Thyroid Function in Patients with Atrial Fibrillation and Stroke

Thyroid-related issues?

Hello, Director Hsiao.
My mother is 64 years old and experienced a mild stroke in early March 2014.
She is currently showing stable and improving recovery.
Due to her atrial fibrillation, her attending physician prescribed Dronedarone for treatment, and she is also taking anticoagulants (Rivaroxaban), antihypertensive medications, and cholesterol-lowering drugs as part of her comprehensive treatment.

In July of this year, her thyroid function tests showed T3 at 0.4, T4 at 9.1, and TSH at 15.799.
I would like to ask if these values indicate hypothyroidism? Is it possible that the medications have affected the test results, or could there be other reasons for the low levels? I have read in medical literature (package insert) that Dronedarone may potentially cause hypothyroidism.
Currently, my attending physician has stated that these values do not have any significant impact on her health and has not prescribed any thyroid-related medications, suggesting that we should retest in 3-6 months.
I would like to inquire whether not taking thyroid medication could affect my mother's health.
We have reduced the Dronedarone dosage to one tablet per day (the thyroid blood test was done while she was taking two tablets per day).
Will the T3, T4, and TSH levels potentially return to normal due to the reduced Dronedarone dosage? What would be the most appropriate treatment moving forward?
I appreciate your guidance on these questions.
Thank you very much!

KK, 30~39 year old female. Ask Date: 2014/08/09

Dr. Xiao Yongxun reply Internal Medicine

1.
Amiodarone is a commonly used medication for the treatment of arrhythmias, and it is quite effective.
However, it can affect iodine metabolism, leading to either hyperthyroidism or hypothyroidism; therefore, regular monitoring of thyroid function is necessary.
If such conditions arise, the dosage is typically reduced or the medication may be discontinued, which can restore normal function; however, continuous regular monitoring of thyroid function is required.
Evidence-based medicine does not recommend the use of any thyroid medications.
2.
The patient's T3 level is 0.4, T4 is 9.1, and TSH is 15.799.
It is unclear what testing method was used and what the units are.
The normal reference ranges are as follows: Triiodothyronine (T3): 0.45-1.37 ng/ml, Thyroxine (T4): 4.5-12 µg/dl, Thyroid-Stimulating Hormone (TSH): 0.49-4.67 µIU/ml.
Based on our hospital's reference values, the patient's condition should be acceptable.
It is advisable for you to discuss this with the patient and their attending physician before making any decisions.

Reply Date: 2014/08/09

More Info

Understanding thyroid function in patients with atrial fibrillation (AF) and stroke is crucial, especially in the context of your mother's recent health developments. Based on the thyroid function test results you provided—T3 at 0.4, T4 at 9.1, and TSH at 15.799—it does indeed suggest hypothyroidism. In this scenario, the elevated TSH level indicates that the pituitary gland is producing more thyroid-stimulating hormone in an attempt to stimulate the thyroid gland to produce more thyroid hormones (T3 and T4), which are low.

Hypothyroidism can have various causes, including autoimmune diseases (like Hashimoto's thyroiditis), iodine deficiency, or it can be secondary to medications. You mentioned that your mother is taking several medications, including Dronedarone (the drug referred to as "臟得樂錠"), which has been associated with thyroid dysfunction in some patients. While Dronedarone is primarily used to manage AF, it can indeed affect thyroid hormone levels, potentially leading to hypothyroidism. However, it’s essential to consider that the thyroid function can also be influenced by other factors, including underlying health conditions, dietary factors, and other medications.

Your mother's physician's decision to monitor her thyroid function without immediate treatment may be appropriate, especially if she is asymptomatic. Many patients with mild hypothyroidism can remain stable without treatment, and the levels may normalize on their own, particularly if the underlying cause is addressed (like adjusting medications). The recommendation to recheck thyroid levels in 3-6 months is a standard approach to ensure that any changes in thyroid function are monitored closely.

Regarding the reduction of Dronedarone dosage, it is possible that this may lead to an improvement in thyroid function tests over time. However, it is not guaranteed, as the thyroid gland's ability to produce hormones can be influenced by various factors, including the duration of hypothyroidism and the presence of any autoimmune conditions.
In terms of potential impacts on your mother’s health, untreated hypothyroidism can lead to symptoms such as fatigue, weight gain, depression, and cognitive impairment. However, if she is currently stable and not exhibiting any symptoms, the risk may be lower. It is essential to maintain regular follow-ups with her healthcare provider to monitor her condition and adjust treatment as necessary.

If her thyroid levels do not improve or if she begins to exhibit symptoms of hypothyroidism, it may be necessary to initiate thyroid hormone replacement therapy, typically with levothyroxine. This treatment is generally well-tolerated and can effectively normalize thyroid hormone levels, improving overall health and potentially reducing the risk of complications associated with both hypothyroidism and atrial fibrillation.

In summary, while your mother's thyroid function tests indicate hypothyroidism, the decision to treat or monitor should be based on her overall clinical picture, symptoms, and response to any medication adjustments. Regular follow-up and communication with her healthcare provider will be crucial in managing her health effectively.

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