GDF15 and pulmonary arterial hypertension: Our results showed that there was no statistically significant difference in survival between the normal GDF-15 group and the elevated GDF-15 group, which may be related to our small sample size, or it may be the elevated levels of GDF-15 are linked to increased inflammation in the more ill patient, or related to a subclass of PAH, which warrants more detailed study in the future.