IGF1R and pulmonary arterial hypertension: IGFBP-4 can accelerates PAH progression by driving PASMC proliferation and EndMT through IGF-1/IGF-1R signaling, PI3K/Akt, and MAPK/ERK pathways, contributing to vascular wall thickening and inflammation. and It represents a candidate biomarker and potential target for IGFBP-4–directed inhibition