Thymulin (FTS) is a 9-amino-acid zinc metallopeptide (sequence: pyroGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn, MW ~858 g/mol) secreted exclusively by thymic epithelial cells. It requires zinc binding for biological activity and plays a central role in T-cell differentiation and maturation. Thymulin serum levels decline with age and thymic involution, and it has been investigated as an immunomodulator in immunodeficiency states and aging.
Category: Immune Modulator. Evidence rating: C (early/mixed human evidence).
Clinical status: Investigational. Small clinical studies in immunodeficiency and aging; no approved therapeutic indication.
Thymulin binds zinc in a 1:1 stoichiometric ratio, which is required for its active conformation and receptor binding. It acts on T-cell precursors and mature T cells to promote differentiation, modulate cytokine production, and enhance T-cell-mediated immune responses. Thymulin induces…
Safety considerations: No large-scale human safety trials have been conducted; Small clinical studies in immunodeficient patients reported no serious adverse effects; Zinc supplementation required for activity may carry risk of copper depletion at high doses.
Reviewed by the PeptideAtlas Editorial Team. Last reviewed: 2026-08-12.
Related peptides: Thymosin Alpha-1, IM862.
Compare: Thymulin vs Thymosin Alpha-1, Thymulin vs IM862.
Zinc is essential for thymulin biological activity. The peptide must bind zinc in a 1:1 ratio to adopt the active conformation required for receptor binding and T-cell modulation. Zinc deficiency abolishes thymulin function even when peptide levels are normal.
Yes. Thymulin is produced exclusively by the thymus, which undergoes progressive involution with age. Serum thymulin levels peak in childhood and decline significantly by the fifth decade of life, correlating with reduced T-cell function in aging.
No. Thymulin (FTS) is a 9-amino-acid zinc metallopeptide produced by thymic epithelial cells, distinct from thymosin alpha-1, which is a 28-amino-acid peptide with a different mechanism and clinical development history (thymosin alpha-1 is approved in some countries as Zadaxin).