What Causes Low TSH Levels While On Medication?

Posted on Sun, 5 Jul 2015

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

Sun, 5 Jul 2015 Answered on

Mon, 27 Jul 2015 Last reviewed on

Question : I have a thyroid problem and have been on thyroid med's for 32 years. But I have very very low tsh.
Always I am running into the problem where the doctor can't understand why my blood results are in good range on T3,T4,and T7 but so low on tsh when taking throid med;s. I also get hospitalize when not taking my med's. What is my problem?

Answered by Dr. Ajish TP (6 hours later)

Brief Answer:
You may have to decrease the dose of thyroxine

Detailed Answer:
Hi,

Welcome to HCM. I have gone through the question and understand your concerns. The condition in your question is not a common situation.

If you were initially started on thyroid medications for primary hypothyroidism ( low T3, T4 and high TSH), you need to decrease the dose of thyroid medications to 100 mcg now.

Please do a free T3 & free T4 while doing thyroid function test next time.

Hypothyroidism with low TSH is seen in

1. Thyroid hormone over dosage - where you have to decrease the dose
2. Central hypothyroidism - here pituitary is not producing enough TSH

Hope I have answered your questions. If you have any further queries I will be happy to help you

Regards,

Dr Ajish TP [MD,DM]
Consultant Endocrinologist

Above answer was peer-reviewed by : Dr. Raju A.T

Follow up: Dr. Ajish TP (38 minutes later)

I have tried to drop the dose of thyroid med, and it was so bad that I was told to take an extra dose. How do I find out, about the pituitary problem you spoke of?
Thank you.

Answered by Dr. Ajish TP (1 hour later)

Brief Answer:
Please check the initial thyroid function reports

Detailed Answer:
Hi,

Welcome back.

The initial thyroid function before stating thyroid medications will tell you whether you have a pituitary problem or not. In pituitary problems the initial report will show low T4, T3 and TSH.

If you don't remember the initial thyroid function test, the only way is to gradually decrease the thyroid medications and follow up the thyroid function tests. If you find it difficult to decrease dose abruptly, you can do it in small increments of 12.5 mcg every 6 weeks.

Another way is to look at other pituitary hormones like cortisol, prolactin and LH.

Regards

Dr Ajish TP

Above answer was peer-reviewed by : Dr. Raju A.T