Riis J, Andersen SL, Gade GV, et al. - Older adults with a history of hyperthyroidism and moderate iodine deficiency experienced elevated mortality in relation to iodine fortification (IF). Thus, the necessity for cautious iodine supplementation and for monitoring of IF is emphasized.

• A transient increase in hyperthyroidism occurrence ensued the introduction of IF of salt in Denmark.

• A retrospective cohort analysis of all 68-year-olds from the general population in the city of Randers, to assess the link between thyroid function and mortality in older adults prior to and following nationwide implementation of IF.

• Median urinary iodine level was 42 µg/L at baseline consistent with moderate iodine deficiency.

• IF raised mortality in participants with hyperthyroidism, according to Kaplan–Meier survival curves.

• No significant connection was found between hyperthyroidism and mortality before IF vs euthyroid ones, however, after IF hyperthyroid individuals exhibited an elevated mortality (adjusted hazard ratio: 2.22).