Does the gut microbiome affect the development of Thyroid Cancer?

The gut microbiome — the community of microorganisms living in your digestive tract — may play a role in thyroid cancer development. Research suggests a 'gut-thyroid axis' where gut bacteria and their byproducts affect thyroid health by influencing immune function, hormone metabolism, and inflammation ⁴⁶. While most evidence comes from animal studies and small human trials, early findings indicate that changes in gut bacteria composition (dysbiosis) are linked to thyroid cancer ⁶⁷.

What the research says

A 2024 review in Nature Reviews Endocrinology notes that the gut microbiota can regulate the immune system, contribute to thyroid hormone metabolism, and generate or break down cancer-causing substances, all of which are relevant to thyroid cancer ⁶. The same review states that reports of a role for the microbiota in thyroid cancer are limited, but evidence supports a relationship between gut dysbiosis and thyroid cancer ⁶.

A 2022 study compared gut bacteria in 50 thyroid cancer patients and 58 healthy controls. It found that the diversity and richness of gut bacteria were significantly lower in thyroid cancer patients. The composition also shifted, with a dominant enterotype (a type of bacterial community) in the cancer group. The study identified specific bacterial genera and metabolites that could distinguish cancer patients from healthy individuals with high accuracy ⁷.

Another review from 2024 highlights that the gut microbiome influences systemic immunity and intestinal barrier integrity, and that microbial metabolites like short-chain fatty acids and secondary bile acids may impact thyroid cancer development ⁴. The same source notes that microbiota-targeted interventions such as probiotics and dietary changes are being explored as potential adjunctive therapies ⁴.

While these findings are promising, direct causal evidence in humans is still emerging. Most studies show associations, not proof that gut bacteria cause thyroid cancer. Larger, long-term studies are needed to confirm these links and determine whether modifying the microbiome could help prevent or treat thyroid cancer ⁶⁷.

What to ask your doctor

• Could my gut health or diet affect my thyroid cancer risk or treatment?
• Are there any recommended dietary changes or probiotics that might support my thyroid health?
• Should I consider any tests to evaluate my gut microbiome?
• What is the current evidence on the gut-thyroid axis and its relevance to my condition?
• Are there any clinical trials studying the microbiome and thyroid cancer that I might join?