TGFA and myalgic encephalomeyelitis/chronic fatigue syndrome: Transforming Growth Factor α (TGFα) and Interleukin-33 were found to inversely correlate with headaches in the ME/CFS EV samples (r = −0.66, p = 0.002 and r = −0.63, p = 0.005 for TGFα and IL-33 respectively, Additional file 2: Figure 2d, e), and these correlations were unique in patients with ME/CFS compared to the control group.