Exploring hormonal deficiency detection in dental tissues through biogeochemical analysis

The relationship between health status and variations of trace element concentrations in mineralized dental tissues represents an innovative research field yet to be extensively explored through the lens of bioarchaeology. Coupled with biogeochemical studies, the study of microstructural and micromorphological features of dental tissues enables retrieving many biological variables associated with individuals’ life histories. A deeper understanding of the development and function of the endocrine system in past individuals is instrumental in elucidating the evolution of hormonal disorders, such as hypothyroidism. This study investigates the potential correlation between variations in trace element (TE) concentration in mineralized dental tissues and hormonal fluctuations using histology coupled with laser-based mass spectrometry (LA-ICPMS). To this end, five teeth from three contemporary individuals with known medical and nutritional histories were analysed, each with different forms of hypothyroidism and treatment histories: (a) congenital hypothyroidism treated with levothyroxine (L-T4) since birth; (b) untreated Hashimoto’s thyroiditis diagnosed in adulthood; and (c) untreated hypothyroidism discovered in childhood. These were compared with fifteen healthy modern individuals. TE variations were then measured in ten archaeological specimens. Results indicate significant differences in TE patterns between individuals with and without endocrine pathology and between treated and untreated cases. In non-pathological individuals, enamel’s Mg/Ca ratio decreases progressively from prenatal to postnatal periods. Treated hypothyroid individuals exhibit postnatal Mg/Ca concentrations comparable to healthy subjects, while untreated individuals show stable magnesium concentrations in pre-and postnatal enamel, without the expected decrease. Similarly, archaeological specimens exhibit consistent Mg/Ca concentrations between prenatal and postnatal enamel, lacking the anticipated decline. Conversely, Zn/Ca patterns reveal ambiguous trends. In healthy individuals, Zn/Ca remains uniform along the enamel-dentine junction (EDJ), whereas in pathological subjects, it fluctuates, suggesting disturbances during enamel mineralization. This study offers insights into disentangling past individuals’ life histories, offering a method to identify endocrine dysfunction in the past.