Mads Petersen1, Nils Knudsen2, Allan Carlé1, Stig Andersen3, Torben Jørgensen4,5,6, Hans Perrild2, Lars Ovesen7, Lone Banke Rasmussen2, Betina Heinsbæk Thuesen4, Inge Bülow Pedersen1. 1. Department of Endocrinology, Aalborg University Hospital, Aalborg, Denmark. 2. Department of Endocrinology, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark. 3. Department of Geriatrics, Aalborg University Hospital, Aalborg, Denmark. 4. Centre for Clinical Research and Prevention, Bispebjerg/Frederiksberg Hospital, Copenhagen, Denmark. 5. Department of Public Health, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark. 6. Faculty of Medicine, Aalborg University, Aalborg, Denmark. 7. Department of Gastroenterology, Slagelse Hospital, Slagelse, Denmark.
Abstract
OBJECTIVE: To monitor the impact of a cautious iodine fortification (IF) on the incidence of overt hypothyroidism in two subpopulations with different levels of preexisting iodine deficiency (ID). DESIGN: A 20-year (1997 to 2016) prospective population-based study identified all new cases of diagnosed overt biochemical hypothyroidism in two open cohorts: a western cohort with moderate ID (n = 309,434; 1 January 1997) and an eastern cohort with mild ID (n = 224,535; 1 January 1997). A diagnostic algorithm was applied to all thyroid function tests performed within the study areas, and possible new cases were verified individually. Mandatory IF of salt was initiated in mid-2000 (13 ppm). The current study is a part of the DanThyr study. RESULTS: At baseline, standardized incidence rates (SIRs) of hypothyroidism were 32.9 and 47.3/100.000/y in the cohorts with moderate and mild ID, respectively. The SIR of hypothyroidism increased significantly in both cohorts after implementing mandatory IF, with peak values of 150% in 2014 to 2016 for the moderate ID cohort and 130% in 2004 to 2005 for the mild ID cohort. Significant increases in SIR were seen among the young and middle-aged participants of both cohorts, whereas no changes were seen among the elderly participants (≥60 years). The follow-up period for the mildly iodine-deficient cohort was restricted up to and including 2008. CONCLUSION: The cautious initiation of the IF program in Denmark caused a sustained increase in hypothyroidism incidence among subjects residing in areas of moderate and mild ID but only among the young and middle-aged participants.
OBJECTIVE: To monitor the impact of a cautious iodine fortification (IF) on the incidence of overt hypothyroidism in two subpopulations with different levels of preexisting iodine deficiency (ID). DESIGN:A 20-year (1997 to 2016) prospective population-based study identified all new cases of diagnosed overt biochemical hypothyroidism in two open cohorts: a western cohort with moderate ID (n = 309,434; 1 January 1997) and an eastern cohort with mild ID (n = 224,535; 1 January 1997). A diagnostic algorithm was applied to all thyroid function tests performed within the study areas, and possible new cases were verified individually. Mandatory IF of salt was initiated in mid-2000 (13 ppm). The current study is a part of the DanThyr study. RESULTS: At baseline, standardized incidence rates (SIRs) of hypothyroidism were 32.9 and 47.3/100.000/y in the cohorts with moderate and mild ID, respectively. The SIR of hypothyroidism increased significantly in both cohorts after implementing mandatory IF, with peak values of 150% in 2014 to 2016 for the moderate ID cohort and 130% in 2004 to 2005 for the mild ID cohort. Significant increases in SIR were seen among the young and middle-aged participants of both cohorts, whereas no changes were seen among the elderly participants (≥60 years). The follow-up period for the mildly iodine-deficient cohort was restricted up to and including 2008. CONCLUSION: The cautious initiation of the IF program in Denmark caused a sustained increase in hypothyroidism incidence among subjects residing in areas of moderate and mild ID but only among the young and middle-aged participants.
Authors: Line Tang Møllehave; Marie Holm Eliasen; Ieva Strēle; Allan Linneberg; Rodrigo Moreno-Reyes; Ludmila B Ivanova; Zvonko Kusić; Iris Erlund; Till Ittermann; Endre V Nagy; Ingibjorg Gunnarsdottir; Jonathan Eli Arbelle; Aaron Milton Troen; Valdis Pīrāgs; Lisbeth Dahl; Alicja Hubalewska-Dydejczyk; Malgorzata Trofimiuk-Müldner; João Jacome de Castro; Mafalda Marcelino; Simona Gaberšček; Katja Zaltel; Manuel Puig-Domingo; Lluis Vila; Sofia Manousou; Helena Filipsson Nyström; Michael Bruce Zimmermann; Karen R Mullan; Jayne Valerie Woodside; Henry Völzke; Betina Heinsbæk Thuesen Journal: Endocr Connect Date: 2022-03-10 Impact factor: 3.335