Abstract
BackgroundOnly a few studies like ours have investigated the effect of long-term stable iodine supply on thyroid disorders in a historically iodine-deficient population, but not with a long follow-up time of 10 years.MethodsData were derived from two independent population-based cohorts of the Study of Health in Pomerania (SHIP-0 [1997–2001] and SHIP-TREND [2008–2012]) comprising 4308 and 4420 subjects, respectively. Diagnosed thyroid disorders were assessed. Thyroid gland dimensions were examined by ultrasound. Levels of serum thyrotropin (TSH) and autoantibodies to thyroperoxidase (anti-TPO Abs) were measured from blood samples.ResultsMedian urinary iodine excretion levels decreased from 123.0 μg/l to 112.0 μg/l (p = <0.001) between 2000 and 2010. The prevalence of known thyroid disorders increased from 7.6 % [CI 6.9–8.5] to 18.9 % [CI 17.6–20.1] and of thyroid medication use from 6.2 to 11.1 %. The prevalence of goiter decreased from 35.1 to 29.4 % (p = <0.001), while the prevalence of positive anti-TPO Abs decreased from 3.9 to 2.9 % (p = 0.022). Median serum TSH levels increased from 0.69 mIU/L to 1.19 mIU/L (p = <0.001). Consequently, prevalence of high TSH (mIU/L) increased from 2.6 to 2.9 % (p = 0.452), and low TSH (mIU/L) decreased from 6.6 to 6.4 % (p = 0.737).ConclusionThe decreased prevalence of iodine-deficient disorders and a stable prevalence of markers of autoimmune thyroid disorders argue for an improved iodine supply of the adult population in Northeast Germany. In contrast, the prevalence of diagnosed thyroid disorders and the intake of thyroid medication increased, although this might be related to inappropriate therapeutic decisions.Electronic supplementary materialThe online version of this article (doi:10.1186/s12963-016-0111-3) contains supplementary material, which is available to authorized users.
Highlights
A few studies like ours have investigated the effect of long-term stable iodine supply on thyroid disorders in a historically iodine-deficient population, but not with a long follow-up time of 10 years
Data from the first cohort of Study of Health in Pomerania (SHIP) (SHIP-0), which started a few years after the introduction of the efficient iodine deficiency disorder (IDD) prevention program in Germany, demonstrated a high prevalence of goiter, thyroid nodules, and hyperthyroidism in the general adult population of Northeast Germany [1]
Diagnosed thyroid disorders and medication There was an increase in the prevalence of diagnosed thyroid disorders between SHIP-0 and SHIP-TREND from 7.6 % [confidence interval (CI) 6.9–8.5] to 18.9 % [CI 17.6–20.1]
Summary
A few studies like ours have investigated the effect of long-term stable iodine supply on thyroid disorders in a historically iodine-deficient population, but not with a long follow-up time of 10 years. The monitoring of iodine fortification programs is important in order to observe the benefits of iodine fortification in populations and to recognize unintended effects early. The main consequences of long-term iodine deficiency in adults are a high prevalence of goiter, thyroid nodules, and hyperthyroidism. Data from the first cohort of SHIP (SHIP-0), which started a few years after the introduction of the efficient IDD prevention program in Germany, demonstrated a high prevalence of goiter, thyroid nodules, and hyperthyroidism in the general adult population of Northeast Germany [1]. The question arises as to whether a further decade of IDD prevention
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