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

•A multicenter cross-sectional study was conducted in three altitudes and found adequate iodine status in Tibet.•Iodine status evaluated by urinary iodine concentration (UIC) in Tibetan adults was lower than reported in other Chinese regions located at lower altitudes.•Contrary to UIC (µg/L) and adjusted UIC (µg/gCr), serum iodine concentration (µg/L) was not associated with age or sex, and correlations with thyroid-related hormones were significantly higher.•The prevalence of thyroid disorders was higher in women than in men.