The thyroid gland produces and releases two hormones Liothyronine and Thyroxine. Thyroxine is converted to liothyronine in other areas of the body. Liothyronine is the more active hormone in the body. It is responsible for maintaining a normal rate of metabolism for the whole body.

When the thyroid gland is unable to produce normal amounts of liothyronine and thyroxine, the blood levels of thyroid hormones decrease (hypothyroidism). Extremely low levels of thyroid hormones can result in a condition known as myxoedema. Myxoedema can involve many symptoms such as hair loss and blood disorders.

In extreme cases this condition may result in psychosis or coma. It is under these circumstances that liothyronine is most effective. This is because liothyronine is in the active form (it does not have to be converted from thyroxine) and can therefore act quickly.

Liothyronine tablets are given to replace the liothyronine that would normally have been produced by the thyroid gland. This does not stimulate the thyroid gland to produce greater amounts of thyroid hormones; it simply acts to quickly return the blood levels of liothyronine to normal levels.