Iodine is an essential trace-element required for the normal function of the thyroid gland. Iodine deficiency interferes with the capacity of the thyroid gland to meet the metabolic changes presented by pregnancy, leading to significant repercussions for both the maternal and fetal thyroid function. In pregnant women urinary iodine excretion was significantly elevated at the first 4.5 months, compared to values of non-pregnant women and decreased in the last 4.5 months of pregnancy. Iodine was measured by a modification of the spectrophotometric method of Sandell-Kolthoff since 90% of the free iodine is excreted through urine. The Sandell-Kolthoff reaction is an oxidizing-reducing reaction based on the catalytic effect of iodine, the rate of which depends on the iodine concentration. Ammonium persulfate was used as an oxidizing agent for the elimination of the interfering substances in urine before the measurement by the Sandell-Kolthoff reaction. The relative standard deviation (RSD) for the method was 9.5% and the lower limit of detectability was 0.024 μΜ. Urine iodine concentrations were determined by ammonium persulfate method in 69 samples collected from a mixed population of healthy women, pregnant or not, living in Athens. Iodine concentrations ranged from 2.3 μΜ to 5.6 μΜ for the pregnant women (4-18 weeks) (n = 24), from 1.57 μΜ to 5.6 μΜ for the pregnant women (19-36 weeks) (n = 15) and from 0.8 μΜ to 4.4 μΜ for the non-pregnant women. Moderate iodine deficiency was evident in 7% of the pregnant women (19-36 weeks) and 7% of non-pregnant women. Mild iodine deficiency was evident in 8% of the pregnant women (4-18 weeks), 7% of the pregnant women (19-36 weeks) and 10% of the non-pregnant women.
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