Introduction

If you have a thyroid condition—or a family history of one—you may be wondering whether Zepbound (tirzepatide) is safe to use. This is a smart question, especially given that GLP-1 medications carry a warning about thyroid tumors in animal studies.

In this blog, we’ll break down the facts about Zepbound and thyroid health, who should avoid it, what labs to monitor, and how to use it safely if you have a thyroid condition like hypothyroidism, Hashimoto’s, or thyroid nodules.

Does Zepbound Affect the Thyroid?

Not directly—but it carries a black box warning due to a rare type of thyroid cancer seen in rodents during long-term studies: medullary thyroid carcinoma (MTC).

This risk has NOT been confirmed in humans, but out of caution:

Zepbound is not recommended for people with a personal or family history of:

• MTC (medullary thyroid carcinoma)

• MEN-2 (Multiple Endocrine Neoplasia Syndrome type 2)

Common Thyroid Conditions vs. MTC

Condition	OK to Use Zepbound?	Notes
Hypothyroidism	Yes	Most common, safe with monitoring
Hashimoto’s	Yes	Autoimmune—still okay if stable
Thyroid nodules	Possibly	Check with provider & monitor labs
History of MTC	No	Zepbound is contraindicated
MEN-2	No	Genetic cancer syndrome—avoid use

Should You Get a Thyroid Ultrasound or Labs First?

If you have:

• A family history of thyroid cancer

• A history of thyroid nodules or goiter

• Unexplained neck swelling or hoarseness

…then it’s a good idea to:
Get a thyroid ultrasound
Run baseline TSH, Free T4, and Calcitonin labs

Calcitonin is a marker that may be elevated in cases of medullary thyroid carcinoma.

What About People With Hypothyroidism or Hashimoto’s?

Most people with underactive thyroid (even autoimmune Hashimoto’s) can safely use Zepbound, and many report:

Easier weight loss
More consistent energy
Improved insulin resistance (common in hypothyroid patients)

Tip: Monitor thyroid hormone levels every 8–12 weeks, especially if:

• Your dose of thyroid meds hasn’t been changed in a while

• You lose a lot of weight quickly

• You start feeling fatigue or cold again

What to Watch For

Mild, normal thyroid function changes:

• Slight TSH fluctuations with weight loss

• Improved T3 conversion due to less inflammation

Seek medical advice if you notice:

• New swelling or lump in the neck

• Persistent hoarseness or difficulty swallowing

• Elevated calcitonin levels

Safe Use Checklist for Thyroid Patients on Zepbound

No personal/family history of MTC or MEN-2
Stable TSH and T4 levels
Baseline thyroid labs and optional ultrasound
Open communication with your endocrinologist or PCP
Weight loss progress without fatigue or cold intolerance

Learn more: Can You Stay on Zepbound Long-Term?

Final Thoughts

Zepbound is safe for most people with thyroid conditions like hypothyroidism or Hashimoto’s—but should be avoided if you or a family member has a history of MTC or MEN-2. With proper monitoring and communication with your doctor, you can lose weight while keeping your thyroid healthy.

Monitor TSH and thyroid function throughout treatment
Report any unusual neck symptoms promptly
Enjoy better weight loss results—especially if thyroid-related weight gain has been a struggle

Visit our Zepbound & Thyroid Health Center for checklists, lab trackers, and guidance on coordinating with your care team.