An evaluation of urine and serum iodine status in the population of Tibet, China: No longer an iodine-deficient region.

Abstract

Iodine is a critical trace element for the synthesis of thyroid-related hormones, and either low or high iodine status can lead to thyroid dysfunction. This study aimed to evaluate the iodine status of the Tibetan population. From September 2016 to August 2018, we enrolled 1499 healthy adults from three areas of varying altitudes in Tibet. Urine iodine concentrations (UICs), adjusted UICs, and serum iodine concentrations (SICs) were measured using inductively coupled plasma mass spectrometry. The median UIC, adjusted UIC, and SIC was 137.9 μg/L, 118.4 µg/gCr, and 58.3 μg/L, respectively. Of the participants, 30.4% had UICs <100 µg/L, 63.0% had UICs ranging from 100 to 300 µg/L, and 9.6% had UICs >300 µg/L. The correlation between UIC, adjusted UIC, and SIC was good (r > 0.65, P < 0.01). The SICs were more stable than the UICs, and were not associated with age or sex. The prevalence of clinical hyperthyroidism, clinical hypothyroidism, subclinical hyperthyroidism, subclinical hypothyroidism, positive thyroid peroxide antibody, positive thyroglobulin antibody, either positive and both positive was 0.5%, 1.3%, 1.7% and 17.9%, 9.3%, 6.5%, 12.5%, and 2.5%, respectively. The prevalence of almost all thyroid disorders was higher in women than in men. This multicenter cross-sectional study found that the human iodine status of adults in Tibet was considered adequate, based on the World Health Organization's criteria.