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Oxford University Press (OUP), The Journal of Clinical Endocrinology & Metabolism, 12(99), p. E2722-E2729

DOI: 10.1210/jc.2014-2849

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Effects of Early Thyroxine Treatment on Development and Growth at Age 10.7 Years: Follow-Up of a Randomized Placebo-Controlled Trial in Children With Down's Syndrome

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

Context: In 2-years-old children with Down syndrome (DS), early T4 treatment was found to result in slightly better motor development and growth. Objectives: To determine long-term effects of early T4 treatment on development and growth in children with DS with either an elevated or normal neonatal TSH concentration. Design: Single follow-up visit, 8.7 years after a randomized placebo controlled trial (RCT) comparing T4 and placebo treatment during the first two years of life. Setting: Dutch Academic Hospital. Participants: All children who completed the RCT (N=181, of 196 randomized children) were invited for the follow-up study. 123 participants enrolled, at a mean age of 10.7 years. Interventions: T4 or placebo treatment from the neonatal period until age two years. Main outcome measures: Primary: mental and motor development. Secondary: communication skills, fine-motor coordination, height, weight, and head circumference (HC). Outcomes were compared between T4 and placebo-treated children, and between treatment groups with either normal (<5 mIU/L), or elevated (≥5 mIU/L) TSH concentration at original trial entry. Results: Mental or motor development, communication skills, or fine-motor coordination did not differ between T4 (N=64) and placebo treated-children (N=59). T4-treated children had a larger HC (50.4 vs. 49.8 cm, P=.04) and tended to be taller (133.2 vs. 131.1 cm, P=.06). These differences were somewhat greater in children with TSH ≥5 mIU/L (HC: T4 50.5 vs. placebo 49.7 cm, P=.01; height: T4 133.8 vs. placebo 130.8 cm, P=.02), but were not found in children with TSH <5 mIU/L (HC: T4 50.1 vs. placebo 50.0 cm, P=.75; height: T4 132.1 vs. placebo 131.6 cm, P=.22). Conclusions: Early T4 treatment of children with DS does not appear to benefit mental or motor development later in life. However, the positive effect on growth is still measurable, especially in children with an elevated plasma TSH concentration in the neonatal period.