Thyroid Function Impact from Heart Medications: A Patient's Guide

Consultation on the Effects of Medications on Thyroid Function

Hello, Director He.
My mother is 65 years old and has a history of atrial fibrillation.
She previously used the medication Amiodarone for about a year and a half (it was switched to Sotalol in July 2015).
During the use of Amiodarone, she developed hypothyroidism, and her internist prescribed half a tablet of Levothyroxine (100 mcg per tablet) to be taken every morning after breakfast.
However, her latest lab results showed FREE T4: 0.85 (reference range: 0.71-1.85) and TSH: 52.913 (reference range: 0.55-4.78), indicating that her thyroid function is still low.
Recently, during a clinic visit, her attending physician noted that the results were not critically low, so they decided to maintain the current dosage of half a tablet of Levothyroxine every morning after breakfast.

I would like to ask you, Director He, whether my mother's lab values indicate that her thyroid function is very low or just mildly low (she currently does not exhibit common symptoms of hypothyroidism).
Additionally, how should we manage her thyroid medication moving forward? Is there a need to change the Levothyroxine to be taken before breakfast instead of after?
I also have a couple of additional questions:
1.
I have referred to the Levothyroxine medication guide, which suggests that older patients or those with arrhythmias may require a lower dosage.
Is it possible that our physician prescribed the half-tablet dosage based on this principle?
2.
Since my mother has previously taken Levothyroxine and experienced elevated thyroid function when taking a full tablet before breakfast, leading to a temporary discontinuation of the medication, is that why our physician recommended taking it after breakfast instead?
Thank you for your time and assistance with these questions.

JJ, 30~39 year old female. Ask Date: 2016/03/30

Dr. He Dongjin reply Cardiology

Hello, in my personal opinion, it is advisable to temporarily maintain the current dosage.
Free T4 levels have increased, while TSH remains low.
If you are still concerned, you may consider taking it before meals.
We can decide on any adjustments after the next blood test.
A peaceful and joyful heart is indeed good medicine.
Changhua Hospital cares about you.

Reply Date: 2016/03/30

More Info

When managing thyroid function in patients with heart conditions, particularly those on medications like antiarrhythmics, it is crucial to understand the interplay between these medications and thyroid hormones. In your mother's case, her history of atrial fibrillation and the use of antiarrhythmic medications such as Dronedarone (Zyban) and subsequently Sotalol (Xarelto) may have contributed to her thyroid dysfunction, specifically hypothyroidism.

The recent lab results indicate a significantly elevated TSH level (52.913) and a low Free T4 level (0.85), which indeed suggest that your mother's thyroid function is quite low. In general, a TSH level above 10 is considered indicative of hypothyroidism, and levels above 20 often warrant treatment adjustments. Given that her TSH is markedly elevated, it suggests that her thyroid is not producing sufficient hormones, which could lead to symptoms such as fatigue, weight gain, and even cardiovascular issues if left untreated.

Your mother's physician's decision to maintain her current dosage of Levothyroxine (the medication she is taking to supplement her thyroid hormone) at half a tablet daily may be based on her overall clinical picture and the absence of severe symptoms. However, it is essential to monitor her thyroid function closely, especially since she has a history of fluctuating thyroid levels. Regular follow-ups with blood tests every 6-8 weeks are advisable to ensure that her TSH levels are trending down towards the normal range (0.55-4.78).

Regarding the timing of her medication, taking Levothyroxine on an empty stomach is generally recommended for optimal absorption. However, if she has previously experienced issues with her thyroid levels being too high when taking it before meals, it may be worth discussing with her physician the possibility of adjusting the timing or dosage. The goal is to find a regimen that maintains her thyroid levels within the normal range without causing adverse effects.

It is also important to consider the potential side effects of her heart medications. Some antiarrhythmic drugs can affect thyroid function, and it may be necessary to evaluate whether her current heart medications are contributing to her thyroid issues. A thorough discussion with her cardiologist about her current medications and any potential alternatives that may have a lesser impact on thyroid function could be beneficial.

In summary, your mother's thyroid function is currently low, and while her physician believes it is not critically low, it is essential to continue monitoring her levels and adjust her medication as necessary. Regular follow-ups, potential adjustments in the timing of her Levothyroxine intake, and discussions with her healthcare providers about her heart medications will be crucial in managing her overall health effectively. Always consult with her healthcare team before making any changes to her medication regimen.

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