Clinical and Biochemical Monitoring of Monocarboxylate Transporter 8 Deficiency (Allan-Herndon-Dudley Syndrome) across the Lifespan: Practical Considerations for Multidisciplinary Care

Pathogenic mutations in the SLC16A2 gene can result in partial or complete loss of function of the critical and highly specific monocarboxylate transporter 8 (MCT8), a thyroid hormone transporter. MCT8 deficiency (Allan-Herndon-Dudley syndrome) is a rare X-linked genetic disorder that causes profound neurodevelopmental delay, movement disorders, and peripheral thyrotoxicosis secondary to elevated serum tri-iodothyronine. The condition is chronic and life-limiting, with patients requiring regular multidisciplinary monitoring to manage their symptoms. This guideline proposes a comprehensive, multidisciplinary management strategy for healthcare professionals caring for patients with MCT8 deficiency across all age groups, monitoring key symptoms and sequelae. It highlights the substantial heterogeneity in symptoms and long-term outcomes associated with the condition, underscoring the need for individualized patient care plans.

Published by Hormone research in paediatrics, 2026. The guideline itself is at the source linked here.

doi.org/10.1159/000551857