MON-096 - Rapid Onset Panhypopituitarism with Pituitary Mass: An Unusual Initial Presentation of Lung Adenocarcinoma

Background: Metastatic spread to the pituitary is exceedingly rare, and accounts for less than 1% of pituitary masses seen in clinical practice. Distinguishing benign pituitary masses from malignant tumors based on radiologic appearance alone is challenging. Furthermore, the presentation of these masses is often nonspecific but may also present with manifestations of panhypopituitarism.

Clinical

Case: A 64-year-old woman with history of smoking and hypertension initially presented due to headaches, polyuria and polydipsia. Workup was done including an MRI which revealed a hypoenhancing heterogenous pituitary mass, measuring 1.4 cm in the greatest dimension. Patient was also diagnosed with central diabetes insipidus and was seen by outpatient endocrinology. Further workup initially did not show evidence of anterior pituitary dysfunction. Due to this presentation, the initial concern was for hypophysitis. Patient then developed progressive symptoms including nausea, vomiting and hypoglycemia. She was admitted to the hospital and was evaluated by our inpatient endocrinology team. She was found to have a low random cortisol, low ACTH, low TSH and low free T4 levels as well. She was started on treatment for secondary adrenal insufficiency and central hypothyroidism. Repeat MRI was done of the brain which showed an increase in size of the pituitary mass to 2.6 cm in greatest dimension, now with mass effect on the optic chiasm. Shortly thereafter, she developed significant shortness of breath. During further investigation of her symptoms, a CT of the chest, abdomen and pelvis was done which showed a left lung mass with numerous hepatic metastases. A biopsy of the lung mass established a diagnosis of invasive lung adenocarcinoma. Given the rapid enlargement of the pituitary mass and progressive loss of pituitary function, it was thought to be more compatible with a pituitary metastasis instead of a macroadenoma or hypophysitis. A PET scan showed that the mass was FDG avid, consistent with malignancy. The patient continued to receive treatment for panhypopituitarism and received stereotactic radiosurgery for management of pituitary metastasis. She is currently undergoing palliative chemoimmunotherapy for her metastatic lung adenocarcinoma.

Conclusion: Rapidly progressive loss of pituitary function in the setting of a pituitary mass is atypical. This usually prompts urgent treatment and timely initiation of hormone replacement under the care of an endocrinologist. Having a high index of suspicion to diagnose pituitary metastasis and differentiate it from a benign mass or hypophysitis is crucial when evaluating patients with symptoms of panhypopituitarism.

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