Information for patients about T3 (liothyronine)

We are sorry to inform you that T3 (liothyronine) treatment for hypothyroidism (either alone or in combination with T4 [levothyroxine]) is no longer available through the NHS in this area. This is a local policy which applies to prescriptions from GPs and from NHS endocrinology clinics. It is supported by national recommendations.

This policy is in accordance with the position statement The diagnosis and management of primary hypothyroidism which is endorsed by the Royal College of Physicians, the Society for Endocrinology, the British Thyroid Association, the British Thyroid Foundation Patient Support Group, and the Royal College of General Practitioners. It is also consistent with guidance from NICE (the National Institute for Health and Care Excellence, NG 145, 2019).

Evidence from a number of carefully conducted research trials does not support the routine use of T4 (levothyroxine) / T3 combination therapy. In clinical practice, a small number of patients do seem to benefit from T4/T3 combination therapy, and research studies are ongoing to look into possible biological explanations for this observation. However at present NICE feel that there is insufficient evidence of clinical benefit to support its use.

T3 therapy is much more expensive than levothyroxine (T4) therapy (one T3 tablet is approximately 100 times more expensive than one levothyroxine tablet). The decision is based on insufficient evidence of clinical and cost-effectiveness of T3 treatment (either alone or in combination with T4 [levothyroxine]). There is also a safe alternative (levothyroxine [T4] treatment).

Normally the thyroid produces T4 and T3, but about 85% of the hormone released from the thyroid into the blood stream is T4 (thyroxine) and 15% is T3. T3 is the active hormone. Every target organ in the body that requires thyroid hormones can convert T4 to make T3.

Levothyroxine is the synthetic form of the natural ‘T4’ hormone (thyroxine). It works in the same way and can be measured in the same blood tests. Levothyroxine provides stable natural thyroid hormone replacement therapy. Target organs can convert levothyroxine to T3.

T3 is much shorter-acting than T4, so levels vary widely during the day, even in patients on multiple daily doses. It is difficult to replicate the natural balance of T4/T3 in the circulation using T4/T3 combination therapy, risking side-effects from slight over-treatment in the long term. These side-effects include atrial fibrillation (an erratic heart beat which increases the risk of stroke) and loss of bone strength (increasing the risk of osteoporosis and fractures). Patients who are trying for a baby should not take T3, as it does not cross the placenta, so it will not support the development of the baby during pregnancy.

The average dose of thyroxine is 100 – 150 microgrammes per day. Your GP will check your thyroid function tests (blood tests) once you have been on a stable dose of levothyroxine for 6-8 weeks. They will use the results to adjust the dose of levothyroxine if necessary. It is helpful to take your levothyroxine separate to any other tablets or medicines (including vitamin or mineral supplements). Sometimes levothyroxine is better absorbed if it is taken last thing at night. It can take a few months to feel fully better even when the dose of levothyroxine is correct. Depending on your symptoms, your GP may feel it would be helpful to check other blood tests, to screen for conditions that are more common in patients with hypothyroidism (for example, coeliac disease [gluten sensitivity] or anaemia [caused by vitamin B12 deficiency]).