Adrenal gland response to adrenocorticotropic hormone is intact in patients with postural orthostatic tachycardia syndrome

Background

Many patients with postural orthostatic tachycardia syndrome (POTS) are hypovolemic with plasma volume deficits of 10–30 %. Some also have low levels of aldosterone and diminished aldosterone-renin ratios despite elevations in angiotensin II, pointing to potential adrenal dysfunction. To assess adrenal gland responsiveness in POTS, we measured circulating levels of aldosterone and cortisol following adrenocorticotropin hormone (ACTH) stimulation.

Methods

While on a low Na⁺ diet (∼10 mEq/day), 8 female patients with POTS and 5 female healthy controls (HC) received a low dose (1 μg) ACTH bolus following a baseline blood sample. After 60 min, a high dose (249 μg) infusion of ACTH was administered to ensure maximal adrenal response. Venous aldosterone and cortisol levels were sampled every 30 min for 2 h.

Results

Aldosterone increased in both groups in response to ACTH but was not different between POTS vs. HC at 60 min (53.5 ng/dL [37.8–61.8 ng/dL] vs. 46.1 ng/dL [36.7–84.9 ng/dL]; P = 1.000) or maximally (56.4 ng/dL [49.2–67.1 ng/dL] vs. 49.5 ng/dL [39.1–82.8 ng/dL]; P = 0.524). Cortisol increased in both groups in response to ACTH but was not different in patients with POTS vs. HC at 60 min (39.9 μg/dL [36.1–47.7 μg/dL] vs. 39.3 μg/dL [35.4–46.6 μg/dL]; P = 0.724) or maximally (39.9 μg/dL [33.9–45.4 μg/dL] vs. 42.0 μg/dL [37.6–49.7 μg/dL]; P = 0.354).

Conclusions

ACTH appropriately increased the aldosterone and cortisol levels in patients with POTS. These findings suggest that the response of the adrenal cortex to hormonal stimulation is intact in patients with POTS.