[MCT8-specific thyroid hormone cell transporter deficiency: a case report and review of the literature].

Introduction: MCT8 is a specific transporter for the T4 and T3 thyroid hormones that allows their entry in the brain and other organs. Mutations in MCT8 (Allan-Herndon-Dudley syndrome) lead to a severe form of X-linked psychomotor retardation, which is characterised by elevated plasma T3 and low T4.

Aim: We describe the first case diagnosed in Spain with this syndrome and review the published literature about this topic.