SAT338 Desmopressin Stimulation Test As A Valuable Tool In Establishing Cushing Syndrome Etiology

Disclosure: A. Aponte Velez: None. A. Figueroa Cruz: None. M.M. Mangual Garcia: None. Hypercortisolism diagnosis may be challenging based on its nonspecific signs and symptoms. The challenge continues when establishing the etiology of Cushing’s syndrome (CS). Based on ACTH levels, which are episodic and can provide equivocal results, further testing is guided to determine pituitary, adrenal or ectopic etiology. Various approaches have been proposed to assess ACTH dependent CS with negative pituitary imaging leading to recommend invasive procedures such as IPSS. This procedure is not widely available and can lead to conflicting results which does not always assist in selecting appropriate therapy. Data on the use of desmopressin stimulation test has suggested a limited role in distinguishing etiology of CS. It is mostly recommended to distinguish Cushing Disease from ectopic secretion, but it can provide further information. A 30 year old female with medical history of arterial hypertension, prediabetes and hypothyroidism was referred due to inconclusive etiology of hypercortisolism. Patient reported a 1.5 year onset of worsening fatigue, lower extremity edema, hair loss, violaceous abdominal striae and easy bruising. Physical exam remarkable for an overweight patient, with elevated blood pressure, moon facies, abdominal violaceous striae >1cm, ecchymosis, dorsocervical fat pad, increased abdominal adiposity and proximal muscle weakness. Hypercortisolism was confirmed biochemically with elevated late night salivary cortisol test, urinary free cortisol and 1mg dexamethasone suppression test. ACTH was found inappropriately normal (19-33 pg/mL) suggestive of ACTH dependent CS. ACTH levels raised suspicion for pituitary etiology, for which brain MRI was performed twice and was found negative for pituitary adenoma. Further laboratories revealed low DHEA-S (7mcg/dL) that on the contrary suggested adrenal etiology. Based on this scenario, patient underwent desmopressin stimulation test without an increase in ACTH or cortisol levels suggestive of adrenal source of hypercortisolism. Adrenal CT scan with and without contrast demonstrated right adrenal mass with defined borders, approximately 2cm in diameter, and contrast enhancement with 65% washout. Patient underwent successful right unilateral adrenalectomy. She was started on glucocorticoid replacement therapy with improvement in clinical symptoms, weight loss and control of hypertension and prediabetes. Postoperative evaluation revealed suppressed cortisol levels, and no electrolyte imbalances. This case describes the challenge of determining the etiology of CS using a combination of endocrine tests and imaging. Owing to increased mortality of untreated CS, it is essential for adequate identification of cause for curative therapy. We promote a non-invasive approach using the desmopressin stimulation test for successful identification in patients with discordant serum and imaging results. Presentation: Saturday, June 17, 2023