Thyroid nodules in an 11-year DanThyr follow-up study

Area of Science:

• Endocrinology
• Public Health
• Ultrasound Imaging

Background:

• Longitudinal data on thyroid structure changes due to iodine fortification (IF) are scarce.
• Understanding IF's impact on thyroid morphology in populations with varying iodine intake is crucial.

Purpose of the Study:

• To investigate how IF influenced thyroid gland structure in two Danish regions with different baseline iodine intake levels.
• To compare the effects of IF in Copenhagen (mild iodine deficiency) and Aalborg (moderate iodine deficiency).

Main Methods:

• A longitudinal population-based study (DanThyr) involving 2465 adults examined before (1997) and after (2008) mandatory salt iodization (2000).
• Standardized ultrasonography was used to assess changes in thyroid gland structure, including nodularity.

Main Results:

• Prevalence of multinodular goiter increased significantly (9.8% to 13.8%), especially in Aalborg (9.1% to 15.4%).
• Solitary nodule prevalence remained stable (5.6% to 5.1%).
• Thyroid nodule normalization (disappearance) occurred frequently (21.2 per 1000 person-years), with solitary nodules normalizing more than multiple nodules.

Conclusions:

• Iodine fortification programs are associated with common dynamic changes in thyroid gland structure, including both the development and disappearance of thyroid nodules.
• Regional differences in normalization rates for multiple nodules were observed, suggesting varying impacts of IF based on baseline iodine status.