Endocrine Abstracts

Background: About one in 3000 babies born in the UK have congenital hypothyroidism (CHT), which is usually due to an agenesis of the thyroid gland, but some are due to dyshormogenesis, which can be transient or permanent.

Method: Retrospective analysis of medical notes of infants referred as ‘suspect’ congenital hypothyroidism from the newborn blood spot screening centre to the paediatric endocrinology service at our hospital from January 2002 to January 2013. Data collection and analysis was performed on Microsoft Excel.

Results: Sixty-seven infants were referred to our service, of which 33 infants had ‘confirmed’ CHT. Thyroxine was started at 12 days (median) at a dose of 8.5 μg/kg per day (median) with a dose range from 6.1 to 11.7 μg/kg per day. Serum free T₄ reached the upper end of reference range at 2.1 weeks (median) and serum TSH normalised at 3.4 weeks (median) after start of treatment. Three infants developed significant elevation of free T₄ levels at follow-up, requiring reduction of thyroxine dose. Assessment of permanence of CHT was done at 3 years of life in two infants, who came off thyroxine and five infants were eligible for trial off thyroxine treatment.

Conclusion: Although we are using less than the recommended dose of thyroxine (recommended dose is 10–15 μg/kg per day), we are able to normalise the thyroid function tests in line with the national standards. Thus we have chosen to continue with our current starting doses. The audit has highlighted the importance of assessing permanence of congenital hypothyroidism at 2–3 years of age by a trial off thyroxine and checking thyroid function tests in 6 weeks.