Monocarboxylate transporter 8 (MCT8)

Monocarboxylate transporter 8 (MCT8) is an integral membrane transporter belonging to the solute carrier family 16 (encoded by the SLC16A2 gene) that specifically mediates the cellular import and export of the thyroid hormones triiodothyronine (T3) and thyroxine (T4)[1][6][7]. MCT8 exhibits high affinity and selectivity for thyroid hormones, and its function is critical for normal brain development, especially in the fetal and neonatal period[2][4][5]. Pathogenic mutations in SLC16A2 cause Allan-Herndon-Dudley syndrome (AHDS), an X-linked disorder characterized by intellectual disability, profound motor impairment, and elevated serum T3 with reduced T4[2][5][7]. MCT8 plays a central role in transporting thyroid hormones across the blood-brain barrier and into neurons, and is widely expressed in several tissues, notably the CNS and placenta[5][7]. Few drug interactions are well-characterized; however, some tyrosine kinase inhibitors and natural compounds can inhibit MCT8, and research continues for substrates that bypass or compensate for MCT8 function[1][5]. MCT8's centrality to developmental and metabolic processes, as well as its disease relevance and limited therapeutic options, make it a prominent and challenging therapeutic target.

Other names

SLC16A2Solute carrier family 16 member 2MCT7XPCTDXS128DXS128EAHDSMRX22Monocarboxylate transporter 7X-linked PEST-containing transporter

Inhibitors: Block thyroid hormone (T3/T4) transport across cellular membranes, reducing hormone uptake into sensitive tissues[1][5]. Substrate analogs (like DITPA): Compensate for impaired T3 transport by entering the CNS through alternative mechanisms[5].