We have had a number of enquiries about the use of Mounjaro® (Tirzepatide) and similar medications (e.g. Wegovy®, etc) in individuals with neuroendocrine cancer.
Here we provide a summary of information currently available, which we hope will address some of the concerns raised.
Please note:
The information provided here is NOT a replacement for clinical guidance.
We would strongly recommend that clinical guidance is sought from your neuroendocrine cancer and diabetic specialists before starting Mounjaro® or any other treatment or medication
and that HCPs/prescribers refer to BNF/NICE guidance.
🟡 Background on Mounjaro® (Tirzepatide)
- Mounjaro® is a dual GIP and GLP-1 receptor agonist used for the treatment of Type 2 diabetes and is under investigation/used off-label for weight management.
- Like other GLP-1 receptor agonists (e.g., semaglutide), it improves insulin sensitivity, promotes weight loss, and reduces appetite.
Further information is available on the Diabetes UK website here
⚠️ Concerns raised:
🧬 Pre-clinical animal studies
- In preclinical animal studies (rats), Mounjaro® and similar drugs caused thyroid tumours, including medullary thyroid carcinoma (MTC).
- However, these findings have not been replicated in human studies to date.
🔬 Human Studies (So Far)
- Follow-up human studies (1.8 to 3 years) found no significant increase in thyroid cancer risk.
- The evidence is still too limited to exclude long-term risks, especially for rare tumors like MTC.
- Because of the lack of long-term data and the rarity of MTC, risk cannot be fully ruled out.
References:
Baxter, S.M. et al. (2025) “Glucagon-Like Peptide 1 Receptor Agonists and Risk of Thyroid Cancer: An International Multisite Cohort Study” Thyroid, 35(1) https://doi.org/10.1089/thy.2024.0387
Pasternak, B. et al. (2024) “Glucagon-like peptide 1 receptor agonist use and risk of thyroid cancer: Scandinavian cohort study” The BMJ, 385 https://doi.org/10.1136/bmj-2023-078225
Melville (2025) Medscape Medical News: https://www.medscape.com/viewarticle/glp-1s-show-no-increased-risk-thyroid-cancer-2025a100011a
🚫 Recommendations
Avoid / Cautious use of Mounjaro® if:
- You have a personal or family history of:
- Medullary thyroid carcinoma (MTC)
- Multiple Endocrine Neoplasia Type 2 (MEN2)
🔍 MTC: medullary thyroid carcinoma (a form of neuroendocrine cancer that starts in the thyroid gland).
🔍 MEN2: is a rare inherited (genetic) disorder that can lead to medullary thyroid cancer.
Further information on MTC and MEN2 can be found at our sister charity AMEND
Mounjaro in Other Neuroendocrine Cancers (NETs/NECs)
- No known or identified risk found
- However, caution and an individual assessment of use is recommended, due to potential side effects that may exacerbate neuroendocrine cancer-related symptoms or or interact with treatments.
📌 Potential side-effects:
- Pancreas and Gallbladder
- Pancreatitis is a possible side effect → Discontinue if suspected.
- May exacerbate gallstone disease, cholecystitis, or cholangitis.
- Gastrointestinal Effects
- Delayed gastric emptying can:
- Affect oral drug absorption
- Reduce effectiveness of drugs like oral contraceptives → Consider barrier methods of contraception.
- Malabsorption & Enzyme Supplementation
- Patients on PERT (e.g., Creon) for pancreatic insufficiency need monitoring.
- May affect absorption of other medications, particularly in those with diarrhoea, steatorrhea, or symptoms of malabsorption.
- Diabetes Management
- Only for Type 2 or 3 diabetes (not Type 1).
- Should be used under joint care of the neuroendocrine cancer and diabetes teams.
- May require adjustments in diabetic medications due to blood glucose changes.
✅ Recommendations Before Starting Mounjaro® or similar medications
- Discuss with all relevant medical teams: oncologist, endocrinologist, diabetes specialist, pharmacist.
- Review:
- Personal/family cancer history
- Current medications
- Pancreatic/gallbladder health
- Diabetes control
- Malabsorption symptoms or treatments
- Refer to BNF/NICE guidelines as part of prescribing decision-making
🔗 Additional Resources
- For further guidance on MTC and MEN2, refer to AMEND
- What is Mounjaro? Uses, How it Works and Side Effects – Diabetes UK
- BNF/NICE guidance on Tirzepatide