In previous studies, we examined predictive indices of metoprolol efficacy before treating patients with POTS by detecting plasma levels of norepinephrine, copeptin and C-type natriuretic peptide (CNP) (Zhang et al., 2014; Zhao et al., 2014; Lin et al., 2015b). The gene discussed is CNP; the disease is postural orthostatic tachycardia syndrome.