The management of patients with an under active thyroid has for many years followed a standard protocol using thyroxine (T4) tablets.

Taking synthetic T4 ensures that the bloodstream is replenished with thyroxine up to a concentration which laboratory tests indicate to be a normal level.

The blood test not only indicates the level of thyroxine but also the body’s marker of thyroxine need, the TSH level. The aim of treatment has traditionally been to re-establish the TSH back into the normal range and assume that the patient is now back to normal

Thyroxine is a metabolic hormone needed for all cells of the body to convert food into energy. The abbreviation T4 denotes the number of iodine molecules attached to the hormone structure. The cell take off one iodine molecule and make the more active component T3 within the cells. The question therefore arises as to whether thyroid therapy should also contain T3 as well as T4 and whether patients would feel better if they were given this combination.