IGF1 and pulmonary arterial hypertension: In the aspect of promoting vascular growth, IGF-1 can inhibit cellular apoptosis by phosphorylating apoptosis protein BAD through the IGF-1-IRS-1-PI3K-IGFR-1R/AKT pathway, which has been found to be activated in hypoxia-induced PAH (Madonna et al., 2015).