The thymus is the central lymphoid structure where T-cell differentiation takes place, and a crucial organ for the maintenance of homeostasis in the immune system. Thymopoiesis includes intrathymic proliferation of T-cell precursors, selection and output of both self-tolerant and competent effector T cells, as well as of natural regulatory T cells (nTreg). In the crosstalk between the neuroendocrine and immune systems, peptide hormones have been more and more implicated in immunomodulation for

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... he last thirty years. The somatotrope growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis in particular has been repeatedly shown to play a major regulatory role upon thymus function and T-cell development. This review will focus on the important thymotropic properties of the somatotrope GH/IGF-1 axis, and will try to discriminate these properties in function of the endocrine or paracrine/autocrine pathways involved in their mediation. Most importantly, in light of an increasing number of recent studies, GH and IGF-1 now appear as novel therapeutic agents that could be used for enhancing thymopoiesis in different cases of immune deficiencies, including aging-related immune dysfunction.