Increased adrenocortical activity in patients with vasovagal syncope

Objective

Syncope is a transient loss of consciousness resulting from cerebral hypoperfusion. Vasovagal syncope (VVS) is a form of orthostatic intolerance (OI). Its clinical signs such as dizziness and hypotension may mimic symptoms of adrenal insufficiency. The objective of this study was to evaluate the adrenal gland function in patients with vasovagal syncope after stimulation with synthetic adrenocorticotropic hormone (ACTH).

Design

Case-control study on patients with VVS and healthy controls.

Methods

The study involved 42 participants, including 27 patients diagnosed with VVS using the head-up tilt test and 15 healthy individuals with no history of syncope or any orthostatic symptoms. Serum cortisol and aldosterone concentrations were measured under basal conditions and at 30 and 60 min after intramuscular ACTH stimulation.

Results

Patients with VVS had significantly higher cortisol levels at baseline (441 ± 143 vs. 331 ± 84.7 nmol/L, p = 0.01), at 30 min (802 ± 143 vs. 686 ± 105 nmol/L, p = 0.01) and at 60 min (931 ± 141 nmol/L vs. 793 ± 147 nmol/L, p = 0.001) after ACTH administration (Synacthen 250 μg). Plasma aldosterone increased after ACTH stimulation, but did not show significant differences among groups. Furthermore, there was also no significant correlation between cortisol levels and blood pressure or heart rate.

Conclusion

Patients diagnosed with VVS have higher cortisol levels both at baseline and after ACTH stimulation. This finding indicates that individuals with VVS have higher adrenocortical activity potentially as a response to the orthostatic stress induced by syncope, which acts as a stressful stimulus on the autonomic nervous system.