Weight Loss Medications in Endocrine Diseases

Medications are available to help people with obesity or who are overweight lose weight. Some of the most commonly used are called ‘Glucagon-like peptide-1 receptor agonists (GLP1-RA)’ or ‘GLP-1s’ for short. These medications are used to treat diabetes and to support weight loss in people with obesity or who are overweight with weight-related health problems. In all groups of patients, they should be used alongside a reduced-calorie diet and regular exercise.

In the UK, there are three licensed GLP1-RA medications: Semaglutide (also called Wegovy, Ozempic and Rybelsus), tirzepatide (this medication also activates the GIP receptor and is called Mounjaro) and liraglutide (sold under various brand names). You should only use weight loss injections if they have been prescribed for you by a healthcare professional after a full discussion about the benefits and risks of these treatments based on your individual circumstances.

Studies using some GLP1-RA medications in rats have shown they may cause a rare thyroid cancer called medullary thyroid cancer. Studies so far using weight loss injections in the short to medium term in humans have not shown that their use is associated with an increased risk of thyroid cancer, however, it may be considered too early to make this conclusion.

GLP1-RA medications should not be used if there is a personal or family history of a thyroid cancer called medullary thyroid carcinoma (MTC). This also applies to anyone with a personal or family history of Multiple Endocrine Neoplasia Syndrome type 2 (MEN 2), a condition in which almost 100% of people develop MTC before the age of 40.

Patients with a history of other types of endocrine disease and/or any cancers should discuss the potential risks and benefits with their doctor before starting treatment.

If you are taking levothyroxine to treat hypothyroidism (underactive thyroid), you may need to have your thyroid function checked approximately 2-3 months following substantial weight loss. This is to establish whether your levothyroxine dose needs adjusting.

Please consult your healthcare professional, the manufacturer’s patient information leaflet and The Medicines and Healthcare products Regulatory Agency (MHRA) for up-to-date information about benefits and risks and how to use these medicines safely.  We highly recommend that you let your endocrinologist and GP know that you are taking or thinking about taking weight loss injections.

This is a rapidly developing area; therefore, please consult a healthcare professional for the latest information and guidance.

This information on this webpage was developed from an original information resource of the British Thyroid Foundation updated April 2026