In situ characterization of human fingernails by optical front-face fluorescence for the identification of primary hypothyroidism

Abstract Primary hypothyroidism is classified as a public health issue by the World Health Organization. The technique for diagnosing hypothyroidism is the measurement of thyroid stimulating hormone (TSH) and thyroxine (FT4). It is necessary to develop new methods that are more accessible, especially for developing countries. The aim of this work is the in-situ use of nail fluorescence for a simple and rapid preliminary diagnosis of primary hypothyroidism. The choice of the nail as biological tissue is justified because nails have a long-term memory, act as a mirror of health, and serve as an early warning system as well as a window of systemic disease. The in situ analysis of the nails of the patients shows good results. Specially, a clear separation was obtained between healthy controls and patients and also between low- and high-level hypothyroidism. Moreover, a strong correlation between fluorescence spectra and TSH values for the population with hypothyroidism was clearly established. Moreover, linear discriminant analysis shows that it is possible to predict the state of test patients after the training of a fraction of the population.