Intraocular pressure and its correlation with midnight plasma cortisol level in Cushing's disease and other endogenous Cushing's syndrome

PURPOSE The purpose of this study is to measure intraocular pressure (IOP) and evaluate the correlation between IOP and midnight plasma cortisol (MPC) level in patients with Cushing's disease (CD) and other endogenous Cushing's syndrome (ECS). METHODS This is a cross-sectional study from a single center including newly diagnosed patients with CD or ECS. All patients underwent detailed ophthalmological evaluation. IOP was measured by Goldmann applanation tonometry in the morning and evening on two consecutive days. MPC value was obtained for each patient. The data were compared using paired and unpaired t-test, Mann-Whitney U-test, and Spearman's rank correlation coefficient. RESULTS Among 32 patients, 22 were CD (68.75%) and 10 patients were other ECS (31.25%). A total of 25 patients (78.12%) in our study group had normal IOP (<22 mmHg), and seven patients (21.88%) had increased IOP (≥22 mmHg). The percentage of patients with normal IOP was found to be significantly higher compared to percentage of patients with high IOP (P = 0.001) using one-sample Chi-square test. Mean MPC value was 468.6 ± 388.3 nmol/L in patients having IOP ≥22 mmHg and 658.5 ± 584 nmol/L in those with IOP <22 mmHg from both CD and ECS groups, but the difference was not statistically significant. No correlation was found between IOP and MPC (Spearman's rank correlation rho = -0.16 [P = 0.38]). CONCLUSION In CD and ECS patients, IOP elevation is an uncommon feature, and high IOP in either group does not correlate with MPC level.