FGF21 and idiopathic pulmonary arterial hypertension: In this study, we found altered adipose tissue secretory pattern characterized by increased circulating levels of FABP-4, adiponectin, and FGF-21 in patients with IPAH compared to healthy controls, as well as a significant positive correlation of serum FABP-4 with FGF-21 levels in IPAH, accompanied by an increase in FABP-4 and FGF-21 mRNA expression in lungs from patients with PAH.