Clin Invest. 1988. PMID 3262625
Kanemaru H, et al. Thymulin restrains age-associated myeloid inflammation and enhances cancer immunotherapy. Nat Commun. 2026. PMID 42481458
Safieh-Garabedian B, et al. Potent analgesic and anti-inflammatory actions of a novel thymulin-related peptide in the rat. Br J Pharmacol. 2002. PMID 12110619
Goya RG, et al. Thymulin and the neuroendocrine system. Peptides. 2004. PMID 15003367
Reggiani PC, et al. Physiology and therapeutic potential of the thymic peptide thymulin. Curr Pharm Des. 2014. PMID 24588820
Reggiani PC, et al. Thymulin-based gene therapy and pituitary function in animal models of aging. Neuroimmunomodulation. 2011. PMID 21952687
Dardenne M, Bach JF. Interactions between zinc and thymulin. Met Based Drugs. 1994. PMID 18476235
US Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks. Category 2 lists. fda.gov
World Anti-Doping Agency. The 2026 Prohibited List. In force 1 January 2026. wada-ama.org

Inside Your Peptides is published by the owners of the next lab, a vendor graded elsewhere on this site. We sell nothing here, and this page carries no vendor link. Grades follow the published criteria in our editorial policy — never referral terms. Research and education only. Not medical advice.