Frequency distribution of urinary and breast-milk iodine concentrations in postpartum period, Gorgan, 2003

ABSTRACT

Adequate dietary iodine is essential for the production of thyroid hormones. Breastfed infants are reliant on adequate maternal iodine intake. The aim of this study was to evaluate iodine sufficiency in lactating women in Iran. The study population included 100 randomly selected lactating mothers referred to the Taleghani Hospital of Gorgan between April and June 2003. Subjects were within the 1[st]-6[th] month of their postpartum period. Goiter was graded according to WHO classification. Spot urine [2-3 ml] and breast-milk [5-10 ml] samples were collected for the measurement of iodine concentrations using acid digestion method. Urine iodine concentrations [UIC] of <100 and breast-milk iodine concentrations [MIC] of <50 micro g/L were considered as iodine deficiency. Mean [ +/- SD] age of women was 25.6 +/- 1.6 years. 43% and 8% had grade 1 and 2 goiters, respectively. The median [range;%95 CI] UIC was 259micro g/L [35-519; 226-275]. UIC of <100 micro g/L was detected in 16%, 50-99 in 13% and 20-49 micro g/L in 3%. Grade 1 and 2 goiters were present in 8% and 8% of mothers with UIC <100 micro g/L, respectively. The median [range;%95 CI] MIC was 93.5 micro g/L [17-696; 97-137]. MIC of <50 micro g/L was reported in 19%, 35-49 in 13%, 20-34 in 3%, and <20 micro g/L in 3%. Grade 1and 2 goiters were present in 11% and 8% of women with MIC <50 micro g/L, respectively. MIC was significantly correlated with UIC levels [r=0.44, p < 0.0001]. Meanwhile, there was a significant association between iodine-deficiency and goiter [p < 0.0001]. UIC and MIC levels show sufficient iodine supplementation in Gorgan. However, some infants remain at risk for low iodine intake via breast milk