Fig. 2.

Effect of plasticizers associated with MPs/NPs on the thyroid gland. Thyrotropin-releasing hormone (TRH) is released from the hypothalamus, signalling the pituitary gland to release thyroid-stimulating hormone (TSH). TSH binds to its receptor (TSHr) at the follicle of the thyroid gland, initiating the synthesis of thyroid hormones T3 and T4. These hormones are transported through the bloodstream to target tissues, where they enter the cytoplasm via membrane transporters. Within the cytoplasm, they regulate the synthesis of metabolites and transcriptional activities. Plasticizers found in MPs/NPs, such as perchlorate, mono(2-ethylhexyl) phthalate (MEHP), and di(2-ethylhexyl) phthalate (DEHP), downregulate sodium-iodide symporter (NIS) expression by activating the NF-κB pathway, consequently impairing iodine uptake [83,84]. Plasticizers like PCB, phthalates, etc. interfere with thyroid hormone receptors, and cause disruption in the thyroid hormone related gene expression activity (e.g. Dio1/dio2 gene expression) [79,171].