MON-246 A Diagnostic Dilemma of Primary Versus Secondary Thyroid and Adrenal Hormone Insufficiencies: A Unique Case of Widely Metastatic Renal Cell Carcinoma After Brain Radiation

Background Identifying the etiology of hormonal insufficiency is important for correct diagnosis and for appropriate hormone supplementation. Usually multiple hormone deficiencies are driven by pituitary pathology, but here we present a case that poses a unique diagnostic and therapeutic dilemma. Clinical Case A 55 y/o lady with HTN and recently diagnosed metastatic Renal Cell Carcinoma (RCC) presented with weakness, dizziness, altered mental status, polydipsia and polyuria. Her metastases included the bilateral adrenal glands, thyroid, brain, and she had a sellar lesion displacing the pituitary as well as infundibular thickening. She had been treated with dexamethasone due to vasogenic edema, whole brain radiation, and was going to start immunotherapy (Ipilumimab&Nivolumimab). On exam she had relative hypotension and tachycardia (BP 115/58, HR 108). She was diagnosed with non-PTH mediated hypercalcemia (Ca 13.9/ 15.3 corrected for albumin 2.3, PTH 6.5, PTH-RP 69, Vitamin D-25 19.4). Her calcium normalized after fluid resuscitation and bisphosphonate treatment, but weakness and hypotension persisted. We tested thyroid and adrenal function given the location of her lesions, recent whole brain radiation, and recent steroid use. Her TSH was 0.017 (0.270 - 4.200 µIU/mL), fT4 0.84 (0.80 - 1.50 ng/dL), T3 0.59 (72.0 - 153.0 ng/dL), ACTH was 1.7 (7.2-63.3 pg/ml), cortisol 1.3 (6.0 - 18.4 ug/dL), aldosterone 3 (< or = 28 ng/dL), renin 7.87 (0.25 - 5.82 ng/mL/h), renin/aldosterone 0.4 (0.9 - 28.9). At 30 minutes after cosyntropin administration cortisol was 7.7 ug/dL, aldosterone 26 ng/dL, and at 60 minutes cortisol was 10.3 ug/dL. Hydrocortisone was initiated while tapering off dexamethasone, and levothyroxine was offered but declined. She opted to postpone further workup. Conclusion This patient presents a dilemma in identifying the primary causes of hormonal abnormalities given potential pituitary and primary thyroid and adrenal disease. The thyroid abnormalities could represent sick euthyroid physiology with lower T4 to T3 conversion or the effects of steroids which can also suppress TSH vs. hypothalamic or pituitary disease. Primary hypothyroidism from gland destruction was unlikely. The low ACTH and cortisol levels were expected since she was on dexamethasone, but low aldosterone with raised renin activity was concerning for primary adrenal insufficiency. However, after cosyntropin the suboptimal cortisol yet preserved aldosterone response supported secondary or tertiary adrenal insufficiency, and only cortisol was supplemented. Understanding her endocrine disease had implications for longer term management given that replacement may only need to be temporary and adrenal recovery might be possible. Further, the use of a 30 minute aldosterone level can be helpful in cases where multiple factors and discrepant laboratory findings may exist.