Hypopituitarism as the Initial Presentation of Pituitary Metastasis From Lung Cancer

Introduction: The annual incidence of hypopituitarism 4.2 cases of 100,000. Causes include primary tumor, metastasis, and non-tumor causes such as radiation therapy, infiltrative lesions, infection, and traumatic brain injury. Metastatic pituitary tumors constitute about 7-9% of the cases, with lung and breast cancers are the most common primary tumors. Case Presentation: 48-year-old Caucasian female patient with 30 pack-year smoking history presented to the emergency department with abdominal pain, diarrhea, fatigue, and headache. Review of systems was significant for loss of appetite, left eye visual field defect, anorexia, cold intolerance, and shortness of breath. Physical examination was remarkable for decreased visual acuity. Vital signs notable for hypotension BP 92/63. Notable labs include glucose of 53 mg/dL, TSH 0.50 [0.49 - 4.67 uIU/mL], low free T4 0.52 ng/dL, low FSH 1.3 mIU/ml, low LH <0.2 mIU/ml, low ACTH 1.4 pg/mL, low morning cortisol 2.2 ug/dL, low DHEA-SO4 3ug/dL, low IGF-1 16 ng/ml. She was diagnosed with hypopituitarism and started on IV hydrocortisone 50 mg every 6 hours with 75 mcg levothyroxine daily. MRI brain showed interval growth of pituitary lesion into the suprasellar cistern with a mass-effect on the optic chiasm measuring 2.4 X1.6X 1.9 cm with a lesion in the right cerebellar hemisphere. Vertebral MRI showed multiple metastatic lesions in cervical/thoracic/lumbar vertebral bodies. On day two of hospital stay, she developed hypertonic hyponatremia (sodium 156 mmol/L, urine osmolarity 81 mOsm/kg, plasma osmolarity 328 mOsm/kg), and she was started on desmopressin 2 mg IV for diabetes insipidus. CT chest showed spiculated left upper lobe mass consistent with primary malignancy, and biopsy showed metastatic poorly differentiated epithelial malignancy likely from lung primary. Patient was discharged on desmopressin 100 mcg nightly, hydrocortisone 20 mg morning with 10 mg evening, levothyroxine 100 mcg daily with plans for further oncologic workup. Discussion: Patient’s 2011 MRI brain showed a mildly enlarged pituitary gland. MRI brain two months before admission showed a pituitary gland diameter of 1.6 cm, while an MRI at presentation showed a pituitary gland size of 2.4 cm with a new cerebellar lesion. She reported symptoms of nausea, vomiting, and weakness for more than one year ago but biochemical testing was not performed. The fact that the patient had pituitary enlargement eight years ago likely delayed the diagnosis of pituitary metastasis. Patient age precluded lung cancer screening despite smoking history and family history of lung cancer. Conclusion: Symptomatic patients with pituitary enlargement on brain imaging may benefit from a close follow-up and biochemical testing for early diagnosis and treatment, especially if they have risk factors for malignancy.