Exploring Combined T4 and T3 Therapy Post-Thyroidectomy in Taiwan - Internal Medicine

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After undergoing a total thyroidectomy, managing thyroid hormone replacement therapy can be complex, particularly when considering the combination of levothyroxine (LT4) and liothyronine (LT3). In your case, you have been on a stable dose of LT4 (100 mcg daily) since your surgery in July 2022, but you are experiencing symptoms such as fatigue, difficulty concentrating, and weight gain, which can be indicative of inadequate thyroid hormone levels or improper dosing.

The thyroid hormone replacement therapy primarily aims to normalize TSH (Thyroid Stimulating Hormone) and free T4 levels. Your recent lab results show elevated T4 levels (7.16 and 8.97 ng/dL) and a significantly elevated TSH (6.2813 u IU/mL), which suggests that your current LT4 dosage may not be adequately suppressing TSH production. This could explain some of the symptoms you are experiencing, as high TSH levels can lead to hypothyroid-like symptoms despite elevated T4 levels.

In terms of your question about the addition of LT3 to your regimen, this is a topic of ongoing debate in the medical community. Some studies suggest that combining LT4 with LT3 can improve symptoms in patients who do not feel well on LT4 alone, particularly those who report fatigue or cognitive issues. However, this approach is not universally accepted, and many endocrinologists prefer to manage thyroid hormone levels with LT4 alone, as it is more stable and has a longer half-life, which allows for once-daily dosing.

In Taiwan, the standard practice typically involves adjusting LT4 dosage to achieve optimal TSH and T4 levels. The use of LT3 is less common and may not be routinely prescribed unless there is a clear indication that a patient is not responding adequately to LT4 alone. If you are considering increasing your LT4 dosage to 150 mcg, it is crucial to consult with your healthcare provider before making any changes. Self-adjusting your medication can lead to further complications, including hyperthyroidism if the dosage is too high.

Regarding Natural Desiccated Thyroid (NDT), it is a combination of T3 and T4 derived from porcine thyroid glands. While some patients report better symptom relief with NDT, it is not widely used in Taiwan and may not be readily available. The choice between synthetic hormones (LT4 and LT3) and NDT often depends on individual patient response and physician preference.

It is also essential to monitor your thyroid hormone levels regularly, including free T4 and free T3, to ensure that your therapy is effective. If your physician has not ordered these tests, you may want to discuss this with them, as they can provide valuable information about your thyroid function and help tailor your treatment plan.

In summary, while the combination of LT4 and LT3 therapy may benefit some patients, it is essential to approach this under the guidance of a healthcare professional. Regular monitoring and open communication with your endocrinologist will help ensure that your thyroid hormone levels are optimized and that your symptoms are managed effectively.