Thymulin
ZnFTS, serum thymic factor, FTS
Thymulin (ZnFTS, serum thymic factor, FTS) is a longevity & bioregulators research compound. A nine-amino-acid hormone from thymic epithelial cells whose activity is ZINC-DEPENDENT — the peptide is inactive until zinc binds it. It drives T-cell maturation and helps set the balance between T-cell subsets. Thymulin falls sharply with age alongside thymic involution, and it also falls in zinc deficiency, which is why zinc status and thymulin activity are hard to separate.
Thymulin quick facts
| Reported research dose | 1-2mg daily over a 10-20 day course |
| Route | Subcutaneous |
| Frequency | 1x Daily · Daily during a course |
| Half-life | Minutes in circulation |
| Forms | Injectable |
| Evidence level | Correlative — human immunology is well described, administration data is old and thin |
The zinc dependence is the practical point and it is often missed: in a zinc-deficient person, circulating thymulin can be present but inactive. Correcting zinc restores measured thymulin activity on its own. Check zinc before assuming the peptide is what is needed.
How Thymulin works
A nine-amino-acid hormone from thymic epithelial cells whose activity is ZINC-DEPENDENT — the peptide is inactive until zinc binds it. It drives T-cell maturation and helps set the balance between T-cell subsets. Thymulin falls sharply with age alongside thymic involution, and it also falls in zinc deficiency, which is why zinc status and thymulin activity are hard to separate.
Proposed benefits
Immune modulation and T-cell maturation — with the catch that it is inactive without zinc, so correcting zinc may do the same job for less.
Where to get Thymulin
Buy Thymulin at Biolongevity Labs →Bacteriostatic water is the diluent — sterile water with 0.9% benzyl alcohol, which is what lets a vial be drawn from more than once. It does not come with the vial, and unlike the compound it is bought again every time.
Need bacteriostatic water? Get it at AminoWell USA (my company) → Code CAMERON.
The evidence for Thymulin
Graded by what exists behind each claim.
✅ Clinically validated
- Human administration data exists but is old, small, and mostly European work from the 1980s-90s in primary immunodeficiency and in ageing — not the randomized, powered trials that would settle whether it does anything useful in a healthy adult.
📊 Correlative data
- Thymulin activity falls steeply with age, in parallel with thymic involution, and the decline is measurable in serum. It also falls in zinc deficiency, in protein-energy malnutrition, and in several chronic illnesses — which makes the age association hard to isolate from general health.
- Restoring zinc in zinc-deficient older adults raises measured thymulin ACTIVITY without giving any thymulin. That is a genuine and repeatedly observed finding, and it reframes low thymulin as sometimes being a zinc problem wearing a peptide costume.
🧪 Theoretical / extrapolated
- Its activity is gated by zinc, not just influenced by it. The peptide is biologically inert until a zinc ion binds; the zinc-bound form is the active hormone. So the same amount of circulating peptide can be fully active or fully inactive depending on zinc status, which is a mechanism with an obvious and cheap first step.
- Rodent work also reports antinociceptive and anti-inflammatory effects independent of the T-cell story, via peripheral and central pathways. Interesting, unreplicated in humans, and not a reason to expect it in a person.
How to read these tiers: they say how much human evidence exists, not how well something works — and ✗ flags harm, never a disappointing trial. How the evidence tiers work →
What Thymulin actually does
Thymulin is the only molecule in this Vault that is not fully a molecule. It is a nonapeptide plus a zinc ion, and without the zinc it is not thymulin. That is not a formulation detail. It is the defining fact of the compound and it changes what a person should measure.
The zinc is structural and it is obligatory. The peptide produced by thymic epithelial cells binds a single Zn(II) ion, and only the zinc-bound form is biologically active. The apo-peptide — the same nine residues without the metal — is inactive, and in the classical literature it competes with the active form. So the amount of thymulin in a person is not set by how much peptide the thymus makes; it is set by how much of that peptide has zinc bound to it, and that is why thymulin activity falls in zinc deficiency and rises again on repletion Haase 2009.
Which means the historical assay measured something different from a concentration. Thymulin was defined and quantified by a rosette bioassay — a functional readout of what serum did to lymphocytes — rather than by mass. A functional assay reports activity, and activity here is peptide multiplied by zinc occupancy. Half a century of literature reporting low thymulin in aging and in illness may be reporting low zinc as often as low peptide, and the two have completely different answers.
Where it comes from and why it disappears. Thymulin is produced by thymic epithelial cells, so its output tracks the thymus. The thymus involutes from adolescence onward, and thymic output is also sensitive to nutritional state — the relationship between the thymus, undernutrition and infection is a field in its own right Savino 2022. Thymic function is additionally under growth-hormone and IGF-1 control through an intrathymic somatotropic circuit, and that circuit is one of the levers on involution Reis 2023. Falling thymulin with age is therefore a symptom of thymic involution, not a cause of it, and that distinction decides whether replacing it could work.
What zinc is actually doing, at a receptor, in modern terms. The classical account of zinc and thymic function is nutritional. A more recent one is pharmacological: activating the zinc-sensing receptor GPR39 promotes T-cell reconstitution after hematopoietic cell transplant in mice Iovino 2022. That is a named receptor with a named ligand producing a named immunological outcome, and it is a far more tractable target than a metal-dependent nonapeptide — which is a real argument against this compound rather than for it.
And a neuroendocrine loop that explains part of the literature. The thymus and the pineal gland are reciprocally connected, with melatonin influencing thymic function and thymic peptides influencing the pineal Rezzani 2020. That axis is why thymulin appears in aging papers alongside melatonin, and why its levels have a diurnal component that single-timepoint studies ignore.
Cell, rodent, human — and where it stops
Step one, the classical literature: real, and old. Thymulin was isolated, sequenced and assayed in the 1970s and 1980s, and its zinc dependence was established then. An honest statement about this compound has to include the shape of its evidence base: most of it predates modern indexing, a large share is in French, and a PubTator3 search for the compound name returns a handful of records rather than a field. That is not a reason to dismiss it and it is a reason to be careful about what is citable.
Step two, the zinc arm, which is where the modern evidence is. Zinc's role in immune function during aging is well characterized, including its effect on thymic peptides Haase 2009, and thymic function in undernutrition is an active field Savino 2022. The strongest translational statement anybody can make about thymulin is about its cofactor.
Step three, animals, with a modern mechanism and a hard endpoint. GPR39 activation promotes T-cell reconstitution after transplant in mice Iovino 2022. T-cell reconstitution after transplant is exactly the endpoint a thymic peptide would need to move, and it was moved by a zinc-sensing receptor agonist rather than by thymulin.
Step four, humans, and this is where it stops. There is no modern randomized controlled trial of thymulin in humans for any indication. The growth-hormone-thymus circuit Reis 2023 and the pineal-thymus axis Rezzani 2020 are mechanistic reviews. Nothing on this page is a clinical result.
Where the chain breaks. (1) A nonapeptide injected subcutaneously is cleared in minutes — the card says minutes and it is right — and the classical physiology is a continuously secreted thymic factor, which an intermittent injection does not reproduce. (2) The zinc problem is fatal to any product: a synthesized peptide supplied without its metal is the inactive form, and nothing on a certificate of analysis says whether zinc is bound. (3) The historical assay was functional rather than mass-based, so old serum levels and a modern product's milligrams are not the same units. (4) The upstream cause is thymic involution Savino 2022 Reis 2023, and replacing a downstream product does not regrow the organ that made it.
What would have to be true, and how you would know it was not
Three predictions. The first is the one that should be done before anything else, and it may make the compound unnecessary.
1. Measure zinc first, because the cofactor is the likeliest explanation of everything thymulin is supposed to fix. Zinc plasma and, better, zinc RBC at baseline. Plasma zinc falls in any acute-phase response and is a poor index of stores; the red-cell measure reflects a longer window. If zinc is low, the mechanistically correct intervention is zinc Haase 2009, and no peptide substitutes for the metal it requires. This is the single most useful sentence on the page.
2. If a thymic peptide is doing anything immunological, the T-cell compartment is where it shows. A CBC with differential gives the total lymphocyte count for almost nothing. The informative version is a lymphocyte subset panel with a CD4/CD8 ratio at baseline and at 12 weeks. The prediction that would be genuinely convincing is a rise in naive T cells, because naive cells are thymic output and memory cells are not — and a claim about a thymic peptide that does not move naive T cells has not demonstrated a thymic effect.
3. The falsification test, and it is a null. Given a nonapeptide cleared in minutes, supplied without a guarantee of zinc occupancy, against an organ that has physically involuted, the prediction of this page is that lymphocyte subsets and the CD4/CD8 ratio do not change. hs-CRP at the same time points catches the alternative outcome that matters — a non-specific inflammatory response to an injected foreign peptide, which would look like an immune effect and would not be the intended one.
What nobody has tested yet
Four experiments nobody has run, and the first is embarrassingly simple.
Nobody has published the zinc occupancy of commercially available thymulin. The molecule is inactive without its metal Haase 2009. Determining whether a vial contains the zinc-bound or the apo-peptide is a routine analytical measurement. Nobody has published it for any product, which means nobody selling thymulin can say whether they are selling thymulin.
Nobody has run a modern trial with modern immunology. The classical literature used a rosette bioassay. A trial in older adults with flow cytometry, naive and memory T-cell subsets, T-cell receptor excision circles as a direct measure of thymic output, and vaccine response as a functional endpoint would settle in one study what fifty years of assay-limited work could not.
Nobody has compared thymulin against zinc alone. This is the trial that would decide whether the compound exists for a reason. Three arms — thymulin, zinc, and both — in zinc-replete and zinc-deficient participants, with the same immunological endpoints Haase 2009 Iovino 2022. If zinc alone does everything thymulin does, the peptide is redundant.
Nobody has tested the GPR39 route in people. A zinc-sensing receptor agonist promoted T-cell reconstitution in mice Iovino 2022. That is a druggable receptor with an immunological endpoint, and it is a far more plausible route to the same goal than a metal-dependent nonapeptide — which is the kind of conclusion this page should reach when the evidence points away from the compound it is about.
Thymulin — its own safety story, not its class's
Thymulin is not an approved medicine anywhere and has no modern human safety data. The class block above is not the right instrument, and the honest specific risks are these.
The product may not be the molecule. Activity requires bound zinc Haase 2009. A synthetic nonapeptide supplied without its metal is the inactive form. The most likely outcome of using a thymulin product is nothing at all, and that is a statement about chemistry rather than a criticism of any seller.
An immune-modulating claim is a two-directional risk. Anything that genuinely alters T-cell function can alter it the wrong way. In anyone with an autoimmune condition, a transplant, or on immunosuppressive therapy, an unstudied immunomodulator is a meaningful hazard rather than a neutral experiment — and the absence of trials means the direction of effect in those people is genuinely unknown.
Injected foreign peptides can raise antibodies. Repeated subcutaneous administration of a synthetic peptide is a standard way to generate an antibody response. For a peptide with a native human counterpart, an antibody response is not only a loss of effect — it is a theoretical route to interfering with the endogenous molecule.
Zinc is not automatically safe either. If a person reasonably concludes from this page that zinc is the more sensible intervention, chronic high-dose zinc induces copper deficiency, which causes anemia and a myelopathy that can be irreversible. Zinc is the right lever and it still has a dose above which it does harm, and copper status belongs in any long-term zinc plan.
What this page will not do. Print a dose. There is no modern human trial to derive one from, the compound's activity depends on a cofactor no product documents, and the measurement that would actually help — a zinc level — costs less than the peptide.
Sources read for this page
- Haase H, Rink L. The immune system and the impact of zinc during aging. Immunity and Ageing 2009 · PMID 19523191
- Iovino L, et al. Activation of the zinc-sensing receptor GPR39 promotes T-cell reconstitution after hematopoietic cell transplant in mice. Blood 2022 · PMID 35357432
- Savino W, et al. Thymus, undernutrition, and infection: Approaching cellular and molecular interactions. Frontiers in Nutrition 2022 · PMID 36225882
- Reis MDDS, et al. Intrathymic somatotropic circuitry: consequences upon thymus involution. Frontiers in Immunology 2023 · PMID 37426675
- Rezzani R, et al. Thymus-Pineal Gland Axis: Revisiting Its Role in Human Life and Ageing. International Journal of Molecular Sciences 2020 · PMID 33233845
Thymulin — safety, predicted from mechanism
Predicted from mechanism, not from a human safety trial. How that reasoning works →
What the mechanism predicts
Derived from the molecule, not a trial.
- A nine-amino-acid thymic hormone whose activity is zinc-dependent — the peptide is biologically inactive until zinc binds it. It drives T-cell maturation and helps set the balance between T-cell subsets, and it falls with thymic involution and again in zinc deficiency.
- The first prediction is that in a zinc-deficient person it may do nothing at all. The cofactor is the rate-limiting part, which is why zinc status and thymulin activity are so hard to separate in the literature — and why a null result on it is uninterpretable without knowing zinc status.
- The second prediction is the one that matters. Anything that shifts T-cell subset balance is acting on the machinery that distinguishes self from non-self. In someone with autoimmune disease, or on immunosuppression, that is not a neutral direction, and the mechanism does not tell you which way an individual moves.
- It is worth saying what this is not: thymulin is not a Khavinson bioregulator and does not inherit that class's reasoning. It is a characterized endogenous hormone with a known mechanism, so the uncertainty here is about the product and the use, not about whether the molecule does anything.
What has actually been reported
- No meaningful human safety data for thymulin given as a research peptide. The molecule has a long research history — it was characterized as serum thymic factor decades ago and its zinc dependence is well established — but that history is physiology. It is not a tolerability record for an injected product, and the two are constantly confused in the marketing around it.
How to reduce the risk
Same mechanism as the prediction.
- Check zinc before, not after. It is the cheapest thing on this card and it decides whether the rest of the experiment means anything.
- Run one immune-axis compound at a time, for the same reason.
- A new rash, new joint pain or an unexplained systemic symptom on an immune-modulating peptide is a reason to stop and get looked at, not a reason to adjust the dose.
What it does to your bloodwork
A fact about the assay.
- Zinc status first, not last. The mechanism is zinc-dependent, so a zinc-deficient person is running an experiment they cannot interpret either way. Serum zinc is an imperfect test and it is the one that exists.
- Full blood count with differential — the lymphocyte count, and subsets if you can get them, are the honest endpoint for something acting on T-cell maturation.
- There is no clinical assay for thymulin itself.
What it overlaps with
- Zinc is not a stack here, it is the cofactor — but sustained high-dose zinc depletes copper over months, which is its own problem and its own marker.
- Stacking it with other thymic peptides is several inputs to one axis. If something changes, attribution is gone.
Don't run this if
- Autoimmune disease, or a transplant on immunosuppression. The mechanism is immune modulation and the direction in an individual is not predictable.
- Active malignancy on immunotherapy, without the treating team knowing — checkpoint therapy is T-cell manipulation and this is a second, uncharacterized input to the same system.
- Pregnancy and breastfeeding.
The honest unknown
- Whether an involuted thymus can respond to it at all. Thymulin falls with age because the tissue that makes it has largely gone. Supplying the hormone does not obviously supply the tissue, and nobody has shown that it does. Unproven is not ineffective — but this is the specific thing nobody has tested.
- Human pharmacokinetics, and whether the zinc-bound active form survives injection and reaches anything.
Not medical advice. If you take prescription medication or have a diagnosed condition, check this with a pharmacist or doctor.
Thymulin — interference & stacking
Predicted from mechanism, not from an interaction study. How mechanism-predicted claims are made →
What Thymulin moves on your bloodwork
Expected direction, not a measured one.
- Comprehensive Metabolic Panel (CMP) — ◆ worth watching
These are short peptide fragments given in microgram amounts and there is no mechanism predicting a specific marker shift. Listing markers here would be padding.
What to do: Test the organ system the bioregulator is aimed at, not a generic panel — that is the only measurement that would tell you anything.
The evidence base here is almost entirely one research group's, largely in Russian, and rarely replicated independently. That is the single most important thing to know before running a course, and it is more useful than any interaction list.
- How to work up to it, and when not to
- When to take it, and why that window
- Cycle length
- Time off between cycles
- Fasted or fed, and when in the day
- Needle gauge and injection site
- Coach Cam's personal notes
- Which compounds push the same lever, and why the dose adds up faster than people count
- What blunts it — the stacks that waste your money
- What compounds the risk, so a side effect arrives sooner than any one of them suggests
- Coach Cam's read on running it alongside the rest of your protocol
Everything above is free and stays free. Skool is where it becomes a plan — Thymulin in an order, with the rest of what you're running.
Unlock in Skool — $10/mo →Bloodwork to run alongside Thymulin
Baseline first, then again at 8–12 weeks.
| Marker | What it’s watching for |
|---|---|
| hs-CRP (High-Sensitivity C-Reactive Protein) | Chronic low-grade inflammation is the process most of these target |
| ApoB (Apolipoprotein B) | Counts the particles that actually cause plaque, unlike LDL-C |
| HbA1c (Hemoglobin A1c) | Glycation, which is the other half of the ageing story |
| Comprehensive Metabolic Panel (CMP) | Liver and kidney — the two organs that clear everything you take |
| Complete Blood Count (CBC) with Differential | The cheapest broad screen there is |
The Longevity Baseline panel covers these in one order — 13 markers, $219.10 with the discount applied.
Check results you already have → · All 103 markers A–Z
Thymulin — frequently asked questions
What is Thymulin?
Thymulin (ZnFTS, serum thymic factor, FTS) is a longevity & bioregulators research compound. A nine-amino-acid hormone from thymic epithelial cells whose activity is ZINC-DEPENDENT — the peptide is inactive until zinc binds it. It drives T-cell maturation and helps set the balance between T-cell subsets. Thymulin falls sharply with age alongside thymic involution, and it also falls in zinc deficiency, which is why zinc status and thymulin activity are hard to separate.
Is the full Thymulin protocol on this page?
The reported research dose is on this page, along with how Thymulin works and the evidence behind it. The protocol — how to work up to it, frequency, cycle length, time off, what not to stack it with and Coach Cam's notes — is inside Skool.
What is the half-life of Thymulin?
Thymulin has an approximate half-life of Minutes in circulation, which is part of what determines how often it's dosed.
What's the evidence behind Thymulin?
Current evidence level: Correlative — human immunology is well described, administration data is old and thin. Thymulin is offered for research purposes only and is not an approved medicine.
Thymulin inside a finished plan
One arm of 1 Protocol Blueprint, free to read in full.
What Thymulin is used for
Thymulin appears under 2 goals in the goal router.
Related Longevity & Bioregulators compounds
Where this goes next
Thymulin is the adaptive arm of this plan. The page above is the free breakdown of one compound; the plan it belongs to — the dosing, the order to correct things in, the week-by-week schedule and what to retest — is a lesson inside Skool.