MON-083 A Needle in a Haystack: A Case of Double Pituitary Adenomas in a Patient With Cushing’s Disease

Abstract Disclosure: D. Schwartz: None. M. Umphlett: None. R. Shrivastava: None. A.C. Levine: None. Background: Double pituitary adenomas are a rare phenomenon. Here, we present a case of GH and ACTH secreting double pituitary adenomas presenting clinically as Cushing’s Disease. Clinical Case: Our patient is a 26 year old male with a recent diagnosis of type 2 diabetes and hypertension who presented to endocrine clinic for evaluation of an elevated serum cortisol. He showed typical symptoms of Cushing’s disease including violaceous striae, proximal muscle weakness, supraclavicular fullness and easy bruising. Initial lab tests showed a random serum cortisol of 25.1mcg/dL (6.7-22.6mcg/dL), ACTH of 141.4pg/mL (7.2-63pg/mL), midnight salivary cortisols of 1.61ug/dL, 1.90ug/dL. 1.270ug/dL (<0.010-0.090ug/dL), and urine free cortisol of 1997ug/24 hours (5-64ug/24 hours). 1mg dexamethasone suppression test was attempted but dexamethasone level on measurement the following morning was undetectable (< 30ng/dL). MRI pituitary with and without IV contrast revealed a pituitary macroadenoma 1.8 x 2.4 x 1.9cm compressing the optic chiasm and abutting the cavernous sinus. The patient was referred to neurosurgery for transsphenoidal resection (TSA). A pre-operative serum hormone panel revealed an elevated IGF-1 of 582ng/mL (101-307ng/mL) and GH of 12.2ng/mL (0.0-10.0ng/mL). Confirmatory testing was not done prior to OR. The patient denied increasing hand or ring size. Post procedure MRI showed residual tumor for which the patient underwent repeat TSA five days later. Pathology reports from the first TSA revealed two synchronous pituitary adenomas with distinct tumor lineages. The majority of the tumor cells were positive for GH and PIT1 consistent with somatotroph lineage and a smaller population of tumor cells were positive for ACTH and TPIT consistent with corticotroph lineage. The pathology report from the patient's repeat TSA was positive for GH and PIT1 consistent with somatotroph lineage. Conclusion: This case highlights a rare finding in a young patient that points to an early developmental defect in a common pituitary progenitor cell. The majority of pituitary tumor cells in this case were somatotroph in origin but the patient's clinical presentation corresponded to the smaller population of ACTH tumor cells. As a result, this case underscores the importance of a full hormonal workup prior to surgery for pituitary tumors so that hormonal markers can be properly followed postop and appropriate treatments can be utilized postoperatively as needed. Presentation: Monday, July 14, 2025