Which is the best predictor of thyroid cancer: thyrotropin, thyroglobulin or their ratio?

Since documented incidence of thyroid cancer has been rising over time, in part due to incidental small papillary cancer, several studies have been carried out to investigate the role of possible serum markers of thyroid cancer prior to surgery.

Prospective cohort study.

To investigate the role of thyroglobulin (Tg), thyrotropin (TSH) and the TSH:Tg, Tg:TSH ratio in the preoperative diagnosis of thyroid cancer.

Between January 2014 and January 2015, 202 of 242 consecutive patients scheduled for surgical treatment for thyroid disorders at Şişli Etfal Training and Research Hospital, General Surgery Clinic were included in the study. Prospective data collection included demographics, thyroid function tests, Tg levels, fine needle aspiration biopsy (FNAB) results (208 FNABs in 187 patients), surgical procedures and final histopathological examinations.

There were 134 patients with benign thyroid diseases and 68 patients with thyroid gland malignancy. Preoperative Tg level was significantly lower in the malignant group (64 ng/mL vs. 20ng/mL, p<0.001, respectively), whereas there was no difference in TSH between groups. TSH:Tg levels were found to be significantly higher in patients with malignant thyroid diseases (0.24±1 vs. 0.87±3.4, p=0.024). Although univariate analysis showed that the TSH:Tg ratio was a predictor for thyroid malignancy (OR 0.001; 95% CI, 0.01-0.125; p=0.007) in conjunction with FNAB, multivariate analysis failed to demonstrate any statistical significance for any factor except FNAB.

Preoperative assessment of serum Tg and TSH levels appear not to be helpful in identifying patients with thyroid cancer. However, a higher preoperative serum TSH:Tg ratio may hint at an increased risk for thyroid carcinoma. Further studies are needed to elucidate the potential role of preoperative laboratory values of thyroid function.