Medical Health Encyclopedia

T3 and T4 Combinations. Triiodothyronine (T3), the other important thyroid hormone, is not ordinarily prescribed except under special circumstances. Most patients respond well to thyroxine (T4) alone, which is converted in the body into T3. In addition, the use of T3 may cause disturbances in heart rhythms. Still, some patients treated only with thyroxine continue to have mood and memory problems or other symptoms. Combination products containing T4 and T3, such as liotrix (Thyrolar), are available, but there is some controversy concerning their benefits. Several 2005 studies suggested that although some patients may prefer combination therapy, T3 and T4 together do not work better than T4 alone. Patients might like the combined drugs because they cause more weight loss, or a placebo effect may be involved. It does not appear that combination products offer any advantage for normalizing TSH levels.

Levothyroxine Regimens

Levothyroxine only needs to be taken once a day. It is slowly assimilated by body organs, so it usually takes up to six weeks before symptoms improve in adults. Nevertheless, many patients feel better after two to three weeks of treatment. The speed at which specific symptoms improve vary:

• Weight loss, less puffiness, and improved pulse usually occur early into the treatment.
• Improvements in anemia and skin, hair, and voice tone may take a few months.
• High LDL cholesterol levels decline very gradually. (HDL levels, the so-called good cholesterol, are not affected by treatment.)
• Goiter size declines very slowly and some patients may require high-dose thyroid hormone (called suppressive thyroid therapy) for a short period.

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It should be noted that levothyroxine reduces blood pressure in about half of hypothyroid patients with hypertension, although blood pressure medications may still be needed.