Thyrotoxicosis does not protect against incidental papillary thyroid cancer

Abstract

Thyroid cancer is the 10th most commonly diagnosed cancer in Australia, and many studies have linked thyroid-stimulating hormone (TSH) and papillary thyroid cancer (PTC). Low TSH is thought to be protective against thyroid cancer. Our aim was to evaluate the relationship between thyrotoxicosis, in particular Graves' disease, and the incidence of incidental PTC. After ethics approval, a review of the thyroid database at Monash University Endocrine Surgery Unit was performed. Data was obtained for the period September 1994 to August 2012 and identified those patients who underwent total thyroidectomy (n = 1,898). Those patients with known or suspected malignancy were excluded from the study (n = 390). The remaining patients (n = 1,508) were divided into 3 groups: Graves' disease (n = 250), toxic multinodular goiter (MNG; n = 295), and nontoxic MNG (n = 963) based on indication for surgery and thyroid status. Data were analyzed for the presence of malignancy in each group. Of the 1,508 patients included in the study, 96 (6.4%) had thyroid cancer, and the incidence of PTC was similar between the 3 groups. There were 16 cases (6.4%) in the Graves' group, 48 cases (5%) in the nontoxic MNG group, and 20 cases (6.8%) in the toxic MNG group (P = .41). The incidence of malignancy, particularly PTC, is similar in patients with Graves' disease, toxic MNG, and nontoxic MNG. This study demonstrates no protective effect of thyrotoxicosis on the incidence of incidental thyroid cancer.