Thyroid Hormone is produced in response to the release of thyroid stimulating hormone (TSH) from the pituitary gland and helps the body convert food into energy and heat, regulates body temperature, and impacts many hormonal systems in the body.
Thyroid Hormone exists in two major forms: Thyroxine (T4), an inactive form that is produced by the thyroid gland and converted to T3 in other areas of the body, and Triiodothyronine (T3), the active form.
When T4 and T3 levels drop, TSH levels normally increase, and TSH measurement is the standard way to diagnose hypothyroidism. However, there are many factors contributing to hypothyroidism that are not revealed by standard TSH, T4 and T3 testing.
Often, patients with hypothyroidism are treated only with levothyroxine (synthetic T4). A randomized, double-blind, crossover study found inclusion of T3 in thyroid hormone replacement improved cognitive performance, mood, physical status, and neurophychological function in hypothyroid patients. Two-thirds of patients preferred T4 plus T3, tended to be less depressed than after treatment with T4 alone, and stated they had more energy, were better able to concentrate, and simply felt better.
One reason that T3 is not commonly prescribed is because the only commercially available form of T3 is synthetic liothyronine sodium (Cytomel®). This immediate release formulation is rapidly absorbed, and may result in higher than normal T3 concentrations throughout the body causing serious side effects such as heart palpitations. Research has shown that use of compounded sustained-release T3 preparation significantly decreased the incidence of adverse effects.
The expertise of the practitioner, appropriate testing and proper interpretation of results, and dosing and formulation of thyroid hormones will ultimately determine the success of treatment.