Late manifestation of Immunotherapy induced hypothyroidism with high antibody titers

Abstract

Immune checkpoint inhibitors are widely used in the treatment of cancers. They are known to cause multisystem immune related adverse effects, including endocrinopathies. Primary thyroid dysfunction has been documented as an adverse effect of immunotherapy. We report a case of primary hypothyroidism detected in a patient after treatment with anti -PD-L1 agent, Atezolizumab. The patient presented with altered mental status 6 months after the initiation of immunotherapy. TSH was measured as part of the workup for encephalopathy, revealing TSH >20 with undetectable free T3, free T4. Anti TPO antibodies were elevated to >7500 IU/ml with anti thyroglobulin antibodies elevated to about 50U/ml. Thyroid ultrasound showed a diffusely heterogeneous gland with no other abnormalities. Patient was detected to have metastatic disease to the brain and spinal cord likely causing her change in mental status and was treated with steroids and radiation after which she improved. She was started on Levothyroxine 50mcg daily and discharged on the same dose. This case illustrates the need for measurement of TSH in all patients prior to the initiation of immunotherapy given the possibility of development of primary thyroid dysfunction mediated by inflammatory thyroiditis in these settings.