Urinary iodine percentile ranges in the United States.

Background: The status of iodine nutrition of a population can be determined by measurement of urinary iodine concentrations since it is thought to indicate dietary iodine intake. Normally, these results are compared to population-based criteria, since there are no reference ranges for urinary iodine.

Objective: To determine the percentile ranges for urinary iodide (UI) concentrations in normal individuals in the United States.

Materials And Methods: The third National Health and Nutrition Examination Survey (NHANES III) (1988-1994) database of the civilian, non-institutionalized, iodine-sufficient US population was used. The 2.5th to 97.5th percentile ranges for urinary iodine and for urinary iodine per gram creatinine ratio (UI/Cr) (microg/g) were calculated for females and males, 6-89 years of age, each stratified by age groups.

Results And Conclusions: We calculated the percentile ranges for urinary iodine. After exclusions of subjects with goiter or thyroid disease, the study sample included 21,530 subjects; 10,439 males and 11,091 females. For women of childbearing age (14-44 years), urinary iodine concentration 2.5th to 97.5th percentiles are 1.8-65 microg/dl or 36-539 microg/g creatinine. For pregnant women, the ranges are 4.2-55 microg/dl or 33-535 microg/g creatinine.