PS-C21-3: URINARY FREE CORTISOL EXCRETION AS A MARKER OF DECREASED BONE DENSITY IN PATIENTS WITH ADRENAL CUSHING'S SYNDROME

Abstract

Objective: Patients with adrenal Cushing's syndrome (CS) have a poor prognosis due to the autonomous hypersecretion of endogenous cortisol from the adrenal gland. Although several clinical examinations have been developed to manifest the autonomous hypersecretion of endogenous cortisol in this syndrome, it is unknown which parameter of cortisol overproduction is best associated with adrenal cortisol content and the bone and vascular complications of this syndrome. Therefore, the present study was undertaken to evaluate the parameter(s) associated with adrenal cortisol content in patients with adrenal CS, as well as to assess the associations between these parameters and the vascular and bone complications of this syndrome. Design and method: Patients with CS who were over 18 years old and had undergone adrenalectomy for this syndrome were enrolled in this study. Patients who were pregnant, had an allergy to iodine, or who were receiving medications that may interfere with the evaluation of 131I-adosterol single-photon emission computed tomography (SPECT) /computed tomography (CT) were excluded. Those taking medications that may interfere with the evaluation for the diagnosis of CS were also excluded. Relationships between office blood pressure and pulse rate, urinary examinations, blood examinations, endocrinological examinations, CT and 131I-adosterol SPECT/CT data, bone density, physiological function tests, and adrenal cortisol concentration/content were examined. In addition, relationships between the parameter associated with adrenal cortisol concentration/content and complications of CS were investigated. Results: Cardiovascular factors, except for diastolic blood pressure, failed to show an association with adrenal cortisol content. 24-h urinary free cortisol excretion (ρ = 0.893, P = 0.007) and plasma cortisol levels after the 1 mg (ρ = 0.857, P = 0.014) or 8 mg (ρ = 0.900, P = 0.037) overnight dexamethasone suppression test, but not plasma cortisol levels in the morning or at late night or indices of 131I-adosterol SPECT/CT, were significantly and positively associated with adrenal cortisol content. 24-h urinary free cortisol excretion, and not plasma cortisol levels after the 1 or 8 mg overnight dexamethasone suppression test was significantly and negatively associated with lumbar spine bone density (lumbar spine T-score, ρ = -0.883, P = 0.009; lumbar spine Z-score, ρ = -0.883, P = 0.009). Conclusions: 24-h urinary free cortisol excretion is best associated with a decrease in bone density via increased adrenal cortisol overproduction and suggested that it could be used as a marker for osteoporosis in these patients.