Mifepristone Treatment for Mild Autonomous Cortisol Secretion Due to Adrenal Adenomas: A Pilot Study

Objective: Adrenal incidentalomas are increasingly detected with the widespread use of thoracic and abdominal imaging. The most common secretory syndrome in adrenal nodules is autonomous cortisol secretion (ACS). Recent data show that even mild cortisol excess is associated with adverse outcomes. The glucocorticoid receptor antagonist mifepristone has been used in patients with overt Cushing syndrome and hyperglycemia. The purpose of our study was to determine the effect of mifepristone on metabolic parameters in patients with ACS and concomitant prediabetes or diabetes.Methods: Eight patients with either unilateral or bilateral adrenal nodules with ACS were included in the study. Fasting laboratory tests including glucose and insulin levels to calculate homeostatic model assessment for insulin resistance (HOMA-IR) were performed at baseline and again after either 3 months (3 patients) or 6 months (5 patients) on mifepristone 300 mg daily treatment. Patients also completed several validated surveys on mood and quality of life at baseline and follow-up.Results: There were significant reductions in fasting glucose measurements and insulin resistance as measured by HOMA-IR in the 6 of 8 study patients in whom these measurements were available (P = .03).Conclusion: This pilot study demonstrates that mifepristone treatment of ACS is associated with a significant decrease in fasting glucose and insulin resistance as measured by HOMA-IR scores. Mifepristone treatment of ACS may be considered as a medical option for patients with ACS due to adrenal adenomas with concomitant abnormal glucose parameters in whom surgical removal is not being considered.Abbreviations: ACS = autonomous cortisol secretion; ACTH = adrenocorticotropic hormone; AI = adrenal incidentaloma; DHEAS = dehydroepiandrosterone sulfate; GR = glucocorticoid receptor; HbA1c = hemoglobin A1c; HOMA-IR = homeostatic model assessment for insulin resistance; ODT = overnight dexamethasone suppression test; QoL = quality of life; STAI = state trait anxiety inventory; TSH = thyroid stimulating hormone; UFC = urinary free cortisol