Thyroid cancer risk is not increased in diabetic patients

This study evaluated thyroid cancer risk with regards to diabetes status and diabetes duration, and with the use of anti-diabetic drugs including sulfonylurea, metformin, insulin, acarbose, pioglitazone and rosiglitazone, by using a population-based reimbursement database in Taiwan.

A random sample of 1,000,000 subjects covered by the National Health Insurance was recruited. After excluding patients with type 1 diabetes, 999730 subjects (495673 men and 504057 women) were recruited into the analyses. Logistic regression estimated the odds ratios (OR) and their 95% confidence intervals (CI) for independent variables including age, sex, diabetes status/duration, anti-diabetic drugs, other medications, comorbidities, living regions, occupation and examinations that might potentially lead to the diagnosis of thyroid cancer in various models.

The diabetic patients had a significantly higher probability of receiving potential detection examinations (6.38% vs. 5.83%, P<0.0001). After multivariable-adjustment, the OR (95% CI) for diabetes status was 0.816 (0.652-1.021); and for diabetes duration <1 year, 1-3 years, 3-5 years and ≥ 5 years vs. non-diabetes was 0.071 (0.010-0.507), 0.450 (0.250-0.813), 0.374 (0.203-0.689) and 1.159 (0.914-1.470), respectively. Among the anti-diabetic agents, only sulfonylurea was significantly associated with thyroid cancer, OR (95% CI): 1.882 (1.202-2.947). The OR (95% CI) for insulin, metformin, acarbose, pioglitazone and rosiglitazone was 1.701 (0.860-3.364), 0.696 (0.419-1.155), 0.581 (0.202-1.674), 0.522 (0.069-3.926) and 0.669 (0.230-1.948), respectively. Furthermore, patients with benign thyroid disease or other cancer, living in Kao-Ping/Eastern regions, or receiving potential detection examinations might have a significantly higher risk; and male sex, hypertension, dyslipidemia, chronic obstructive pulmonary disease, vascular complications or use of statin, aspirin or non-steroidal anti-inflammatory drugs might be associated with a significantly lower risk.

There is a lack of an overall association between diabetes and thyroid cancer, but patients with diabetes duration <5 years have a significantly lower risk. Sulfonylurea may increase the risk of thyroid cancer.