Many studies have linked insulin resistance and the metabolic syndrome to PAH [27, 40–43], the lack of data in our study on insulin levels, fasting blood glucose and hemoglobin A1C level and other lipoproteins could suggest that the observed finding of association between HDL-C in CTEPH with larger decrease in PVR post PTE and decreased prevalence of right ventricular dilation on echocardiography could be related to insulin resistance. This evidence concerns the gene INS and pulmonary arterial hypertension.