Incidental thyroid cancer in toxic and nontoxic goiter: Is TSH associated with malignanCy rate? Results of a meta-analysis.

OBJECTIVE: In the last 6 years, several studies reported a positive association between thyrotropin (TSH) and papillary cancer risk. The rationale is based on stimulatory action exerted by TSH on thyroid cell proliferation and/or progression of a pre-existing papillary carcinoma. To validate this hypothesis, we performed a meta-analysis comparing the incidence of thyroid cancer in 2 groups of patients who underwent surgery for toxic or nontoxic nodular goiter.

METHODS: Using data from 2,150 patients with toxic multinodular goiter (TMNG) and 873 patients with toxic adenoma (TA), the overall incidence of thyroid cancer (and 95% confidence interval [CIs]) was estimated to be 5.9% (3.9 to 8.3) for patients with TMNG and 4.8% (2.5 to 7.9) for patients with TA. Four studies were included in the meta-analysis with a total of 1,964 subjects undergoing thyroidectomy for allegedly benign thyroid disease (520 patients with TMNG or TA and 1,444 for multinodular goiter [MNG] or uninodular goiter [UNG]).

RESULTS: We did not find any significant differences in the risk of incidental thyroid cancer (ITC) in patients with TMNG versus MNG (odds ratio [OR]: 0.91, 95% CI: 0.47 to 1.77, I²: 62.6%), TA versus uninodular goiter (UNG) (OR: 0.46, 95% CI: 0.12 to 1.79, I²: 12%), and TMNG or TA versus MNG or UNG (pooled analysis) (OR: 0.86, 95% CI: 0.46 to 1.60, I²: 51.5%).

CONCLUSIONS: The results of this meta-analysis did not confirm an association between low TSH values and lower thyroid cancer rate, at least in patients with nodular disease.