Assessment of Iodine Status in Adults and Establishment of Reference Ranges for Urine Iodine Concentration in Turkey.

Abstract

Background: Iodine is essential for thyroid hormone production and is critical for growth, development, and reproductive health. It also acts as an antioxidant and influences cell differentiation. Iodine deficiency can lead to hypothyroidism. Urinary iodine concentration (UIC), often assessed through spot samples for convenience, is a valuable indicator of iodine intake. The median UIC of spot samples is commonly used to categorize a population's iodine status. This study aimed to assess the prevalence of iodine deficiency and establish reference ranges for iodine levels in adults aged 18 and above in Turkey.

Methods: Spot urinary iodine concentrations were measured at Istanbul Medical Faculty between July 2018 and July 2023. Iodine measurements were conducted using a modified microplate method based on the Sandell-Kolthoff reaction. The reference ranges for the urine iodine test were calculated using the Hoffman method.

Results: The iodine levels varied in this study: 13% had < 50 µg/L, 24% had 50 - 99 µg/L, 25% had 100 - 149 µg/L, 16% had 150 - 199 µg/L, 12% had 200 - 299 µg/L, and 10% had > 300 µg/L. The median UIC for Turkish adults was 122 µg/L, considered optimal by WHO standards. The iodine reference range for 18- to 80-year-olds was 20 - 330 µg/L, with a 116 µg/L median. There was no significant correlation between iodine levels and thyroid hor-mones or antibodies.

Conclusions: The results of this study indicate that iodine levels among adults in the Turkish population from 2018 to 2023 are sufficient. Furthermore, the established reference intervals will facilitate the effective monitoring of iodine status by health professionals in clinical and laboratory settings.