Peptide Schedule
Thymulin (FTS)9 residues (approx.)QAKSQGGSNEach bubble = one amino acid. Size = residue mass. Color = chemical class.Uses closest standard amino acids for non-standard residues.Thymulin (FTS)
Benefits
About Thymulin (FTS)
Thymulin, originally known as Facteur Thymique Serique (FTS) or Serum Thymic Factor, is a metallopeptide hormone produced exclusively by thymic epithelial cells. It is a nonapeptide (pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn) with a molecular weight of 858.9 Da that requires equimolar zinc binding to adopt its biologically active conformation. The zinc ion coordinates through the side chains of Lys3 and Ser4 and the backbone carbonyl of Ala2, creating a specific three-dimensional structure confirmed by NMR studies. Without zinc, the peptide is inactive. This zinc dependency means that thymulin serves as a direct molecular link between zinc nutritional status and immune function. Thymulin acts primarily on T-cell populations, promoting the differentiation and maturation of immature T-cell precursors in the thymus and periphery. It binds to high-affinity receptors on T cells and enhances allogenic cytotoxicity, suppressor cell function, and interleukin-2 (IL-2) production. Beyond T-cell effects, it modulates natural killer cell activity, influences dendritic cell function, and has emerged as a significant anti-inflammatory molecule. Circulating thymulin levels peak during early childhood and decline progressively with age, mirroring thymic involution. By age 60, serum levels are often undetectable. This age-related decline has made thymulin a target of interest in immunosenescence research, with gene therapy approaches being explored to restore sustained production.
Who Should Consider Thymulin (FTS)
- Individuals over 50 experiencing age-related immune decline
- People with documented zinc deficiency and impaired T-cell function
- Researchers studying thymic involution and immunosenescence interventions
- Those with chronic low-grade inflammation seeking immune rebalancing under medical supervision
- Individuals recovering from prolonged illness with suppressed T-cell counts
How Thymulin (FTS) Works
Thymulin exerts its effects through a zinc-dependent conformational activation mechanism. The inactive apoform of the nonapeptide binds one zinc ion in an equimolar ratio, coordinating through Lys3, Ser4 side chains and the Ala2 backbone carbonyl. This metalation induces a specific three-dimensional structure that exposes the biologically active epitope recognized by T-cell surface receptors. Once bound to high-affinity receptors on T-cell precursors, thymulin activates intracellular cAMP signaling cascades that drive T-cell differentiation, enhancing the expression of maturation markers including CD4, CD8, and the T-cell receptor complex. In mature T cells, it increases IL-2 production, enhances allogenic cytotoxicity, and promotes suppressor cell function. The anti-inflammatory activity of thymulin is NF-kB-dependent. Thymulin downregulates the nuclear localization and activation of NF-kB through the IkB-alpha/pIkB-alpha pathway, reducing transcription of pro-inflammatory genes. This leads to decreased production of TNF-alpha, IL-1beta, and IL-6, while maintaining or upregulating anti-inflammatory IL-10. The anti-inflammatory effect is mediated through cAMP elevation and is synergistically amplified by the presence of zinc. In the central nervous system, intracerebroventricular thymulin administration reduced hippocampal NF-kB activation and attenuated neuroinflammatory damage, suggesting neuroprotective potential. Thymulin also prevents LPS-induced overproduction of heat shock protein Hsp70, indicating it can modulate the cellular stress response during inflammation.
What to Expect
Treatment initiation alongside zinc pre-loading. Thymulin begins interacting with T-cell precursors. No outward immune changes expected during this window. Mild injection site reactions may occur. Ensure zinc supplementation is consistent.
Early T-cell modulation may begin. In animal studies, thymulin administration during this timeframe produced measurable changes in T-cell subpopulations and cytokine profiles. Some individuals report subtle improvements in energy or reduced frequency of minor infections.
Anti-inflammatory effects become more established. In colitis mouse models, thymulin at 15 mcg/100g body weight significantly reduced pro-inflammatory cytokine accumulation in this timeframe. T-cell maturation markers and NK cell activity may show improvement on blood panels.
Peak treatment effects expected. Immune rebalancing is most apparent with sustained use. Assess results through bloodwork (T-cell subsets, inflammatory markers). Evaluate whether to continue another cycle after the off-period.
Dosing Protocol
| Level | Dose / Injection | Frequency |
|---|---|---|
| Beginner | 50mcg | 2x/week |
| Moderate | 100mcg | 3x/week |
| Aggressive | 200mcg | Daily |
Note: Zinc-dependent nonapeptide thymic hormone. Requires equimolar zinc binding for biological activity. Co-administer with 15-30 mg/day elemental zinc. Extremely short plasma half-life means frequent dosing or sustained-release strategies may be needed. Distinct from Thymalin — Thymulin is a single defined 9-amino-acid peptide (pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn), while Thymalin is a polypeptide thymic extract.
How to Inject Thymulin (FTS)
Subcutaneous injection into abdominal fat, rotating injection sites. Reconstitute lyophilized powder with bacteriostatic water and gently swirl — do not shake. Due to thymulin's extremely short serum half-life (~10 minutes), daily dosing or multiple daily administrations may be needed for sustained effect. Always co-supplement with 15-30 mg/day elemental zinc, taken with food, to ensure the peptide can adopt its active zinc-bound conformation. Begin zinc supplementation at least 7 days before starting thymulin. Inject at a consistent time each day, preferably morning. Store reconstituted vials upright in the refrigerator. This is a research compound — all dosing is derived from animal studies and limited clinical observations.
Cycling Protocol
No standardized human cycling protocols exist. The 8-on/4-off recommendation is based on animal study durations and the general principle of allowing immune system recalibration between treatment periods. Zinc supplementation (15-30 mg/day elemental zinc) should begin 1 week before starting thymulin and continue throughout the cycle. Monitor zinc and copper levels during extended use, as chronic zinc supplementation can deplete copper stores.
Pharmacokinetics
Source: Serum half-life of thymulin is approximately 10 minutes based on clearance studies. This extremely short duration is one of the primary pharmacokinetic limitations, and gene therapy approaches have been explored to achieve sustained endogenous production. Circulating levels in healthy humans range from 0.5-3 pg/mL, peaking in early childhood and becoming undetectable by age 60.
Loading the interactive decay curve.
Side Effects
Thymulin is generally well-tolerated based on animal studies and limited human data. Mild injection site redness or discomfort may occur. Some users report transient fatigue during the first few days as immune recalibration occurs. Rare: nausea or headache. No significant adverse effects were reported in zinc supplementation studies supporting thymulin activity. Long-term human safety data for exogenous thymulin administration is limited.
Contraindications
- Active autoimmune disease flare-ups — thymulin stimulates T-cell activity and could worsen autoimmune reactions
- Organ transplant recipients on immunosuppressive therapy — immune stimulation risks graft rejection
- Active cancer without oncologist approval — T-cell and NK cell activation may interact unpredictably with tumor biology
- Pregnancy or breastfeeding — no reproductive safety data exists for exogenous thymulin
- Known thymus abnormalities including thymoma or thymic hyperplasia
- Wilson's disease or copper metabolism disorders — zinc supplementation required for thymulin use can further disrupt copper balance
Drug Interactions
- Immunosuppressants (cyclosporine, tacrolimus, mycophenolate) — thymulin's immune-stimulating effects may counteract immunosuppressive therapy
- Corticosteroids — chronic corticosteroid use suppresses thymic function and may blunt thymulin's effects; interaction effects are poorly characterized
- Zinc supplements — required for thymulin activity, but doses above 40 mg/day may cause copper depletion; monitor copper levels
- Copper supplements — high-dose zinc co-administered with thymulin can reduce copper absorption; separate dosing by 2+ hours if supplementing both
- Other thymic peptides (Thymosin Alpha 1, Thymalin) — additive immune stimulation possible; no formal combination studies exist
- Checkpoint inhibitors (nivolumab, pembrolizumab) — combined T-cell activation effects are unstudied and could be unpredictable
Storage & Stability
Molecular Profile
Related Peptides
References
- Interactions between zinc and thymulin (Coto et al., 2008)Review
- Thymulin, a zinc-dependent hormone (Dardenne et al., 1989)PubMed 2657247
- In vivo treatment with FTS ameliorates chronic colitis induced by dextran sulphate sodium in mice (Lunin & Bhatt, 2007)PubMed 17499195
- Thymulin prevents overproduction of pro-inflammatory cytokines and Hsp70 in inflammation-bearing mice (Lunin & Novoselova, 2008)PubMed 18991101
- Thymulin and its role in immunomodulation (Hadden, 1992)Review
- The anti-inflammatory and immunomodulatory activity of thymulin peptide is NF-kB-dependent and involves downregulation of IkB-alpha (Safieh-Garabedian et al., 2011)PubMed
- Physiology and therapeutic potential of the thymic peptide thymulin (Reggiani et al., 2014)Review
- Thymulin (FTS) and zinc contents of the thymus glands of malnourished children (Chevalier et al., 1987)PubMed 3136643