Effects of Thyroid Deficiency During Pregnancy | Action Medical Research | Children's Charity

The harmful effects of thyroid deficiency during pregnancy

This research was completed on 27 May 2008

Published on 6 October 2006

Thyroid deficiency during pregnancy can cause brain damage in unborn babies. It can lead to long-term health problems, such as mental impairment and learning difficulties. Researchers are investigating the molecular mechanisms behind the supply of thyroid hormone to an unborn baby’s developing brain. They hope to reveal possible ways of sparing babies from brain damage in the future.

What's the problem and who does it affect?

Unborn babies at risk of poor mental development

Each year, many unborn babies around the world develop irreversible brain damage because they lack sufficient levels of thyroid hormones during pregnancy. They may go on to suffer serious health problems late into childhood. They can have poor mental functioning, a low IQ and learning disabilities.

Many different disorders can lead to a lack of thyroid hormones in unborn babies. Iodine deficiency during pregnancy causes many of the most severe cases of mental impairment and cretinism worldwide. The World Health Organisation has estimated that millions of people have some degree of brain damage due to iodine deficiency experienced before their birth.

Within the UK, estimates suggest some two to five percent of pregnant women have an underactive thyroid gland without even realising it – they have no symptoms.1Their babies can develop problems such as difficulties with schoolwork and low IQs. Babies with poor growth in the womb – which affects up to 10% of pregnancies – can also be affected by low thyroid hormone levels, which may be associated with learning difficulties in childhood.2

What is the project trying to achieve?

The vital supply of thyroid hormones to the brain

Researchers working on this project are investigating the molecular mechanisms that are responsible for keeping up the crucial supply of thyroid hormones to the developing brains of unborn babies.

They are focusing on a particular protein, called MCT8. They suspect MCT8 plays a major role in the delivery of thyroid hormone from the blood into brain cells – a recent discovery shows some people with very severe mental impairment have abnormalities in the gene for MCT8.

The researchers hope to reveal important new information about the role of MCT8 in babies’ brains as they develop and grow during pregnancy. They are looking at how much MCT8 is produced, where it’s is located and how it affects the development of nerve cells. They are also looking for any changes in MCT8 in babies who don’t grow properly in the womb.

What are the researchers' credentials?

Project LeaderProfessor J A Franklyn MD PhD FRCP FMedSci
Project team
  • Dr Shiao-yng Chan PhD MRCOG
  • Prof Mark D Kilby MD MRCOG
  • Prof Ann Logan PhD
  • Dr Christopher J McCabe PhD
LocationDivision of Medical Sciences, University of Birmingham and Department of Fetal Medicine, Birmingham Women's Hospital
Other locations
  • Department of Fetal Medicine, Birmingham Women’s Hospital, Birmingham
  • Division of Medical Sciences, University of Birmingham, Wolfson Research Laboratories, Birmingham
  • Division of Medical Sciences, University of Birmingham, Institute of Biomedical Research, Birmingham
DurationOne and a half years
Grant awarded6 July 2006
Start date1 November 2006
End date27 May 2008
Grant amount£26,071.00
Grant codeSP4142

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The researchers working on this project are experts in the study of how thyroid hormones function in unborn babies’ brains, thanks to a long-standing collaboration between three internationally renowned academics. Professor Jayne Franklyn is an expert in the function of thyroid hormones, Professor Mark Kilby has detailed knowledge of the fetus and placenta, and Professor Ann Logan has expertise in the biology of the nervous system. This multidisciplinary team has published many eminent papers in peer-reviewed journals. The experiments will take place within the Institute of Biomedical Research, opened in 2003, which has state-of-the-art facilities. The laboratories are next to the Birmingham Women’s Hospital, a tertiary referral hospital with one of the leading Fetal Medicine Departments in the country. Some 7,000 women give birth at the hospital each year, meaning the researchers have ready access to patients for their studies.

Who stands to benefit from this research and how?

Towards new treatments that prevent learning disabilities

A large number of people worldwide are suffering from chronic health problems because of deficiencies in thyroid hormones they experienced before birth. The results of this project should improve understanding of the mechanisms that cause these common conditions.

Researchers hope this important new information will give clinicians the insight they need to develop potential new treatments, which might improve the delivery of thyroid hormones to unborn babies. The ultimate aim is to find treatments that prevent or minimise the risk of impairments in mental function.

The devastating conditions caused by thyroid deficiencies during pregnancy carry a significant personal, social and financial cost to the individuals concerned, their families and the state. In the long term, this research could help improve the quality of many children’s lives, and reduce the financial costs of special education and social care to the state.


  1. Lazarus JH, Premawardhana LD. Screening for thyroid disease in pregnancy. J Clin Pathol. 2005, May;58(5):449-52.
  2. Chan S, Rovet J. Thyroid hormones in fetal central nervous system development. Fetal and Maternal Medicine Reviews 2003, 14: 177-208.
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