Thymulin — Research, Dosing & Price Guide

Thymulin (facteur thymique serique, FTS) is a zinc-dependent nonapeptide hormone produced by thymic epithelial cells. It is the only thymic hormone that requires a metal cofactor (zinc) for biological activity. Thymulin plays a critical role in T-cell differentiation and maturation, and its levels decline dramatically with age as the thymus involutes — making it a target for immune reconstitution in aging.

Thymulin (pyro-Glu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn) requires zinc binding for biological activity — the zinc atom coordinates with the peptide's asparagine and serine residues, inducing a conformational change necessary for receptor binding. Active thymulin-zinc complex binds to specific receptors on T-cell precursors, promoting their differentiation into mature functional T cells. It enhances interleukin-2 (IL-2) receptor expression on T cells, promotes CD4+ and CD8+ T-cell maturation, and modulates cytokine production. Thymulin also influences the hypothalamic-pituitary-adrenal (HPA) axis, suggesting neuroendocrine-immune crosstalk. Its levels decline from peak production in puberty to near-undetectable levels by age 60, correlating with thymic involution and age-related immune decline (immunosenescence). Zinc supplementation alone can partially restore thymulin activity in zinc-deficient elderly individuals, highlighting the metal-peptide interdependence.

• Bach et al. (1977, Proceedings of the National Academy of Sciences) first characterized thymulin as a zinc-dependent thymic hormone essential for T-cell maturation
• Mocchegiani et al. (1995, Journal of Pharmacy and Pharmacology) showed zinc supplementation restored thymulin activity and T-cell function in elderly subjects
• Studies demonstrated that thymulin levels decline to near-zero by age 60, correlating with thymic involution
• Thymulin has been shown to reduce neuroinflammation and promote remyelination in animal models of multiple sclerosis
• Safieh-Garabedian et al. (2011, Neuroscience) showed thymulin had analgesic and anti-inflammatory effects in pain models
• Research suggests thymulin modulates the HPA axis, linking immune function to neuroendocrine regulation

• Research protocols: 1–5 mcg subcutaneously or intranasally daily
• Often combined with zinc supplementation (15–30 mg elemental zinc daily) to ensure cofactor availability
• Cycle: 10–30 day courses, repeated every 3–6 months
• Some anti-aging protocols use low-dose thymulin (1 mcg) daily for extended periods
• Intranasal delivery may provide superior access to neuroimmune pathways
• No established pharmaceutical-grade dosing — most protocols are based on research literature

Known Side Effects

• Minimal side effects reported in research settings
• Potential for mild immune activation symptoms (low-grade fever, fatigue) at initiation
• Zinc supplementation may cause GI discomfort (nausea, metallic taste) if taken on an empty stomach
• Theoretical risk of immune stimulation in autoimmune conditions
• Long-term safety data in humans is limited

Safety Profile

Thymulin is an endogenous hormone with inherent biocompatibility. It has been studied in research settings for decades without significant safety concerns. The zinc dependency provides a natural safety mechanism — without adequate zinc, the peptide is inactive, preventing accidental overdose of immune stimulation. However, clinical safety data is limited to small research studies rather than large-scale trials. As with other thymic peptides, caution is advised in autoimmune conditions and in organ transplant recipients. The neuroendocrine effects (HPA axis modulation) are not fully characterized and warrant monitoring. Thymulin is not regulated as a pharmaceutical in most jurisdictions.

Week 1–2: No obvious effects. Immune modulation is occurring at the cellular level. Ensure adequate zinc intake to activate the peptide. Week 2–4: Subtle improvements in immune resilience may become noticeable — fewer minor illnesses, faster recovery from infections. Week 4+: Immune parameters may show improvement if measured (T-cell counts, NK cell activity). Benefits are most apparent in elderly or immunocompromised individuals. Effects are gradual and cumulative with repeated courses.

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