SAT-458 Mifepristone-induced gynecomastia, hyperestrogenemia, and secondary hypogonadism in a male with primary bilateral macronodular adrenal hyperplasia

Abstract Disclosure: A.M. Gonzalez Gil: None. E.F. Elli: None. R.J. Singh: None. S. Peres: None. A.Y. Chang: None. Background: Treatment of hypercortisolism in primary bilateral macronodular adrenal hyperplasia (PBMAH) with mild autonomous cortisol secretion (MACS) can be challenging. Medical treatment is useful for therapeutic purposes and as a bridge for adrenalectomy. We present the case of a patient who benefited from mifepristone but developed hyperestrogenism. Clinical Case: A 64-year-old man with prediabetes, hypertension, and cardiovascular disease had incidentally discovered bilateral nodular adrenal enlargement on CT scan following coronary artery bypass surgery. A few months later, he reported increasing fatigue, brain fog, weight gain, and worsening blood pressure. Physical exam showed no features of hypercortisolism. Work-up revealed baseline AM cortisol 17.3 mcg/dL [reference range (RR) 4.8-20], ACTH 10 pg/mL (RR 7.2-63) and DHEA-S 55 mcg/dL (RR 12-227); two abnormal AM cortisols after 1 mg overnight dexamethasone (5.4 and 6.9 mcg/dL; cut-off <1.8), and a normal 24-hour urine free cortisol (23 mcg/24h, RR 3.5-45). 24-hour urine metanephrines and aldosterone/renin ratio were normal. A 2-hour 75 g oral glucose tolerance test was diagnostic for type 2 diabetes mellitus (2-hour glucose 214 mg/dL). Baseline total testosterone (TT) was 366 ng/dL (RR 264-916) with normal follicle stimulating hormone (FSH) and luteinizing hormone (LH)concentrations. After a diagnosis of MACS, adrenal vein sampling showed bilateral excess cortisol secretion (lateralization ratio 1.09). Medical management versus right adrenalectomy based on nodule burden were offered, and he started mifepristone. With initial symptom improvement, his dose was increased from 300 mg to 300 mg alternating with 600 mg daily. When he developed increased blood pressure and hypokalemia, eplerenone was added. After 6 months of mifepristone and 5 months eplerenone 50 mg daily, he developed tender gynecomastia with elevated estradiol (106 pg/mL, RR ≤39), low TT (112 ng/dL) and undetectable FSH and LH. As expected with mifepristone, 17-hydroxyprogesterone was high (933 ng/dL, RR 51-190), but androstenedione and DHEA-S were normal. Reduction in mifepristone and eplerenone decreased estradiol levels (56 pg/mL) but gonadotrophins remained undetectable and TT decreased to 72 ng/dL. Despite discontinuation of eplerenone for 1 month, estradiol again increased (91 pg/mL), TT remained low (77 ng/dL), and mastalgia persisted. A decision to stop mifepristone and proceed with right adrenalectomy was made. Conclusion: This is a previously unreported incident of symptomatic estradiol-induced secondary hypogonadism on mifepristone therapy. Hyperestrogenism with gynecomastia and secondary hypogonadism with mifepristone suggests that some individuals may convert cortisol precursors to estradiol. Presentation: Saturday, July 12, 2025