The second wave of the Controlled Antenatal Thyroid Screening (CATS II) study: the cognitive assessment protocol.

Mohd S Draman,Aled Rees,Marian Ludgate,Colin M Dayan,Charlotte Hales,Ruth Paradice,Ilaria Muller,Dionne Shillabeer,John Lazarus,Peter N Taylor,Sue Channon,John W Gregory

doi:10.1186/1472-6823-14-95

Abstract

BackgroundChildren whose mothers had low thyroid hormone levels during pregnancy have been reported to have decreased cognitive function. The reported research is part of the follow-on study of the Controlled Antenatal Thyroid Screening Study (CATS I), a randomised controlled trial which investigated the impact of treated vs. untreated low thyroid hormone level in women during pregnancy with the primary outcome being the child’s IQ at age 3. No significant differences in IQ were found between the treated and untreated groups. These children are now aged between 7 and 10 years and aspects of their cognitive functioning including their IQ are being reassessed as part of CATS II.Methods/DesignCognitive assessments generate an IQ score and further tests administered will investigate long term memory function and motor coordination. The aim is to complete the assessments with 40% of the children born to mothers either in the treated or untreated low thyroid hormone groups (n = 120 per group). Also children born to mothers who had normal thyroid functioning during CATS I are being assessed for the first time (n = 240) to provide a comparison. Assessments are conducted either in the research facility or the participant’s home.DiscussionThe study is designed to assess the cognitive functioning of children born to mothers with low thyroid hormone levels and normal thyroid functioning during pregnancy. This is the largest study of its type and also is distinguishable in its longitudinal design. The research has the potential to have a significant impact on public health policy in the UK; universal screening of thyroid hormone levels in pregnancy may be the recommendation.

Highlights

Children whose mothers had low thyroid hormone levels during pregnancy have been reported to have decreased cognitive function
The study is designed to assess the cognitive functioning of children born to mothers with low thyroid hormone levels and normal thyroid functioning during pregnancy
The current research is, to the authors’ knowledge, the largest of its kind in the world to have a treated compared to untreated model of Suboptimal Gestational Thyroid Function (SGTF) at this age group; it has the potential to have a significant impact in the UK and may be policy changing; universal screening for SGTF may be the outcome based on the study recommendations

Summary

Introduction

Children whose mothers had low thyroid hormone levels during pregnancy have been reported to have decreased cognitive function. The reported research is part of the follow-on study of the Controlled Antenatal Thyroid Screening Study (CATS I), a randomised controlled trial which investigated the impact of treated vs untreated low thyroid hormone level in women during pregnancy with the primary outcome being the child’s IQ at age 3. No significant differences in IQ were found between the treated and untreated groups These children are aged between 7 and 10 years and aspects of their cognitive functioning including their IQ are being reassessed as part of CATS II. Subclinical Hypothyroidism (SH), defined as an elevated level of thyroid stimulating hormone (TSH) with normal circulating levels of free thyroxine (T4) and free triiodothyronine (T3) [1], affects 3-6% of the UK population [2,3]. As measured by Intelligence Quotient (IQ) tests has been shown to predict a range of life outcomes such as academic performance, job performance, years in education and even physical health [19,20,21,22,23,24,25]

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