Re: Should we treat subclinical hypothyroidism in obese children? Planned Down’s syndrome trial may provide relevant evidence
The practice review by Niranjan and Wright  highlights the ongoing uncertainty on whether or not subclinical hypothyroidism in obese children should be treated with thyroxine. The authors pointed out that they reviewed the clinicaltrials.gov database and found no current studies that are looking at this specific question. They concluded that subclinical hypothyroidism seems to be a consequence rather than the cause of obesity and thyrotropin levels often normalise after weight loss and therefore thyroxine treatment is not supported by the available evidence.
I just wanted to highlight the fact that in children, a number of studies on subclinical hypothyroidism have been focused on children with Down’s syndrome. [2,3,4] While it seems most of these studies have concluded that subclinical hypothyroidism is often transient in Down’s syndrome and does not require treatment with thyroxine, one area of uncertainty is whether or not a prolonged period with subclinical hypothyroidism has negative consequences on the developing brain and on cardio-metabolic health. The potential cognitive consequences of subclinical hypothyroidism are particularly important for children with Down’s syndrome which is already associated with intellectual impairment.
There is a double blind randomised placebo controlled trial  that was registered in 2015 with the clinicaltrials.gov database (ClinicalTrials.gov Identifier: NCT01832753) which will look at the change in non-HDL cholesterol and lipid profiles as the primary outcome in children with Down’s syndrome treated with thyroxine versus placebo. It is expected to conclude sometime in 2017. The investigators are exploring the hypothesis that treatment with thyroxine will improve cardio-metabolic health and quality of life. Results from this trial may be relevant to Niranjan and Wright’s question since a number of children with Down syndrome suffer from obesity.  The secondary outcome measures will be measurement of the quality of life and perception of body image. It is worth noting that Down’s syndrome patients may not be necessarily representative of the population of non-syndromic obese children given the complexities of Down’s syndrome but the trial will give more insights into the role if any of thyroxine in subclinical hypothyroidism.
 Niranjan U, Wright NP. Should we treat subclinical hypothyroidism in obese children? BMJ 2016; 352 :i941
 Claret C, Goday A, Benaiges D et al. Subclinical hypothyroidism in the first years of life in patients with Down syndrome. Pediatric Research (2013) 73, 674–678 doi:10.1038/pr.2013.26
 Editorial: Subclinical hypothyroidism in children with Down syndrome: To treat or not to treat???. The Egyptian Journal of Medical Human Genetics (2015) 16, 87–88 http://dx.doi.org/10.1016/j.ejmhg.2014.10.005
 Toscano E, Pacileo G, Limongelli G, et al. Subclinical hypothyroidism and Down’s syndrome; studies on myocardial structure and function. Archives of Disease in Childhood. 2003;88(11):1005-1008. doi:10.1136/adc.88.11.1005.
 Treatment Trial of Subclinical Hypothyroidism in Down Syndrome. ClinicalTrials.gov Identifier: NCT01832753. Link: https://clinicaltrials.gov/ct2/show/NCT01832753
 van Gameren-Oosterom HBM, van Dommelen P, Schönbeck Y et al. Prevalence of Overweight in Dutch Children With Down Syndrome. Pediatrics, Nov 2012, doi: 10.1542/peds.2012-0886
Competing interests: No competing interests