Australasian Science: Australia's authority on science since 1938

Newborn Thyroid Activity Linked to Academic Struggles

Babies born with moderately high concentrations of thyroid-stimulating hormone (TSH) have a higher risk of poor educational and development outcomes at school age, according to a study published in The Lancet Diabetes & Endocrinology.

About one in 2000 children are born with congenital hypo­thyroidism each year. If untreated for several months after birth, abnormal thyroid function can lead to growth failure and permanent intellectual disability.

Screening for congenital hypothyroidism is usually done by testing concentrations of neonatal TSH in the blood, providing an opportunity to identify infants with abnormal thyroid hormone concentrations. Currently, only newborns with TSH concentrations at the 99.95th percentile of the population range are diagnosed with congenital hypothyroidism and treated with thyroxine.

The study, conducted at The University of Sydney, linked data collected from more than 500,000 infants between 1994 and 2008, including newborn TSH levels, to subsequent assessments of childhood development and school performance. These included NAPLAN results for numeracy and reading at ages 7–15 years, and teacher assessments reported after the first year of school as part of the Australian Early Development Census.

The researchers found a gradually increasing risk of poor educational and development outcomes for newborns with increasing TSH concentrations from the 75th to the 99.95th percentile.

“The results showed a clear dose–response association between neonatal thyroid-stimulating hormone and risk of scoring below the national minimum standard for numeracy and reading,” said the study’s senior author, A/Prof Natasha Nassar.

“This study can’t prove a cause and effect relationship between thyroid-stimulating hormone levels in newborns and educational and development outcomes in school-age children, but it suggests an urgent need for prospective studies examining different thyroid hormone thresholds for intervening with thyroxine,” said Dr Bridget Wilcken the Children’s Hospital at Westmead.

“Given that thyroxine is a relatively safe medication when indicated and properly monitored, this simple intervention may prevent significant learning and developmental problems in a small group of affected children.”