PT - JOURNAL ARTICLE AU - Hiroyuki Koyama AU - Rei Hattori AU - Hiroyuki Sagawa AU - Tomohiro Tanaka TI - Progressive loss of the thyroid tissue integrity visualised by serial CT scans AID - 10.1136/bcr-2022-251857 DP - 2022 Sep 01 TA - BMJ Case Reports PG - e251857 VI - 15 IP - 9 4099 - http://casereports.bmj.com/content/15/9/e251857.short 4100 - http://casereports.bmj.com/content/15/9/e251857.full SO - BMJ Case Reports2022 Sep 01; 15 AB - A man in his 70s developed thyrotoxicosis due to painless thyroiditis after starting nivolumab, which was subsequently followed by severe hypothyroidism. We diagnosed him as chronic thyroiditis, initiated levothyroxine supplementation and treated appropriately. Retrospective CT images of the thyroid gland during the clinical course revealed that the CT attenuation value was high at first but gradually decreased. The high-density signal of the normal thyroid tissues reflects its function of concentrating inorganic iodine, and the progressive decrease of the CT density in the present case can be viewed as a reflection of the thyroid destruction and progressive loss of iodine during the clinical course of the development of chronic thyroiditis. Considering the high incidence rate of functional thyroid disease in patients treated with immune checkpoint inhibitors, CT density of the thyroid gland needs to be paid attention to as the first sign of thyroiditis in this patient population.