8479 A Challenging Case of Hypercortisolism in an Adult Patient With McCune Albright Syndrome

Abstract Disclosure: P. Kesavan Chary: None. S. Jasim: None. Background: McCune Albright Syndrome (MAS) is a rare genetic disorder that occurs due to a spontaneous post-zygotic missense mutation in the GNAS gene resulting in activating gain of function mutations in G-proteins. MAS classically presents as a triad of café-au-lait skin pigmentation, fibrous dysplasia of bone, and precocious puberty. However, continuous autonomous stimulation of endocrine glands can also result in various other endocrinopathies. We present a rare case of hypercortisolism due to bilateral multinodular adrenal hyperplasia (BMAH) in an adult patient with MAS. Case Report: A 38 year old female had MAS, clinically manifested by precocious puberty, renal phosphate wasting with rickets and osteomalacia, fibrous dysplasia of bone with history of multiple fractures, growth hormone excess, and multinodular thyroid status-post total thyroidectomy. A surveillance CT abdomen showed bilateral (right 3.8 x 1.3 cm and left 1.0 x 0.9 cm) adrenal adenomas with low intrinsic attenuation and washout. On diagnosis, the patient had an AM cortisol of 32.5 ug/dL (6.2-19.4 ug/dL) after a low-dose dexamethasone suppression test (DST), and an AM cortisol of 27.3 ug/dL after a high-dose DST. Late night salivary cortisol was 0.518 ug/dL (<0.010-0.090 ug/dL), 24-hour urine cortisol was 78 ug/24hrs (6-42 ug/24hrs), and ACTH was <1.5 pg/mL (7.2-63.3 pg/mL). The patient was initially asymptomatic and monitored for a few months, but subsequently developed easy bruising, recurrent skin infections, and irritability. The patient declined surgical intervention and was initiated on Osilodrostat. Shortly after medication initiation, she was hospitalized for perforated diverticulitis, hypokalemia, and hypomagnesemia. During hospitalization, AM Cortisol was 49 mcg/dL (4.8-19.5 mcg/dL) and 24-hour urine cortisol was 1023 mcg/24hrs (normal range 3.5-45 mcg/24hrs; the patient’s level prior to admission was 170-190 mcg/24hrs). Osilodrostat was held and the patient was initiated on Etomidate infusion. Once plasma cortisol levels normalized, she resumed Osilodrostat prior to discharge. The patient subsequently tried multiple medical therapy options before undergoing a bilateral adrenalectomy as a definitive treatment choice. Conclusion: The gain of function mutations in MAS result in autonomous endocrine gland function that can manifest clinically as various endocrinopathies. While the most common endocrinopathies in MAS are precocious puberty, hyperthyroidism, and pituitary dysfunction, active surveillance is critical to monitor for less common presentations such as hypercortisolism. This is the first report of adrenal Cushing’s in an adult patient with MAS. Presentation: 6/3/2024