Influence of iodine-deficiency on thyroid hormones homeostasis in rats

Impact of fluoride on thyroid function and histopathology in cyprinus carpio: Implications for aquatic ecosystems

Fluoride pollution in freshwater bodies is becoming alarming because it interferes with the endocrine system of water-dwelling organisms. In this study, we evaluated the effects of sublethal fluoride levels on thyroid hormone levels and histological alterations in Cyprinus carpio, a popular model fish species used in ecotoxicity experiments. The low, medium, and high fluoride groups received 1, 5, and 10 mg/L fluoride, respectively, and thyroxine plasma levels (T4) and triiodothyronine plasma levels (T3) were assessed at 7, 14, 21, and 35 days. The findings revealed that both T4 and T3 levels significantly decreased with increasing dose and ranged from to 10-41 % lower than controls in the 10 mg/L fluoride group. On day 35, T4 levels were reduced by 42 % and T3 levels were reduced by 50 % in the high fluoride exposure group compared to those in the control group. Changes in the thyroid gland were observed under a light microscope that included, but were not limited to, small follicle size, epithelial hypertrophy, and epithelial hyperplasia, especially in the high-fluoride group. These results suggest that elevated fluoride exposure causes a hormonal imbalance in Cyprinus carpio by affecting thyroid hormone biosynthesis and functionality, which may result in growth and reproductive failure. The eminent dose-response data on fluoride concentration and the degree of thyroid disruption clearly emphasise the severe endocrine-disruptive effects of fluoride at increased concentrations. The results of the present study agree with those of other studies that have described the inhibitory effect of fluoride on thyroid function in different fish species. Therefore, we conclude that fluoride may be a potent endocrine disruptor in the environment. As thyroid hormones play significant roles in metabolic and physiological functions in fish, these findings underscore the importance of improving fluoride standards in freshwater habitats. Research on the molecular pathways that lead to thyroid dysfunction when exposed to fluoride and other effects of this chemical substance on the environment.

A Novel and Fast Online-SPE-LC-MS/MS Method to Quantify Thyroid Hormone Metabolites in Rat Plasma

Since the focus in regulatory toxicology has drifted toward the identification of endocrine disruptors, the improvement in determination of alterations in the thyroid hormone system has become more important. THs are involved in several molecular processes important for a proper pre- and postnatal development so that disturbances can inter alia lead to incorrect brain maturation and/or disturbed metabolic processes (thermogenesis or lipolysis). In this publication, a new automated online solid-phase extraction (SPE)-liquid chromatography (LC)-tandem mass spectrometry (MS/MS, xLC-MS/MS) is introduced which simultaneously analyzes total T4, T3, rT3, T2, and T1. Method validation parameters are presented, and the method was positively verified by analyzing control and PTU-treated rat plasma samples (time points day 7, 14, and 28) for their total TH content. The obtained results were compared to published results by using a radioimmunoassay method. The automated SPE system ensures a consistent unified sample preparation, and this method overall showed sufficient specificity and accuracy to detect the given analytes in rat plasma. For the preparation of 50 μL of rat plasma, the following LOQs were established: 0.020 nM for T1, 0.029 nM for T2, 0.023 nM for rT3 and T3, and 3.22 nM for T4. This method is suitable to assess the identification of mechanisms leading to adverse effects, such as disturbed TH metabolism and regulation.

In Vivo Evaluation of Transdermal Iodide Microemulsion for Treating Iodine Deficiency Using Sprague Dawley Rats

The objective of this study was to evaluate the transdermal efficiency of iodide microemulsion in treating iodine deficiency using rats as an animal model. Animals were fed either iodine-deficient diet (20 μg/kg iodide) or control diet (200 μg/kg iodide) over a 17-month period. At month 14, iodide microemulsion was applied topically in iodine-deficient group and physiological evaluations of thyroid gland functions were characterized by monitoring the thyroid hormones (T3, T4), thyroid-stimulating hormone (TSH), iodide ion excretion in urine, and the overall rat body weights in both groups. Moreover, morphological evaluations of thyroid gland before and after treatment were performed by ultrasound imaging and through histological assessment. Prior to microemulsion treatment, the levels of T3, T4, and TSH in iodine-deficient group were statistically significant as compared to that in the control group. The levels of T3 and T4 increased while TSH level decreased significantly in iodine-deficient group within the first 4 weeks of treatment. After treatment, iodide concentration in urine increased significantly. There was no statistical difference in weight between the two groups. Ultrasound imaging and histological evaluations showed evidence of hyperplasia in iodine-deficient group. Topical iodide microemulsion has shown a promising potential as a novel delivery system to treat iodine deficiency.