How Should I Adjust The Dosage Of Thyroid Medication To Be Taken During First Trimester?

Posted on Fri, 20 Dec 2013

Medically reviewed by Ask A Doctor - 24x7 Medical Review Team

Fri, 20 Dec 2013 Answered on

Mon, 13 Jan 2014 Last reviewed on

Question : Hello, I am 10 weeks pregnant and have no thyroid (thyroidectomy). I was on 125 mcg Synthroid with a TSH of 0.27 pre-pregnancy. After pregnancy was confirmed, my dosage was increased by one extra 125 mcg tab/week. At 6 weeks pregnant, TSH was 1.13, T4 12.7 and Free T4 1.49. At 10 weeks pregnancy, TSH is 3.75, T4 is 13.7, T3 uptake 22, free T4 1.35, and Free T3 2.2. American Thyroid association guidelines state that TSH should be lower than 2.5 in first semester - How should I adjust dosage?

Answered by Dr. Shehzad Topiwala (27 minutes later)

Brief Answer: Yes Detailed Answer: The TSH target you are referring to is correct. However, since you had thyroid cancer and radio ablation,the target is different. It is important to take relatively higher doses of synthroid to suppress the TSH although it can be kept at detectable levels. The 3 circumstances where such intentional over-dosing is avoided are 1) osteoporosis 2) irregular heart rhythm problem 3) chest pain for heart blockage. When I see someone like this in my practice I recommend taking another 125 mcg in addition to the one extra per week already on board. So effectively this would entail taking 9 tablets a week. So one daily and 2 on saturday and 2 on sunday. I check TSH and free T4 in 30-40 days to ensure optimal replacement ie avoid over or under dosing. I strongly recommend you see an endocrinologist for the duration of pregnancy and thereafter because managing synthroid dose during pregnancy, especially in context of thyroid cancer, requires finesse and experience

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar

Follow up: Dr. Shehzad Topiwala (17 minutes later)

Thank you so much for your prompt and detailed reply Doctor Shehzad Topiwala, I truly appreciate it. I am followed by an endocrinologist but she has only checked total T4 and said that other tests were not relevant during pregnancy, which prompted me to do additional blood tests independently and seek out a second opinion. Could I follow up with you when I get my next blood test results? Should I test only for TSH and Free T4 then in 4 weeks? Also, do you think that my current TSH of 3.75 could have had a negative impact on the fetus (I have read literature regarding cognitive impairment in babies whose mothers had higher TSH levels) or is a TSH of 3.75 not overly concerning? Thank you in advance for your help.

Answered by Dr. Shehzad Topiwala (8 hours later)

Brief Answer: Follow up Detailed Answer: Speak with your endocrinologist as to why he or she has not targeted a suppressed TSH in view of your thyroid cancer history. Regardless, I would increase the dose as described above if I saw someone in your situation. You are welcome to send me the lab results for TSH and free T4 done 4 weeks after dose change. However, I reiterate the importance of an endocrinologist closely following you during the entire pregnancy. By that I mean, someone you can visit or call or see in person regularly. Regarding how much the TSH of 3.75 is of concern is tough to answer categorically because studies address large numbers of people statistically, so it is hard to predict the outcome in a given individual. The good news is that at at 6 weeks you achieved a TSH of 1.35 which is well within the desired range for optimal thyroid status. Of course, suppression to lower levels due to the cancer history, was not achieved but that can be aimed for now

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar

Follow up: Dr. Shehzad Topiwala (10 hours later)

Thank you very much for your feedback. I will try reaching my endocrinologist again to address these concerns, and hopefully get a better line of communication going. It has been quite hard to get in touch with her as she does not speak to patients unless it is during appointments, and I was unable to schedule an appointment until mid-march. I will try my best, but if this persists I will contact you again in 4 weeks with lab results. Thank you again for your expert advice and have a wonderful day.