Endocrine Abstracts

Background: Syncope is a transient loss of consciousness resulting from cerebral hypoperfusion. Despite the extensive efforts by the scientific community over decades, the pathophysiology remains unclear. Although syncope itself is a reversible, short-lasting, benign condition, it negatively impacts quality of life. 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 ACTH.

Methods and results: The study involved 42 participants (33 females and 9 males, aged 22–82 years, median 51 years), including 27 patients diagnosed with vasovagal syncope using the head-up tilt (HUT) test. The control group consisted of 15 healthy individuals with no history of syncope. Serum cortisol and aldosterone concentrations were measured under basal conditions and at 30 and 60 min after intramuscular ACTH stimulation. 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=0.009) and at 60 min (931±141 nmol/l vs 793±147 nmol/l, P=0.005) after ACTH administration (Synacthen 250 μg). Plasma aldosterone increased after ACTH stimulation, but did not show significant differences between the two studied groups. There were no significant differences in measured hormones between males and females. Furthermore, there was also no significant correlation between cortisol levels and systolic or diastolic 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 a hyperactivated adrenal cortex potentially as a response to the orthostatic stress induced by syncope, which acts as a stressful stimulus on the autonomic nervous system.

Key words: orthostatic intolerance, vasovagal syncope, adrenal cortex, cortisol, aldosterone