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Thymulin

Tier 3 · Reported use
Also known as Facteur Thymique Serique · FTS peptide · Zinc-thymulin

The strongest evidence present is Tier 1: human observational studies and tier-1 reviews on zinc deficiency, malnutrition, aging and thymic-peptide immunomodulation1,2,3,4,6, plus a Tier 1-labeled report of two randomized, double-blind, placebo-controlled human efficacy trials (one source, describing Amor 1987 in rheumatoid arthritis and Roullet 1989 in multiple sclerosis, both negative). However, sources emphasize that no modern Phase 2/3 randomized interventional trial exists, zero clinical trials are registered per one profile, and much mechanistic and efficacy detail rests on animal, in-vitro, theoretical or vendor sources. Higher-tier human data is largely observational (zinc deficiency, malnutrition, anorexia, aging) rather than interventional. Vendor/blog efficacy claims17 are not supported by controlled human data.

Half-life
~0.17 h
Routes
Subcutaneous · Intraperitoneal (animal research) · Intranasal (explored for CNS effects)
Goals
Immune modulation / immune senescence research · Anti-inflammatory research · Age-related immune decline · Zinc-status biomarker research · Neuropathic pain research (analog PAT, animal/in-vitro)
Cost / mg
Not recorded

How it works

Reference profiles describe thymulin as a small nine-amino-acid hormone made by the epithelial cells of the thymus gland(vendor claim). Sources report that it only works when bound to zinc in a 1:1 ratio — the zinc-free form is described as biologically inactive, and in-vitro work reports that removing zinc with chelators abolishes activity while adding zinc back restores it. Sources report thymulin helps immature T-cells mature and differentiate, tunes the balance of T-cell subsets, boosts natural killer cell activity (an effect said to depend on adequate zinc), and dampens excessive inflammatory signaling. Because it needs zinc, sources report that serum thymulin drops in zinc deficiency and serves as a sensitive biomarker of zinc status. Profiles also note thymulin levels peak in childhood and fall with age as the thymus shrinks.

Overview

Overview

Reference profiles describe thymulin (also called Facteur Thymique Serique, FTS peptide, or Zinc-thymulin) as a zinc-dependent nonapeptide (9-amino-acid) hormone produced exclusively by thymic epithelial cells(vendor claim). One profile notes it is the only known thymic hormone that requires a metal cofactor — equimolar zinc (Zn2+) — for its biological activity. A tier-1 review describes thymulin as one of the most important thymic hormones1, and a tier-1 study characterizes it as a pharmacologically active metallopeptide whose activity and antigenicity depend on zinc4.

Discovery and Identity

Sources disagree on the discovery timeline. One profile states thymulin was discovered in 1977 by Jean-François Bach and Mireille Dardenne at the Institut Necker in Paris using a rosette-formation bioassay in mouse thymocytes; another states it was first isolated by Bach and colleagues in Paris in 1975 from porcine and human serum and renamed thymulin in 1981 once its zinc-dependence was established; a vendor source attributes first isolation to Dardenne et al. 1974(vendor claim). One profile reports the sequence pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn was established by Pleau and colleagues in 1977, with the N-terminal residue being pyroglutamic acid formed by spontaneous cyclization of glutamine, and gives CAS number 63958-90-7. One profile states Dardenne and colleagues established zinc-dependence in a landmark 1982 PNAS paper (PMID 6957870), noting the apopeptide does nothing in any reliable bioassay. Profiles give the free-peptide molecular weight as ~857–858.86 g/mol (formula C33H54N12O15) and the zinc-bound active form as ~921–924 Da17,18.

Profiles note thymulin is a distinct molecule from Thymosin Alpha-1 (a separate 28-residue peptide that does not require zinc) and from Thymalin (a Russian polypeptide extract), and that the three are not interchangeable.

Reported Mechanism

In-vitro work reports zinc coordinates with the peptide (attributed variously to Lys3/Ser4 and the backbone carbonyl of Ala2, or to Ser4, Ser8, N-terminal pGlu and possibly Gln5) creating a conformational change that exposes the biologically active epitope18. Chelation of zinc by EDTA or DTPA is reported to completely abolish thymulin activity, restorable by adding exogenous zinc. Sources report metallothionein within thymic epithelial cells transfers zinc to the peptide, and that the ratio of zinc-bound to total thymulin serves as a sensitive biomarker for zinc status. A tier-2 study describes an endocrine function of the thymus as packaging zinc in zinc-thymulin for delivery to the periphery8.

Sources report thymulin promotes maturation of T-lymphocyte precursors both within the thymus and in peripheral circulation, induces CD2 and CD3 expression on immature thymocytes, promotes the double-negative to double-positive transition, modulates CD4/CD8 ratios, and enhances alloantigen recognition. It is reported to suppress excessive TNF-alpha, IL-1beta and IL-6 (via inhibition of NF-kB activation and p38 MAPK phosphorylation) while maintaining or enhancing IL-10 and IL-218, and to enhance NK cell cytotoxicity in a zinc-dependent manner. One profile reports high-affinity binding with an apparent Kd of ~5×10⁻⁷ M at physiological pH. Reviews describe thymulin as a hypophysiotropic peptide within a hypophyso-thymic axis, with feedback on its own secretion and cross-talk with growth hormone, prolactin, thyroid hormone and ACTH-linked circadian rhythm5,15. Animal studies report GH stimulates thymulin secretion via specific GH receptors, and that bovine/ovine somatotropin partially restored low thymulin in old dogs, mice and rats5.

Aging, Zinc and Nutrition

Profiles report serum thymulin peaks during childhood (ages 2–10), declines after puberty, and becomes very low or undetectable after about age 60, paralleling thymic involution. Prasad et al. (1988) showed mild zinc deficiency in elderly subjects reduced plasma thymulin activity, restored by zinc supplementation. Mocchegiani et al. (1995) demonstrated zinc supplementation in the elderly restored both thymulin levels and NK cell function. A tier-1 study reported that during zinc deficiency serum thymulin activity decreased and was restored by supplementation, with zinc deficiency causing a TH1/TH2 imbalance and reduced NK lytic activity even when mild3,6. A tier-2 study of 58 Senegalese children reported severe protein-energy malnutrition was associated with a tiny thymus containing very little thymulin11, and a tier-2 study of anorexia nervosa patients found significantly reduced thymulin activity attributed to thymic atrophy13.

Research Applications and Evidence Base

Animal studies report exogenous thymulin can partially restore T-cell function in aged or thymectomized animals, prevents overproduction of IL-1beta, IL-2, IL-6 and TNF-alpha while reducing Hsp70 in inflamed tissue, and reduces neutrophil infiltration and alveolar damage in lung inflammation models. Animal work also reports analgesic effects in the CNS possibly via α7-nicotinic acetylcholine receptor potentiation18, and that gene therapy delivering synthetic thymulin genes to the hypothalamus of aged animals restored thymic function markers. One profile states current scientific activity is preclinical gene-therapy work centered at the University of La Plata in Argentina5. A tier-1 review states thymic peptides including thymulin are used in treatment of neoplastic diseases, viral infections, autoimmune diseases and immunodeficiencies1.

Human efficacy evidence is limited. One profile reports the only randomized, double-blind, placebo-controlled human trials (under the synthetic-analog name nonathymulin) were Amor 1987 in rheumatoid arthritis (PMID 3310925) and Roullet 1989 in multiple sclerosis (PMID 2618585), and that both were negative, with neither producing significant clinical benefit over placebo. Another profile reports zero registered clinical trials and no controlled human therapeutic trials, while citing a literature base of 373 published studies and noting the basic science is well-regarded across multiple laboratories. A tier-1 study noted thymulin's effect on suppressor T-cells was the most remarkable and suggested it should be the first to find clinical applications4. By contrast, vendor sources claim broad benefits — immune restoration in aging/chronic illness/autoimmunity, reduced flare-ups in rheumatoid arthritis and lupus, antiviral effects against EBV and herpes, reduced neuroinflammation, and hair follicle support17 — none supported by controlled human data.

Regulatory Status

Profiles state thymulin is not FDA-approved (nor approved by EMA or Health Canada), is not on the FDA 503A bulks list — meaning U.S. compounding pharmacies cannot lawfully prepare it — was not among the 12 peptides FDA removed from Category 2 on April 15, 2026, and had no commercial pharmaceutical sponsor advancing an NDA as of June 2026. These regulatory specifics come from a single lower-tier source.

What the research shows

128 findings extracted from the 18 sources cited below, strongest evidence first within each group. Every one links to the source it came from.

What human studies found

Based on 1 human trial finding, 16 human study findings, 4 animal findings and 6 expert opinion findings.

  • human trialImmunomodulatory effects of thymic peptides have been confirmed in numerous clinical studies1

  • human studyDuring zinc deficiency, serum thymulin activity (a thymic hormone) was decreased3

  • human studySerum thymulin activity was restored following zinc supplementation3

  • human studyT cell functions were affected adversely even when the deficiency of zinc was mild in humans3

  • human studyZinc deficiency decreased NK cell lytic activity3

  • human studyZinc deficiency caused a decrease in the percentage of CD8+ CD73+ T cells which are known to be predominantly precursors of cytotoxic T cells3

  • human studyThymulin is a pharmacologically active metallopeptide that induces the differentiation of T-cells4

  • human studyThymulin enhances several functions of the various T-cell subsets in normal or partially thymus-deficient recipients4

Show 19 more findings

  • human studyZinc supplementation to humans decreased the gene expression and production of pro-inflammatory cytokines and decreased oxidative stress markers6

  • human studyRecent efforts to treat successfully immune deficiency in aged and cancer-bearing humans will be presented8

  • human studyProtein-energy malnutrition (PEM) leads to an immune deficiency11

  • human studyIn severe forms of malnutrition (marasmus, kwashiorkor, and marasmic kwashiorkor) the thymus was tiny and contained very little thymulin11

  • human studyZinc content of the thymus was high whatever the nutritional state of the subject and was related significantly only to the presence of infections11

  • human studyIn Senegalese children thymic atrophy and depleted thymulin content are associated with severe PEM but not systemic infection or depleted thymic Zn content11

  • human studyThymulin activity determined by rosette assay was significantly reduced in anorexia nervosa patients compared to sex- and age-matched healthy control subjects13

  • human studyAnorexia nervosa patients were characterized by very depressed plasma levels of triiodothyronine (T3) but exhibited normal concentrations of thyroxine (T4), thyroxine-binding globulin (TBG), cortisol and zinc13

  • human studyDistribution of peripheral lymphocyte cells into several subsets was not affected in anorexia nervosa patients13

  • animalTreatment of old dogs with bovine somatotropin partially restored their low serum thymulin levels5

  • animalTreatment of aged mice with ovine somatotropin increased their low plasma thymulin levels and also raised the concanavalin A (Con A)-dependent proliferative response of their thymocytes as well as interleukin-6 production5

  • animalCombined treatment of old rats with somatotropin and thyroid hormone (T4) partially restored their reduced thymulin serum concentration5

  • animalGene therapy for thymulin may be an effective therapeutic strategy to prevent hormonal and reproductive abnormalities in congenitally athymic (nude) mice5

  • expert opinionThymulin influences tumor cell biology and response of patients with cancer to therapies2

  • expert opinionThymulin and a synthetic analog act as anti-inflammatory and analgesic peptides in the central nervous system brain and other organs5

  • expert opinionThymulin endocrine influences decline with age and are associated with thymic menopause and cellular immune senescence10

  • expert opinionThymulin has anti-inflammatory and immunomodulatory effects17

  • expert opinionPreclinical research suggests anti-inflammatory and immune-modulating properties17

  • expert opinionResearch shows promise in lung diseases, neuropathic pain, and age-related immune dysfunction, though human clinical trials remain limited18

How it works

Based on 15 human study findings, 12 animal findings, 7 in vitro findings, 28 expert opinion findings and 14 theoretical findings.

  • human studyThymic peptides including thymulin stimulate the differentiation and maturation of T cells1

  • human studyThymic peptides including thymulin regulate the activity of natural killer cells and dendritic cells1

  • human studyThymic peptides including thymulin induce the release of proinflammatory cytokines1

  • human studyThymic peptides act in multiple manners on the immune system with modulation of physiological processes such as stimulation or suppression of immune responses, angiogenesis, and wound healing1

  • human studyZinc deficiency caused an imbalance between TH1 and TH2 functions with decreased production of IFN-g, IL-2, TNF-a (products of TH1 cells)3

  • human studyThymulin is a nonapeptide hormone produced by thymic epithelial cells4

  • human studyIts biological activity and antigenicity depend upon the presence of the metal zinc in the molecule4

  • human studyZinc deficiency in humans decreases the activity of serum thymulin (a thymic hormone), which is required for maturation of T-helper cells6

Show 68 more findings

  • human studyT-helper 1 (Th(1)) cytokines are decreased but T-helper 2 (Th(2)) cytokines are not affected by zinc deficiency in humans6

  • human studyShift of Th(1) to Th(2) function results in cell-mediated immune dysfunction6

  • human studyIL-2 production (Th(1) cytokine) is decreased, this leads to decreased activities of natural-killer cell and T cytolytic cells, which are involved in killing viruses, bacteria, and tumor cells6

  • human studyIn humans, zinc deficiency may decrease the generation of new CD4+ T cells from the thymus6

  • human studyZinc deficiency is important in thymic involution and changes in cellular immunity11

  • human studyMA-FTS could recognize FTS (or FTS-like molecule) in human serum15

  • human studyMA-FTS could absorb completely the FTS-like activity from human serum15

  • animalThymulin exerts a feedback action on its own secretion both in vivo and in vitro5

  • animalGH stimulates thymulin secretion from TEC lines via specific receptors for GH5

  • animalHypothalamus extract injected in old mice results in reappearance of circulating FTS (facteur thymique serique/thymulin)12

  • animalHypothalamus extract injection in adult thymectomized animals was not able to induce FTS activity12

  • animalPretreatment of hypothalamus extract donors with thymosin fraction 3 greatly diminishes the capacity of hypothalamus preparation to induce FTS reappearance in old animals12

  • animalThe capacity of the thymus to secrete FTS depends on a hypothalamic factor12

  • animalThe absence of FTS in the aged reflects a failure of the thymus linked to its impaired neurologic control12

  • animalA feedback system operates to regulate the release of the hypothalamus stimulatory factor for FTS12

  • animalAnti-FTS antibodies are fixed specifically on floccular material present in cytoplasmic vacuoles of epithelial cortical and medullary cells in normal young C57BL mice16

  • animalIn aged auto-immune SWAN mice, anti-FTS antibodies show activity only in granules present in vacuoles or free in cytoplasm of epithelial cells16

  • animalFTS positive granules show a repetitive structure characteristic of crystalline protein formations16

  • animalFTS is stored in granules of epithelial cells in vivo during the auto-immune process16

  • in vitroIn cell culture studies (HUT-78, a Th(0) human malignant lymphoblastoid cell line), as a result of zinc deficiency, nuclear factor-kappaB (NF-kappaB) activation, phosphorylation of IkappaB, and binding of NF-kappaB to DNA are decreased and this results in decreased Th(1) cytokine production6

  • in vitroIn HL-60 cells (a human pro-myelocytic leukemia cell line), zinc deficiency increased the levels of TNF-alpha, IL-1beta, and IL-8 cytokines and mRNA6

  • in vitroIn HL-60 cells, zinc induced A20, a zinc finger protein that inhibited NF-kappaB activation via tumor necrosis factor receptor associated factor pathway, and this decreased gene expression of pro-inflammatory cytokines and oxidative stress markers6

  • in vitroThymic function at the local level requires complex cellular interactions among thymic stromal cells and developing thymocytes involving paracrine and autocrine mediators including interleukins (ILs) 1, 2, 6, 7, 8, colony-stimulating factors (CSFs), interferon-gamma, thymosin alpha 1, and zinc-thymulin8

  • in vitroAn important endocrine function of the thymus is to package zinc in zinc-thymulin for delivery to the periphery8

  • in vitroMonoclonal antibody against facteur thymique serique (FTS), a thymic hormone, was generated by hybridization between mouse NS-1 myeloma cells and BALB/c splenocytes15

  • in vitroThe monoclonal antibody (MA-FTS) was highly specific for FTS and did not cross-react with other thymic hormones or other unrelated peptides15

  • expert opinionThymulin is one of the most important thymic hormones produced by the thymus1

  • expert opinionThymulin is a thymic peptide hormone produced by stromal cells in the thymic microenvironment2

  • expert opinionThymulin can circulate to impact immune cells and other cellular components in the periphery2

  • expert opinionThymulin regulates mechanisms supporting intrathymic T cell differentiation2

  • expert opinionThymulin is a thymic hormone exclusively produced by the epithelial cells of the thymus5

  • expert opinionThymulin consists of an inactive nonapeptide component named FTS coupled in an equimolecular ratio to the zinc ion, which endows the molecule with biological activity5

  • expert opinionThymulin is a thymus peptide involved in several stages during intra-and extrathymic T-cell differentiation5

  • expert opinionThe active form of the metallopeptide has a specific molecular conformation that has been demonstrated by nuclear magnetic resonance5

  • expert opinionThe production and secretion of thymulin are strongly influenced by the neuro-endocrine system5

  • expert opinionThymulin is a hypophysiotropic peptide5

  • expert opinionThymulin is a thymic hormone exclusively produced by the epithelial cells of the thymus5

  • expert opinionProduction and secretion of thymulin are strongly influenced by the neuro-endocrine system5

  • expert opinionThymulin is a hypophysiotropic peptide5

  • expert opinionA synthetic DNA sequence encoding a biologically active analog of thymulin, metFTS, was constructed and cloned in a number of adenovectors5

  • expert opinionBidirectional regulatable Tet-Off vector systems can simultaneously express metFTS and green fluorescent protein and can be down-regulated reversibly by the addition of doxycycline5

  • expert opinionThymulin is a thymic hormone exclusively produced by the thymic epithelial cells7

  • expert opinionThymulin consists of a nonapeptide component coupled to the ion zinc, which confers biological activity to this molecule7

  • expert opinionThymulin was characterized as a thymic hormone involved in several aspects of intra- and extrathymic T-cell differentiation7

  • expert opinionThymulin production and secretion is strongly influenced by the neuroendocrine system7

  • expert opinionThymulin is a hypophysotropic peptide7

  • expert opinionThymulin is an important player in the hypophyso-thymic axis7

  • expert opinionThymulin is a putative thymic hormone reported to circulate and act on both prothymocytes and mature T-cells in the periphery10

  • expert opinionThymulin maintains T-cell commitment to the T-cell system and its functions10

  • expert opinionThymic epithelial cells secrete thymic hormones, exemplified by the zinc-thymulin complex, under stimulation with IL-1 and other hormonal influences10

  • expert opinionThe decrease of thymulin activity in anorexia nervosa might be the consequence of thymic atrophy secondary to malnutrition and/or hormonal disturbances13

  • expert opinionThymulin is a nonapeptide produced by the thymus17

  • expert opinionThymulin helps regulate the immune system and T-cell activity17

  • expert opinionThymulin is involved in immune regulation and T-cell differentiation17

  • theoreticalThymulin, a thymic hormone involved in T-lymphocyte maturation, is known to be Zn dependent9

  • theoreticalThymulin is adversely affected by Zn deficiency9

  • theoreticalAn adverse effect of Zn deficiency may be in lymphocyte differentiation and maturity9

  • theoreticalThymulin is a 9-amino acid metallopeptide hormone produced exclusively by thymic epithelial cells18

  • theoreticalThymulin requires zinc binding in 1:1 equimolecular ratio for biological activity18

  • theoreticalThe zinc-thymulin complex adopts a specific three-dimensional conformation essential for its immunomodulatory functions18

  • theoreticalThymulin induces T-cell differentiation, NK cell enhancement, and suppressor T-cell regulation18

  • theoreticalThymulin demonstrates potent anti-inflammatory and analgesic properties through inhibition of NF-κB, p38 MAPK, and pro-inflammatory cytokines18

  • theoreticalSerum thymulin levels decline progressively with age, peaking in pre-adolescence, contributing to immunosenescence18

  • theoreticalZinc-thymulin binds to high-affinity T-cell receptors18

  • theoreticalThymulin acts through NF-κB inhibition, p38 MAPK suppression, and reduction of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6)18

  • theoreticalThymulin may act through α7-nicotinic acetylcholine receptor potentiation for analgesic effects18

  • theoreticalApo-thymulin without zinc is biologically inactive18

  • theoreticalZinc coordination in thymulin involves Ser4, Ser8, N-terminal pGlu, and potentially Gln518

Dosing

Based on 2 animal findings, 1 expert opinion finding and 1 anecdotal finding.

  • animalAnimal research protocol for inflammation uses 15 μg/100g body weight as single dose or short course via IP or SubQ18

  • animalPAT analog pain research protocol uses 25-50 μg per rat (100-200 μg/kg) 30 minutes before inflammatory challenge via IP18

  • expert opinionThymulin peptide should be stored at -20°C, dry and dark conditions; protected from moisture17

  • anecdotalAnecdotal human protocol uses 1-5 mg per injection once daily for 5-10 days via SubQ18

How the body handles it

Based on 2 theoretical findings.

  • theoreticalThymulin has very short half-life of approximately 10 minutes18

  • theoreticalNatural thymulin follows circadian rhythm correlating with ACTH18

Safety and side effects

Based on 2 human study findings and 2 expert opinion findings.

  • human studyAn important feature of thymus preparations is their therapeutic safety—even long-term use does not cause side effects1

  • human studyThymulin is not toxic4

  • expert opinionCorticosteroids require monitoring when combined with Thymulin18

  • expert opinionThymulin requires adequate zinc intake or supplementation for biological activity18

What people use it for

Based on 1 human study finding, 3 animal findings, 8 expert opinion findings and 1 theoretical finding.

  • human studyThymic peptides are used in the treatment of neoplastic diseases, viral infections, autoimmune diseases or immunodeficiencies1

  • animalGene therapy for thymulin may be an effective therapeutic strategy to prevent some of the hormonal and reproductive abnormalities that typically appear in congenitally athymic (nude) mice5

  • animalThymic involution has been treated with interleukins, thymic hormones, growth hormone, prolactin, melatonin, zinc, and others8

  • animalWork to reverse thymic involution in hydrocortisone-treated, aged mice with interleukins, thymosin alpha 1, and zinc will be reviewed8

  • expert opinionThymulin's effect on suppressor T-cells is the most remarkable and should be the first to find useful clinical applications4

  • expert opinionThymulin and a synthetic analog act as anti-inflammatory and analgesic peptides in the central nervous system brain and other organs5

  • expert opinionThe fall in thymulin level might explain the variability of cellular immune responses in anorexia nervosa patients and occurrence of energy when weight loss is far advanced13

  • expert opinionThymulin is investigated for potential applications in immune dysfunction, inflammation, and dermatological health17

Show 5 more findings

  • expert opinionSome studies suggest Zinc-Thymulin may support hair follicle health, but clinical data is limited17

  • expert opinionThymulin is primarily studied for immune modulation, anti-inflammatory effects, and potential applications in skin and hair health17

  • expert opinionThymulin has zinc supplementation as synergistic interaction18

  • expert opinionThymulin is compatible with Thymosin Alpha-1, Thymosin Beta-4, Epithalon, and NSAIDs18

  • theoreticalGene therapy could potentially restore circulating thymulin levels in thymodeficient animal models and eventually in humans5

Other findings

Based on 1 human study finding and 1 expert opinion finding.

  • human studyThymulin is a natural hormone available in synthetic form4

  • expert opinionThymulin was first characterized by Bach and colleagues in 197718

Points of contention

Where the evidence is unsettled, thin, or says less than the popular claim — worth knowing before you draw conclusions.

Contested

Human clinical evidence: negative trials versus optimistic vendor efficacy claims

A tier-3 profile (Thymulin Peptide Guide 2026: Zinc-Bound Thymic Hormone) reports the only randomized double-blind placebo-controlled human trials (Amor 1987 in rheumatoid arthritis, Roullet 1989 in multiple sclerosis) were both negative, and another (Thymulin (Facteur Thymique Serique, FTS) | PeptideTrace — PeptideTrace) reports zero registered clinical trials and no controlled human therapeutic trials. In contrast vendor/blog sources (Peptide Therapy - Thymulin – Revolution Health & Wellness, China Thymulin Peptide Manufacturers Suppliers - Cost Price Thymulin Peptide for Sale - NovoPept Biotech) claim broad benefits for immune restoration, autoimmune disease, antiviral effects and hair health without controlled human data.

Limited evidence

Most mechanistic and efficacy claims rest on animal, in-vitro or theoretical/vendor sources

Much of the reported activity (analgesia, neuroprotection, gene therapy, cytokine modulation, lung inflammation) comes from animal, in-vitro, or theoretical/vendor sources; higher-tier human data is largely observational (zinc deficiency, malnutrition, anorexia, aging) rather than interventional. No modern Phase 2/3 randomized trial exists and no pharmaceutical company has advanced thymulin through Phase 3.

Single source

Regulatory and dosing specifics come from single lower-tier sources

Details such as absence from the FDA 503A bulks list, exclusion from the 12 peptides FDA removed from Category 2 on April 15 2026, and no NDA sponsor as of June 2026 come only from Thymulin Peptide Guide 2026: Zinc-Bound Thymic Hormone. Human dosing (1–5 mg once daily for 5–10 days) is explicitly labeled anecdotal (Thymulin - Research, Dosing & Protocols | Pep-Pedia), and research doses (1–10 mcg) come from a single profile (Thymulin Overview, Dosing & Safety | Peptide Database); these should not be read as validated clinical regimens.

Other

Reported molecular weights and half-life vary slightly between sources

Free-peptide molecular weight is given as ~857, 857.85, 858.85 or 858.86 Da and the zinc-bound form as ~921, ~922 or ~924 Da across sources; half-life is described variously as 'minutes' or 'approximately 10 minutes.'

Inconsistency

An anecdotal human dose of 1–5 mg of thymulin per day is thousands of times larger than any amount used in actual research and is almost certainly a milligram-for-microgram mix-up.

One vendor-style source lists an "anecdotal human protocol" of 1–5 mg per injection once daily for 5–10 days. That is 100–5,000 times higher than the doses used in genuine research: research-oriented profiles describe roughly 1–10 micrograms per injection, and published animal work uses microgram amounts (for example 15 µg per 100 g of body weight). Thymulin is a tiny nine-amino-acid hormone that the body normally makes in trace quantities and that is cleared from the blood within minutes, so a milligram-scale injection has no basis in the science and most likely reflects a units error (milligrams written where micrograms were meant) rather than a real regimen anyone has followed. No human trial has validated any thymulin dose.

Using it with other compounds

Check a stack
  • VilonComplementary

    May be complementary

    Both are thymus-linked immune bioregulators that push the immune system toward balance rather than pure stimulation. Vilon is reported to stimulate thymus tissue growth and improve CD4/CD8 ratios, while thymulin drives T-lymphocyte maturation and normalizes CD4/CD8 balance from the endocrine side. They approach the same immune-normalizing endpoint by different routes, which makes them reasonably complementary for restoring aged/depleted immunity.

    Tier 4Theoretical — not established

    Shares innate immune · anti inflammatory · T cell regulation · NF kB modulation

  • ImunofanSame mechanism

    Worth caution

    Both are thymus-derived peptide hormones that normalize T-cell maturation, CD4/CD8 balance and NK cytotoxicity while dampening pro-inflammatory cytokines. Because they converge on the same thymic immune-tuning output, running them together is largely redundant rather than additive — pick one thymic immunomodulator rather than stacking two.

    Tier 4Theoretical — not established
    What the research doesn't establish
    Although both peptides influence T-cell maturation, CD4/CD8 balance, NK activity and cytokine levels, they act through different molecular routes: Imunofan signals via thymopoietin receptors and cyclase/PKC pathways, whereas Thymulin depends on zinc-activated peptide, NF-κB/p38 MAPK inhibition and α7-nicotinic receptors. Shared functional endpoints do not establish that the two work through the same mechanism or that combining them is redundant.

    Shares innate immune · anti inflammatory · T cell regulation

  • ElafinComplementary

    No documented conflict

    Thymulin normalizes T-cell balance and tamps down excess pro-inflammatory cytokines via NF-κB inhibition, while elafin controls neutrophil protease-driven tissue damage. They modulate adaptive and innate immunity from different angles toward a calmer, better-regulated immune response.

    Tier 4Theoretical — not established

    Shares innate immune · anti inflammatory · NF kB modulation

  • KlothoComplementary

    No documented conflict

    Both restrain excess pro-inflammatory signaling with reported NF-κB inhibition — Klotho via NLRP3/NF-κB suppression and antioxidant pathways, thymulin via immune normalization and cytokine (TNF/IL-6) dampening. They approach inflammation from different systems (renal/metabolic vs. thymic/immune), so the anti-inflammatory effect is complementary rather than redundant.

    Tier 4Theoretical — not established

    Shares anti inflammatory · NF kB modulation

  • KPVComplementary

    No documented conflict

    Thymulin normalises T-cell balance and suppresses excess proinflammatory cytokines via NF-κB and p38 MAPK inhibition, while KPV independently dampens NF-κB-driven cytokine production. Both converge on restraining overactive inflammation through complementary immune mechanisms (adaptive T-cell tuning vs innate cytokine suppression).

    Tier 4Theoretical — not established

    Shares innate immune · anti inflammatory · NF kB modulation

  • LactoferrinComplementary

    No documented conflict

    Thymulin fine-tunes T-cell maturation and dampens excess pro-inflammatory cytokines, while lactoferrin acts on the innate/antimicrobial front. Their immune roles are distinct but converge on balanced immune function, making them a plausible complementary immune-support pairing.

    Tier 4Theoretical — not established

    Shares innate immune · anti inflammatory

  • LL-37Complementary

    No documented conflict

    Thymulin normalizes T-cell balance and dampens excess pro-inflammatory cytokines via NF-κB/p38 modulation, while LL-37 provides antimicrobial and TLR/FPR2-based innate immune actions. Their different immune targets can complement each other in immune support.

    Tier 4Theoretical — not established

    Shares innate immune · anti inflammatory

  • PidotimodSame downstream effect

    Worth caution

    Thymulin is a thymic hormone that drives T-lymphocyte maturation, tunes CD4/CD8 balance and boosts NK cytotoxicity — the same adaptive-immunity endpoints pidotimod promotes through dendritic-cell maturation and Th1 differentiation. They reach the same destination by different upstream mechanisms, which can be complementary for immune-deficiency support but also overlapping; stacking multiple immunostimulants adds little beyond one and should be monitored.

    Tier 4Theoretical — not established

    Shares innate immune · anti inflammatory · T cell regulation

  • SelankComplementary

    Worth caution

    Selank is built from tuftsin, an immune-signaling antibody fragment, and shares T-cell/cytokine-balancing and anti-inflammatory activity with thymulin. They modulate immunity through different mechanisms (thymic-hormone maturation vs. tuftsin-like Th1/Th2 balancing), so they can complement each other in immune normalization.

    Tier 4Theoretical — not established

    Shares T cell regulation · anti inflammatory

  • Alpha-MSHComplementary

    No documented conflict

    Alpha-MSH suppresses NF-kB (preserving IkBα) and calms inflammatory cytokines through melanocortin receptors, a different upstream mechanism than thymulin's zinc-dependent immune regulation, but both converge on reduced inflammatory cytokine output.

    Tier 4Theoretical — not established

    Shares anti inflammatory · NF kB modulation

  • ThymalinSame mechanism

    Worth caution

    Both are thymus-derived immune regulators that drive T-lymphocyte precursor maturation, normalize CD4/CD8 balance, boost NK activity, and dampen NF-kB-driven pro-inflammatory cytokines (IL-1, IL-6, TNF-alpha). Thymulin is essentially one of the discrete thymic hormones whose activity Thymalin (a thymic peptide complex) is meant to restore. Running both together is largely redundant rather than additive — pick one thymic immunomodulator and dose it properly rather than layering two overlapping thymic signals.

    Tier 4Theoretical — not established

    Shares innate immune · anti inflammatory · T cell regulation · NF kB modulation

  • Thymosin Alpha-1Same mechanism

    Worth caution

    Thymulin is a thymic hormone that, like Thymosin Alpha-1, drives T-lymphocyte precursor maturation, tunes CD4/CD8 balance, enhances NK cytotoxicity, and suppresses excess inflammatory cytokines. They occupy the same thymic-immune niche, so combining them mostly duplicates the same effect rather than adding a new mechanism.

    Tier 4Theoretical — not established

    Shares innate immune · anti inflammatory · T cell regulation

Safety and side effects

Safety Profile

A tier-1 review states that an important feature of thymus preparations is their therapeutic safety, noting that even long-term use has not caused side effects1. A tier-1 study similarly states thymulin is not toxic and is a natural hormone available in synthetic form4.

These favorable safety statements should be read against the limits of the evidence base. Sources report that no modern Phase 2/3 randomized trial exists and no pharmaceutical company has ever brought thymulin through Phase 316; the strongest interventional human data come from two 1980s–90s randomized trials that were both negative, and much of the mechanistic and efficacy literature is animal, in-vitro, or vendor-based. A structured safety database from controlled human dosing is therefore not described in the sources.

Interactions and Cofactor Requirements

One profile reports thymulin requires adequate zinc intake for biological activity and lists zinc supplementation as synergistic18. The same profile describes thymulin as compatible with Thymosin Alpha-1, Thymosin Beta-4, Epithalon and NSAIDs, and states that corticosteroids require monitoring when combined18. Because the zinc-free apopeptide is reported to be biologically inactive, zinc status is central to any reported activity.

Regulatory Caveat

Profiles state thymulin is not approved by the FDA, EMA or Health Canada, is absent from the FDA 503A bulks list (so U.S. compounding pharmacies cannot lawfully prepare it), and had no NDA sponsor as of June 2026. These regulatory details come from a single lower-tier source. Nothing here should be read as clinical guidance.

Reconstitution and handling

Dosing

No dose has been established for this compound. There is no regulatory label for thymulin — sources report it is not FDA-, EMA- or Health Canada-approved — so the figures below are what individual sources report, not guidance, and none are validated clinical regimens.

  • One lower-tier (tier-3) research-oriented profile lists a typical research dose of 1–10 mcg per injection given daily, administered subcutaneously or intraperitoneally, with intranasal delivery explored for CNS effects; this is not a validated clinical dose.
  • One source describes an animal inflammation research protocol using 15 μg/100 g body weight as a single dose or short course via IP or SubQ, and a PAT-analog pain research protocol using 25–50 μg per rat (100–200 μg/kg) given 30 minutes before inflammatory challenge via IP18.
  • One source describes an anecdotal human protocol of 1–5 mg per injection once daily for 5–10 days via SubQ18. This is explicitly labeled anecdotal and is orders of magnitude above the microgram research doses cited elsewhere.

No human trial has validated any of these regimens; the only randomized controlled human trials described (Amor 1987, Roullet 1989, under the analog name nonathymulin) were both negative.

Reconstitution and Storage

Profiles advise storing lyophilized thymulin at -20°C (dry, dark, protected from moisture) and reconstituted thymulin at 2–8°C, used within roughly 4 weeks — though one source states a shorter 7–10 day reconstituted window17,18.

Sources note the peptide's practical fragility: thymulin activity depends on zinc, and the peptide is reported to be sensitive to chelation (zinc removal by agents such as EDTA or DTPA abolishes activity) and to thermal degradation. Because the zinc-free apopeptide is reported to be biologically inactive, handling that preserves the zinc-bound (Zn-FTS) complex is emphasized. One vendor product page is sold as a 10 mg total active Zn-FTS complex.

Sources

Ordered by evidence quality — the strongest first.

  1. Review of Thymic Peptides and Hormones: From Their ...(opens in a new tab)
    Tier 1Web · link.springer.com · 2024
  2. Thymus-derived hormonal and cellular control of cancer.(opens in a new tab)
    Tier 1PubMed · pubmed.ncbi.nlm.nih.gov · 2023
  3. Zinc and immunity.(opens in a new tab)
    Tier 1PubMed · pubmed.ncbi.nlm.nih.gov · 1998
  4. Thymulin, a zinc-dependent hormone.(opens in a new tab)
    Tier 1PubMed · pubmed.ncbi.nlm.nih.gov · 1989
  5. Physiology and Therapeutic Potential of the Thymic Peptide Thymulin(opens in a new tab)
    Tier 2Web · doi.org · 2014
  6. Zinc: mechanisms of host defense.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 2007
  7. Thymulin and the neuroendocrine system.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 2004
  8. Thymic endocrinology.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 1998
  9. Zinc: an overview.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 1995
  10. Thymic endocrinology.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 1992
  11. Thymulin (facteur thymique serique) and zinc contents of the thymus glands of malnourished children.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 1988
  12. Neuroendocrine regulation of thymus hormones: hypothalamic dependence of "facteur thymique serique" level.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 1986
  13. Thymulin (Zn-facteur thymique serique) activity in anorexia nervosa patients.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 1985
  14. Thymulin.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 1985
  15. Generation of a monoclonal antibody against facteur thymique serique (FTS).(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 1982
  16. Location of FTS (facteur thymique sérique) in the thymus of normal and auto-immune mice.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 1982
  17. China Thymulin Peptide Manufacturers Suppliers - Cost Price Thymulin Peptide for Sale - NovoPept Biotech(opens in a new tab)
    Tier 3Web · novopept.com
  18. Thymulin - Research, Dosing & Protocols | Pep-Pedia(opens in a new tab)
    Tier 3Web · pep-pedia.org

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