Effects of Immune Checkpoint Inhibitor-induced Thyroid Dysfunction on Cardiac Troponin Levels.

Immune checkpoint inhibitor (ICI)-induced thyroid dysfunction is the most frequent endocrine immune-related adverse event (irAE). Thyroid hormones have various effects on the cardiovascular system; however, the impact of thyroid irAEs on the development of cardiovascular diseases is not fully understood. This retrospective study included 94 patients who received ICIs and had thyroid function and troponin T levels, markers of cardiac damage, measured at the National Cancer Center Hospital East between January 2017 and July 2022. Of the 94 patients, 36 (38%) showed elevated troponin levels after ICI treatment during the follow-up period. The median observation period was 249 days (interquartile range, 124-502 d). Thyroid irAEs [hypothyroidism (n=13) and hyperthyroidism (n=3)] associations were found in 16 (44%) of these 36 patients. None of the patients developed overt cardiovascular disease or died of heart disease, regardless of whether they experienced thyroid irAEs. The troponin levels increased with increasing thyroid stimulating hormone (TSH) levels. In particular, troponin levels were significantly elevated in patients with TSH >20 μIU/mL after ICI treatment ( P =0.009). In conclusion, thyroid irAEs may cause cardiac damage indicated by elevated troponin levels, necessitating special attention, particularly in cases of hypothyroidism where TSH exceeds 20 μIU/mL. Therefore, it is important to monitor cardiac markers along with thyroid function after ICI treatment.