Iodine deficiency is the leading preventable cause of intellectual impairment in the world. Although iodine supplementation is generally considered to be safe, there is a possibility of high doses of iodine suppressing maternal thyroid function.
The objective of this review was to assess the effects of iodine supplementation before or during pregnancy in areas of iodine deficiency.
We searched the Cochrane Pregnancy and Childbirth Group trials register.
All acceptably controlled trials of maternal iodine supplementation during pregnancy with clinical outcomes.
Eligibility and trial quality were assessed by two reviewers.
Three trials involving 1551 women were included. In two trials, iodine supplementation was associated with a statistically significant reduction in deaths during infancy and early childhood (relative risk 0.71, 95% confidence interval 0.56 to 0.90). Iodine supplementation was associated with decreased prevalence of endemic cretinism at the age of four years (relative risk 0.27, 95% confidence interval 0.12 to 0.60) and better psychomotor development scores between four to 25 months of age.
Iodine supplementation in a population with high levels of endemic cretinism results in an important reduction in the incidence of the condition with no apparent adverse effects.
[Show abstract][Hide abstract] ABSTRACT: Iodine is a trace element essential for synthesis of the thyroid hormones, triiodothyronine and thyroxine. These hormones play a vital role in the early growth and development stages of most organs, especially the brain. The World Health Organization (WHO) has declared that, after famine, iodine deficiency is the most avoidable cause of cerebral lesions including different degrees of mental retardation and cerebral paralysis. The main function of iodine in vertebrates is to interact with the thyroid hormones. During pregnancy sufficient quantities of iodine are required to prevent the appearance of hypothyroidism, trophoblastic and embryonic or fetal disorders, neonatal and maternal hypothyroidism, and permanent sequelae in infants. Thyroid hormone receptors and iodothyronine deiodinases are present in placenta and central nervous tissue of the fetus. A number of environmental factors influence the epidemiology of thyroid disorders, and even relatively small abnormalities and differences in the level of iodine intake in a population have profound effects on the occurrence of thyroid abnormalities. The prevalence of disorders related to iodine deficit during pregnancy and postpartum has increased. Iodine supplementation is an effective measure in the case of pregnant and lactating women. However, it is not implemented and the problem is still present even in societies with theoretically advanced health systems. During pregnancy and postpartum, the WHO recommends iodine intake be increased to at least 200 microg/day. Side-effects provoked by iodine supplementation are rare during pregnancy at the recommended doses.
[Show abstract][Hide abstract] ABSTRACT: (131)I, when released in a radiological or nuclear accident as happened recently in Fukushima, Japan, may cause thyroid cancer as a long-term consequence. Iodine thyroid blocking (ITB) is known to reduce the risk of developing thyroid cancer. Potential adverse effects of ITB have not been systematically investigated so far. This article summarises the results of a review on adverse effects of ITB based on a systematic literature search in scientific medical databases. A meta-analysis was not performed as identified studies displayed major heterogeneity. The search resulted in 14 articles relevant to the topic, reporting mostly on surveys, ecological and intervention studies. Only one study from Poland focused on effects (both desired and adverse) of an ITB intervention following the Chernobyl accident. All other studies reported on iodine administration in a different context. Overall, the studies did not reveal severe adverse reactions to potassium iodide in the general public. Since ITB is a protective measure only applied in very specific circumstances, scientifically sound studies of adverse effects are scarce and consequently the evidence base is weak. The assessment of adverse effects of ITB relies on indirect evidence from related areas. This study may contribute to ongoing developments in pharmacoepidemiology aiming to better quantify adverse effects of medications and health care interventions including ITB.
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