MON-418 Symptomatic Pituitary Metastasis: Two Case Reports with Contrasting Clinical Presentations

Introduction: Pituitary metastases (PM) are a rare occurrence with a poor prognosis. The most common cancers to metastasize to the pituitary are breast and lung. Most PMs are asymptomatic, but when symptoms occur the most commonly reported presentation is central DI. Clinical Cases: Case 1. An 86 year old male presented to the hospital with progressive weakness, fatigue and low appetite. He had a history of widely metastatic papillary thyroid cancer treated with thyroidectomy, repeated doses of RAI and repeated neck dissections. Most recent TG was 27,405 ng/mL (nl 2.8-40.9). An 8AM cortisol was checked and found to be low at 0.8 mcg/dL (nl 10-20). Further hormonal workup showed low ACTH, TSH <0.01uIU/mL (nl 0.3-5), FT4 1.43 ng/dL (nl 0.76-1.46) while on LT4, prolactin 38.94ng/mL (nl 2.1-17.7), low LH and FSH consistent with panhypopituitarism. Pituitary MRI showed an infiltrative process enlarging the pituitary gland, with extension into the stalk and hypothalamus concerning for metastatic disease. He was started on steroid replacement. He underwent systemic tyrosine kinase inhibitor therapy as well as pituitary radiation, but unfortunately, he died 7 months after presenting with central AI. Case 2. A 56 year old male was referred to endocrine clinic for polydipsia, polyuria and nocturia. Initial labs showed normal glucose, Na 145 mmol/L (nl 136-145), serum Osm 299mOsm/kg (nl 276-305), and urine Osm 92mOsm/kg (nl 500-800). Water deprivation test confirmed central DI. Further labs showed intact anterior pituitary function. Pituitary MRI showed an infiltrative process in the pituitary gland, affecting stalk and hypothalamus concerning for metastatic disease. Imaging was obtained and showed masses in the lung, kidney, spine, and mediastinal lymph nodes. The patient had a remote history of colon cancer and underwent biopsy of the lymph and renal masses, both showing metastatic colorectal cancer. He was started on DDAVP and symptoms improved. Three weeks later he presented with severe fatigue, dizziness, and hot flashes. Workup showed panhypopituitarism. Repeat MRI showed interval growth of the pituitary lesion. He underwent pituitary radiation and chemotherapy. He did not tolerate the side effects of systemic therapy and enrolled in hospice care. Conclusions: The most commonly reported symptomatic presentation of PM is central DI, however the reported incidence of anterior pituitary dysfunction is rising and clinicians should be aware. Pituitary metastases should remain on the differential in any case of anterior or posterior pituitary dysfunction, particularly in patients with any history of malignancy.