GH1 and postural orthostatic tachycardia syndrome: Plasma levels of GH were significantly lower in POTS patients compared with controls (median 0.53 ng/mL, IQR, 0.10–2.83 vs. 2.33 ng/mL, IQR, 0.26–7.2, p = 0.04, Fig. 1), although the GH levels were still within the normal range.