In a pig study, giving growth hormone (porcine somatotropin) raised thymus size and levels of a related peptide called thymosin beta‑4, but it only slightly changed thymosin‑alpha‑1, and that change was linked to the sex of the pig, not the hormone dose. The results are in animals and don’t give a clear way to use thymosin‑alpha‑1 in people.

Experiment 1 involved genetically lean and obese gilts and barrows injected for 42 d with 0, 2, or 4 mg/d of porcine somatotropin (pST; n = 96). Blood was collected at 0, 6, and 24 h after the initial pST injection and thereafter every 2 wk. Experiment 2 involved lean and obese gilts and barrows (n = 48) that were administered implants that released 0, 2, or 4 mg/d of pST for 42 d. Blood was collected at d 0, 7, 14, 28, and 42 of the study. Thymic weights and a final blood sample were collected at the end of the 42-d trial. Thymic weights increased (P < .01) with dose of pST in injected and implanted animals. Thymosin beta 4 increased (P < .05) in a pST dose-dependent manner in injected and implanted animals, but concentrations were increased more in implanted animals. Concentrations of thymosin beta 4 decreased or reached a plateau in gilts but continued to increase in barrows to the end of the trial. Thymosin alpha 1 concentrations were increased (P < .01) in barrows compared with gilts, but the concentrations were not related to dose of pST. Concentrations of pST in injected animals increased (P < .01) within 6 h after injection and had returned to basal concentrations by 24 h after injection. Concentrations of pST in implanted animals were dose-dependent (P < .05) and remained increased throughout the trial. Concentrations of IGF-I and -II were pST-dependent (P < .01) and increased throughout the trial period. Outside of the pST dose relationships, temporal changes in thymosin beta 4 were not highly related to changes in pST, IGF-I, or IGF-II. The pST dose-related increases in thymic weights and thymosin beta 4 concentrations are consistent with pST stimulation of the immune function in conjunction with overall increases of growth and efficiency of live weight gain in swine.