MON-479 Adrenal Insufficiency in the Context of Abiraterone Treatment: Clinical Findings and Implications

Abstract Disclosure: N. Chamorro-Pareja: None. M.E. Manning: None. M.S. Haines: BioAge - Scientific Advisory Board. K.K. Miller: Amgen - Received study medication and investigator-initiated research grants, Bristol-Myers Squibb - Equity, General Electric - Equity, Boston Scientific - Equity, Becton Dickinson - Equity. Abiraterone, an androgen-production inhibitor, was FDA-approved in 2011 to treat metastatic prostate cancer. By inhibiting 17α-hydroxylase and C17,20-lyase, it also decreases cortisol production. Although prednisone 5-10 mg daily is routinely prescribed to prevent mineralocorticoid excess and concomitantly serves as glucocorticoid replacement therapy, adrenal insufficiency as a complication of this treatment may be under-recognized, resulting in underutilization of stress dose steroids during acute illness in this group of patients particularly prone to medical crises. Objective: To characterize the clinical presentation of patients receiving abiraterone who underwent cortisol testing and to evaluate the risk of adrenal insufficiency in this group. Methods: The Mass General Brigham Research Patient Database Registry was used to search patient medical records from January 1, 2014 to July 31, 2024. “Definite” adrenal insufficiency was defined as an outpatient AM serum cortisol <3 ug/dL (before 10AM) or a peak serum cortisol <15 ug/dL on a cosyntropin stimulation test (CST). Probable adrenal insufficiency was defined as an inpatient AM serum cortisol <3 µg/dL or outpatient AM serum cortisol 3-5 µg/dL. The medical records of these patients, including provider encounters, laboratory results, and medication records were reviewed. Results: Out of >4000 patients who received abiraterone, only 171 (4%) underwent cortisol testing of any kind. Among these, 23 (13%) met criteria for adrenal insufficiency, and 14 (8%) met the criteria for probable adrenal insufficiency. In patients with definite adrenal insufficiency, median age was 74 years (IQR 70-82), and 87% were White. Testing was prompted by symptoms in 83% of patients, with the most common being fatigue (57%), anorexia/weight loss (35%), and orthostatic hypotension/dizziness (39%). The median AM cortisol was 2.5 µg/dL (IQR 0.8-3.9) and the median peak cortisol on CST was 5.1 µg/dL (IQR 2.6-9.1). Forty-three percent (n=10) received stress dose steroids or sick day dosing after diagnosis of adrenal insufficiency. Conclusion: Despite the known effect of abiraterone on cortisol synthesis, fewer than 5% of patients treated with this medication underwent cortisol testing, yet nearly 15% of those tested met criteria for adrenal insufficiency. The true incidence of adrenal insufficiency in this population remains uncertain. However, our findings underscore the importance of maintaining a high clinical suspicion for adrenal insufficiency in patients on abiraterone. Educating patients about this complication and ensuring timely administration of stress dose steroids during acute illness are critical. Further studies are warranted to clarify the incidence and optimal management strategies for adrenal insufficiency in this setting. Presentation: Monday, July 14, 2025