Short-term effectiveness of mandatory iodization of table salt, at an elevated iodine concentration, on the iodine and goiter status of schoolchildren with endemic goiter

Abstract

Background: Goiter rates and iodine deficiency usually show marked improvement in efficacy studies of mandatory iodization of salt, but little is known about the short-term effectiveness of mandatory iodization. Objective: The aim of the study was to evaluate, after 1 y, the effectiveness of mandatory iodization of salt at an iodine concentration higher than that occurring under optional iodization on the goiter rates and iodine status of schoolchildren living in an endemically goitrous area. Design: Goiters, measured by palpation, and urinary iodine concentrations of children in grades 4-7 in 4 schools in a known goitrous area in South Africa were assessed before and 1 y after the introduction of mandatory iodization at a higher iodine concentration than occurred with optional iodization. Estimates of the iodine concentration of iodized salt and the proportion of households using iodized salt were also made. Results: Iodine concentration in table salt and household use of iodized salt improved within 1 y. Goiter rates, which varied at baseline from 14.3% to 30.2% in the 4 schools, remained unchanged, with an overall mean (±SE) prevalence of 25.6±2.5% at baseline and of 27.5±2.7% 1 y later. The distribution of urinary iodine concentrations in the 4 schools improved substantially from the baseline deficient range. The overall median urinary iodine concentration increased from 0.17 to 1.47 μmol/L. Conclusions: Mandatory iodization of salt virtually eradicated iodine deficiency within 1 y in South African schoolchildren, but the goiter rate in these children did not decline. Measurement of goiters by palpation may not be appropriate in short-term evaluations of mandatory iodization programs.