SUN-176 A Case of Aldosterone-Producing Adenoma with Preoperative Use of a Novel Mineralocorticoid Receptor Antagonist Esaxerenone

Background: Esaxerenone is a novel mineralocorticoid receptor antagonist (MRA) with nonsteroidal structure and high selectivity to MR, which became clinically available in Japan in 2019. Clinical Case: A 57-year-old woman showed a left adrenal incidentaloma (15mm) on MRI. Serological tests confirmed a diagnosis of primary aldosteronism: baseline plasma aldosterone concentration (PAC) was elevated (47.3 ng/dL, n < 15.9 ng/dL), and plasma renin activity (PRA) below sensitivity. PAC after saline infusion was 43.2 ng/dL. Overnight 1mg dexamethasone suppression test was negative. Her blood pressure had been well-controlled with amlodipine 5mg daily. Despite of large amount of potassium supplementation (96 mmol/day orally and 50 mmol/day intravenously), the level of serum potassium remained low (3.2 mmol/L). Adrenal venous sampling (AVS) was performed successfully, showing laterality index of 45.8 on left. Segmental AVS supported aldosterone hypersecretion from the tumor. After diagnosis, esaxerenone was introduced and the patient became normokalemic without potassium supplementation after a week. No adverse effect occurred in a period of two months before surgery. She underwent laparoscopic left total adrenalectomy. The tumor was positive for CYP11B2, consistent with aldosterone producing adenoma (APA). She became normotensive and normokalemic without any medications. Conclusion: This case illustrates the preoperative effectiveness of esaxerenone on blood pressure and hypokalemia in patients with APA. Key words: Esaxerenone; mineralocorticoid receptor antagonist; case report; adrenal venous sampling; primary aldosteronism; aldosterone producing adenoma