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

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

J Clin Endocrinol Metab. 2018 Mar 23;:

Authors: Kitahara CM, Farkas DKR, Jørgensen JOL, Cronin-Fenton D, Sørensen HT

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 following diagnoses of a wide range of benign thyroid conditions.
Design: Hospital and cancer registry linkage cohort study for the years 1978-2013.
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% CI 1.32-2.92), nontoxic nodular goiter (n=83, SIR=4.91, 95% CI 3.91-6.09), simple goiter (n=8, SIR=4.33, 95% CI 1.87-8.53), other/unspecified goiter (n=20, SIR=3.94, 95% CI 2.40-6.08), and adenoma (n=9, SIR=6.02, 95% CI 2.76-11.5) 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.

PMID: 29590402 [PubMed - as supplied by publisher]

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