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Evidence

Query: Is there a link between maternal thyroid issues and children with attention deficit hyperactivity disorder (ADHD) and/or autism spectrum disorders (ASD)?

Response posted: March 2015

We searched electronic databases (NICE, NHS Evidence, Cochrane Library, TRIP Database and PubMed) using the terms "hyperthyroidism", "hypothyroidism", "thyroid" "maternal thyroid" AND "attention deficit hyperactivity disorder", "ADHD", "ASD", "autism spectrum disorder".

The causes of ADHD and ASD are not known. Current understanding suggests that these conditions are likely to be caused by various combinations of genetic and environmental factors.

The thyroid gland produces hormones that affect certain bodily functions. Hyperthyroidism is a medical condition in which there is too much thyroid hormone in the body (overactive thyroid gland), while hypothyroidism is when there is too little (underactive thyroid gland). 1, 2

A large body of evidence proposes thyroid hormone is an important factor contributing to normal fetal brain development.3  There is some evidence that undiagnosed or poorly treated maternal hypothyroidism can result in developmental problems in children.4,5   Two studies found that children of mothers with hypothyroidism during pregnancy scored slightly lower on tests for intelligence and physical functioning (such as hand-eye coordination), than children of mothers with normal thyroid levels.6, 7,   

Three recent European population-based studies have explored whether there is an association between thyroid problems and either ASD or ADHD. 8, 9, 10 These studies compared maternal thyroid function during or after pregnancy, and examined whether children were subsequently diagnosed with, or showed symptoms of ASD or ADHD.  These studies found a slightly increased risk for some sub-groups to have symptoms of ASD or ADHD following exposure to maternal thyroid problems in pregnancy.

While these studies have large sample sizes, it is difficult to take account of the many lifestyle and other factors that might also affect the risk of developing ASD or ADHD. For example, another study found that women with hypothyroidism may be more likely to have a premature birth, and so it is difficult to confirm whether it is the thyroid disease, or the prematurity, which may have a negative effect on child development.11

Nevertheless, there is evidence that there are risks of children showing developmental symptoms associated with ASD and/or ADHD following thyroid problems in pregnancy.  Current clinical guidance recognises the importance of managing thyroid conditions before, during and after pregnancy to reduce risks to both the mother and the child. 12, 13

References

1 NHS Choices (2014) http://www.nhs.uk/conditions/Thyroid-over-active/Pages/Introduction.aspx

2 NHS Choices (2014) http://www.nhs.uk/conditions/Thyroid-under-active/Pages/Introduction.aspx

3 Abalovoch M et al (2007) Management of Thyroid Dysfunction during Pregnancy and Postpartum:  An Endocrine Society Practice Guideline. Available here:

http://press.endocrine.org/doi/abs/10.1210/jc.2007-0141

4 National Institute for Clinical Excellence (2011) http://cks.nice.org.uk/hypothyroidism#!supportingevidence1:1

5 UK consensus guideline (2006) Association for Clinical Biochemistry, British Thyroid Association, and the British Thyroid Foundation http://www.british-thyroid-association.org/info-for-patients/Docs/TFT_guideline_final_version_July_2006.pdf

6 Haddow, J.E., Palomaki, G.E., Allan, W.C. et al. (1999) Maternal thyroid deficiency during pregnancy and subsequent neuropsychological development of the child. New England Journal of Medicine 341(8), 549-555.

7 Pop, V.J., Kuijpens, J.L., van Baar, A.L. et al. (1999b) Low maternal free thyroxine concentrations during early pregnancy are associated with impaired psychomotor development in infancy. Clinical Endocrinology 50(2), 149-155.

8 Andersen SL et al (2014) Attention Deficit Hyperactivity Disorder and Autism Spectrum Disorder in Children Born to Mothers with Thyroid Dysfunction: A Danish Nationwide Cohort Study. BJOG Available here: http://www.ncbi.nlm.nih.gov/pubmed/24605987

9 Pakkila F et al (2014) The Impact of Gestational Thyroid Hormone Concentrations on ADHD Symptoms of the Child. J Clin Endocrinol Metab, 99 (1) E1 – E8. Available here: http://www.ncbi.nlm.nih.gov/pubmed/24384024

10 Ghassabian A et al (2012) Maternal Thyroid Autoimmunity During Pregnancy and the Risk of Attention Deficit/Hyperactivity Problems in Children: The Generation R Study. THYROID 22 (2) 178. Available here: http://www.ncbi.nlm.nih.gov/pubmed/22175242

11 Casey, B.M., Dashe, J.S., Wells, C.E. et al. (2005) Subclinical hypothyroidism and pregnancy outcomes. Obstetrics & Gynecology 105(2), 239-245.

12 National Institute for Clinical Excellence (2013): http://cks.nice.org.uk/hyperthyroidism

13 National Institute for Clinical Excellence (2011): http://cks.nice.org.uk/hypothyroidism

Signposting to further information:

The British Thyroid Foundation and Thyroid UK are both organisations which provide information and support for people with thyroid disorders.