TGFB1 and autoimmune thrombocytopenic purpura: The median model analysis showed that VitD had a significant negative overall effect on ITP risk (regression coefficient = -0.014, p = 0.004), but its direct effect was no longer significant after the introduction of TGF-β1 and Treg, suggesting a complete mediation effect, where the path of VitD affecting ITP via TGF-β1 is significant (effect value = -0.015, p  < 0.001), but the mediated pathway involving Treg was not statistically significant.<h4>Conclusion</h4>There is dysregulation of VitD, TGF-β1, and Treg cells in newly diagnosed children with ITP.