Thyroid Nodules in an 11-Year DanThyr Follow-Up Study

Context: Limited longitudinal data are available on changes in the thyroid gland structure in a population and how this is influenced by iodine fortification (IF). Objective: Our objective was to clarify how IF influenced thyroid gland structure in 2 regions with different iodine intake at baseline (Copenhagen, mild iodine deficiency [ID]; Aalborg, moderate ID). Design and Setting: We conducted a longitudinal population-based study (DanThyr) where participants were examined before (1997) and after (2008) the Danish mandatory IF of salt (2000). Participants: We examined 2465 adults, and ultrasonography was performed by the same sonographers using the same equipment, after controlling performances. Main Outcome Measure: Change in thyroid gland structure was evaluated. Results: The follow-up period saw an increased prevalence of multinodularity (9.8%-13.8%, P