Higher TSH level is a risk factor for differentiated thyroid cancer.

OBJECTIVES

Higher thyroid-stimulating hormone (TSH) levels are associated with differentiated thyroid cancers (DTC). To validate this association, we compared TSH levels obtained from euthyroid patients with DTC with TSH levels from controls in the general population.

DESIGN AND PATIENTS

The case group included 1759 patients with DTC, who underwent thyroid surgery at Chonnam National University Hwasun Hospital. The control group (n = 1548), who had participated in the Thyroid Disease Prevalence Study were used as a healthy control group. The subjects were divided into four groups of similar size according to their TSH levels, with the first quartile used as a reference group.

RESULTS

The mean TSH level of the case group was significantly higher than the mean TSH level of the control group (1.95 ± 0.9 mIU/l vs 1.62 ± 0.8 mIU/l, P < 0.001), and was associated with DTC risk. Multiple logistic regression, after controlling for age, gender and the presence of a family history of thyroid cancer, showed that the odds ratios and 95% confidence intervals for the second, third and fourth quartiles of TSH levels were 1.27 (1.03-1.57), 1.55 (1.25-1.92) and 2.21 (1.78-2.74) respectively. No significant differences were observed in mean TSH levels in patients with different tumour stages and tumour sizes.

CONCLUSION

Having a high TSH level within the normal range is an independent risk factor for DTC, and may contribute to the initiation of thyroid carcinogenesis. TSH levels in patients with thyroid nodules may be used as diagnostic adjuncts for the identification of high-risk patients, who require further investigation and/or surgical intervention.