Adrenergic Antibodies in Postural Tachycardia Syndrome

Eligibility Details: Inclusion Criteria: - Patients who have been previously diagnosed with POTS - Control subjects (patients not diagnosed with POTS) - Age between 18 - 60 years - Males and Females (Give that >80% of POTS patients are female, we will attempt to enroll a similar percentage of female control subjects) - Able and willing to provide consent Exclusion Criteria: - Smokers - Overt cause for postural tachycardia, i.e., acute dehydration - Significant cardiovascular, pulmonary, hepatic, or hematological disease by history or prior testing - Highly trained athletes - Subjects with somatization or severe anxiety symptoms will be excluded - Use of drospirenone (a spironolactone analogue) containing oral contraceptive agent - Hypertension defined as supine resting BP>145/95 mmHg off medications or needing antihypertensive medication - Other factors which in the investigator's opinion would prevent the participant from completing the protocol, including poor compliance during previous studies or an unpredictable schedule - Unable to give informed consent