Hashimoto's thyroiditis (HT) is an autoimmune disease, and a major cause of hypothyroidism. Due to its insidious nature, non-presence of clear clinical symptoms, there is often a delay in getting a diagnosis for HT, which leads to irreversible damage. Therefore, early screening and improving diagnostic accuracy are essential to the treatment of HT. There are few studies on the application of infrared thermal imaging technology as an auxiliary diagnostic tool for HT.

To explore the features of metabolic calorific values measured by infrared thermal imaging in female adults with HT.

Participants were recruited from the Affiliated Hospital of Chengdu University of Traditional Chinese Medicine from April 2019 to June 2021, including 100 adult gynecological outpatients with HT, and 100 healthy, adult female physical examinees. Both groups completed the Classification and Determination of Constitution in TCM (ZYYXH/T157-2009) for assessing the constitution in TCM. Thyroid function test was performed to understand levels of thyroid function parameters〔thyroglobulin antibody (TGAb) , thyroid peroxidase antibody (TPOAb) , thyroid-stimulating hormone (TSH) , free triiodothyronine (FT₃) , free thyroxine (FT₄) 〕. Full body thermography using infrared thermal imaging was implemented to examine the calorific values of the left and right lobes of the thyroid gland, the uterus, the Shenque acupoint and the Governor vessel. The aforementioned parameters were compared between HT patients and physical examinees to identify intergroup differences. The calorific values of thyroid left and right lobes, the uterus, the Shenque acupoint and the Governor vessel were compared across HT patients with 9 types of constitution in TCM, and the associations of them with thyroid function parameters were explored, then their associations with infertility in HT were evaluated using binary logistic regression analysis.

The top 4 types of constitution in TCM in HT patients were yang-deficiency, qi-stagnation, damp-heat, and phlegm-dampness. The calorific values of Shenque acupoint and the Governor vessel varied significantly across HT patients by types of constitution (n=9) in TCM (P<0.05) . Compared with the control group, the levels of TGAb, TPOAb and TSH in HT group increased (P<0.05) . There was no significant difference in FT₃ and FT₄ levels between the two groups (P>0.05) . HT patients had higher calorific values of thyroid left and right lobes and lower calorific values of the uterus, Shenque acupoint and the Governor vessel than physical examinees (P<0.05) . In the HT group, the calorific value of the left or right lobe of the thyroid gland was positively correlated with TGAb (r_s=0.260, 0.198, P<0.05) , and the calorific value of the uterus was negatively correlated with TSH (r_s=-0.313, P<0.05) . The calorific values of the uterus〔OR=0.413, 95%CI (0.180, 0.945) 〕, the Governor vessel〔OR=0.270, 95%CI (0.075, 0.971) 〕, and the Shenque acupoint〔OR=0.264, 95%CI (0.073, 0.954) 〕were associated with infertility in HT (P<0.05) .

In adult female HT patients, the most common four types of constitution in TCM were yang-deficiency, qi-stagnation, damp-heat, and phlegm-dampness. The metabolic calorific values measured by infrared thermal imaging were featured by higher values of thyroid left and right lobes, and lower values of the uterus, Shenque acupoint and the Governor vessel, which may be new theoretical evidence obtained from clinical practice explaining infertility in HT. Furthermore, the calorific values of thyroid left and right lobes could be used as parameters for early screening or identifying HT. So infrared thermal imaging could be used as an auxiliary diagnostic tool to improve the diagnostic efficiency of HT.