Detecting hyper-/hypothyroidism from tongue color spectrum

In this article, we present hyperspectral analysis of the tongue and correlation between its color and values of thyroid hormones. In Kampo medicine (Japanese traditional herbal medicine), the tongue acts as a mirror reflecting the internal state of the body. By assessing the patient's complexion of the tongue, we are able to assess the changes including initial change of typical hyper-/hypothyroidism. However, examination methods in Kampo is empirical and require much experience. Therefore, we performed hyperspectral tongue analysis to turn the empirical observation into the change in substantial factor. One hundred hyperspectral tongue images and blood samples were acquired from 50 outpatients. The principal component analysis was performed for tongue color spectra, and correlation to thyroid hormones was calculated with the vector rotation method. As the result, TH4 showed large correlation with the tongue color spectra. Our method would help non-invasive screening in low cost. The tongue examination seems to be reliable for acquiring the state of the body.