To investigate the early laboratory and clinical manifestations of thyroid dysfunction induced by immune checkpoint inhibitors (ICIs) in the treatment of malignant tumors.

A retrospective analysis was conducted on malignant tumor patients who received ICIs treatment during hospitalization between January 1, 2020, and December 31, 2021. Data collected included patients'general information, ICIs treatment regimens, and thyroid function indicators, including the initial onset time of treatment-related thyroid dysfunction, patterns of abnormal manifestations, and thyroid imaging findings.

Among 156 enrolled patients, the five most frequently used ICIs were sintilimab (n =40), camrelizumab (n =38), tislelizumab (n = 32), toripalimab (n =25), and pembrolizumab (n =14). The overall incidence of thyroid dysfunction was 55.13% (86/156). The median time to initial thyroid laboratory function abnormality was 104 days (14.86 weeks), with the shortest being 4 days and the longest 2.4 years. The most frequent onset period of initial thyroid index abnormality was >112 days (16 weeks), accounting for 47.89%. Thyroid laboratory index abnormality presented in various forms, with one or more indices being elevated or decreased. In terms of the number of abnormal indicators, single indicator abnormality was the most common (72.09%), among which hyroid-stimulating hormone (TSH) abnormality (including elevation and reduction) was the most prevalent, accounting for 41.86%. In terms of TSH change patterns, elevated TSH accounted for the highest proportion (44.19%), followed by normal TSH (33.72%), and low TSH (20.93%). After ICIs treatment, 16.28% of patients had conversion of thyroid autoantibodies to positive. Thyroid B-ultrasound findings were abnormal in four patients, mainly presenting as diffuse thyroid changes (n =2), bilateral thyroid volume reduction (n =1), and bilateral thyroid echo hanges (n=1), all of whom had abnormal thyroid antibodies. The thyroid function abnormalities included in this study were all Grade 1 or 2, and most patients had no obvious clinical symptoms. Finally, only three patients continued to take levothyroxine half a year after the end of immunotherapy.

Thyroid dysfunction caused by ICIs often presents as atypical clinical symptoms and mainly manifests as abnormal laboratory tests. Initial thyroid index abnormalities present various manifestations, with TSH abnormalities being the most common. Understanding the early manifestations of thyroid dysfunction caused by ICIs is helpful for oncologists in the diagnosis and treatment of this adverse reaction.