SUN-062 Pituitary Macroadenoma With Suprasellar Extension and Optic Chiasm Compression Causing Cushing’s Disease: a Case Report

Abstract Disclosure: D. Yepez Romero: None. J. Joseph: None. J. Mulayamkuzhiyil Saju: None. T. Ojukwu Perdomo: None. J. Khan: None. S. Basant: None. N. Desouza: None. Cushing disease, caused by an ACTH-secreting pituitary adenoma, presents with hypercortisolism. We present a young female with years of weight gain and progressive muscle weakness, now mostly homebound, who presented with visual disturbances. A 45-year-old female arrived at the ED with sudden-onset, bifrontal, throbbing headache, nausea, and blurred vision. She reported years of unexplained weight gain and proximal muscle weakness, which limited her mobility. She reports her symptoms worsened after intralesional glucocorticoids injections for Lichen Simplex Chronicus. Exam showed hypercortisolism features: moon facies, dorsocervical fat pad and central obesity. Confrontation test revealed a right upper quadrant visual deficit. Afternoon cortisol was 60.02 µg/dL, and ACTH was 189 pg/ml. Brain CT without contrast showed a mixed-density sellar/suprasellar lesion compressing the prechiasmatic optic nerves and chiasm. Pituitary MRI with contrast showed a 2.9 × 2.3 × 1.6 cm peripherally enhancing, partially T2 hyperintense cystic lesion. Low-dose dexamethasone failed to suppress ACTH (107 pg/mL), and morning cortisol decreased slightly (77.22 to 55.23 µg/dL). After high-dose dexamethasone, morning cortisol was mildly elevated (27.59 µg/dL), and ACTH was suppressed (50.4 pg/ml), confirming Cushing’s disease. The patient had mild bitemporal hemianopsia and ganglion cell layer binasal thinning on ophthalmology testing. Ketoconazole was started as Levoketoconazole was not approved by insurance, and she was referred for surgery.Pituitary ACTH-dependent Cushing disease is rare, with high morbidity and mortality, peaking in the 3rd–4th decade (female:male 3:1). Clinical features include obesity, hypertension, gonadal dysfunction, and protein/bone wasting. Optic chiasm involvement is a significant risk with larger or invasive adenomas. Asymptomatic patients require high suspicion for diagnosis. Given the underlying hypercortisolism, additional glucocorticoid exposure can further suppress the hypothalamic-pituitary-adrenal (HPA) axis and lead to adverse outcomes. Screening includes a 1 mg dexamethasone suppression test, late-night salivary cortisol, and 24-hour urinary free cortisol. ACTH dependency is then assessed and will be present in Cushing disease and ectopic ACTH secretion. Brain MRI and a high-dose dexamethasone test follow. If an adenoma >6 mm is found, surgery is performed. If <6 mm, bilateral inferior petrosal sinus sampling with CRH or desmopressin stimulation is needed. Presentation: Sunday, July 13, 2025