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Congenital Hypothyroidism (CHT)

The test used to screen for CHT is thyroid stimulating hormone (TSH), which is measured by immunoassay (AutoDELFIA®).

All raised TSH levels (>5 mU/L) are checked in duplicate on the original sample and the average result is taken.  Samples with confirmed levels >20 mU/L are treated as positive and urgent follow up is arranged at RMCH, unless the baby was still in a local hospital in which case follow up is initiated by the corresponding medical team.

Confirmed TSH levels between 8 and 20 mU/L are treated as borderline and a repeat sample is requested, to be taken 7-10 days after the first sample, to allow for normalisation of transient increases. If the borderline result is persistent or has moved into the positive range (>20 mU/L) clinical follow up is initiated at RMCH.

Babies born at a gestation of less than 32 weeks require a repeat sample on day 28 (date of birth counted as day 0) or at discharge from hospital, whichever is sooner.

Transient hypothyroidism can be related to prematurity, acute illness, drugs, maternal antibodies, maternal iodine supplements and exposure to iodine-containing compounds in imaging/surgery.

In the case of a positive CHT result on screening, the laboratory will telephone the relevant community midwives office and request that a midwife visits the family the same afternoon, unless it is a Friday. If a positive result occurs on a Friday, the midwife should visit on Sunday to inform the family. The appointment takes place the following working day (unless advised otherwise) and the family should report to the Medical Investigations Unit on Ward 76 of RMCH, as close to 9am as possible.

Once on the ward the following will be performed: blood tests for thyroid function on baby and mother, clinical examination and thyroid scan of baby. When the results of the tests are available (usually around lunchtime) a doctor will discuss them with the family. If hypothyroidism is confirmed treatment (in tablet form) will commence immediately. Advice will be given on the condition and how best to give the tablets. The visit is usually complete by mid-afternoon.

At the initial home visit the family should be given a copy of the 'Congenital Hypothyroidism is suspected' leaflet.