Educational use only — not medical advice. This guide summarizes information reported in published research and community practice for educational purposes. It is not medical advice and not a recommendation to use any compound. Any doses, schedules, or combinations shown are examples of what has been reported, not instructions for you. Many peptides described here are research compounds that are not FDA-approved for the uses discussed and may be investigational or restricted. Effects, risks, and legal status vary; individual needs and results vary. Consult a qualified, licensed healthcare professional before making any decision. Do not use this content to diagnose, treat, or dose yourself.
Thymulin at a glance
- What it is
- A nonapeptide hormone secreted by thymic epithelial cells, formerly called FTS (facteur thymique serique). The biologically active form is the zinc-bound complex, which is why it is written FTS-Zn.
- Not to be confused with
- Thymalin (a Russian thymus-extract peptide preparation), thymosin alpha-1 (28 amino acids) and thymopentin/TP-5. Secondary sources conflate these constantly; they are different substances with different evidence.
- Researched for
- T-cell differentiation and suppressor T-cell function; trialled in rheumatoid arthritis and multiple sclerosis in the 1980s.
- Human evidence
- Two randomised double-blind placebo-controlled RA trials reported significant clinical improvement at 5 mg/day; a randomised double-blind MS trial reported no benefit.
- Published trial doses
- 1, 5 and 10 mg/day were compared in the RA trials, with 5 mg/day the most effective arm. These are published trial figures, not recommendations.
- Route in the trials
- Subcutaneous injection (MS trial); daily dosing in the RA trials.
- Plasma half-life
- Not established — no published human pharmacokinetic study reports a half-life figure for thymulin. Treat any specific number found online as unsourced.
- Regulatory status
- Never approved in any jurisdiction, in more than 45 years since its characterisation. Research/educational use only.
Educational reference. This page does not publish dose ranges or reconstitution arithmetic.
What it is / mechanism
Thymulin is a nonapeptide (pyroglutamyl-alanyl-lysyl-seryl-glutaminyl-glycyl-glycyl-seryl-asparagine) produced by thymic epithelial cells. Its defining property is that it is a metallopeptide: the peptide chain alone is biologically inert, and both its biological activity and its antigenicity depend on a zinc ion bound within the molecule. This is why the literature writes it as FTS-Zn and why zinc status and thymulin activity track together in human studies — the zinc-free apopeptide is not simply weaker, it is inactive. In research settings the peptide is described as inducing T-cell differentiation and enhancing functions across T-cell subsets, with the most consistently reported effect being on suppressor T-cell activity. Its original name, facteur thymique serique (FTS), reflects that it was first identified as a circulating thymic factor in serum rather than isolated from tissue.
Researched effects
The honest summary is that thymulin's reported effects are far better characterised in immunology assays than in outcomes. Research consistently describes T-cell differentiation and modulation of suppressor T-cell function, and zinc-repletion studies in humans show plasma thymulin concentrations recovering alongside zinc. What does not follow from that is a demonstrated clinical benefit: the one condition where randomised double-blind data reported improvement is rheumatoid arthritis, and notably that improvement was not accompanied by clear changes in the immunological parameters measured. In multiple sclerosis, a randomised double-blind trial found no effect on any disability measure. Broad claims about immune restoration, anti-ageing or general immune enhancement do not have human trial support behind them.
Evidence & regulatory status
- Positive human evidence: two randomised, double-blind, placebo-controlled trials of nonathymulin (the synthetic form) in rheumatoid arthritis compared 1, 5 and 10 mg/day. The 5 mg/day arm was the most effective, with global assessment improvement in 56% of patients versus 17% on placebo (p<0.02) and improvement on four objective parameters, with minimal adverse effects (Annals of the Rheumatic Diseases, 1987; PMID 3310925). The authors noted the clinical effect was not accompanied by clear changes in immunological parameters.
- Negative human evidence: a randomised, double-blind, placebo-controlled trial in 40 matched patients with evolutive multiple sclerosis and moderate disability gave subcutaneous nonathymulin or placebo for 6 months with a further 6 months of follow-up. There was no significant difference on the Kurtzke disability scores, Ambulation Index or Functional Scale, and the authors concluded it is not effective in this population (Acta Neurologica Scandinavica, 1990; PMID 2618585).
- Mechanistic basis: thymulin's zinc dependence — activity and antigenicity both requiring the bound metal — is established in the primary literature (Medical Oncology and Tumor Pharmacotherapy, 1989; PMID 2657247), alongside NMR conformational characterisation of the free and zinc-bound peptide.
- Regulatory: never approved for any indication anywhere, despite human trials beginning in the 1980s. There has been no modern replication of the rheumatoid arthritis result. Sold for research use only; nothing here is medical advice or an endorsement of human use.
A printable protocol sheet with a reconstitution reference and an injection log comes with All-Access Lifetime.
Half-life & pharmacokinetics
There is no published human pharmacokinetic study establishing a plasma half-life for thymulin, and this is worth stating plainly because specific half-life figures circulate on commercial pages without a traceable source. What the literature does establish is that circulating thymulin activity is zinc-dependent and falls with zinc deficiency, and that the peptide was dosed daily in the human trials — a schedule consistent with short persistence, but not itself a measured half-life. Treat any precise number found elsewhere as unverified until a primary source is produced for it.
Side effects, safety & contraindications
The randomised rheumatoid arthritis trials reported minimal adverse effects at 1-10 mg/day, and the multiple sclerosis trial recorded no significant side effects over 6 months of subcutaneous dosing. That is a genuinely reassuring short-term safety signal by the standards of this market — but it comes from two small trials in the 1980s, and there is no long-term human safety data, no modern pharmacovigilance, and no data in healthy subjects rather than patients. As with any injected peptide, injection-site reactions are possible, and material of unverified purity carries risks unrelated to the peptide itself.
Storage & handling
- Lyophilized (powder): store refrigerated at 2-8C, protected from light; long-term storage is commonly reported in a freezer.
- Reconstituted (in bacteriostatic water): refrigerate at 2-8C; swirl gently and do not shake, and do not freeze once mixed. Because the active form is a zinc complex, degradation costs activity as well as content.
References
Primary sources: the two randomised double-blind placebo-controlled rheumatoid arthritis trials of nonathymulin (Annals of the Rheumatic Diseases, 1987; PMID 3310925); the randomised double-blind multiple sclerosis trial (Acta Neurologica Scandinavica, 1990; PMID 2618585); and the characterisation of thymulin as a zinc-dependent hormone (Medical Oncology and Tumor Pharmacotherapy, 1989; PMID 2657247), alongside NMR conformational studies of the free and zinc-bound nonapeptide. Thymalin is described separately in the Khavinson peptide-preparation literature and is not the same substance. Figures are educational examples drawn from published trials, not medical advice.
Related peptide guides
Continue exploring related educational guide topics in the Medibact library.
Guide FAQ
Quick answers about guide scope, access, and educational use context.
Is thymulin the same as Thymalin?
No, and this is the single most common error about it. Thymulin is a defined nine-amino-acid hormone, formerly called FTS, whose activity depends on a bound zinc ion. Thymalin is a peptide preparation from the Russian Khavinson research line, described in that literature as a thymus-derived preparation rather than a single characterised nonapeptide. The two have different structures, different literatures and different evidence, and vendor pages routinely present one's research under the other's name. Medibact keeps a separate Thymalin guide for that reason.
Is thymulin the same as thymosin alpha-1?
No. Thymosin alpha-1 is a 28-amino-acid peptide with a substantially larger clinical literature of its own. Thymulin is a nonapeptide — nine residues — and is zinc-dependent, which thymosin alpha-1 is not. Both are thymic peptides, which is the entire basis for the confusion; they are not interchangeable and evidence for one says nothing about the other.
Why is thymulin written as FTS-Zn?
FTS stands for facteur thymique serique, its original French name from when it was identified as a circulating thymic factor in serum. The Zn denotes the bound zinc ion. The notation exists because the zinc is not incidental: the primary literature establishes that both biological activity and antigenicity depend on the metal being present, so the zinc-free peptide is inactive rather than merely less potent.
Does thymulin have real human trial data?
Yes, and unusually for this market, it includes randomised double-blind placebo-controlled trials — with results going in both directions. Two such trials in rheumatoid arthritis reported significant clinical improvement at 5 mg/day (56% global improvement versus 17% on placebo, p<0.02, 1987). A randomised double-blind trial in multiple sclerosis found no benefit on any disability measure and concluded it was not effective in that population (1990). A guide that cites only the first of these is telling half the story.
What dose was used in the human trials?
The rheumatoid arthritis trials compared 1 mg, 5 mg and 10 mg per day of the synthetic form and found 5 mg/day the most effective arm — the highest dose was not the best one. The multiple sclerosis trial used subcutaneous administration over 6 months. These are reported trial figures given for educational context, from studies conducted under clinical supervision in patient populations, and they are not dosing guidance for anyone.
What is thymulin's half-life?
No published human pharmacokinetic study reports one. This matters because specific half-life values do circulate on commercial pages, and none of them trace back to a primary source. Daily dosing in the human trials is consistent with short persistence in circulation, but a dosing schedule is not a measured half-life. If a figure is quoted anywhere, ask which study produced it before relying on it.
Is thymulin approved anywhere?
No. It has never been approved for any indication in any jurisdiction, despite having been characterised in the 1970s and trialled in humans in the 1980s. There has been no modern replication of the rheumatoid arthritis finding. It is sold strictly for research purposes, and nothing in this guide is medical advice or an endorsement of human use.
Compliance and trust notes
- Educational content only; no personalized health or outcome claims.
- No personalized use recommendation outputs.
- Use this material for general learning and research-context literacy.
