A systematic 11-year follow-up study in Danish adults offers new insights into the relationships between thyroid nodularity, age and iodine intake.

Mandatory iodine fortification of all salt used in making bread was introduced in Denmark in 2000. Using ultrasonography, Krejbjerg and colleagues assessed the thyroid glands of 2,465 Danish adults (mainly women) 2–3 years before and 8–10 years after introduction of iodine fortification.

Participants from Aalborg, who had lower iodine intakes at baseline but a higher increment in iodine intake following iodine fortification, had a higher incidence of new thyroid nodules and lower nodule disappearance rates than participants in Copenhagen. These findings have implications for public health, as they suggest that increased severity of iodine deficiency in a population leads to increased time to normalization of thyroid nodules after salt iodization, particularly in women aged >40 years.