Thyroid disrupting effects of exposure to sunscreens: in vitro and in vivo evidence of the impact of organic UV-filters.

Abstract

BACKGROUND: Ultraviolet radiation (UVR), primarily from sunlight, is a natural component of environmental exposure and can cause genomic damage, photoaging, and skin cancer. Sunscreens containing UV-filters are widely used to prevent these effects and are also found in many personal care products. Despite their protective role, concerns have emerged regarding the accumulation of UV-filters in the environment and human matrices, along with their ability to act as endocrine disruptors, which main target include also thyroid hormone regulation. METHODOLOGY: This narrative review was performed through a systematic search of PubMed (Medline), Embase, and the Cochrane Library. Global legislations were reviewed from institutional websites and official databases of major international agencies. MAIN BODY: Various studies have shown that several UV-filters are detectable in human tissues, blood, urine, breast milk, and fetal circulation, suggesting systemic absorption and long-term exposure. Experimental evidence indicates that some UV-filters may affect hormone regulation by interacting with nuclear receptors, particularly those involved in thyroid function. Thyroid hormones are crucial for development, metabolism, and neurological function, mainly during critical life stages such as pregnancy and infancy. Disruption of thyroid hormone homeostasis may result in long-lasting adverse effects. While previous research has mainly focused on estrogenic and androgenic effects, increasing evidence highlights the need to assess thyroid-specific endpoints. This review summarizes current in vitro and in vivo findings on the potential thyroid-disrupting effects of UV-filters. CONCLUSION: A better understanding of how UV-filters may interfere with thyroid hormone regulation is essential for evaluating their safety and informing regulatory decisions. Given the global variability in regulatory frameworks, this issue is particularly relevant for risk assessment and the development of safer and more sustainable alternatives in cosmetic formulations. Future research and awareness campaigns should focus on chronic exposure, mainly on vulnerable populations.