Controversies in urinary iodine determinations

Abstract

Iodine deficiency (ID) is associated with increased prevalence of goiter, increased risk for neurodevelopmental disorders, and is the world's leading cause of intellectual deficits. Iodine nutritional status of a population is assessed by measurements of urinary iodine concentrations which are also used to define, indicate, survey and monitor iodine deficiency and consequently its treatment. Several methods are available for urinary iodine determination. Discussed here are some of the limitations and controversies related to urinary iodine determinations, and recent findings with emphasis on measurements of urinary iodine concentrations in children and during pregnancy.

Urinary iodine percentile ranges in the United States

“…Urinary iodine concentration is currently the most practical biochemical marker for determining the iodine nutrition of populations at the time of measurement [2]. The NHANES data represents casual spot urine samples, reflecting the findings of a population at a point in time, known to include wide variations both in regional and in individual UI concentrations [7]. Some of the variation was overcome by measurements of urinary creatinine to correct for urinary dilution that could affect urinary iodine concentrations.…”

Avaliação funcional e histológica da tireoide de ovinos suplementados com fluoreto de sódio por um período de 150 dias

“…Quanto ao I, as concentrações séricas e urinárias mantiveram-se constantes durante todo o período experimental, demonstrando que não houve interferência na absorção desse elemento pelo F. Cabe ressaltar que tanto para o F como para o I, a principal via de excreção é a urinária. Geralmente, o status nutricional de I é estimado por meio de sua excreção urinária total em 24 horas (Soldin, 2002).…”

Iodine status of Queensland children and the associations with diet and thyroid function

“…The accuracy of the approach, however, is largely affected by the significant within-person variation in UIC (1,19,20). Adjustment for within-person variation will have little effect, if any, on the mean value within a population but it will increase the precision of the variance within the population, reducing the proportion of individuals with very low or very high UIC (21).…”

“…C personal communication). Typically observed when assessing UIC (1,19,20), the large standard deviation 80.1 in conjunction with a mean of 135ug/L lead to a large CV of over 60%, indicating a large spread across the distribution of UIC and potentially misrepresenting the actual spread. Other Australian surveys have used repeated measurements of UIC in iodine surveys in older populations where at least one repeated measure was used (22,23), however, this thesis aims to explore the advantages of up to four UIC samples from younger individuals.…”

“…(Cr) (product of muscle metabolism) can reduce the impact of this variation on the interpretation of iodine nutrition (20,44,45). The challenge in correcting for creatinine is that it is influenced by BMI, age, gender and ethnicity and has no validated cut-off criteria for iodine nutrition (20,46).…”