Journal Article

Benign Thyroid Diseases and Risk of Thyroid Cancer: A Nationwide Cohort Study

Kitahara, Cari M, Kӧrmendiné Farkas, Dóra, Jørgensen, Jens Otto L, Cronin-Fenton, Deirdre, Sørensen, Henrik Toft

2018

Overview

Abstract Context Thyroid nodules, adenomas, and goiter have consistently been associated with thyroid cancer risk. Few studies have assessed whether thyroid dysfunction and thyroid autoimmunity influence this risk. Objective To examine thyroid cancer risk after diagnoses of a wide range of benign thyroid conditions. Design Hospital and cancer registry linkage cohort study for the years 1978 to 2013. Setting Nationwide (Denmark). Participants Patients diagnosed with hyperthyroidism (n = 85,169), hypothyroidism (n = 63,143), thyroiditis (n = 12,532), nontoxic nodular goiter (n = 65,782), simple goiter (n = 11,582), other/unspecified goiter (n = 21,953), or adenoma (n = 6,481) among 8,258,807 residents of Denmark during the study period. Main Outcome Measures We computed standardized incidence ratios (SIRs) for differentiated thyroid cancer, excluding the first 12 months of follow-up after benign thyroid disease diagnosis. Results SIRs were significantly elevated for all benign thyroid diseases apart from hypothyroidism. SIRs were higher for men than women and in the earlier follow-up periods. Elevated SIRs were observed for localized and regional/distant thyroid cancer. After excluding the first 10 years of follow-up, hyperthyroidism [n = 27 thyroid cancer cases; SIR = 2.00; 95% confidence interval (CI): 1.32 to 2.92], nontoxic nodular goiter (n = 83; SIR = 4.91; 95% CI: 3.91 to 6.09), simple goiter (n = 8; SIR = 4.33; 95% CI: 1.87 to 8.53), other/unspecified goiter (n = 20; SIR = 3.94; 95% CI: 2.40 to 6.08), and adenoma (n = 9; SIR = 6.02; 95% CI: 2.76 to 11.5) remained positively associated with thyroid cancer risk. Conclusions We found an unexpected increased risk of differentiated thyroid cancer, including regional/distant disease, following diagnosis of hyperthyroidism and thyroiditis that could not be solely attributed to increased medical surveillance. Hypothyroidism was less clearly associated with thyroid cancer risk. This large nationwide study provides strong evidence for an increased risk of differentiated thyroid cancer following diagnosis of hyperthyroidism and thyroiditis.

• Publisher: Endocrine Society,Copyright Oxford University Press,Oxford University Press
• Subject: Adenoma / Adult / Aged / Autoimmunity / Benign / Cancer diagnosis / Cancer research / Clinical s / Cohort analysis / Cohort Studies / Denmark - epidemiology / Development and progression / Diagnosis / Female / Goiter / Health risk assessment / Humans / Hyperthyroidism / Hyperthyroidism - complications / Hypothyroidism / Hypothyroidism - complications / Incidence / Ionizing radiation / Male / Middle Aged / Nodules / Registries / Risk / Risk factors / Sex Factors / Surveys / Thyroid cancer / Thyroid diseases / Thyroid hormones / Thyroid Neoplasms - epidemiology / Thyroid Neoplasms - etiology / Thyroiditis / Thyroiditis - complications / Tumors