Association of hypokalemia with cortisol and ACTH levels in Cushing's disease

Hypokalemia is a common feature in patients with Cushing's syndrome (CS). Whether the occurrence of hypokalemia is associated with cortisol and adrenocorticotropic hormone (ACTH) levels is still unclear. Approximately 80% of cases of endogenous CS are due to Cushing's disease (CD). The purpose of this study was to determine the association of hypokalemia with cortisol and ACTH levels in patients with CD. The retrospective study included 195 patients with CD referred to our medical center from January 2011 to December 2017. The results show that 25.64% (50/195) of the patients had hypokalemia. The 24-h urinary free cortisol (UFC) and plasma cortisol levels were significantly higher in patients with hypokalemia than those with normokalemia (P 0.05). Cortisol levels were negatively correlated with plasma potassium levels (08:00: r = -0.344 (P 0.05), 00:00: r = -0.184 (P > 0.050)). Our current data suggest that cortisol level, instead of ACTH level, is correlated with plasma potassium level. A high cortisol level may be the principal cause of hypokalemia.