About 1 in 4,000 babies born in the UK has congenital hypothyroidism (CHT). Babies with CHT do not have enough of the hormone thyroxine. The commonest cause of CHT is a poorly developed or absent thyroid gland .The screening test is measurement of thyroid stimulating hormone (TSH). Without thyroxine, babies do not grow properly and can develop serious, permanent, physical and mental disability. Screening means that babies with CHT can be treated early with thyroxine tablets, which will prevent serious disability and allow them to develop normally. If babies are not screened and are later found to have CHT, it may be too late to prevent them becoming seriously disabled.
These thyroid defects may be permanent or transient. Although the baby with CHT should be started on thyroxine promptly, they should be evaluated at some time later to exclude a transient problem.