Thymulin

Thymulin (Facteur Thymique Sérique, FTS) is a nonapeptide hormone secreted by thymic epithelial cells that requires zinc binding for biological activity. The active zinc-thymulin complex is essential for T-lymphocyte differentiation, immune system maturation, and maintenance of immune homeostasis. As thymic function declines with age, thymulin production decreases substantially, contributing to immunosenescence—the gradual deterioration of immune function associated with aging. Research demonstrates thymulin influences T-cell development, cytokine networks, and the balance between different T-cell subsets. The peptide also exhibits neuroendocrine effects through interactions with the hypothalamic-pituitary axis. Studies suggest potential therapeutic applications for restoring immune function in elderly subjects, supporting immune reconstitution, and modulating autoimmune responses. Thymulin's anti-inflammatory and analgesic properties have been documented independent of its immunomodulatory effects. The absolute requirement for zinc highlights the importance of zinc status in immune function and the potential for zinc deficiency to impair thymulin activity.

Human evidence is decades old, small, and inconsistent; no modern large trials exist; bioavailability and dosing of exogenous thymulin are not established; zinc status confounds its biological activity.

Thymulin is a nonapeptide (pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn) secreted by thymic epithelial cells; it requires zinc for biological activity (zinc-thymulin, Zn-FTS). Plasma levels fall with age as the thymus involutes. No approved pharmaceutical form exists for general use.