Exploring the Impacts of Fluoride-Induced Thyroid Toxicity: A Comprehensive Review

Fluoride exposure via contaminated drinking water is a significant global public health concern. Fluoride being beneficial at minimal concentrations was used for dental caries prevention, but excessive exposure of fluoride has been associated with numerous health disorders including skeletal and dental fluorosis, weakening of bones making them more prone to fractures, impaired intelligence, stunted growth, reduced birth and fertility rates, and disruption of thyroid function. This review provides a concise overview of all the existing literature on the effects of fluoride on the thyroid gland till date. Various data collection methods including PubMed, Scopus, ResearchGate, and Google Scholar were used to collect relevant research papers using keywords "changes caused by fluoride in thyroid" or "fluoride induced toxicity on the thyroid gland" ranging from 1976 till date. Fluoride adversely affects thyroid function via interfering with iodine metabolism (replacing iodine in the gland and also inhibiting its uptake). It also disrupts T₃ and T₄ production causing decrease in their levels, increased TSH, oxidative stress, and downregulated antioxidant and thyroid-related genes. Histopathological alterations caused by fluoride includes thyroid follicular cell apoptosis, necrosis, and hyperplasia of thyroid gland. Thyroid gland, in particular, is highly susceptible to fluoride accumulation, making it one of the most affected organs. Numerous studies have evaluated the impact of fluoride on mammalian models, with a focus on endocrine system particularly the thyroid gland. Fluoride exposure can lead to hypothyroidism, particularly detrimental during fetal and early developmental stages affecting IQ, brain, and hearing development.