A randomized trial for the treatment of mild iodine deficiency during pregnancy: maternal and neonatal effects.

Abstract

One hundred and eighty euthyroid pregnant women were selected at the end of the first trimester of gestation on the basis of biochemical criteria of excessive thyroid stimulation, defined as supranormal serum thyroglobulin (TG > 20 micrograms/L) associated with a low normal free T4 index (< 1.23) and/or an increased T3/T4 ratio (> 25 x 10(-3)). Women were randomized in a double blind protocol into three groups and treated until term with a placebo, 100 micrograms potassium iodide (KI)/day, or 100 micrograms iodide plus 100 micrograms L-T4/day. Parameters of thyroid function, urinary iodine excretion, and thyroid volume were monitored sequentially. Neonatal thyroid parameters, including thyroid volume by echography, were also assessed in the newborns from mothers of the three groups. In women receiving a placebo, the indices of excessive thyroid stimulation worsened as gestation progressed, with low free T4 levels, markedly increased serum TG and T3/T4 ratio. Serum TSH doubled, on the average, and was supranormal in 20% of the cases at term. Urinary iodine excretion levels were low, around 30 micrograms/L at term. The thyroid volume increased, on the average, by 30%, and 16% of the women developed a goiter, confirming the goitrogenic stimulus associated with pregnancy. Moreover, the newborns of these mothers had significantly larger thyroid volumes at birth as well as elevated serum TG levels. In both groups of women receiving an active treatment, the alterations in thyroid function associated with pregnancy were markedly improved. The increase in serum TSH was almost suppressed, serum TG decreased significantly, and changes in thyroid volume were minimized (group receiving KI) or almost suppressed (group receiving KI combined with L-T4). Moreover, in the newborns of the mothers in the two groups receiving an active treatment, serum TG was significantly lower, and thyroid volume at birth was normal. The effects of therapy were clearly more rapid and more marked in the group receiving a combination of T4 and KI than in the women receiving KI alone. The differences could be partly attributed to the slightly higher amount of iodine received by women in the combined treatment. However, the main benefits of the combined treatment were almost certainly attributable to the hormonal effects of the addition of L-T4. Furthermore, the study demonstrated that the administration of T4 did not hamper the beneficial effect of iodine supplementation. In conclusion, the present work emphasizes the potential risk of goitrogenic stimulation in both mother and newborn in the presence of mild iodine deficiency.(ABSTRACT TRUNCATED AT 400 WORDS)

Seasonality in urinary and household salt iodine content among pregnant and lactating women of the plains of Nepal

“…Within each season, differences in UI between pregnant and lactating women were significant by median two-sample test, Po0.005. (Pedersen et al, 1993;Glinoer et al, 1995;Caron et al, 1997;Elnager et al, 1998) and Sudan (Elnager et al, 1998;Eltom et al, 2000). However, compared to European women, women in this region of Nepal are subject to additional environmental and nutritional stresses (West et al, 1999;Dreyfuss et al, 2000) that may compound the health consequences of mild-to-moderate iodine deficiency for themselves and their offspring.…”

“…Stunted growth and neuromotor, intellectual, behavioral and cognitive impairment have been described in children whose mothers were moderately to severely iodine deficient during pregnancy (Pharoah & Connolly, 1987;Fierro-Benitez et al, 1988;Azizi et al, 1995). Transient hypothyroidism and increased thyroid volume have been observed in women and in neonates of women with mild-tomoderate iodine deficiency during pregnancy (Pedersen et al, 1993;Glinoer et al, 1995;Kung et al, 1997). Studies suggest that cognitive impairment may exist among children whose mothers were even mildly iodine deficient during pregnancy (Glinoer & Delange, 2000).…”

Iodine supplementation of pregnant women in Europe: a review and recommendations

“…No significant differences were found between groups comparing maternal or cord T4, T3, and FT4. In a double-blind, placebo-controlled trial, Glinoer et al (1995) supplemented pregnant women (n ¼ 120; median UI 36 mg/l; biochemical criteria of excess thyroid stimulation) with 100 mg iodine/day or control from B14 weeks to term. Treatment had no significant effect on maternal or cord T3, FT4, and T3/T4 ratio.…”

“…However, sample sizes were small, and more data, particularly from TPO-Ab þ women, would be valuable. For the newborn, most data suggest supplementation is safe, although the studies of and Glinoer et al (1995) reported higher newborn TSH levels with supplementation. Iodine supplementation is efficacious, both for the mother and newborn.…”

The current salt iodization strategy in Kyrgyzstan ensures sufficient iodine nutrition among school-age children but not pregnant women

“…The median UIC of 111 mg/l in the pregnant women in the present survey does not attain this range, indicating that their iodine consumption is insufficient. This conclusion is supported by finding an increasing thyroid volume with the duration of pregnancy, since an increase in thyroid size during pregnancy has been a classical indicator of iodine deficiency (24,25) . The finding in a population-representative survey that pregnant women, while consuming the same diet, have lower UIC than school-age children is not unique for Kyrgyzstan (26)(27)(28) .…”