CLINICAL STUDY Geographic variations in the frequency of thyroid disorders and thyroid peroxidase antibodies in persons without former thyroid disease within Germany C Meisinger 1,2 , T Ittermann 3 , H Wallaschofski 4 , M Heier 1,2 , H Below 5 , A Kramer 5 , A Do ¨ring 6 , M Nauck 4 and H Vo ¨lzke 3 1 Helmholtz Zentrum Mu ¨nchen, Institute of Epidemiology II, German Research Center for Environmental Health (GmbH), Neuherberg, Germany, 2 Central Hospital of Augsburg, MONICA/KORA Myocardial Infarction Registry, Stenglinstr. 2, D-86156 Augsburg, Germany, 3 Institute for Community Medicine, University of Greifswald, Greifswald, Germany, 4 Institute of Clinical Chemistry and Laboratory Medicine, University of Greifswald, Greifswald, Germany, 5 Institute of Hygiene and Environmental Medicine, University of Greifswald, Greifswald, Germany and 6 Helmholtz Zentrum Mu ¨nchen, Institute of Epidemiology I, German Research Center for Environmental Health (GmbH), Neuherberg, Germany (Correspondence should be addressed to C Meisingerat Central Hospital of Augsburg, MONICA/KORA Myocardial Infarction Registry; Email: christa.meisinger@helmholtz-muenchen.de) Abstract Objective: To investigate regional variations in the frequency of undiagnosed thyroid disorders among 25- to 88-year-old men and women in two communities in the northeast and the south of Germany. In addition, autoantibodies to thyroperoxidase (TPO-Abs) and urinary iodine excretion were determined. Methods: Two population-based surveys of men and women using a common standardized protocol, the Study of Health in Pomerania (SHIP) in the northeast of Germany (2505 participants) and the Kooperative Gesundheitsforschung in der Region Augsburg (KORA) in the south of Germany (2316 participants), were compared with regard to the frequency of undiagnosed thyroid disorders. Results: Compared with the northeast of Germany, urinary iodine excretion and serum thyroid- stimulating hormone (TSH) levels were significantly higher in the south. The median urinary iodine concentration was 110 mg/l (64; 169 mg/l) in SHIP and 151 mg/l (97; 214 mg/l) in KORA, and the median TSH value was 0.81 mIU/l (0.56; 1.15 mIU/l) in SHIP and 1.22 mIU/l (0.84; 1.80 mIU/l) in KORA. The frequency of elevated TSH (TSH R2.12 mIU/l) was 4.3% in SHIP and 14.1% in KORA (P!0.001); the corresponding values for suppressed TSH (!0.25 mIU/l) were 3.5 and 1.7% (P!0.001). The proportion of ultrasonographic findings was 55.5% in SHIP and 68.0% in KORA. The frequency of serum TPO-Abs did not differ significantly between northeast and south Germany. Conclusions: There were considerable regional disparities in the frequency of thyroid disorders within Germany. These differences can be explained not only bydifferent regional histories of natural iodine deficiency but also by current differences in the iodine supply under an identical nationwide iodine fortification program. European Journal of Endocrinology 167 363–371 Introduction Thyroid disorders such as goiter, nodules, auto- immune thyroid disease, and thyroid dysfunction affect a considerable portion of the population (1, 2). The spectrum of thyroid disorders depends on ethnic and environmental factors, especially on iodine intake (3, 4, 5). For years, iodine intake of many European populations was below the level rec- ommended by international organizations (6). Until the mid 1990s, Germany was generally considered an iodine-deficient area (7). Iodine supply varied within Germany: while the north-eastern part of Germany was an area with a moderate iodine deficiency, the iodine deficiency was moderate to severe in south Germany (8, 9). Since the beginning of the 1980s, a voluntary iodine supply program has been introduced stepwise to decrease the prevalence of iodine deficiency disorders (10). The activities differed between the eastern and western parts of Germany (11). In 1983, a general iodine fortification program was implemented in the eastern part, but iodine deficiency could not be corrected until 1989, and after reunification, this effect was initially lost. In 1993, by law a regulation concerning the iodization of table salt became effective, which led to an increase in the use of iodized salt for food production. Thus, during the past 15 years, the iodine supply in Germany remained stable. A nation- wide iodine survey conducted in children found that the median urinary iodine concentrations were in the lower section of the recommended range, suggesting European Journal of Endocrinology (2012) 167 363–371 ISSN 0804-4643 q 2012 European Society of Endocrinology DOI: 10.1530/EJE-12-0111 Online version via www.eje-online.org