Relative Impact of Iodine Supplementation and Maternal Smoking on Cord Blood Thyroglobulin in Pregnant Women with Normal Thyroid Function

Abstract

Objective: To assess the impact on cord blood (CB) thyroglobulin (Tg) of early iodine supplementation during pregnancy. Methods: A total of 111 healthy pregnant women with normal thyroid function were included in a prospective randomized study and divided into two groups with (150 µg/day) or without iodine supplementation started during the first trimester. Maternal smoking was assessed qualitatively by self-reported statements and quantitatively by cotininuria. Exhaustive thyroid tests were performed at delivery in the mother and in CB. Results: Third-trimester ioduria documented compliance with iodine supplementation (160 vs. 76 µg/l in controls). CB Tg was not different between the iodine and control groups (median 77 vs. 79.5 ng/ml, respectively) and did not correlate with maternal ioduria. CB Tg was higher in newborns from smoking mothers (114 vs. 64.7 ng/ml) and correlated with self-reported smoking status more than with maternal cotininuria. Nonsmokers had no difference in CB Tg whether they took iodine supplementation or not, as opposed to smokers, who tended to benefit from supplementation. Conclusions: Iodine supplementation does not significantly impact CB Tg in healthy nonsmoker pregnant women selected for normal thyroid function, as opposed to maternal smoking. CB Tg appears to be a marker of in utero tobacco exposure. In areas of mild iodine deficiency, iodine supplementation could especially benefit the fetuses of smokers.

Iodine Supplementation throughout Pregnancy Does Not Prevent the Drop in FT4 in the Second and Third Trimesters in Women with Normal Initial Thyroid Function

“…However, when looking at Tg levels, iodine supplementation prevented the rise observed in controls, particularly in the paired analysis. We had also shown previously in the same population that maternal Tg at delivery was higher in the control group [30] . Our results on Tg are similar to those of Glinoer et al [10] and Pedersen et al [17] , but at odds with those of Liesenkotter et al [18] , Nohr et al [14] and Antonangeli et al [16] .…”

Thyroid hormone signaling: Contribution to neural function, cognition, and relationship to nicotine

“…As mentioned previously, smoking during pregnancy induced a mild iodine deficiency (Hiéronimus et al, 2012), which may contribute to long-lasting cognitive deficits in children (Bath et al, 2013). Prospective iodine treatment of smoking-induced mild iodine deficiency ameliorated negative effects on infant thyroid function (Hiéronimus et al, 2012), which may reduce the risk of adverse cognitive effects in these children.…”

“…Further, studies have found that smoking increased the rate of hypothyroxinemia (low T 4 ) in women of reproductive age (Vanderver et al, 2007), which may adversely affect their children (this will be discussed in more detail later in this review). Maternal smoking during pregnancy may also induce a mild iodine deficiency, which indicates a disruption in thyroid function (Hiéronimus et al, 2012). Mild iodine deficiency during pregnancy contributed to long-lasting cognitive deficits in children (Bath et al, 2013), presumably due to iodine’s role in thyroid hormone synthesis.…”

“…Prospective iodine treatment of smoking-induced mild iodine deficiency ameliorated negative effects on infant thyroid function (Hiéronimus et al, 2012), which may reduce the risk of adverse cognitive effects in these children. Similarly, a study conducted by Chanoine et al (1991) observed an increase in the size of the thyroid in infants born to smoking mothers.…”

The Importance of Iodine Supplementation and Smoking for Maternal and Fetal Thyroid Health in Pregnant Women

“…In the presented study, the authors indicated only the status of anti-Tg. Serum cotinine levels in smokers increase in direct proportion to the Dear Editor, We read the article 'Relative impact of iodine supplementation and maternal smoking on cord blood thyroglobulin in pregnant women with normal thyroid function' by Hiéronimus et al [1] with great interest. The authors concluded that iodine supplementation does not significantly impact cord blood (CB) thyroglobulin (Tg) in healthy nonsmoking pregnant women selected for normal thyroid function, as opposed to smoking women, and stated that CB Tg appears to be a marker of in utero tobacco exposure.…”