PMON18 A Case of Hypophysitis and Hyperthyroidism Following COVID-19 Vaccine in a Patient Receiving Immune-Checkpoint Inhibitor Therapy

INTRODUCTION: Immune Checkpoint inhibitors (ICI) have been associated with multiple endocrinopathies including hypothyroidism, hyperthyroidism, primary and secondary adrenal insufficiency, hypophysitis and type 1 diabetes. Unlike other adverse effects from ICI, endocrinopathies tend to be irreversible. There are limited reports on the interaction of Covid-19 vaccine in patients receiving ICI for cancer treatment. CLINICAL CASE: A 56 year old man with history of non-small cell lung cancer presents to the hospital with nausea, decreased appetite, fatigue and 30lb unintentional weight loss. He had been started on immunotherapy with pembrolizumab 4 months prior to symptom onset (total of 4 doses). His symptoms began the day after he received his first Covid-19 vaccine injection. At an outside hospital, his initial work up showed TSH of 0.02mcU/mL, free T3 of 8.3pg/mL and free T4 of 2.8ng/dL. Thyroid stimulating immunoglobulin (TSI) was negative and he did not undergo thyroid uptake scan due to recent contrast load for CT abdomen imaging. Patient was diagnosed with hyperthyroidism and started on methimazole 10mg daily. He presented to our hospital after two weeks at his oncologist's recommendation due to worsening symptoms and concern for failure to thrive. On admission, he was noted to have hypotension and tachycardia. Given the severity of his symptoms, we obtained an AM cortisol and ACTH. His baseline cortisol was 1.2mcg/dL, so he underwent a cosyntropin stimulation test. Patient was diagnosed with adrenal insufficiency given his subnormal response on cosyntropin stimulation test. He was treated with intravenous hydrocortisone 50mg every 8 hours and methimazole 20mg daily with dramatic clinical improvement within 24 hours. ACTH obtained prior to initiation of steroids subsequently resulted as undetectably low. Further hormonal work up including LH, FSH and IGF-1 were in the normal range with mildly elevated prolactin. MRI pituitary demonstrated a 4mm hypo-attenuation in the posterior pituitary. DISCUSSION: Thyroid dysfunction is the most common adverse effect occurring in up to 30% of patients on ICI. Although less common, hypophysitis has been documented in 0.6-3.2% of patients on ICI depending on the drug. Many patients present only with adrenal insufficiency especially in those treated with pembrolizumab. Additionally, not all cases will present with radiographic findings of enhancement or inflammation of the pituitary gland. We describe a patient who developed acute symptoms of hyperthyroidism and adrenal insufficiency within 24 hours of receiving his Covid vaccine. We hypothesize that the vaccination may have triggered ICI-induced hypophysitis and hyperthyroidism in our patient. Resolution is yet to be determined. CONCLUSION: Hypopituitarism and hyperthyroidism can be life-threatening if undiagnosed and untreated. Patients on ICI should be closely monitored for adrenal insufficiency and other endocrinopathies after receiving Covid-19 vaccine. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.