Endocrine Abstracts

A 64-year-old man with a history of diffuse large B-cell lymphoma in remission presented with confusion, blurred vision and hypotension. MRI revealed an enhancing mass lesion involving the hypothalamus and optic chiasm; separate from the pituitary gland but with infiltration of infundibulum, suggesting a relapse of CNS lymphoma. Two days into chemotherapy, he developed polyuria with a 24-hour urine output of 10 litres, hypernatraemia of 150 mmol/l and serum osmolality of 300 mOsm/kg, suggesting diabetes insipidus. While receiving hydration for his chemotherapy, a water deprivation test could not be performed safely. He was empirically started on desmopressin 100 microgram TDS to which he responded with a sodium of 141 mmol/l at discharge. Seven days later, he represented with neutropenic sepsis, hypotension and hyponatraemia of 120 mmol/l. Desmopressin was initially suspended but restarted when polyuria reappeared of 11 litres/day. Repeat 9 am cortisol of 110 nmol/l with hypotension and persistent hyponatraemia prompted suspicion of adrenal insufficiency, although previous Short synacthen test was not indicative of adrenal insufficiency, he responded promptly to hydrocortisone. Subsequent pituitary profile revealed panhypopituitarism; TSH 0.02 mIU/l, FT4 9.2 pmol/l, FT3 <2 pmol/l, ACTH 7 ng/l, FSH 0.7 IU/l, LH <0.1 IU/l, IGF-1 8.9 nmol/l. He is currently well having completed chemotherapy and autologous bone marrow transplant; maintained on hormone replacement therapy with daily levothyroxine 50 microgram, hydrocortisone 10 mg,10 mg,5 mg, and desmopressin 200 microgram TDS. This case illustrates a rare but critical presentation of CNS lymphoma relapse; where hypothalamic infiltration led to severe panhypopituitarism and central diabetes insipidus. The challenge in achieving fluid balance and sodium equilibrium in a case of panhypopituitarism, in an unwell patient with multi-system involvement is highlighted. Combining aggressive chemotherapy with targeted hormone replacement can achieve favourable outcome in such complex cases.