SAT-184 Silent Pheochromocytoma Complicated by Adrenal Insufficiency After Unilateral Adrenalectomy

Abstract

Background: Adrenal insufficiency (AI) following unilateral adrenalectomy for pheochromocytoma (PCC) is an exceedingly rare occurrence described previously in 1 study in only 4 out of 13 patients with unilateral PCC. We discuss an unusual case of a patient with incidentally discovered PCC who underwent unilateral adrenalectomy and subsequently developed AI. Clinical Case: 61-year-old male in overall good health taking no medications presented with left flank and groin pain after a handlebar injury in a bicycle crash. CT angiogram Abdomen & Pelvis revealed a complex enhancing left adrenal mass with internal necrosis measuring 13 x 12 cm. He denied history of headaches, diaphoresis, chest pain or hypertensive crisis. He did endorse palpitations which had resolved with reduced caffeine intake. Labs showed plasma free metanephrine 3,295 pg/mL (ref range <57) and normetanephrine 68,472 pg/mL (<148), 24hr urine metanephrine 192,677 ug (52-341), 24hr urine normetanephrine 171,880 ug (88-444), 24hr urine vanillylmandelic acid (VMA) 182 mg (1.8-6.7), serum aldosterone 8.1 ng/dL (<39.2), serum free cortisol 0.47 ug/dL (0.07-0.93), 24hr urine cortisol 41.6 ug (<60), DHEA sulfate 37 ug/dL (42-290). He was started on phenoxybenzamine and underwent left adrenalectomy. Of note patient remained only minimally hypertensive with tumor manipulation intraoperatively. Pathology was consistent with PCC with no evidence of regional or distant metastases. Postop-labs showed plasma free metanephrine <25 pg/mL and normetanephrine 122 pg/mL. Calcitonin and parathyroid hormone levels were normal. Patient was evaluated in endocrinology clinic 4 weeks after surgery for complaint of severe fatigue, weight loss, anorexia and myalgias. Adrenocorticotropic hormone (ACTH) level was 31 pg/mL (7.2-63) with AM cortisol of 2.1 ug/dL (5-23) which increased to 7.4 ug/dL 1 hour after Cosyntoprin 250 mcg stimulation. He was started on prednisone 10 mg once daily with significant improvement in his symptoms. Conclusion: PCCs typically manifest as sustained or paroxysmal hypertension, episodic headaches, palpitations or diaphoresis. Our patient was found to have a PCC with strikingly elevated levels of catecholamines without typical signs and symptoms of PCC. To the best of our knowledge this is the 5th reported case where a patient developed AI after unilateral adrenalectomy for PCC. There are case reports describing PCCs which secrete both catecholamines and ACTH. However, our patient lacked clinical or biochemical evidence of hypercortisolism preoperatively and his tumor cells in path sample stained negative for ACTH. Other possible pathophysiologic mechanisms include ectopic corticotropin releasing factor production leading to subclinical Cushing syndrome (SCS). Clinicians should have a high suspicion for SCS in the setting of PCC to promptly diagnose and treat AI after unilateral adrenalectomy.