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Hypothyroidism
Published in David S. Cooper, Jennifer A. Sipos, Medical Management of Thyroid Disease, 2018
Uptake of T3 into the brain is dependent on organic anion transporter P1C1 (OATP1C1), which transports T4 across the blood brain barrier, and monocarboxylate transporter 8 (MCT8), which transports T3 across nerve cell membranes into neurons. Once inside cells, T3 binds to a thyroid hormone receptor (TR). T3 bound to TR associates with a cofactor, the retinoid X receptor (RXR) along DNA regulatory elements to stimulate or suppress the expression of thyroid hormone responsive genes. Thyroid hormone–regulated messenger RNA is then translated into proteins, some of which then undergo post-translational modifications before mediating the ultimate tissue effects of thyroid hormone (5). Theoretically genetic or epigenetic alterations at any of these steps could result in deficient thyroid hormone action at the tissue level.
Analysis of the protective effects of γ-aminobutyric acid during fluoride-induced hypothyroidism in male Kunming mice
Published in Pharmaceutical Biology, 2019
Haoyue Yang, Ronge Xing, Song Liu, Huahua Yu, Pengcheng Li
Thyroid hormone receptor β (TRβ), T4, T3, TG, thyroid peroxidase (TPO), sodium/iodide symporter (NIS), malondialdehyde (MDA), glutathione reductase (GR), ascorbate peroxidase (APX), total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL) and citrate synthase (CS) test kits were purchased from Nanjing Jiancheng Bioengineering Institute, Nanjing, China. The gene expressions of thyroxine deiodinase DI (Dio1), monocarboxylate transporter 8 (MCT8), retinoid X receptor α (RXRα), members of the extracellular signal-regulated kinase (ERK) 1/2 pathway (mitogen-activated protein kinase 1 [MEK1], ERK1 and ERK2) and tryptophan-rich sensory protein (TSPO) were determined by reverse transcription-polymerase chain reaction (RT-PCR; Shanghai Bioengineering Ltd., Shanghai, China). Thyroid tablets were purchased from Laiyang Biochemical Pharmaceutical Factory (Shandong Province, Laiyang, China). Sodium fluoride (NaF), GABA and other chemicals used in this study were of analytical grade and purchased from the Sigma Reagent Company, Shanghai, China.
Free thyroxine measurement in clinical practice: how to optimize indications, analytical procedures, and interpretation criteria while waiting for global standardization
Published in Critical Reviews in Clinical Laboratory Sciences, 2023
Federica D’Aurizio, Jürgen Kratzsch, Damien Gruson, Petra Petranović Ovčariček, Luca Giovanella
Thyroglobulin also serves as the storage receptacle of thyroid hormones in the lumen of follicular cells. If thyroid hormones are required, the thyroglobulin-thyroid hormone complex undergoes internalization to the cytoplasm by the process of endocytosis, as nonselective fluid uptake, or by receptor-related transport [15]. This is followed by enzymatic degradation and hydrolysis of the complex and transport via the basolateral membrane, mainly across the monocarboxylate transporter 8 (Figure 2).