To identify the cause of these conditions, we examined the resting blood adenylate cyclase activity and basic clinical data (blood pressure, pulse rate) of 30 patients diagnosed with orthostatic dysregulation (21 postural orthostatic tachycardia syndrome, eight delayed orthostatic hypotension, one immediate orthostatic hypotension, zero vasovagal syncope) and 20 previously reported healthy adults. The gene discussed is ADCY1; the disease is Vasovagal syncope.