GDF15 and idiopathic pulmonary arterial hypertension: Plasma GDF15 concentrations in patients with PVOD, idiopathic PAH (IPAH), heritable PAH (HPAH), group 2–4 PH (Other PH), and chronic obstructive pulmonary disease without PH (COPD) as well as individuals acting as healthy controls were quantified (Figure 1A).