Endocrine Abstracts

Introduction: Monocarboxylate transporter 8 (MCT8) is a thyroid hormone-specific transmembrane transport protein. Inactivating mutations in MCT8 lead to severe mental retardation, the Allan-Herndon-Dudley syndrome. The severity of the Allan-Herndon-Dudley syndrome differs among MCT8 patients. Partial activity of MCT8 can be caused either by mutations affecting the transport mechanism (e.g. substrate interaction, conformational change) or by inefficient protein expression, memb...

With the identification of mutations in the monocarboxylate transporter 8 (MCT8) gene in patients afflicted with the Allan–Herndon–Dudley syndrome (AHDS), the concept of transporter-mediated transmembrane transport of thyroid hormones was finally accepted. Impaired thyroid hormone transport into neurons and pituitary cells is believed to cause severe psychomotor retardation and altered thyroid hormone function tests. MCT8 is a specific thyroid hormone transporter abl...

The main product of the thyroid gland, T4, is a prohormone. 5’-deiodination is needed to convert T4 into the active, nuclear receptor-binding hormone, T3. Pharmacological modulation of activating 5’-and inactivating 5-deiodination of iodothyronines would be desirable in a number of medical conditions, including hypothyroidism, hyperthyroidism and various cancers. A structural and mechanistic understanding of deiodinase (DIO) catalysis...