Salt iodization decreased the risk of thyrotoxicosis in Denmark by the halve

Abstract

The status of iodine nutrition is a key factor in determining the prevalence of thyroid disorders in adults. The study under discussion provides data on the change in the incidence of nosological subtypes of overt thyrotoxicosis and hypothyroidism in adults during an increase in iodine intake after the introduction of mandatory salt iodization in Denmark. The authors carefully studied the case histories of all new patients with thyrotoxicosis and hypothyroidism registered in 2014–2016 in an open cohort of the population of Northern Jutland (n = 309,434), in which a moderate iodine deficiency has historically been observed and compared with incidence rates in 1997–1998 years before introduction of mandatory salt iodization began 2001. Over this period of time, iodine intake almost doubled. At the same time, the incidence rate of confirmed overt thyrotoxicosis significantly decreased: from the initial rate of 97.5 cases per 100,000 people per year in 1997–2000 to 48.8 cases per 100,000 people per year in 2014–2016. This result was due to a significant decrease in the incidence of multinodular toxic goiter, toxic adenoma and Graves’ disease in all age groups in both women and men. Moreover, the overall incidence of primary overt hypothyroidism has not changed.