Thymulin
A 9-amino-acid peptide naturally produced by the thymus gland that requires zinc to work properly. Distinct from Thymalin (which is a thymic extract mixture). Plays a central role in T-cell development, immune system regulation, and the zinc-thymulin axis that declines with aging. Thymulin levels decrease as the thymus shrinks with age, contributing to immune decline.
Dosage
1-5 mg subcutaneous daily for 10-20 day courses, 2-3x yearly
Dosages shown are for research reference only. Always consult a qualified healthcare provider.
Administration
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Effects
T-Cell Maturation
Zinc-dependent thymic hormone driving CD4/CD8 T-cell differentiation.
Immune Restoration
May partially reverse age-related immunosenescence.
Mechanism of Action
Thymulin (also known as facteur thymique sérique, FTS) is a nonapeptide (Glu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn) that is unique among thymic hormones in requiring a zinc ion for biological activity. The zinc ion is coordinated by the asparagine (position 9), serine (position 4), and the N-terminal glutamic acid, creating a metallopeptide complex where the zinc is essential for the correct three-dimensional conformation needed for receptor binding. Without zinc, thymulin is biologically inactive — this zinc dependency has important implications for immune function in zinc-deficient individuals.
Thymulin is produced exclusively by thymic epithelial cells and is the only thymic hormone that is truly thymus-specific — its serum levels become undetectable after thymectomy (surgical thymus removal). It binds to high-affinity receptors on T-cell precursors (thymocytes) and mature T cells, promoting several key aspects of T-cell biology. It induces the expression of T-cell differentiation markers (CD2, CD3, CD4, CD8), driving immature thymocytes through the stages of T-cell maturation. It enhances the cytotoxic function of CD8+ T cells and the helper function of CD4+ T cells. It modulates the balance between T-helper and T-suppressor (regulatory) cell populations, promoting appropriate immune regulation.
Thymulin also modulates cytokine production — it promotes IL-2 secretion (essential for T-cell proliferation and the generation of effector T cells), enhances IFN-γ production (important for Th1 cellular immunity), and influences the balance of pro-inflammatory versus anti-inflammatory cytokines. Serum thymulin levels peak around puberty and decline progressively with age, becoming virtually undetectable by age 60 — mirroring the age-related involution of the thymus gland. This decline correlates closely with immunosenescence markers: reduced naive T-cell output, skewed CD4/CD8 ratios, impaired vaccine responses, and increased susceptibility to infections and cancer. Zinc supplementation alone can partially restore thymulin activity in zinc-deficient elderly individuals, highlighting the clinical importance of the zinc-thymulin interaction.
Regulatory Status
Not FDA approved. Naturally occurring hormone. Research-grade available from peptide suppliers. Studied for immune reconstitution and anti-aging applications.
Risks & Safety
Common
injection site reactions, mild fatigue.
Serious
very limited human clinical data for supplemental use, may overstimulate immune system in autoimmune conditions.
Rare
allergic reactions.
Compare Thymulin With
Research Papers
11Published: December 11, 2025
AI Summary
Development of neutralizing anti-factor [F]VIII antibodies (inhibitors) follows recognition by CD4+ T cells of epitopes that are presented on the individual's human leukocyte antigen (HLA) class II. Limited blood volumes have presented a major challenge in mapping T-cell epitopes in FVIII, especially as these immune responses typically develop in early childhood..
Published: October 30, 2025
AI Summary
Osteoporosis is a prevalent metabolic bone disorder that significantly impairs patients' quality of life. Mounting evidence suggests a close relationship between systemic inflammation and bone metabolism, yet the causal nature of this association remains unclear. This study aims to elucidate potential causal links between circulating inflammatory factors and osteoporotic pathological fractures.
Published: May 20, 2025
AI Summary
Myasthenia gravis (MG) is an autoimmune disease most frequently caused by autoantibodies (auto-Abs) against the acetylcholine receptor (AChR) located at the neuromuscular junction. Thymic follicular hyperplasia is present in most of the patients with early-onset AChR-Ab+ MG (EOMG), but its cellular and molecular drivers and development remain poorly understood..
Published: April 5, 2024
AI Summary
Prurigo nodularis (PN) is a chronic inflammatory skin disease that is associated with variability in peripheral blood eosinophil levels and response to T-helper 2 targeted therapies (Th2). Our objective was to determine whether circulating immune profiles with respect to type 2 inflammation differ by race and peripheral blood eosinophil count. Plasma from 56 PN patients and 13 matched healthy c...
Published: December 24, 2023
AI Summary
Phosphate and vitamin D homeostasis are controlled by fibroblast growth factor 23 (FGF23) from bone suppressing renal phosphate transport and enhancing 24-hydroxylase (Cyp24a1), thereby inactivating 1,25(OH)2 D3. Serum FGF23 is correlated with outcomes in several diseases. Fasting stimulates the production of ketone bodies.
Published: September 11, 2023
AI Summary
The cytokine thymic stromal lymphopoietin (TSLP) mediates type 2 immune responses, and treatments that interfere with TSLP activity are in clinical use for asthma. Here, we investigated whether TSLP contributes to allergic inflammation by directly stimulating human CD4+ T cells and whether this process is operational in eosinophilic esophagitis (EoE), a disease linked to variants in TSLP. We sh...
Published: September 14, 2023
AI Summary
This study aimed to assess the effects of the immunomodulator thymulin, a thymic peptide with anti-inflammatory effects, and peroxiredoxin 6 (Prdx6), an antioxidant enzyme with dual peroxidase and phospholipase A2 activities, on the blood‒brain barrier (BBB) condition and general health status of animals with relapsing-remitting experimental autoimmune encephalomyelitis (EAE), which is a...
Published: July 16, 2023
AI Summary
The thymus gland is a central lymphoid organ in which developing T cell precursors, known as thymocytes, undergo differentiation into distinct type of mature T cells, ultimately migrating to the periphery where they exert specialized effector functions and orchestrate the immune responses against tumor cells, pathogens and self-antigens. The mechanisms supporting intrathymic T cell differentiat...
Published: June 13, 2022
AI Summary
The inevitability of evolution of the adaptive immune system with its mechanism of randomly rearranging segments of the T cell receptor (TCR) gene is the generation of self-reactive clones. For the sake of prevention of autoimmunity, these clones must be eliminated from the pool of circulating T cells. This process occurs largely in the thymic medulla where the strength of affinity between TCR ...
Published: April 19, 2022
AI Summary
Nutritional zinc deficiency induces thymic atrophy, but the underlying mechanisms remain unknown. In this study, we investigated the mechanism of thymic atrophy and fatty degeneration associated with zinc deficiency and its effect on T cell maturation. Building on previous research demonstrating the beneficial effect of IL-4 administration or zinc supplementation on the spleen in zinc-deficient...
Published: March 28, 2021
AI Summary
Protective effects of peroxiredoxin 6 (PRDX6) in RIN-m5F β-cells and of thymulin in mice with alloxan-induced diabetes were recently reported. The present work was aimed at studying the efficiency of thymulin and PRDX6 in a type 1 diabetes mellitus model induced by streptozotocin in mice. Effects of prolonged treatment with PRDX6 or thymic peptide thymulin on diabetes development were evaluated.
Frequently Asked Questions
What is Thymulin?
A 9-amino-acid peptide naturally produced by the thymus gland that requires zinc to work properly. Distinct from Thymalin (which is a thymic extract mixture). Plays a central role in T-cell development, immune system regulation, and the zinc-thymulin axis that declines with aging. Thymulin levels decrease as the thymus shrinks with age, contributing to immune decline.
What is Thymulin used for?
A 9-amino-acid peptide naturally produced by the thymus gland that requires zinc to work properly. Distinct from Thymalin (which is a thymic extract mixture). Plays a central role in T-cell development, immune system regulation, and the zinc-thymulin axis that declines with aging. Thymulin levels decrease as the thymus shrinks with age, contributing to immune decline.
What is the dosage for Thymulin?
Research: 1-5 mg subcutaneous once daily. Anti-aging protocols: 1 mg subcutaneous once daily for 10-20 day courses. Zinc supplementation (15-30 mg zinc daily) recommended for full biological activity. Courses repeated 2-3 times yearly.
What are the side effects of Thymulin?
Common: injection site reactions, mild fatigue. Serious: very limited human clinical data for supplemental use, may overstimulate immune system in autoimmune conditions. Rare: allergic reactions.
How does Thymulin work?
Thymulin (also known as facteur thymique sérique, FTS) is a nonapeptide (Glu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn) that is unique among thymic hormones in requiring a zinc ion for biological activity. The zinc ion is coordinated by the asparagine (position 9), serine (position 4), and the N-terminal glutamic acid, creating a metallopeptide complex where the zinc is essential for the correct three-dimensional conformation needed for receptor binding. Without zinc, thymulin is biologically inactive — this zinc dependency has important implications for immune function in zinc-deficient individuals. Thymulin is produced exclusively by thymic epithelial cells and is the only thymic hormone that is truly thymus-specific — its serum levels become undetectable after thymectomy (surgical thymus removal). It binds to high-affinity receptors on T-cell precursors (thymocytes) and mature T cells, promoting several key aspects of T-cell biology. It induces the expression of T-cell differentiation markers (CD2, CD3, CD4, CD8), driving immature thymocytes through the stages of T-cell maturation. It enhances the cytotoxic function of CD8+ T cells and the helper function of CD4+ T cells. It modulates the balance between T-helper and T-suppressor (regulatory) cell populations, promoting appropriate immune regulation. Thymulin also modulates cytokine production — it promotes IL-2 secretion (essential for T-cell proliferation and the generation of effector T cells), enhances IFN-γ production (important for Th1 cellular immunity), and influences the balance of pro-inflammatory versus anti-inflammatory cytokines. Serum thymulin levels peak around puberty and decline progressively with age, becoming virtually undetectable by age 60 — mirroring the age-related involution of the thymus gland. This decline correlates closely with immunosenescence markers: reduced naive T-cell output, skewed CD4/CD8 ratios, impaired vaccine responses, and increased susceptibility to infections and cancer. Zinc supplementation alone can partially restore thymulin activity in zinc-deficient elderly individuals, highlighting the clinical importance of the zinc-thymulin interaction.
How is Thymulin administered?
Thymulin is administered via subcutaneous injection.
What is the half-life of Thymulin?
The half-life of Thymulin is 1-2 hours.
Is Thymulin legal?
Not FDA approved. Naturally occurring hormone. Research-grade available from peptide suppliers. Studied for immune reconstitution and anti-aging applications.
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