Impact of 1 mg Osilodrostat Therapy on Mild Autonomous Cortisol Secretion (MACS)

Inclusion Criteria: * Provide written informed consent * Stated willingness to comply with all study procedures and availability for the duration of the study * Age ≥ 18 years * Diagnosed with MACS * At least 2 abnormal post-dexamethasone cortisol results: i. 1 mg post-dexamethasone cortisol \>1.8 mcg/dL or ii. 8 mg post-dexamethasone cortisol \>1 mcg/dL * Historical dexamethasone suppression test results can be used if performed within 24 months prior to enrollment. * Adrenal imaging phenotype consistent with benign disease (adrenal adenoma/s, macronodular or micronodular adrenal hyperplasia) * At least one of the following comorbidities: * Obesity (BMI\>30 kg/m2) * Dysglycemia * Dyslipidemia * Hypertension * Osteopenia * Osteoporosis * Fragility fractures * Ability to take oral medication and be willing to adhere to the study intervention regimen * For persons of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use a contraceptive method with a failure rate of ≤ 5% per year during the treatment period and for 1 month after the last dose of study treatment. Exclusion Criteria: * Planned alternative therapy for MACS during the study period * Current use of oral exogenous glucocorticoid therapy * Current use of opioid therapy \>20 MME/day * Planned use of oral exogenous glucocorticoid therapy * Planned use of opioid therapy \>20 MME/day * Use of injectable glucocorticoid within the last 6 weeks or anticipated glucocorticoid use during the study period. * Hypokalemia of hypomagnesemia at baseline visit * Prolonged QTc on baseline ECG * Concomitant therapy with medications likely to lead to drug-drug interactions (based on PI review). * Investigator's judgement based on history/physical examination that a comorbidity or concomitant medication may impact the hypothalamic-pituitary-adrenal axis or steroid metabolome * Uncontrolled intercurrent illness including, but not limited to: * Ongoing or active infection * Symptomatic congestive heart failure * Unstable angina pectoris * Cardiac arrhythmia * Psychiatric illness/social situations that would limit compliance with study requirements * Pregnancy or lactation * Known allergic reactions to osilodrostat * Suspected false positive post-dexamethasone cortisol results due to increased metabolism, poor absorption, or noncompliance with dexamethasone. * Treatment with another investigational drug or other intervention within lower than specific therapy washout period