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Elevated TSH levels in a mentally retarded boy

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The Allan–Herndon–Dudley syndrome (AHDS; MIM 300523) of X-linked mental retardation and hypotonia is caused by mutations in a thyroid hormone transporter gene—the monocarboxylate transporter 8 (MCT8 also known as SLC16A2) gene. A 23-month-old boy with severe developmental delay, hypotonia, recurrent emesis, and irritability is described. He was diagnosed with hypothyroidism at the age of 4 months. However, T3 level was elevated. Molecular analysis of the MCT8 gene detected a single base duplication in exon 5 c.1614dupC (p.Ile539fs), consistent with a diagnosis of AHDS. While T3 is the best marker for this disorder, elevations in TSH should alert to the diagnosis.

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Fig. 1







Thyroid stimulating hormone

MCT 8 :

Monocarboxylate transporter 8


Allan–Herndon–Dudley syndrome


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Conflict of interest

There is no conflict of interest. No funding was required for this study.

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Correspondence to William Reardon.

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Crushell, E., Reardon, W. Elevated TSH levels in a mentally retarded boy. Eur J Pediatr 169, 573–575 (2010).

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  • Triiodothyronine
  • Hypothyroidism
  • Allan–Herndon–Dudley syndrome
  • X-linked mental retardation
  • MCT 8