maternal Hypothyroidism

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maternal Hypothyroidism

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Dragonfly
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Topics: 27
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08/19/08 - 12:29 PM

I have a question which may be silly but just got me thinking:

as you all know TSH can cross placenta whereas T3/T4 not so much. so in a mother with primary HypoT3/T4 that TSH is high.
does that result in "Hyperthyroidism in fetus" due to high TSH that reaches it?
is this the reason for spont. abortions in them?
(i know most these women are infertile but if they do become pregnant!)

thanks smiling face

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nightflight1945
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08/20/08 - 01:39 PM

First of all I say it is a really wise ,interesting question and second all of us even professors of university are students ,so we don't have anything called silly question.Please feel free to ask any question u have.

As far as I know TSH passes placenta , but not completely and also it is very small amount compared to fetal blood TSH(I can't remember the exact ratio) , and also we don't have anything called fetal hyperthyroidism.

The reason for infertility in hypo is anovulation and for abortion is decreased metabolism of tissues that cannot regenerate and endometer cannot decidualized properly(it is another reason for menorrhagia is hypo)

Eagle_303
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08/20/08 - 08:21 PM

None of The following cross the placenta :

TSH,
T3,
T4 and
TBG

Following do cross the placenta :

TSI
Antithyroid medicines

Best of luck

Dragonfly
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08/21/08 - 12:43 PM

thanks both of you! great points smiling face

Eagle: I am qoating the TSH thing from "moore essentials of GYN". (the book we studied back in med school), there is a table in there and according to that table TSH can cross placent?!

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Eagle_303
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08/21/08 - 01:40 PM

Dragonfly wrote:
thanks both of you! great points smiling face

Eagle: I am qoating the TSH thing from "moore essentials of GYN". (the book we studied back in med school), there is a table in there and according to that table TSH can cross placent?!

Probably you are mistaken.

TSH absolutely never crosses the placenta.T4 and T3 do try to cross but are degraded due to enzymes present in the placenta so their quantity crossing placenta is extremely low.

Ref: http://books.google.com/books?id=YPd9Xqo0dZgC&......

Please check the Question No 84-85
Serum thyroid-stimulating hormone (TSH) was assayed by the radio-biological method of Querido et al. (1953) in 50 pairs of mothers and newborn infants. As a control 20 healthy, non-pregnant women were examined. Compared to that of normal, non-pregnant women the maternal serum TSH concentration was raised. The serum TSH level of the newborn immediately after delivery was about half that of healthy, non-pregnant women and much reduced in comparison with that of the mother in labour. From these results it was concluded that maternal TSH does not pass through the placental barrier. The development and function of the fetal thyroid depend on TSH stimulation from the fetal pituitary and are unrelated to maternal pituitary stimulation.
Reference : http://www3.interscience.wiley.com/journal/119695...

Edited by Eagle_303 on 08/21/08 - 01:58 PM

hopeofglory87
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Topics: 23
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08/28/08 - 02:08 AM

what I've learnt is that
TSH, I, PTU, MZ, antithyroid Ab cross placenta

Dragonfly
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09/03/08 - 01:35 PM

thanks guys. i don't know what to say. about antithyroids though, i know PTU crosses the placenta less than MMZ therefore is more prefered during pregnancy.
any other opinions?

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yukti_5
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10/13/08 - 03:11 PM

Fetal HYPERthroidism can be seen in mothers suffering from Goitre.

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