Can Mounjaro Be Used in Patients with a History of Thyroid Cancer?
Yes, Mounjaro (tirzepatide) can be safely used in patients with a history of differentiated thyroid cancers (papillary or follicular), but is absolutely contraindicated in patients with a personal or family history of medullary thyroid cancer (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). 1, 2
Key Distinction: Type of Thyroid Cancer Matters
The critical factor is identifying which type of thyroid cancer the patient had:
- Differentiated thyroid cancers (papillary, follicular, Hürthle cell): Tirzepatide is NOT contraindicated 1, 2
- Medullary thyroid cancer (MTC): Tirzepatide is absolutely contraindicated due to C-cell tumor risk observed in rodent studies 1, 2
This distinction exists because GLP-1 and dual GIP/GLP-1 receptor agonists like tirzepatide have been associated with thyroid C-cell tumors in animal models, which are relevant to MTC (arising from C-cells), but not to differentiated thyroid cancers (arising from follicular cells) 1, 2.
Prerequisites Before Initiating Tirzepatide in Differentiated Thyroid Cancer Patients
Before starting tirzepatide, verify the following conditions are met:
1. Completed Appropriate Initial Treatment
- Patient must have undergone total or near-total thyroidectomy 1
- Radioiodine ablation should have been completed if indicated based on their risk category 1, 3
- For follicular thyroid cancer, 10-year survival is approximately 85%; for papillary, it's 93% 1
2. Currently in Appropriate Surveillance Program
- Patient should be enrolled in risk-stratified surveillance based on their individual risk category 1, 2
- Very low-risk is defined as unifocal T1 tumors ≤1 cm, intrathyroidal, with no metastases 1
- Risk stratification includes very low-risk, low-risk, intermediate-risk, and high-risk categories 2
3. No Evidence of Active or Recurrent Disease
- Review most recent thyroglobulin levels and imaging studies 1
- Ensure no evidence of structural disease recurrence 1
- Standard thyroid cancer surveillance should continue unchanged regardless of tirzepatide use 2
Practical Clinical Algorithm
Step 1: Confirm thyroid cancer type
- If MTC or MEN 2: Do not prescribe tirzepatide 1, 2
- If papillary, follicular, or Hürthle cell: Proceed to Step 2 1, 2
Step 2: Verify treatment completion
- Confirm total/near-total thyroidectomy was performed 1
- Verify radioiodine ablation if indicated for their risk category 1
Step 3: Assess current disease status
- Review recent thyroglobulin levels 1
- Review recent imaging (ultrasound or other modalities) 1
- Confirm patient is in appropriate surveillance program 1, 2
Step 4: If all conditions met
- Tirzepatide can be safely initiated for diabetes or weight management 1
- Continue existing thyroid cancer surveillance without modification 2
- No additional monitoring is required specifically due to tirzepatide use 2
Important Caveats
Recent Safety Signal Requires Awareness
A 2025 study found an increased risk of new thyroid cancer diagnoses within the first year of GLP-1RA initiation (HR 1.85; 95% CI, 1.11-3.08) compared to other diabetes medications 4. However, this may represent enhanced early detection rather than true causation, and the absolute risk remained low (0.17%) 4. This finding does not change the recommendation for patients with already treated differentiated thyroid cancer, but clinicians should be aware of this signal.
High-Risk Patients
While there is no evidence that tirzepatide increases recurrence risk in differentiated thyroid cancer, high-risk patients may warrant more careful monitoring during the first year of therapy 2. However, this represents clinical prudence rather than a contraindication 2.
Documentation
Document in the medical record:
- Type of thyroid cancer (to confirm not MTC)
- Date and extent of thyroidectomy
- Whether radioiodine was administered
- Most recent thyroglobulin level and imaging results
- Current surveillance schedule