Association between various thyroid gland diseases, TSH values and thyroid cancer: a case-control study.

BACKGROUND The goal of this retrospective cohort study was to analyze the association between benign thyroid alteration and thyroid cancer in patients followed in general practices in Germany. METHODS Patients aged 18-80 who had received an initial diagnosis of thyroid cancer in one of 1261 general practices in Germany between January 2009 and December 2018 were included in this study (index date). These patients were matched (1:1) to non-cancer patients by age, sex, physician and index year. The main outcome of the study was the association between various benign thyroid alterations and thyroid cancer. RESULTS The study included 2787 patients with thyroid cancer and 2787 individuals without cancer (mean age: 52.8 years, 73.5% women). The main finding was that all benign changes in the thyroid with the exception of thyroiditis were associated with thyroid cancer. The strongest association was observed by the nontoxic goiter. Half of the patients with thyroid cancer had nontoxic goiter compared to just one-sixth of the control group. Thyrotoxicosis was found in 12.9% of the cancer group and in 3.9% of the controls. By analyzing TSH in groups, we found an association between suppressed TSH and elevated TSH levels and thyroid cancer. CONCLUSION In accordance with the literature, we confirmed that any kind of benign thyroid alteration was associated with an elevated risk of thyroid cancer. The odds ratio was greatest for nontoxic goiter, followed by benign neoplasms of the thyroid, other disorders of the thyroid such as Hashimoto and thyrotoxicosis. We also found an elevated risk of cancer in patients with either a suppressed or elevated TSH.