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Lookup NU author(s): Dr Salman RazviORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
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 SLC16A2gene 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 two 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.
Author(s): Boelaert K, Bauer A, Cappola AR, Chatterjee K, Dietrich JW, Nicol L, Persani L, Razvi S, Stoupa A
Publication type: Review
Publication status: Published
Journal: Journal of Clinical Endocrinology and Metabolism
Year: 2026
Pages: epub ahead of print
Online publication date: 09/01/2026
Acceptance date: 30/12/2025
ISSN (print): 0021-972X
ISSN (electronic): 1945-7197
URL: https://doi.org/10.1210/clinem/dgaf707
DOI: 10.1210/clinem/dgaf707
Data Access Statement: This article is a narrative literature review and does not involve the generation or analysis of new datasets. All data discussed are derived from previously published studies, which are cited within the manuscript.
