Thyroid Disorders and Influence of Adjusted Iodine Prophylaxis in Pelagonia and Southwest Regions, North Macedonia.

Introduction: Iodine intake influences the incidence of thyroid diseases (TD), but data on its impact after iodine prophylaxis correction remains limited. This study analyzes TD incidence in a part of a country with sufficient iodine status since 2003, covering the period from 1984 to 2021, and evaluates changes following the 1999 iodine prophylaxis correction. Methods: This retrospective longitudinal study reviewed 20,880 medical records from a secondary medical center. Demographic and TD data were analyzed descriptively to compare trends before and after the 1999 iodine prophylaxis correction. Results: Among 20,880 patients aged 46.63 ± 15.06 years, 18,182 (87.1%) were female. Hypothyroidism (40.43%) and euthyroid nodular goiter (ENG) (28.7%) were predominant TD. Before the iodine prophylaxis correction, the mean patient age was 40.03 ± 13.03 years, with ENG (27.29%), hyperthyroidism (24.78%), euthyroid diffuse goiter (EDG) (24.94%), and hypothyroidism (15.84%) dominating. After the 1999 iodine prophylaxis correction, the overall incidence of TD, mean age (47.54 ± 15.1 years), male representation (P < 0.001), and hypothyroidism (43.78%, P < 0.001) increased, while EDG (11.73%), hyperthyroidism (12.28%), toxic nodular goiter (1.42%), and thyroid carcinoma (0.16%) declined (overall P < 0.001). ENG incidence (28.89%, P = 0.102) remained unchanged. Conclusion: Hypothyroidism and ENG were the predominant thyroid disorders in the area. Corrected iodine prophylaxis increased overall TD incidence, age at diagnosis, male representation, and hypothyroidism while reducing most other TD incidences. The stable ENG incidence requires further investigation. Continued monitoring is essential to improve public health strategies for TD management.