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Question :

Posted On : 24 Jul 2006

I need clarification regarding congenital hypothyroidism screening. Some countries do screening for TSH from cord blood while some screen by T4 levels from neonates at Day 5 of life. Why the difference in preferance? Which is more sensitive for detection of primary hypothyroidism?

Expert Answer :

No expert answer available.

Answer Discussion :

Dr Sushil Madan

Maternal TRH can cross the placenta but not the tsh ,while fetal thyroid gland andhypothalimic-pituitary-thyroid axis functionlargely independently of that of the mother.Hence TSH REMAINS THE MOST SENSITIVEINDEXof primary hypothyroidism at birth.After 5 days free T3 ESTIMATION CAN BE DONEwhich is 4 times more potent than T4.

18 years ago

UJWAL KARIHOLU

Hi
I am not sure about measuring T4 levels on day 5 of life, but since I have been working in UK for a few years now I can tell you what is being done here. A test called ' Guthrie ' is done at 7-10 days of life. This basically screens for Congenital Hypothyroidism and several others like Phenylketonuria etc. What basically you are looking at is TSH levels. The problem with this test however is that you can only detect cases of Primary hypothyroidism where TSH would be raised but not Seconday where TSH levels won't be raised. And you do this test at 7-10 days of life as the effect of maternal hormones wears off by this time. I hope that answers your question.

18 years ago

kantakumari

t4 is more specific,

18 years ago

kantakumari

18 years ago

Dr. M Natarajan

cordblood

18 years ago

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