Imaging Biomarkers of Hypothyroidism on Lung Cancer Screening CT.

Abstract Purpose To assess the feasibility of attenuation and size measurement of the thyroid gland as an imaging biomarker for hypothyroidism in patients undergoing lung cancer screening (LCS) with low dose CT. Materials and Methods With institutional review board (IRB) approval, we retrospectively reviewed all patients with LCS CT between September 1, 2016 and March 31, 2020, who had at least 1 thyroid-stimulating hormone (TSH) test within 90 days of the patient's most recent screening CT. Hypothyroid patients were identified through billing diagnosis and/or elevated TSH or those on treatment with thyroxine; normal patients were identified as those without a diagnosis of hypothyroidism and normal TSH. For each hypothyroid patient, an age- and sex-matched normal control was included. The diameters and attenuation of both lobes of the thyroid gland were measured for each case; patients in whom the thyroid gland could not be seen to measure were excluded. Results A total of 304 patients were included. The areas under the receiver operating characteristic curve for size and attenuation of the left lobe were 0.774 (95% confidence interval [CI] 0.714-0.825) and 0.812 (95% CI 0.759-0.861), respectively; and for the right lobe were 0.776 (95% CI 0.719-0.827) and 0.794 (95% CI 0.740-0.847), respectively. We developed a decision tree algorithm to predict hypothyroidism combining the minimum size and attenuation of either lobe of the thyroid gland, with sensitivity, specificity, and accuracy of 76%, 87%, and 82%, respectively. Conclusion Size and attenuation of the thyroid gland can be used to identify potential hypothyroid patients undergoing LCS.