Adrenocorticotropic Hormone Stimulation in Postural Orthostatic Tachycardia Syndrome (POTS)

Patients with postural tachycardia syndrome had a subnormal increment in aldosterone with
upright posture, which might reflect a blunted adrenal response to stimulation upon assuming
upright posture. In this AIM, we propose to assess the adrenal response to aldosterone
stimulation with intravenous adrenocorticotropin hormone.

For this protocol, subjects enrolled in the parent study will be approached about this
sub-study. Subjects will be assured that they are not required to participate in this study
even if they choose to participate in the parent study.

There will be no randomization for this specific sub-study. The order of diets (low sodium
vs. high sodium) will be performed as a part of the parent study, and not as a part of this
sub-study. This sub-study will only be performed in the LOW dietary salt phase.

All subjects will be previously screened and evaluated as a part of the parent study. No
further screening will be performed exclusively for this study. Women of childbearing
potential will have had a serum pregnancy test as a part of the parent study. Pregnant women
will not be allowed to participate.

Inclusion Criteria:

Subjects will be enrolled in the parent study "Dietary Salt in Postural Tachycardia
Syndrome" during the "LOW SALT" phase

Postural Tachycardia Syndrome Diagnosed with postural tachycardia syndrome by the
Vanderbilt Autonomic Dysfunction Center Increase in heart rate ≥30 beats/min with position
change from supine to standing (10 minutes) Chronic symptoms consistent with POTS that are
worse when upright and get better with recumbence

- Control Subjects

- Healthy, non-obese, non-smokers without orthostatic tachycardia

- Selected to match profiles of POTS patients (gender, age)

- Not using vasoactive medication

- Age between 18-50 years

- Male and female subjects are eligible.

- Able and willing to provide informed consent

Exclusion Criteria:

- Overt cause for postural tachycardia (such as acute dehydration)

- Inability to give, or withdrawal of, informed consent

- pregnant

- Other factors which in the investigator's opinion would prevent the subject from
completing the protocol.