SAT-097 - Pituitary Involvement in Primary Central Nervous System Lymphoma: A Rare Presentation in A Young Patient

Primary central nervous system lymphoma (PCNSL) is a rare, aggressive non-Hodgkin lymphoma that affects the brain, eyes, and cerebrospinal fluid, without systemic manifestations. Hypothalamic-pituitary axis (HPA) involvement is extremely rare, accounting for 0.5% of pituitary metastases and associated with poorer outcomes. We present a case of CNS lymphoma with central adrenal insufficiency and hypothyroidism.

A 25-year-old female presented with weight loss, nausea, oligomenorrhea, and abdominal pain followed by confusion, diplopia, and galactorrhea. Workup revealed a sodium of 118 mM, morning cortisol of 1.0 mcg/dL, ACTH 9 pg/mL (6-50), cortisol 30 minutes after cosyntropin of 13.3 mcg/dL, TSH of 0.10 uIU/L and FT4 1.4 ng/dL which declined to 0.67 ng/dL over two weeks, prolactin 133 ng/mL, with undetectable LH, FS, and, estradiol, IGF-1 of 84 ng/mL (Z -1.6). An MRI of the brain showed multiple, nodular, hypercellular, and enhancing lesions with surrounding T2 signal involving the anterior wall of the third ventricle, the tuber cinereum, and the pituitary stalk with associated splaying of the hypothalamic leaflets and prechiasmatic optic nerves. There was no evident diabetes insipidus. She was started on hydrocortisone and levothyroxine. A burr hole biopsy showed B-cell non-Hodgkin lymphoma. She underwent chemotherapy with methotrexate and high dose steroids but had evidence of disease progression and was switched to cytarabine and etoposide. She was hospitalized for an autologous hematologic stem cell transplant (HSCT) eleven months after initial presentation, with her hospital course complicated by the development of mucositis resulting in impairment of PO intake. She was then diagnosed with diabetes insipidus (DI), confirmed by an increase of 50% in urine osmolality after receiving IV DDAVP, as well as an undetectable co-peptin level. She was discharged on DDAVP and had been placed on cabergoline, yet her hypothalamic-pituitary-gonadal axis remained suppressed, suggesting central hypogonadism, and she later started estradiol and progestin.

HPA involvement in PCNSL is extremely rare, and the most common pituitary deficiencies seen are central hypothyroidism (67% of cases), followed by adrenal insufficiency. Posterior pituitary involvement is more prevalent, with DI being the presenting manifestation. Our patient presented with hyponatremia, adrenal insufficiency, central hypothyroidism, and central hypogonadism, complicated by hyperprolactinemia, but was later found to have central DI likely reflecting progression of disease. Full endocrinological recovery is seen in only 12% of cases, and persistent endocrine dysfunction has been seen in refractory or progressive lymphoma. The course and findings suggest the need for early and ongoing endocrinologic care in PCNSL to improve quality of life and cancer surveillance.

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