Earliest prevention of endemic goiter by iodine supplementation during pregnancy

Abstract

During pregnancy complex changes of maternal thyroid function occur and they are influenced by the maternal iodine supply. It has been demonstrated that with decreasing iodine supply maternal goiter and hypothyroxinemia as well as fetal and neonatal hypothyroidism become more prevalent. Therefore iodine supplementation during pregnancy is now strongly recommended also in areas of moderate iodine deficiency. To monitor the success of iodine supplementation and its theoretical risk of increasing the frequency of thyroid autoantibodies, we have investigated the thyroid volume, thyroid function, urinary iodine excretion and antibodies to thyroid peroxidase at 10-12 weeks of gestation and postpartum in 38 mothers receiving 300 micrograms potassium iodide/day and in 70 mothers without iodine supplementation. In all of their newborns thyroid volume was determined by ultrasound. The thyrotropin (TSH) levels and antibodies to thyroid peroxidase (TPO-ab) in the neonates were measured in dried blood spots on filter paper from their newborn screening. Urinary iodine excretion was increased significantly after iodine supplementation in mothers (p < 0.001) and their newborns (< 0.05). No hypo- or hyperthyroidism was observed in the mothers or newborns. Interestingly, no difference of maternal thyroid volumes was observed between the two groups after pregnancy, but the volumes of the thyroid glands in newborns of mothers who received iodine were significantly (p < 0.004) lower (0.7 +/- 0.4 ml) than in the control group (1.5 +/- 1.1 ml). There was no change in the frequency of TPO-ab in either group after pregnancy. In four mothers transplacental passage of these antibodies was documented by positive measurement in the blood sample of the newborn. This study documents that iodine supplementation during pregnancy in an area of moderate iodine deficiency results in a lower size of neonatal thyroid volume and that this supplementation was not accompanied by an increase in the frequency of TPO-ab.

Thyroglobulin as a Biomarker of Iodine Deficiency: A Review

“…One of the studies (80) assessed Tg concentration in the first trimester before supplementation and then again at two weeks postpartum; one study (81) assessed Tg in the first and third trimesters; and one study (82) assessed Tg in all three trimesters and again 12-24 weeks postpartum. Tg concentrations in women in the first trimester (i.e., at baseline before supplementation) ranged from 13 to 25 lg/L, and postpartum, in women that had received any type of additional iodine (i.e., supplements or iodized salt), Tg ranged from 8 to 18 lg/L.…”

“…Tg concentrations in women in the first trimester (i.e., at baseline before supplementation) ranged from 13 to 25 lg/L, and postpartum, in women that had received any type of additional iodine (i.e., supplements or iodized salt), Tg ranged from 8 to 18 lg/L. Of the two studies with postpartum data (80,82), only one study (80) reported that women taking iodine supplementation in pregnancy had a postpartum median Tg <13 lg/L. However, the interpretation of these findings is confounded by differences in study designs, including a lack of a placebo group, relatively small sample sizes (n = 66-131), varying levels and types of supplemental iodine (iodized salt or supplements containing 150-300 lg iodine per day), duration of follow-up (2-24 weeks postpartum), and use of different Tg assays.…”

Iodine intake in Portuguese pregnant women: results of a countrywide study

“…Iodine supplementation in moderately iodinedeficient pregnant women using 150-200 mg/day has no adverse effects (35,37,46). On the contrary, it appears to reduce thyroid volumes and thyroglobulin concentrations in the mother (35) and, above all, it improves neurodevelopment outcomes in children (20,47).…”

Symposium on ‘Geographical and geological influences on nutrition’ Iodine deficiency in industrialised countries

“…The adverse effects on pregnancy of mild iodine deficiency, typical of industrialised countries, remain unclear. Six controlled trials of iodine treatment in pregnant women with iodine deficiency have been conducted in Europe (21)(22)(23)(24)(25)(26) . Overall, these studies suggest that in areas of mild-to-moderate iodine deficiency the maternal thyroid is able to adapt to meet the increased thyroid hormone requirements of pregnancy (27) .…”