Johannes Wolfgang Dietrich

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.

Monocarboxylate transporter 8 (MCT8) deficiency, also known as Allan–Herndon–Dudley syndrome, is a rare, severely debilitating, and life-limiting genetic disorder caused by variants in the SLC16A2 gene that render the MCT8 thyroid hormone transporter partially or completely dysfunctional. MCT8 is highly expressed throughout the body, including the brain. Its deficiency disrupts thyroid hormone homeostasis and is associated with 2 distinct concomitant clinical presentations: persistent peripheral thyrotoxicosis resulting from elevated serum levels of triiodothyronine and neurodevelopmental impairment arising from low thyroid hormone levels in the brain. The disorder severely impacts quality of life and reduces life expectancy to a median of 35 years due to a range of clinical sequelae, with approximately 30% of affected individuals dying during childhood. Recognition and treatment of thyrotoxicosis are crucial to prevent associated symptoms and long-term sequelae.

In his commentary titled “The Paradox of Psychological Denialismin Supporting Thyroid Patients” Massimo Agnoletti argues the case for a better psychological treatment of patients with thyroid conditions, especially addressing stress load. He pleads i...