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Thyroid Diseases

Hypothyroidism Detected During Pregnancy

07/09/2009

Question:

I was detected hypothyroid during my first pregnancy and simultaneously had spontaneous abortion. After two months I have conceived again. this time My T3 and T4 levels are within normal range but my TSH is 11. I am on thyronorm 25mg. What should I do?

Answer:

Your thyroid blood test abnormality (a slightly elevated TSH with a normal T4 and T3) represents a very small amount of hypothyroidism. If your hypothyroidism is due to an autoimmune disease (which is the most common cause) then you would have an increased risk of miscarriage even if your TSH were normal (we're not sure why). Assuming that the pregnancy goes on successfully, it is not clear whether this tiny amount of hypothyroidism has any bad effects on the baby.

A study published in 1999 showed that pregnant women with an elevated TSH at 17 weeks of pregnancy who were being treated with thyroid hormone (as you are) had children with IQ's similar to the IQ's of children born to mothers who had a normal TSH. Thus, if this amount of hypothyroidism has any effect on the baby at all, all indications are that it would be a very small effect. Still, your thyroid pills should be increased to a full replacement dose with the goal being a normal TSH.

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Response by:

Thomas A Murphy, MD, FACP, FACE Thomas A Murphy, MD, FACP, FACE
Associate Professor of Medicine
School of Medicine
Case Western Reserve University