Crooke Cell Adenoma Presenting With Refractory Hypokalemia and Uncontrolled Hypertension

Crooke cell adenomas (CCAs) are a rare subtype of pituitary corticotroph adenomas with a prevalence of less than 1% of pituitary adenomas. CCAs have variable clinical manifestations and can present as functional adenomas secreting adrenocorticotropic hormone (ACTH), resulting in hypercortisolism, as well as silent invasive macroadenomas. CCAs also exhibit a higher risk for recurrence, less biochemical remission, and normalization of pituitary function after tumor resection compared to other secretory corticotroph adenomas. Refractory hypokalemia and hypertension as manifestations of hypercortisolism are more commonly seen in patients with ectopic ACTH syndrome than pituitary-dependent Cushing syndrome. We present a 39-year-old female who presented with refractory hypokalemia, hypertension, lower extremities edema, and newly diagnosed diabetes mellitus. Evaluation revealed an ACTH-dependent hypercortisolemia from a 5- × 3-mm pituitary microadenoma. She underwent transsphenoidal resection of the microadenoma with resolution of symptoms immediately after surgery and up to 20 months of follow-up. The histopathology of the microadenoma revealed more than 50% of corticotrophs demonstrated Crooke hyaline change compatible with Crooke cell adenoma. To our knowledge, only one case of CCA presenting with a microadenoma and similar clinical manifestations has been reported to date. Our case highlights an atypical and infrequent clinical presentation of CCA.