Iodine status and thyroid volume changes during pregnancy: results of a survey in Aran Valley (Catalan Pyrenees)

Abstract

The Aran Valley (Catalan Pyrenees, Spain) has a long-standing history of iodine deficiency. A survey was performed to determine the prevalence of iodine deficiency (urinary iodine<150 microg/l) in pregnant women from this region during the 1st and 3rd trimesters of gestation and to evaluate the changes in thyroid volume (TV). Of all the registered pregnancies in the area, in the first semester of the year 2000, 35 women (90%) were studied. Urinary iodine (UI) was measured and a thyroid ultrasonography performed during the 1st and 3rd trimester and their iodized salt consumption was recorded. Of the whole group, 77.1% of pregnant women reported regular intake of iodized salt.Median UI in the first trimester was 134.5 microg/l. Iodine deficiency was observed in 57.1%of women in the 1st trimester and in 46.7% in the 3rd trimester (p=0.1). In 10 women supplemented with iodine (150 microg/day) from the 1st trimester, median UI increased from 138.5 microg/l in the 1st trimester to 168 mug/l in the 3rd trimester (p=0.037), and no changes were observed in the rest. TV increased in the whole group during pregnancy (median 7.5 ml in the 1st trimester vs 9.5 ml in the 3rd trimester; p<0.001). The change in TV was significant in those cases with iodine deficiency in the 1st trimester, 3rd trimester or both (median 7.5ml in the 1st trimester vs 10.01 ml in the 3rd trimester; p=0.001) and between multiparous women (8.2 vs 10.9 ml; p=0.005). In 2000, iodine deficiency among pregnant women in the Aran Valley was still very high. Iodine deficiency as well as multiparity contributes to goitrogenesis during pregnancy. Taking this data in account, pre-conceptional supplements with iodine are required for its prevention.