12530 Inferior Petrosal Sinus Sampling In Cushing’s Disease

Abstract Disclosure: A. Gondhi: None. S. Antharam: None. I. Moledina: None. Inferior Petrosal Sinus Sampling in Cushing’s Disease Introduction: Cushing's disease (CD) is the most common cause of endogenous Cushing syndrome( CS) caused by ACTH secreting pituitary tumor. MRI is typically used for imaging, but standard MRI may only detect 50% of microadenomas. In these cases, inferior petrosal sinus sampling (IPSS) is the gold standard in detecting pituitary source of ACTH. Case presentation:A 53-year-old man presented with signs and symptoms of CS: fatigue, weight gain, decreased libido, mood swings, new onset prediabetes. Physical examination revealed cushingoid appearance with facial flushing, easy bruising, abdominal purple striae. Initial work up revealed ACTH dependent CS: elevated late night Salivary cortisol 0.39 mcg/dL (<0.09 mcg/dL), 24hr urine free cortisol 192 mcg/24 hour (4 – 50 mcg/24 hour)Non suppressed cortisol 8.1 mcg/dL (<1.8 mcg/dL) after 1mg dexamethasone suppression test8 AM ACTH 56 pg/ml (7.2 – 63 pg/ml), DHEAS 491 mcg/dL (38-318 mcg/dL)Pituitary hormonal work up: normal Prolactin 7.8 ng/mL (2.6-13.1 ng/mL)Low TSH 0.29 ng/ml (0.45-5.3 ng/ml) with normal Free T4 0.76 ng/dl (0.58-1.6 ng/dl)Low Total Testosterone 150 ng/dl (175-781 ng/dl), Low FSH<0.7 mInt units/ml(1.27-19.26 mInt units/ml), Low LH 1 mInt units/ml (1.24- 8.62 mInt units/ml), Normal IGF 180 ng/mL (65-222 ng/mL), A1C 6% (Prediabetes – 5.7-6.4) MRI Brain showed normal pituitary gland. IPSS was performed with DDAVP: +2, +5, +10, +15: Right/ periphery ratio- 31.8, 10.75, 7.6, 5.3. left/periphery ratio- 26.6, 18.8, 8.3, 7.5. All the ratios >=3, which showed clear central to peripheral gradient. and no left or right difference consistent with Cushing's disease. Subsequently, a transsphenoidal pituitary gland resection was performed. Suspicious tissue was excised from both sides during the surgery, showing positive ACTH immunostaining, consistent with pituitary microadenoma. Post-operative labs showed significant improvement with normalization of Cortisol 3.2 mcg/dl, ACTH 45 pg/ml, TSH 3.14 ng/ml, FT4 0.61 ng/dl, FSH 1.7 mInt units/ml, LH 2.4 mInt units/ml, Prolactin 7.1 ng/ml, A1C 5.4 %He was discharged on physiological dose of Hydrocortisone and passed cortisol stimulation test (3.4 mcg/dl ---> 18.1 mcg/dl) Conclusion: Distinguishing between CD and ectopic ACTH secretion is crucial due to the differing treatment options. The most accurate method for differentiation is IPSS, which boasts high sensitivity and specificity compared to other analyses. Despite its invasiveness, IPSS is associated with rare adverse events, making it a valuable tool in clinical practice. Presentation: 6/3/2024