A baby with congenital hypothyroidism (CH) will experience serious learning problems later on in life. Data about CH diagnoses showed laboratories needed to use the same test when screening babies. Data about CH treatment also showed some children no longer need treatment by three years old. Complications from CH are now rare because most babies are diagnosed early and can start lifelong treatment.

Why was the work needed?

A baby with CH does not make enough of the hormones normally produced in the thyroid gland. This can result in poor growth and under-developed brains. In the UK, we screen babies for CH using the ‘heel prick’ test. Over the 30 years of its use, the heel prick test has developed and we now send more babies than ever for follow up tests and treatment. But we don’t really know if more babies are born today with CH than 30 years ago, if testing is getting better or if we are simply over diagnosing CH.

What happened?

The study showed that the number of babies born each year diagnosed with CH has doubled since before screening began. Researchers also found that around 75 of the 500 babies who started on treatment no longer needed it by three years old. They saw that the screening programme was effective with all babies diagnosed before the age of one. However, the laboratories that used more sensitive tests ended up sending more healthy babies for further assessment. Encouraging all laboratories to use the same test could reduce the number of healthy babies being unnecessarily investigated.

What were the benefits?

Clinicians are now given advice to re-test more children on treatment for CH when they are around 3 years old to help decide if treatment needs to continue.

Screening laboratories have agreed to use the same threshold to try to reduce the number of healthy babies being investigated. They have also agreed to monitor this change carefully to make sure that this does not increase the numbers of late diagnoses.

What type of data was involved?

The study used the British Paediatric Surveillance Unit (BPSU) and the UK Newborn Screening Laboratory Network (UKNSLN) to identify all babies diagnosed with CH over one year. Because CH is a rare disease, it is very important to include all children born with CH to get accurate numbers for historical comparisons.

Once cases had been identified, the treating clinician was asked to fill out a questionnaire, outlining demographic and treatment data about the case. Staff at screening laboratories were also asked to fill out a questionnaire, outlining the results of the babies’ heel prick tests. While data about individual children was de-personalised, the data was not completely anonymous as the researchers needed to be sure that two doctors were not reporting the same child.   

Ethical approval for this study was granted by the Cambridgeshire South Research Ethics Committee. Permission was also granted to collect patient identifiable information by the National Information Governance Board, under a Section 251 approval of the NHS Act 2006. Section 251 allows researchers to use identifiable data when it is not possible to get consent from every patient. All patients can opt out of their data being used.

Who funded and collaborated on this work?

The study was funded by Public Health England and the Department of Health. Researchers at the UCL Great Ormond Street Institute for Child Health collaborated with the British Thyroid Foundation, the British Paediatric Surveillance Unit and the UK Newborn Screening Laboratory Network.

Where can I go for more information?

RCPCH: Congenital Hypothyroidism study