E-news: Thr92Ala substitution associated with sub-optimal IQ score in children with low thyroid function

Common genetic variation in the intracellular thyroid hormone pathway appears to substantially modify the effect of low-normal serum thyroid hormone levels on IQ.

A study by Peter Taylor et al highlights the importance of the intracellular pathway in determining an individual's thyroid status and raises the possibility that levothyroxine supplementation in a genotype dependent manner to children with lower thyroid hormone levels may improve cognitive outcomes.

Thyroid hormone is essential for cognitive development. The Thr92Ala substitution in deiodonase-2 appears to reduce intracellular availability of active thyroid hormone. Individuals with low-normal serum thyroid hormone levels and this substitution might have insufficient intracellular thyroid hormone for optimal cognitive development.

The study involved 3,123 individuals with genetic data - thyroid function (at age 7) and cognitive assessments (at age 8) available in a population-based birth cohort (the Avon Longitudinal Study of Parents and Children).