MON-416 A Novel Approach to Ectopic Adrenal Tissue in Nelson's Syndrome

Introduction: Cushing’s disease (CD), a disorder of elevated cortisol secondary to an ACTH-secreting pituitary tumor, is often first treated with transphenoidal resection (TSR). However, recurrences of CD can occur after TSR, and other treatment modalities such as radiotherapy and bilateral adrenalectomy (BLA) must often be utilized. Here we present an interesting case of recurrent CD and the treatment challenges faced. Clinical Case: A 24-year-old Caucasian female was diagnosed with CD and treated with TSR. Post-operatively, she was pan-hypopit with diabetes insipidus and placed on full replacement therapy. Six years after surgery, she developed the same Cushingoid symptoms that had been present prior to her surgery. In spite of holding her hydrocortisone for four months, she had an elevated serum cortisol level after a 1mg dexamethasone suppression test of 12.4 mcg/dL (<1.8mcg/dL), and elevated urinary free cortisol (UFC) studies ranging from 58-104.8 mcg/24h (4.0-50.0 mcg/24h). ACTH was 32 pg/mL (6-50 pg/mL). She underwent a second TSR at the age of 31 years. She was restarted on hydrocortisone which was discontinued after two months. Five months after surgery, she had an elevated 24-hour UFC of 105.6 mcg/24hr and ACTH of 25 pg/mL. She then underwent laparoscopic BLA one year after her second TSR. Adrenal pathology showed bilateral nodular adrenal hyperplasia. Steroid replacement therapy was resumed. Three years after BLA, she again developed CD symptoms despite weaning her hydrocortisone. An evening salivary cortisol was elevated at 1.48 mcg/dL (≤0.09 mcg/dL) and serum ACTH was 386 pg/mL (0-45 pg/mL). A CT abdomen without contrast showed a surgically absent right adrenal gland and a 9mm soft tissue density nodule in the left adrenal fossa suggestive of residual/ectopic adrenal tissue. An MRI brain with and without contrast showed a small focus of enhancing tissue in the right cavernous sinus measuring 7mm x 6mm x 8mm concerning for residual tumor. Findings were consistent with recurrent CD secondary to Nelson’s syndrome stimulating remnant adrenal tissue. She underwent a third TSR followed by pituitary radiosurgery (20 Gy) and stereotactic radiotherapy to the adrenal tissue (39 Gy in 3 fractions) six months post-op. Her serum morning cortisol dropped rapidly from 107.4 mcg/dL (5.0-23.0 mcg/dL) before radiation to 1.6 mcg/dL after. Cortisol replacement therapy was resumed, and the patient has remained cured of CD for over two years. Conclusion: In patients with Nelson’s syndrome, any remnant or ectopic adrenal tissue can produce cortisol. This is the first report of adrenal ablation by radiosurgery in this setting, leading to cure of CD.