Pioneering study identifies over 100 genes linked to thyroid hormone levels

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A new study has identified over 100 genes linked to thyroid hormone levels, shedding light on the causes of hypothyroidism and hyperthyroidism (underactive and overactive thyroid).

A team at the University of Leicester worked together with scientists from Queen Mary University of London and from the University of Tartu in Estonia to undertake the largest ever study of the genetics of thyroid hormones, now published in the journal Nature Communications.  

Not only was it the first of its kind to look at how genes affect the function of the thyroid in different ethnic groups, but it also looked at whether the same genetic variation is linked to thyroid cancer.

The study used electronic health records from nearly 250,000 people participating in studies including UK Biobank, the EXCEED study, Genes & Health and the Estonian Biobank.

It’s thought the findings may help to identify future treatments for underactive and overactive thyroid and thyroid cancer, and could also help to identify people at risk of developing these conditions.

Researchers used a new approach to develop risk scores for individual molecular pathways, enabling them to investigate how these molecular pathways are shared between thyroid diseases and other long-term conditions.

The thyroid is a gland in the neck just below the “Adam’s apple”.  It produces chemicals called hormones which control a vast number of bodily processes.

Over 2 million people in the UK are being treated for hypothyroidism (underactive thyroid), where thyroid hormone levels are lower than they should be, and which requires treatment for life with replacement thyroid hormones.  Underactive thyroid can cause tiredness, depression, weight gain, constipation, weakness and a wide range of other symptoms. 

Overactive thyroid is also common, particularly in women, and can cause agitation, anxiety, weight loss, heat intolerance and eye disease.  Both underactive and overactive thyroid can have long-term consequences, including effects on the heart.

Dr Catherine John, who co-led the study at the University of Leicester, said: “We used innovative ‘data science’ approaches, including utilising records of routinely measured thyroid function in consenting participants. This enabled us to undertake the largest genetic study of its kind, which gave us a much more detailed picture of how our genes affect the way our thyroid works, and how diseases of the thyroid might develop.

“This was the first study to look at how genes affect thyroid disease risk in people from diverse ethnic backgrounds. It’s essential that current and future genetic studies reach out more widely to people from all ethnic groups, so that the findings benefit everyone and don’t exacerbate unfair differences in health.”

Dr Alex Williams, first author of the study, said: “In the future, risk scores like the ones developed in this study could help doctors to understand who is at risk of developing thyroid disease, which treatments might work best for different people, and which treatments should be avoided because of potential side-effects.”

The study was supported by the National Institute of Health and Care Research (NIHR) Biomedical Research Centre in Leicester.