THU011 Cushing’s Disease Diagnosis Challenge With Standard Pituitary MRI: A Clinical Case Report

Disclosure: E. Kasiri: None. N. Shah: None. Introduction: Cushing’s disease (CD); the most common cause of endogenous Cushing’s syndrome (CS) is mainly caused by an adrenocorticotropin (ACTH)-secreting pituitary adenomas. Although MRI remains the preferred imaging to detect these adenomas, still about 50% of microadenomas may be missed using standard 1.5-Tesla MRI and on the other hand higher resolution MRI with 3T magnets is not widely used. Here we present a case of Cushing’s disease with equivocal 1.5T MRI which made a next step of management rather challenging. Case presentation: A 57-year-old female with history of hypertension, type 2 diabetes mellitus and obesity (BMI: 34.41 kg/m(2)) presented to our endocrinology clinic to establish care. Her main complaint was difficulty losing weight. She denied taking any steroids or oral contraceptive pill. Vitals showed BP: 124/85 mm Hg, HR: 100 bpm and T: 98.3 °F. Physical exam was significant for moon facies, buffalo hump and abdominal obesity. She was screened for Cushing syndrome with 1mg overnight low dose dexamethasone test which resulted in abnormal cortisol response with a level of 2.1mcg/dl (<1.8 mcg/dl). A 24hr urine free cortisol: 7.3 mcg/dl (<45 mcg/dl) and two late night salivary cortisol measurements resulted in 0.388 and 0.229 mcg/dl (> 3 times upper limit of normal). Other labs showed elevated baseline ACTH :67.4 pg/ ml (7.2 - 63.3 pg/mL), cortisol :19.4 mcg/dl (4.5-23 mcg/dl) and normal DHEAS:1864.1ng/ml (650-3400 ng/mL). We decided to distinguish ectopic vs pituitary source of hypercortisolism by an 8 mg (high dose) dexamethasone suppression test which showed suppressed ACTH <1.5 pg/ml, Cortisol :2.6 mcg/dl (>50% suppression from baseline) suggesting pituitary origin. The standard pituitary 1.5T MRI with and without contrast as next step resulted in questionable microadenoma in the right aspect of pituitary gland and was equivocal. Within the multidisciplinary team decision was made to perform 3T pituitary MRI rather than invasive inferior petrosal sinus sampling (IPSS) which confirmed the pituitary microadenoma of 8.1 mm size with no mass effect and patient is scheduled for transsphenoidal pituitary surgery without needing further testing. Discussion: 3T MRI, with higher magnetic field than 1.5T allows to improve image quality and help with tumor detection in Cushing’s disease. It reportedly has higher sensitivity (80%) and specificity (∼100%) compared to 1.5T MRI which has overall sensitivity and specificity of 71% and 87% respectively. However, it is not the first to order by the clinicians when evaluating the ACTH secreting pituitary adenoma. In the case of equivocal 1.5 T MRI usually the next step is IPSS which is invasive. With availability of Corticotropin Releasing Hormone in the USA being difficult, limited studies of using DDAVP and limitations in finding tertiary centers to perform IPSS, a 3T MRI would be more feasible as a next step to identify a pituitary adenoma. Presentation: Thursday, June 15, 2023