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What Is The Right Carbimazole Dosage For Hyperthyroidism?

Posted on Sat, 6 Sep 2014

Question: I was recently told i have hyperthyroidism. High free t4, normal t3 and low TSH of 0 (zero). After taking carbimazole for 3 weeks my Free t4 has come back to normal and still going down but TSH is still 0. I was originally admitted for Atrial Fibrallation, which according to the doctor who attended to me told me was caused by my Hyperthyroidism.

Now, even after my T4 coming to normal my doctor tells me to continue the same dosage (15mg) daily for 1 month. I am concerned if I continue my current dosage of 15mg dailly my t4 will go in hypothyroidism. Wanted to seek a second opinion from an Endocrinologist

Answered by Dr. Shehzad Topiwala (8 hours later)

Brief Answer:
Thyroid

Detailed Answer:
It is unlikely you will go into hypothyroidism with this dose. it is a modest dose only.

However, there is no way to predict the response with certainty in a given individual and the hence the standard practice is to check the TSH and free T4 after 4 weeks of treatment with this medication (often along with CBC and liver/kidney/electrolytes/calcium/glucose).

Secondly, the TSH is very well known to take time to recover into the range of normalcy despite the free T4 normalizing much earlier. This is a very well known concept amongst endocrinologists and is referred to as the 'the TSH lagging behind'.
So again this too represents nothing worrisome, as long as the free t4 has significantly improved.

Typically when I see someone like you, I check TSH and Free T4 initially every 4 weeks and then less frequently till a stable dose of carbimazole has been determined, to render the individual in a normal thyroid state. Over time a steady lower dose of carbimazole may suffice.
There are several other facets to attend to in this context such as the consideration of the role of radiation for permanent treatment and attempting a gradual withdrawal of carbimazole about 18 months after diagnosis of hyperthyroidism to see if the condition has improved by itself.
This withdrawal may be attempted sooner or later too depending on how the thyroid blood tests look anytime during the course of this condition.
If possible it is best to be under the care of an endocrinologist for the management of hyperthyroidism.

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

Follow up: Dr. Shehzad Topiwala (3 hours later)

Thanks a lot for your excellent information. You are absolutely right I am not under the care of an endocrinologist. My heart doctors says is something he can manage.

Now, one more thing. Do you think it is necessary for me to use non iodized salts in my food?

Thanks,
XXXXX

Answered by Dr. Shehzad Topiwala (8 hours later)

Brief Answer:
Follow up

Detailed Answer:
No it is not necessary for you to do so.

Note: For more information on hormonal imbalance symptoms or unmanaged diabetes with other comorbid conditions, get back to us & Consult with an Endocrinologist. Click here to book an appointment.

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