From the Research
For a patient with Hashimoto's thyroiditis on 75 µg of levothyroxine who has elevated TSH and low T4 levels, the recommended treatment is to increase the levothyroxine dose. The current dose is insufficient to normalize thyroid function, as evidenced by the laboratory values. The dose should typically be increased by 12.5-25 µg, bringing the total to 87.5-100 µg daily, taken in the morning on an empty stomach at least 30-60 minutes before food or other medications. After dose adjustment, thyroid function tests (TSH and free T4) should be rechecked in 6-8 weeks to assess response. The goal is to achieve a TSH within normal range (typically 0.5-4.5 mIU/L) and normalize free T4 levels. Dose adjustments may need to be made gradually, especially in older patients or those with cardiac conditions. In Hashimoto's thyroiditis, the autoimmune destruction of thyroid tissue progressively reduces the gland's ability to produce thyroid hormone, often requiring periodic increases in replacement therapy over time. Patients should be advised to take levothyroxine consistently at the same time each day and avoid taking it with calcium, iron supplements, or certain foods that may interfere with absorption.
Some key points to consider:
- The study by 1 found that normal T3 levels were achieved with traditional LT4 therapy alone in patients who had undergone near-total or total thyroidectomy.
- The study by 2 suggested that a combination of L-T4+T3S in hypothyroid subjects may allow maintenance of normal levels of serum T3, with restoration of a physiological FT4/FT3 ratio and no appearance of adverse events.
- However, the most recent and highest quality study, 2, does not necessarily support the use of combination therapy for all patients, and the primary goal should be to achieve a TSH within normal range and normalize free T4 levels with levothyroxine monotherapy.
- The study by 3 found that L-T4-replacement therapy alone in hypothyroidism is generally believed to result in a normal serum L-T3 and to reflect a euthyroid state, but the mean free T4 was significantly higher than the values in untreated euthyroid patients or normal individuals and may not result in an appropriately normal serum free T3 concentration.
- The study by 4 compared the dose of levothyroxine required to suppress serum TSH to given levels in two clinical groups and found that patients with thyroid cancer required a higher dose of L-T4 to suppress serum TSH to a given subnormal level.
- The study by 5 found that serum TSH levels alone are not adequate to assess the required dose of thyroxine replacement therapy.
Given the evidence, the most appropriate course of action is to increase the levothyroxine dose and monitor the patient's response, rather than switching to combination therapy or making other changes to the treatment regimen.