The composition, diversity, and function of intestinal flora changed significantly in patients with papillary thyroid cancer after operation, and specific microbial taxa may be associated with fluctuations in thyroid hormone levels.
Key Findings
Results
Significant differences in the diversity and composition of gut microbiota were found in papillary thyroid cancer patients before and after surgery.
20 patients diagnosed with papillary thyroid cancer were included in a paired before-and-after observational study.
Fecal samples were collected within 3 days before operation and 72 hours after operation.
Alpha and beta diversity analyses, PCoA, and ANOSIM were used to characterize microbiota differences.
FDR correction was applied to account for multiple comparisons in statistical analyses.
Results
Eight microbial species showed the most significant differences between pre- and post-operative gut microbiota at the species level.
The eight most significantly different groups were Bacteroides sp., Clostridium sp., Bacteroides fragilis, Alistipes sp., Parabacteroides sp., Bacteroides thetaiotaomicron, Phocaeicola dorei, and Oscillibacter sp.
Clostridium sp. showed higher abundance in the pre-operative group.
Bacteroides sp., Bacteroides fragilis, Alistipes sp., Parabacteroides sp., Phocaeicola sp., and Bacteroides thetaiotaomicron were more prevalent in the post-operative group.
Spearman correlation analysis was used to assess relationships between microbial taxa and hormone levels.
Results
Thyroid and parathyroid hormone levels showed directional changes following surgery in PTC patients.
After operation, FT4 (free thyroxine) showed an upward trend.
TSH (thyroid-stimulating hormone), PTH (parathyroid hormone), and HTG (thyroglobulin) all showed a downward trend post-operatively.
These hormone changes were examined in combination with the collected intestinal microbiota data.
Specific microbial taxa were identified as potentially associated with these fluctuations in thyroid hormone levels.
Results
Differential functional metabolic pathways differed substantially between the pre-operative and post-operative gut microbiota.
The primary differential pathways overall pertained to iron uptake and regulation, polysaccharide utilization and transport, and metabolism and stress response.
The pre-operative group was predominantly involved in ribosome biosynthesis along with amino acid synthesis for valine and leucine.
The post-operative group primarily engaged in lipoic acid metabolism, glycosaminoglycan degradation, and bacterial secretion systems.
KEGG pathway enrichment and correlation network analysis were used to identify these functional differences.
Conclusions
The study suggests that regulating intestinal flora could serve as an adjuvant therapy for hormone regulation in patients undergoing PTC surgery.
The authors propose that microbial changes may interfere with the intestinal-thyroid axis and change systemic thyroid hormone regulation and exogenous treatment response.
Microbial involvement is described as clinically related to long-term metabolic outcomes.
The findings suggest future strategies for microbial targeted adjuvant therapy.
The study provides what the authors describe as 'direct evidence and a comprehensive understanding of the relationship between intestinal flora and thyroid hormone levels before and after surgical treatment.'
What This Means
This research suggests that patients with papillary thyroid cancer (a common form of thyroid cancer) experience notable changes in the community of bacteria living in their gut following surgical removal of the thyroid gland. By analyzing stool samples collected just before and about three days after surgery from 20 patients, the researchers found that both the variety and types of gut bacteria shifted significantly. Certain bacteria like Clostridium species were more common before surgery, while several Bacteroides-related species became more prevalent after surgery. Alongside these microbial shifts, levels of key hormones also changed: free thyroxine (FT4) went up after surgery, while thyroid-stimulating hormone (TSH), parathyroid hormone (PTH), and thyroglobulin (HTG) went down.
The research also found that the functional activities of the gut bacteria changed after surgery. Before surgery, bacteria were more involved in building proteins (ribosome biosynthesis) and amino acid production, while after surgery the dominant bacterial activities shifted toward fat-related metabolism, breaking down certain sugars, and bacterial communication systems. These functional differences, alongside specific bacteria being linked to hormone fluctuations, point to a potential connection between the gut microbiome and how the body regulates thyroid hormones — sometimes called the 'gut-thyroid axis.'
This research suggests that the gut microbiome may play a role in how thyroid cancer patients respond to surgery and subsequent hormone replacement therapy (which is standard after thyroid removal). If specific gut bacteria influence thyroid hormone regulation, then future treatments targeting the gut microbiome — such as probiotics or dietary interventions — might potentially be used as a complementary approach to help stabilize hormone levels in thyroid cancer patients after surgery. However, the study involved only 20 patients and measured changes over a very short post-operative window, so larger and longer-term studies are needed to confirm these findings.
Qin W, Huo J, Xiao X, Li S, Luo H, Wu Y, et al.. (2026). Metagenomic analysis of gut microbiota and its correlation with thyroid hormones in papillary thyroid cancer before and after operation.. PloS one. https://doi.org/10.1371/journal.pone.0356770