SAT-107 Delayed Cushing’s Syndrome from Silent Corticotroph Adenoma

Abstract Disclosure: N. Prasad: None. A. Arida: None. J. Shakil: None. R. Al-ward: None. Central etiologies of Cushing's syndrome are commonly attributed to functional corticotroph adenomas. However, rarely, silent corticotroph adenomas can progress and evolve into functional tumors, presenting as Cushing's syndrome late in the disease course. To our knowledge, only a few cases with such progression have been reported in the literature. Here, we present a case of late-onset Cushing's syndrome due to a silent corticotroph adenoma, emphasizing the aggressive nature of these tumors and the evolution of their clinical presentation. A 40 year old male with no past medical history initially presents with fatigue, diffuse weakness and vision loss. Work up revealed left vagal schwannoma with incidental 3 cm pituitary macroadenoma and normal pituitary hormone panel. Patient underwent subtotal resection of the pituitary tumor with resolution of vision loss. However, four months later, he presented to our institution due to persistent disease. A second transsphenoidal surgery was attempted but proved challenging and was thus converted to a right-sided frontotemporal craniotomy. Pathology revealed weakly positive staining for ACTH and KI67 of 1%. Patient refused further management and was lost to follow up. Patient then presented 7 years later with vision loss, weight gain, new onset hypertension, new onset pre-diabetes and muscle loss. Patient’s physical exam notable only for hyperpigmentation. Biochemical work up showed A1c of 5.9%, DHEA 651 g/dL, ACTH 356 pg/mL, AM Cortisol of 56g/dL. He failed dexamethasone suppression test on two occasions and had high 24 urine cortisol indicative of Cushing’s syndrome. MRI notable for large 3.7 cm macroadenoma with suprasellar extension. Patient underwent subtotal resection. Pathology notable for positive ACTH staining and elevated Ki 67 activity with variable expressivity, with some areas with 3-4% activity and other with 12-15% activity. Postoperative residual tumor was subsequently treated with radiation therapy. Silent corticotroph adenomas comprise almost 20% of corticotroph adenomas and typically present with symptoms of mass effect and are incidentally found on imaging. These tumors are classified as high risk due to high rate of recurrence. Uniquely, these tumors typically do not present with Cushing’s syndrome and very rarely can manifest much later in disease course, as with this patient. The mechanism of “silent” presentation of corticotrophs and conversion to functional corticortophs is unknown. These adenomas typically present with mass effect and are typically diagnosed retrospectively. Silent corticotroph adenomas are an aggressive subsect of corticotroph adenomas that do not initially present with Cushing’s syndrome that is otherwise seen in most corticotrph adenomas. Early diagnosis via pathology and monitoring of these patients for Cushing’s is imperative in appropriately treating these patients. Presentation: Saturday, July 12, 2025