Study of the Prevalence of Endogenous Hypercortisolism in Patients With Resistant Hypertension (MOMENTUM)

Inclusion Criteria: * Each patient must meet all of the following criteria to be enrolled in the study: * Signed and dated Institutional Review Board (IRB)-approved informed consent form (ICF) prior to any study-specific screening procedures. * Male/female patients must be 18 years or older at the time of signing the informed consent. * Meet either of the following criteria: * Has rHTN, defined by the American Heart Association as BP above target (systolic ≥ 130 mmHg for purposes of this study) despite concurrent use of 3 or more antihypertensive medications from different classes at their maximally tolerated doses, and 1 of these agents is a diuretic. * Or, has rHTN, defined by the American Heart Association as SBP at target or above target requiring concurrent use of 4 or more antihypertensive medications of different classes. Exclusion Criteria: * Patients who meet any of the following criteria will not be permitted entry to the study: * White coat hypertension, ie, elevated BP in the office only, as determined by the Investigator. * Non-adherence to BP medications, as determined by the Investigator. * Systemic glucocorticoid medications exposure (excluding inhalers or topical) within 3 months of screening. For temporary exposures to oral glucocorticoids the Medical Monitor may be consulted to determine eligibility. * Has an historical estimated glomerular filtration rate (eGFR) \< 30. * Has severe untreated sleep apnea as determined by the Investigator. * Has excessive alcohol consumption (eg, \> 14 units/week for male, \> 7 units/week for female) as determined by the Investigator. * Has severe acute psychiatric, medical, or surgical illness, as determined by the Investigator. * Is a woman who is pregnant or lactating. For women of childbearing potential, a urine pregnancy test must be negative before doing the DST. A woman of childbearing potential includes women \< 50 years old, women whose surgical sterilization was performed \< 6 months ago, and women who have had a menstrual period in the last 12 months. * Is a woman who is on oral contraceptive pills (OCPs). Women on OCPs may be screened but must be willing and able to stop OCPs for at least 6 weeks prior to screening assessments. OCPs can be resumed immediately after the blood draw for the DST. * Has history of congenital adrenal hyperplasia. * Has had the diagnosis of Cushing syndrome and/or has used or plans to use any of the following treatments for Cushing syndrome: • Mifepristone, metyrapone, osilodrostat, ketoconazole, fluconazole, aminoglutethimide, etomidate, octreotide, lanreotide, pasireotide, longacting octreotide or pasireotide. * Is unable to take dexamethasone due to a history of hypersensitivity or severe reaction to dexamethasone. * Is a staff member working directly on the study or is a family member of someone working directly on the study, including any of the Sponsor's employees, the Investigator or the site staff.