BACKGROUND

To confirm whether clinical and biochemical parameters or Hashimoto's thyroiditis (HT) could predict the risks of malignancy among subjects who underwent thyroidectomy, as well as to determine the influence of HT on the biological behavior of papillary thyroid cancer (PTC).

METHODS

A total of 2,052 patients who underwent initial thyroidectomy were enrolled between June 2006 and August 2008. Serum free T4, free T3, thyrotropin (TSH), thyroglobulin, thyroglobulin antibody, antimicrosomal antibody, tumor-associated status, and thyroid disorders were documented.

RESULTS

Binary logistic regression analysis was performed to define the risk predictors for thyroid cancer. Finally, calcification, HT, TSH, and age, were entered into the multivariate model. Multivariate logistic regression analysis revealed the risk of thyroid cancer increases in parallel with TSH concentration within normal range, and the risk for malignancy significantly increased with serum TSH 1.97-4.94 mIU/L, compared with TSH less than 0.35 mIU/L (OR = 1.951, 95% CI = 1.201-3.171, P = 0.007). Increased risks of thyroid cancer were also detected among the patients with HT (OR = 3.732, 95% CI = 2.563-5.435), and microcalcification (OR = 14.486, 95% CI = 11.374-18.449). The effects of HT on the aggressiveness of PTC were not observed in extrathyroidal invasion (P = 0.347), capsular infiltration (P = 0.345), angioinvasion (P = 0.512), and lymph node metastases (P = 0.634).

CONCLUSIONS

The risk of malignancy increases in patients with higher level TSH within normal range, as well as the presence of HT and microcalcification. No evidence suggests that coexistent HT alleviates the aggressiveness of PTC.