Download Congenital Hypothyroidism (CHT) - Newborn Bloodspot Screening

Congenital Hypothyroidism (CHT)
Information for Health Professionals
What is congenital hypothyroidism?
Version 1 March 2013
Congenital hypothyroidism (CHT) is a condition where the baby’s thyroid gland fails to
develop or work properly and fails to make the thyroid hormone called thyroxine.
Thyroxine is needed for normal growth and development.
What causes congenital hypothyroidism?
If the problem is with the gland itself this is called primary congenital hypothyroidism.
This can be caused by the thyroid gland being absent (agenesis), being positioned in the
wrong place (ectopic thyroid) or severely reduced in size (hypoplastic). Another cause
of primary hypothyroidism is when the gland is normal or enlarged in size and in the
correct position, but there is a problem with the production of thyroxine
(dyshormonogenesis).
Alternatively, hypothyroidism can be caused by defects earlier in the chemical pathway
that regulates the production of thyroxine. The thyroid gland doesn’t work in people
who have very low levels of thyroid stimulating hormone (also called thyrotropin),
produced by the pituitary gland. This is called secondary hypothyroidism. Not all cases
of secondary hypothyroidism are detected by newborn screening.
What are the clinical effects?
The thyroid gland usually starts working in the unborn fetus from about 20 weeks
gestation. The mother’s own thyroid doesn’t provide enough thyroxine to maintain
sufficiently high levels in the fetus.
In very severe cases of CHT babies may be born with, or quickly develop, some of the
signs and symptoms of CHT. These may include feeding difficulties, sleepiness,
constipation and jaundice. However, CHT is rarely diagnosed by clinical means in the
newborn period.
If babies with CHT are not treated, they fail to grow properly and will have ‘mild to
severe’ mental disability. In the most severe cases children also have a lack of coordination, jerky movements and tremors. In general, patients with complete absence
of the thyroid gland (called thyroid agenesis) are the most severely affected.
Babies with secondary hypothyroidism often have additional health problems. These can
include facial features, low blood sugar, jaundice and small genitals. Some children with
secondary hypothyroidism don’t develop the
condition until they are older, and present in
later childhood with reduced physical growth
from associated pituitary insufficiency. These
children will not be identified by newborn
bloodspot screening.
How common is congenital
hypothyroidism?
The flow chart shows the results of babies
screened from April 2011 to March 2012 in
Wales. There were 35,535 babies screened and
20 babies were confirmed to have CHT and 20
babies on further tests were found not to have the condition.
Why does a baby have congenital hypothyroidism?
Congenital hypothyroidism is not usually an inherited condition. In the rare cases it is
inherited, it is usually the condition where the thyroid gland is in the right place but it
cannot produce thyroxine (dyshormonogenesis).
What are the benefits of screening for congenital
hypothyroidism?
The aim of screening is to identify as soon as possible which newborns are more likely
to have CHT so that a diagnosis can be made and treatment can be started. Treatment is
very effective at preventing physical and mental disability. Treatment should start by 21
days of age.
What is the treatment for congenital hypothyroidism?
Babies with primary hypothyroidism are treated by replacing the thyroxine that the body
cannot produce. This is levothyroxine (thyroxine), given once a day, in the form of
crushed tablets by mouth. Regular blood tests are needed to check the thyroxine levels
and make sure the dose is correct. The later the treatment is started, the more the
baby’s development is affected by the condition.
How effective is this treatment?
Experience with screening for congenital hypothyroidism in the UK has found that
almost all children who are diagnosed and treated from an early age will grow and
develop normally.
However, a small proportion of children who have had severe hypothyroidism in the
womb may have some difficulties such as poor hearing, clumsiness or trouble with
learning. These problems can be reduced if hypothyroidism is picked up early and
treated as described above.
Further information
http://www.btf-thyroid.org/
http://www.gosh.nhs.uk/medical-conditions/search-for-medical-conditions/congenitalhypothyroidism/