6630 Crooke Cell Pituitary Adenoma Without a Cushingoid Appearance

Abstract Disclosure: J. Hodge: None. S. Idriss: None. I. Jamal: None. R. Panta: None. Background: Crooke cell pituitary adenomas are corticotroph adenomas with Crooke’s cell changes, which are cytoplasmic accumulation of cytokeratin filaments in response to glucocorticoid excess. They are aggressive, invasive tumors, typically macroadenomas, with a high rate of Cushing’s disease and post -treatment (surgery and/or radiotherapy) recurrence. We present a case of Crooke cell pituitary adenoma without a Cushingoid appearance. Clinical Case: A 66-year-old Hispanic male with a 16-year history type II diabetes mellitus with retinopathy, presented with a pituitary macroadenoma at age 60. This was found incidentally when he had a brain CT for evaluation of vertigo. Subsequent brain MRI demonstrated a large 2.4 x 2.0 x 1.7 cm pituitary macroadenoma with extension into the suprasellar cistern and the left cavernous sinus. He was asymptomatic, without Cushingoid features. Hormonal evaluation revealed central hypogonadism and hypothyroidism, mildly elevated prolactin of 39.3 (4-15.2 ng/mL) and morning cortisol level of 12.7 (6-18.4 ug/dL). A 24-hour urine cortisol was normal. He was started on testosterone and thyroid hormone replacement therapy. His diabetes mellitus became progressively difficult to control with a peak HbA1C of 10.1%, about 7 years prior the macroadenoma finding. His HbA1C remained persistently elevated in the 8.1-9.5% range despite being on 6 anti-hyperglycemic agents, including basal insulin. A morning ACTH level 4 years after the initial visit, was 115 (6-50 pg/mL) with a cortisol level of 13.7 (6-18.4 ug/dL). Repeat morning ACTH and cortisol levels 7 months later were very similar. 5 years after the macroadenoma finding, he was noted to have worsening glaucoma, which was believed to be due to optic nerve compression. Therefore, he underwent endoscopic transphenoidal resection for tumor debulking. Pathology supported the diagnosis of Crooke cell corticotroph pituitary adenoma. Repeat brain MRI 3-months post-surgery demonstrated residual tumor, but normal optic chiasm and optic tracts. He had an abnormal dexamethasone suppression test prior to surgery (cortisol 6.4 ug/dL) and continued to do so post-operatively (cortisol 3.7 ug/dL with persistently elevated ACTH). Just prior to his surgery, testosterone replacement therapy was held. Total testosterone level after surgery was normal 309.6 (280-800 ng/dL) and free testosterone 7 (5-21 ng/dL); he remained off replacement therapy. Conclusion: Crooke cell pituitary adenomas are rare with limited data on prognosis and guidance for clinical management. Some patients may have subtle features of hypercortisolism, such as difficult to control diabetes mellitus, without an overt Cushingoid appearance. Presentation: 6/1/2024