SAN FRANCISCO — The scientific evidence does not support adding T3 therapy to T4 therapy for patients with hypothyroidism, but some patients insist on it, according to Dr. Hossein Gharib.
Most patients do well on T4 therapy alone, but some complain of fatigue, low energy, weight gain, or depressed mood despite adequate thyroid hormone replacement on T4 therapy. They may read on the Internet that some patients with hypothyroidism or their treating psychiatrists report mood improvements after adding T3 to therapy, he said at Perspectives in Women's Health sponsored by OB.GYN. NEWS.
In humans, 20% of T3 is secreted by the thyroid gland. Standard treatment for hypothyroid disease replaces only T4. “There is a feeling among physicians that when symptoms persist despite normal T4 and TSH levels, we should switch to T4 plus T3 therapy,” said Dr. Gharib, professor of medicine at the Mayo Medical School, Rochester, Minn.
Data from thyroid clinics and endocrinology practices, however, do not show any physiologic benefit from adding T3 to therapy, he said. “There are several good studies in the last 5 years that have looked at this, and none of them support a physiologic response,” he said.
Adding T3 to therapy increases the cost of care and requires additional monitoring of hormone levels. If the patient insists on trying it, and thyroid hormone levels are in normal ranges, Dr. Gharib documents the conversation and adds T3 to therapy. When adding T3, he added, the dose of T4 should be lowered by about 20%.
Conventional treatment for hypothyroidism calls for individualized dosing of T4 therapy (based on body size and hormone levels) to reach a target TSH level of 0.3–3.0 mIU/L.
Ask patients who complain about symptoms of hypothyroidism after years of successful T4 therapy about several possible changes in their habits that may be responsible, Dr. Gharib suggested.
The patient may have become less adherent to therapy, or a pharmacist may have convinced the patient to switch to less expensive generic T4 therapy. Alternatively, the patient may be taking one of an increasing number of drugs that necessitate a boost in T4 dosage. Calcium and ferrous sulfate are common inhibitors of T4 absorption. “Take these two agents at different schedules than thyroxine,” he advised.
Dr. Gharib indicated no association with the companies that make the treatments he discussed. OB.GYN. NEWS is published by the International Medical News Group, a division of Elsevier.