MON-090 Crooke Cell Adenoma Presenting with Refractory Hypokalemia and Uncontrolled Hypertension

Abstract Disclosure: H. Yeh: None. H. Nge: None. T. Hashmi: None. K.R. Askari: None. Introduction: Crooke cell adenomas (CCAs) are a rare subtype of corticotroph adenomas, usually presenting as invasive macroadenomas and could be secretory or clinically silent. Refractory hypokalemia as a presentation for Cushing syndrome (CS) is more commonly seen in ectopic ACTH secretion (EAS). We report a case of CCA presenting with refractory hypokalemia, uncontrolled hypertension (HTN), diabetes mellitus (DM) and rapid weight gain. Case Description: A 39-year-old female with a history of hypothyroidism who presented to the clinic with newly diagnosed DM, weight gain of 100 Ibs in 6 months, uncontrolled HTN and refractory hypokalemia requiring frequent hospitalizations and continuous supplementation. Physical exam showed elevated blood pressure of 170/90, round face, dorsocervical fat pads, central obesity and pitting edema. Her BMI is 50.28 kg/m2. Her blood tests showed severe hypokalemia 2.5 mmol/L (3.5-5.2 mmol/L), low aldosterone <1 ng/dL (0.0-30 ng/dL) and a HbA1c of 9.8% (<5.7%). Hypercortisolism work up showed elevated 24-hour urinary cortisol 1107 ug/24 hr (6-42 ug/24 hr), elevated late-night salivary cortisol 3.170 and 4.310 ug/dL (<0.1 ug/dL), elevated baseline ACTH 309 pg/mL (6-50 pg/mL) and cortisol 112 ug/dL (5.2-22 ug/dL). Cortisol was not suppressed after 8 mg of dexamethasone. MRI of the brain revealed a 5 mm pituitary microadenoma. CT chest/abdomen/pelvis did not show any lesions. Inferior petrosal sinus sampling (IPSS) confirmed a central to peripheral ratio of 7.5. The pituitary microadenoma was successfully resected with no residual lesions. Histopathology confirmed a corticotroph adenoma exhibiting features of CCA. Improvements in ACTH 13 pg/mL (6-50 pg/mL), cortisol 4.5 ug/dL (5.2-22 ug/dL), A1c, potassium, and blood pressure were seen in the immediate post-operative period and up to 1 year of follow up. Discussion: Our patient presented with rapidly progressing CS features including newly diagnosed DM, refractory hypokalemia and significant weight gain in short time period. The aggressive hypercortisolism features and the lack of suppression with 8 mg of dexamethasone raised the suspicion of EAS instead of a corticotroph microadenoma. Refractory hypokalemia is thought to be due to saturation of the cortisol-inactivating enzyme 11B hydroxysteroid dehydrogenase (11B HSD2) by the excess cortisol. ACTH was thought to have inhibitory effect on the same enzyme. IPSS remains the standard of care confirming pituitary ACTH secretion and it was used to confirm the pituitary source of ACTH in our case. CCA was confirmed by pathology. In recent study, CCAs have shown lower biochemical cure and higher recurrence rates. Our case has shown complete structural and biochemical remission up to 1 year after surgery. Presentation: Monday, July 14, 2025