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What causes heart palpitations and panic attacks when on Levothroid?

Answered by
Dr.
Dr. Binu Parameswaran Pillai

Endocrinologist

Practicing since :2003

Answered : 1418 Questions

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Posted on Fri, 2 Jan 2015 in Thyroid Problem and Hormonal Problems
Question: I am a 53 year old female. 20 years ago I was diagnosed with Hashimoto's and put on levothroid .85 mcg. After a few years, I found that I was having heart palps so I was switched to Synthroid which seemed to help for many years. Lately, my TSH was up slightly to 5 and so my dr put me on 100 mcg. The heart palps, chest pain, panic attacks began and so I was moved back down. However, the heart pals, chest pain, back ache and heart pounding continues. I have had an echocardiogram, stress test and wore a monitor... heart is fine. But something has changed drastically. When I don't take my synthroid, the palps ease and I feel so much better without any other symptoms...I'm not tired, my hair and nails are fine... but my TSH is now back up to 85. However, all other thyroid tests are okay. Antibodies less than 20, TPO Ab 31, T3 free 1.7 and T4 free .69. Why am I reacting like I'm hyper on almost any synthroid dose... did the formulation change?

BTW, I have Crohn's when I was 16 but after treatment with prednisone, never had another issue with it. Otherwise, I am healthy, active, 150 lbs, 5'9, and eat very well. I don't smoke or do any drugs or caffeine.
doctor
Answered by Dr. Binu Parameswaran Pillai 50 minutes later
Brief Answer:
Small dose of SYNTHROID

Detailed Answer:
Good day,
Noted your concern. . Then the possible cause of your symptoms could be from excess synthroid dose or from menopausal symptoms.

Your TSH is 80 and that means that, you may need to go back on Synthroid 85 mcg. ( I presume you are off Synthroid now)
Synthroid is levothyroxine and the formulation hasn't changed.
Please try to start with a small dose of Synthroid first. Start with 50 mcg for 10 days and go up to 85 mcg after that. Stay on that dose and recheck TSH after 6 weeks.

If you feel hotflushes along with palpitations, menopausal hormone changes could be contributing as well.

Regards
Binu
Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar
doctor
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Follow up: Dr. Binu Parameswaran Pillai 13 minutes later
Hi XXXXXXX

Thanks for your reply. I don't think my palps are related to menopause which I went through easily 5-6 years ago. I don't get hot flashes, I sleep well, eat well, haven't gained or lost weight.

The reason I think it's related to synthroid is this happened before years ago. But this time, any dose seems to bother me. If I am not having any other hypo symptoms (and all other tests were normal) do I really need synthroid? Or what about Armour or Natur-Throid? Wouldn't it make sense to try something else?
doctor
Answered by Dr. Binu Parameswaran Pillai 1 hour later
Brief Answer:
TSH rise is compensatory

Detailed Answer:
Got your point. But you should understand that T4 and T3 are normal at the expense of high TSH. TSH is secreted from pituitary gland and stimulate thyroid gland to produce T3 and T4. If the thyroid is failing, TSH is secreted by pituitary in excess to stimulate thyroid. However, after a while elevated TSH can no longer stimulate thyroid and t4 and t3 will fall. Then you will start getting hypo symptoms.

Hence it is better to start on a smaller dose now.

Armour thyroid is an animal thyroid preparation which is not recommended by most endocrinologists ( including myself). It is difficult to titrate and offer no extra benefits compared to Synthroid. Many patients prefer to take Armour thyroid because of the "natural" tab attached to it.


Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar
doctor
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Follow up: Dr. Binu Parameswaran Pillai 9 hours later
It makes sense... in the past Synthroid has helped immensely. It's just that the heart palps, chest pain and heart pounding only seem to cease, even at a dose as low as 1/2 a .75 mcg, when I stop taking it altogether.

I will try continuing 1/2 a .75 (or .375) each day and see if I can tolerate it. I am just concerned because Synthroid's warning label clearly states to contact your dr. if heart palps, arrhythmia or other side effects are occurring. Are you saying that the side effects will eventually subside?
doctor
Answered by Dr. Binu Parameswaran Pillai 1 hour later
Brief Answer:
Side effects

Detailed Answer:
You are right. In excess doses, Synthroid (levothyroxine) can make the heart to beat faster and can cause an arrhythmia( atrial fibrillation). But that is in high doses. You may start with a small dose as mentioned earlier.
The side effects are minimum if you start at a low dose and titrate it carefully to keep TSH in normal range. You will have to work closely with your Endocrinologist to acheive that goal. The side effects usually settle with a right dose.
Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar
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