Thymulin

Immune modulation, thymic function restoration, T-cell differentiation in aging and immunodeficiency

Thymulin (Facteur Thymique Sérique / FTS) is a zinc-dependent nonapeptide hormone secreted by thymic epithelial cells. It is a key regulator of T-cell differentiation and maturation, and its biological activity requires chelation with zinc. Circulating thymulin levels naturally decline with age, correlating with thymic involution and the age-related decrease in immune competence. Research interest centers on immune restoration, particularly in aging and immunodeficiency contexts. Most evidence is preclinical (animal studies) or mechanistic; limited human clinical data exist. Zinc repletion is a prerequisite for thymulin activity — zinc deficiency renders thymulin inactive regardless of peptide levels.