Functional thyroid diseases and iodine level in the elderly after mandatory iodination in Turkey: 25th anniversary results

Introduction and Aim: Iodine is a micronutrient required for the production of thyroid hormones. Iodine deficiency; it causes iodine deficiency diseases such as hypothyroidism, hyperthyroidism, thyroid nodule and goiter. In Turkey, legal regulations for the compulsory iodinization of table salt were completed in 1999. The aim of this study is to evaluate iodine sufficiency in the elderly in the 25th year of compulsory iodination in Turkey and to investigate the frequency of thyroid diseases in the geriatric population. Material/Method: This study is a retrospective study examining patients who applied to Ankara University Faculty of Medicine, Department of Geriatrics between 01.01.2022 and 30.06.2023, living in Ankara, and whose urine iodine level was requested. 417 patients were included in the study. Age, gender, thyroid disease history, urine iodine level, thyroid function tests and thyroid autoantibody (TOA) results of all patients participating in the study; Thyroid volume, thyroid nodule and parenchyma type data of the patients for whom ultrasonography was requested were recorded. Results: The median value of the patients' Urinary Iodine Concentration (UIC) was found to be 87 µg/L. The rate of patients with UIC below 50 µg/L was found to be 29.2%. The rate of patients with goiter was found to be 16.8% (n: 59). The rate of patients with thyroid nodules was 70.8% (n:252), and the rate of patients with more than one nodule was 37.6% (n:134). The heterogeneous parenchyma rate in patients who underwent ultrasonography was found to be 61.5% (n:219). TOA positivity rate is 19.2% (n:77); While Anti-Thyroid Peroxidase (Anti-TPO) positivity was found to be 13.2%, Anti-Thyroglobulin (Anti-TG) positivity was found to be 11.9%. UIC level in the 75-84 age group was found to be significantly lower than that in the 65-74 age group. (p=0.030) There was no difference in sonographic findings between these groups. The rate of isoechoic nodules and parenchymal heterogeneity was significantly higher in the iodine-deficient group. (p=0.028 and p=0.007 respectively) Discussion and Conclusion: In Ankara province, which had mild-moderate iodine deficiency before 1999, iodine levels in the elderly are still insufficient in the 25th year of iodination. We found that the frequency of goiter decreased compared to 1999 and increased compared to 2009. While iodine deficiency was more evident in the older group, there was no difference between the groups in terms of thyroid diseases. In our study, while isoechoic nodules and heterogeneity were significantly higher in the iodine-deficient group, the rate of goiter and thyroid nodules was not significantly different. More large-scale studies are needed on this subject.