Do GLP-1 drugs like tirzepatide or semaglutide cause thyroid nodules?
What labels, cohort studies and meta-analyses report on GLP-1 receptor agonists and thyroid tumors, and how common thyroid nodules are in screened adults.
Research use only. This page provides scientific background and community-report context. Every compound sold here is supplied strictly for in-vitro research, not for human or veterinary use. Nothing on this page is a protocol, a recommendation or medical advice.
TL;DR: the nodule endpoint remains unmeasured
The question people actually type: do glp-1 drugs like tirzepatide or semaglutide cause thyroid nodules?
What the published data say: US labels describe rodent C-cell tumors with unknown human relevance; human cancer studies report mixed findings. These are tirzepatide and semaglutide label findings and GLP-1 class evidence. [DailyMed SPL, boxed warnings; PMID 36356111; PMID 38683947]
What the documented search did not identify: none of the cited sources measures new thyroid nodule incidence as an endpoint. The evidence cannot establish whether these drugs cause nodules. [PMID 36356111; PMID 38683947; PMID 39772758; PMID 38018310; PMID 19601965; PMID 29509871; PMID 41371825]
What research communities report: in the Reddit corpus we track, 79 question posts in 12 months, 3 in the 4 to 12 Sept 2026 window matched this pattern. These are reports, not evidence of frequency or causation. [M236, community corpus audit]
What do the US labels warn about?
The US boxed warnings describe rodent study findings of thyroid C-cell tumors and an unresolved human question. Mounjaro and Zepbound are tirzepatide label documents; Ozempic and Wegovy are semaglutide label documents. PeptidesDirect does not sell tirzepatide. PeptidesDirect does not sell semaglutide. The brands appear here only as cited label documents. [DailyMed SPL, boxed warnings]
The labels name medullary thyroid carcinoma (MTC) and contraindicate a personal or family history of MTC or multiple endocrine neoplasia type 2 (MEN 2). Mounjaro's carcinogenicity section reports thyroid C-cell adenomas in rats, while its rasH2 transgenic mouse study was not tumorigenic. Those findings do not establish a human nodule incidence rate. [DailyMed SPL, boxed warnings; Mounjaro, section 13.1]
Mounjaro's label describes routine calcitonin testing or thyroid ultrasound as having uncertain value, citing low calcitonin test specificity and a high background incidence of thyroid disease. It also states that detected nodules warrant evaluation. That is a report of label wording: evaluating an individual nodule is a clinical matter this page does not settle. [DailyMed SPL, Mounjaro, section 5.1]
Why does the EU product information read differently?
The EU contraindication sections for Mounjaro and Ozempic list hypersensitivity, without a thyroid entry. Their preclinical sections still discuss the rodent findings. Ozempic's text describes a receptor-mediated mechanism to which rodents are particularly sensitive, with human relevance considered low but not completely excluded; Mounjaro's text calls human relevance unknown. Different placement does not resolve the nodule question. [EMA, Mounjaro and Ozempic EPAR, sections 4.3 and 5.3]
In October 2023, the EMA's PRAC concluded that available evidence did not support a causal association between the reviewed GLP-1 receptor agonists and thyroid cancer in the available studies, and that product-information updates were unwarranted. This was a regulatory assessment of a cancer signal, not a study of new nodules or a retatrutide label decision. [EMA, PRAC highlights, 27.10.2023]
What did the cohorts and meta-analysis find?
The studies disagree on thyroid cancer associations and do not answer whether new nodules develop. The French nested case-control analysis included 2,562 cases and 45,184 controls. After 1 to 3 years of exposure, the study reported an adjusted hazard ratio of 1.58 for all thyroid cancer, with a 95% confidence interval of 1.27 to 1.95; the MTC estimate was 1.78, with an interval of 1.04 to 3.05. [Bezin 2023, PMID 36356111]
The later cohorts reported no increase within their observed follow-up. The comparator column preserves the distinct populations behind those estimates. [Pasternak 2024, PMID 38683947; Baxter 2025, PMID 39772758]
- GLP-1 receptor agonist cohort
- 76 cases / 145,410 participants
- Comparator cohort
- 184 cases / 291,667 participants
- Thyroid cancer result
- HR 0.93, 95% CI 0.66 to 1.31
- GLP-1 receptor agonist cohort
- 98,147 participants
- Comparator cohort
- 2,488,303 participants
- Thyroid cancer result
- Pooled weighted HR 0.81, CI 0.59 to 1.12
Baxter and colleagues explicitly stated that evidence was insufficient to rule out excess risk with long-term use. Silverii's meta-analysis of 64 randomized trials reported an overall thyroid cancer odds ratio of 1.52, with a 95% confidence interval of 1.01 to 2.29. The paper reported a fragility index of 1 and no statistically significant association for either papillary or medullary cancer. These findings leave uncertainty; none supplies a nodule incidence estimate. [PMID 39772758; PMID 38018310]
How common are nodules in adults who are simply scanned?
Nodules were common in ultrasound screening studies, with prevalence differing by imaging sensitivity. Guth's study found nodules in 432 of 635 adults, reported as 68%, compared with 33% in the Papillon study. The comparison involved 13 versus 7.5 MHz ultrasound, and Guth reported no cancerous lesions. Durante's review described detection in up to 65% of the general population, linked to imaging performed for unrelated reasons. These are background prevalence findings. [PMID 19601965; PMID 29509871]
A single-center study observed more thyroid imaging around GLP-1 initiation. Within a subset of 415 people, it recorded 757 nodules, 80 biopsied and 10 malignant. The study describes detection around initiation, not proof that medication created the nodules. The distinction matters when interpreting a newly discovered finding against a common background prevalence. [Raghunathan 2026, PMID 41371825]
What is on record for retatrutide?
There are no published human thyroid nodule outcome data for retatrutide in the documented PubMed search. On 12.09.2026, retatrutide AND (thyroid nodule OR thyroid nodules) returned 0 hits; retatrutide AND thyroid returned 3 hits, none a thyroid outcome study. Retatrutide has no approved label; the FDA approval search returned no approved product. [M236, absence statements A1 to A3; Drugs@FDA]
The posted phase 2 obesity trial tables, covering 52 weeks and 338 participants, list no thyroid nodule or neoplasm term; increased blood calcitonin appears in placebo. The phase 2 trial in participants with type 2 diabetes lists no thyroid term in its posted tables. Missing table terms do not establish absence of risk. [NCT04881760; NCT04867785]
Retatrutide trial eligibility excluded personal or family MTC or MEN 2 history. Those exclusions further limit what the trial record can say about these populations. Class cancer studies and adverse-event tables cannot fill the missing nodule endpoint. [NCT04881760; NCT05929066]
Products mentioned
Retatrutide (LY3437943) is a synthetic 39-amino-acid peptide that acts on three receptors at once: GLP-1, GIP and glucagon. Supplied as a lyophilized powder for in-vitro research, with a batch-specific third-party certificate of analysis.
Sources
- DailyMed. 2026. Mounjaro SPL, boxed warning and sections 5.1 and 13.1. Setid prefix
d2d7da5d, version 02.09.2026. - DailyMed. 2026. Zepbound SPL, boxed warning. Setid prefix
487cd7e7, version 02.09.2026. - DailyMed. 2026. Ozempic SPL, boxed warning. Setid prefix
adec4fd2, version 10.06.2026. - DailyMed. 2026. Wegovy SPL, boxed warning. Setid prefix
ee06186f, version 30.06.2026. - EMA. Ozempic and Mounjaro EPAR, EU product information, sections 4.3 and 5.3.
- EMA. 2023. PRAC highlights, 27.10.2023.
- Bezin. 2023. French nested case-control analysis. PMID 36356111.
- Pasternak. 2024. Scandinavian active-comparator cohort. PMID 38683947.
- Baxter. 2025. International cohort. PMID 39772758.
- Silverii. 2024. Meta-analysis of randomized trials. PMID 38018310.
- Guth. 2009. Thyroid nodule ultrasound prevalence study. PMID 19601965.
- Durante. 2018. Thyroid nodule review. PMID 29509871.
- Raghunathan. 2026. Thyroid imaging around GLP-1 initiation. PMID 41371825.
- ClinicalTrials.gov. Retatrutide phase 2 obesity results and eligibility. NCT04881760.
- ClinicalTrials.gov. Retatrutide phase 2 type 2 diabetes results. NCT04867785.
- ClinicalTrials.gov. Retatrutide phase 3 eligibility. NCT05929066.
- M236 data sheet. 12.09.2026. Documented PubMed searches, Drugs@FDA approval search and community corpus audit, sections 3 and 5.
Research use only. Retatrutide is supplied strictly for in-vitro research, not for human or veterinary use. Nothing here is an application protocol, a recommendation or medical advice.
Research context for English-speaking buyers
Most of our English-speaking customers ship to the UK, Ireland, Malta or other English-as-second-language EU territories. The regulatory picture differs per country.
- Relevant authorities
- MHRA (UK, post-Brexit), HPRA (Ireland, EU-aligned), FDA Section 503A bulks list (US, restricted Cat 2 status of several peptides as of 2026)
- Customs and VAT
- EU shipments include VAT, the rate depends on the destination country; UK shipments after Brexit are now extra-EU and may attract UK VAT plus a handling fee at import
- Typical shipping window
- EU 2-4 working days, UK 4-7 working days, other international 7-14 working days, depending on customs
Research-grade peptides shipped from our EU warehouse are sold for laboratory use only and are not authorised for human or veterinary therapeutic application in any of the destination jurisdictions. US customers should be aware that the FDA Section 503A bulks list classification (and the April 2026 reclassification of twelve compounds) only governs compounding pharmacies, not direct-to-researcher imports for non-clinical work. UK buyers should declare the consignment on import and may be asked for a research justification by HMRC. We provide a CoA per batch identified by colour code rather than serial number; customs sometimes asks for this document when clearing the parcel.