TY - JOUR

T1 - Thyrotoxicosis after iodine fortification

T2 - A 21-year Danish population-based study

AU - Petersen, Mads

AU - Knudsen, Nils

AU - Carlé, Allan

AU - Andersen, Stig

AU - Jorgensen, Torben

AU - Perrild, Hans

AU - Ovesen, Lars

AU - Rasmussen, Lone Banke

AU - Thuesen, Betina Heinsbaek

AU - Pedersen, Inge Bulow

PY - 2018

Y1 - 2018

N2 - ObjectiveMonitoring the influence of cautious iodine fortification (IF) on the incidence rate of overt thyrotoxicosis in Denmark with formerly frequent multinodular toxic goitre.DesignA 21‐year (1997‐2017) prospective population‐based study identified all new cases of overt biochemical thyrotoxicosis in two open cohorts: a Western cohort with moderate iodine deficiency (ID) and an Eastern cohort with mild ID (total n = 533 969 by 1 January 1997). A diagnostic algorithm was applied to all thyroid function tests performed within the study areas. Mandatory IF of salt was initiated in mid‐2000 (13 ppm). This study is a part of DanThyr.ResultsThe standardized incidence rate (SIR) of thyrotoxicosis at baseline (1997‐1998) was 128.5/100.000/year in the cohort with moderate ID and 80.1 in the cohort with mild ID. SIR increased markedly in both cohorts during the initial years of IF (moderate/mild ID: +39/+52% in 2000‐2001/2004‐2005) and subsequently decreased to baseline level (mild ID) or below (moderate ID) by 2008. The decline was due to a marked decrease in the incidence rate among elderly subjects and a moderate decrease among the middle aged. The follow‐up period for the mildly iodine deficient cohort was restricted to 2008. A continuous decline in SIR was observed for the remainder of the study period in the area with moderate ID (33% below baseline in 2016‐2017).ConclusionThe rise in thyrotoxicosis incidence with cautious mandatory IF returned to baseline level after 7‐8 years and levelled out at 33% below baseline in the population with previously moderate ID after 16‐17 years.

AB - ObjectiveMonitoring the influence of cautious iodine fortification (IF) on the incidence rate of overt thyrotoxicosis in Denmark with formerly frequent multinodular toxic goitre.DesignA 21‐year (1997‐2017) prospective population‐based study identified all new cases of overt biochemical thyrotoxicosis in two open cohorts: a Western cohort with moderate iodine deficiency (ID) and an Eastern cohort with mild ID (total n = 533 969 by 1 January 1997). A diagnostic algorithm was applied to all thyroid function tests performed within the study areas. Mandatory IF of salt was initiated in mid‐2000 (13 ppm). This study is a part of DanThyr.ResultsThe standardized incidence rate (SIR) of thyrotoxicosis at baseline (1997‐1998) was 128.5/100.000/year in the cohort with moderate ID and 80.1 in the cohort with mild ID. SIR increased markedly in both cohorts during the initial years of IF (moderate/mild ID: +39/+52% in 2000‐2001/2004‐2005) and subsequently decreased to baseline level (mild ID) or below (moderate ID) by 2008. The decline was due to a marked decrease in the incidence rate among elderly subjects and a moderate decrease among the middle aged. The follow‐up period for the mildly iodine deficient cohort was restricted to 2008. A continuous decline in SIR was observed for the remainder of the study period in the area with moderate ID (33% below baseline in 2016‐2017).ConclusionThe rise in thyrotoxicosis incidence with cautious mandatory IF returned to baseline level after 7‐8 years and levelled out at 33% below baseline in the population with previously moderate ID after 16‐17 years.

KW - epidemiology

KW - hyperthyroidism

KW - incidence

KW - iodine

KW - thyrotoxicosis

U2 - 10.1111/cen.13751

DO - 10.1111/cen.13751

M3 - Journal article

C2 - 29851122

VL - 89

SP - 360

EP - 366

JO - Clinical Endocrinology

JF - Clinical Endocrinology

SN - 0300-0664

IS - 3

ER -