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Under-active thyroid, pregnant. On thyroxine. Is an increased dosage harmful?

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To: Endocrinologist.I am 5 weeks pregnant and have had an under active thyroid for 12 years. Pre-pregnancy my TSH was 0.98 and i was on 100mcg thyroxine a day. I had a blood test done last week (@ 4weeks pregnant) and my TSH is now 6.68, my doctor has increased the thyroxine by 50mcg, 25mcg when i first found out i was pregnant a week ago and 25mcg today after blood results, so i am now on a dose of 150mcg daily, does this sound correct?
Posted Fri, 20 Apr 2012 in Thyroid Problem and Hormonal Problems
Answered by Dr. V. Kumaravel 12 hours later

Thank you for posting your query.

I do understand that you have been suffering from an under-active thyroid and on thyroxine replacement, currently pregnant. Your concern seems to be related to the dose of thyroxine.

Your pre-pregnancy TSH (Thyroid Stimulating Hormone) of 0.98 is perfectly fine and a dose of 100mcg is also adequate. In pregnancy, the demand for thyroxine generally increases as the fetus is also initially dependent on maternal thyroxine. Usually the dose of thyroxine is increased by 50mcg during pregnancy.

Your TSH of 6.68 also signifies that the dose is inadequate and I would concur with your Endocrinologist to increase the dose of thyroxine to 150mcg. You can monitor your TSH and maintain your TSH values to less than 2.5 throughout pregnancy. The dose of thyroxine can be titrated as per your TSH values.

Hope I have answered your query. Please accept my answer in case you do not have further queries.

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