The Stress Hormone ACTH Causes a Prolonged Reduction in Heart Rate Variability

Abstract

Hypoglycemia is a complex stressor that activates multiple hormonal systems and the sympathetic nervous system. Hypoglycemia also impairs autonomic control of blood pressure. It is possible that stress hormones produced during hypoglycemia (such as ACTH) play a role in the attenuation of autonomic function after recurrent hypoglycemia known as “cardiovascular hypoglycemia‐associated autonomic failure”. Prior work from this placebo‐controlled cross‐over study has shown that ACTH infusion reduces Modified Oxford baroreflex gain and that the reduction persists to the following day. The purpose of this analysis was to determine whether measures of heart rate variability (HRV) demonstrate a similar pattern. In the original study, men and women aged 18 – 55 years (n = 22) completed 2 study visits (ACTH or placebo in random order) with a 1–3‐month washout period between. A study visit consisted of a 3‐day/2‐night inpatient stay with the infusion occurring on day 2. Standard HRV measures from 3 minutes of 0.1 Hz breathing (6 breaths/minute) were collected on each of the 3 days. Overall HRV (time or frequency domain), as well as low frequency HRV, were reduced on the infusion day and the day after by ACTH, with no effect on blood pressure variability. Low‐frequency transfer function gain was similarly reduced, but only on day 3. In addition, these frequency domain gains were significantly correlated with the Modified Oxford derived gains. These results suggests that the ACTH impairment of autonomic control of blood pressure is reflected in HRV measures.