Iodine deficiency in pregnant women in Europe

Zimmermann, Michael; Gizak, Małgorzata; Abbott, Karen; Andersson, Maria; Lazarus, John H.

doi:10.1016/s2213-8587(15)00263-6

Cited by 128 publications

(96 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Consequently, the prevalence of IMH is higher in countries with iodine deficiency (Table 1). Even though significant progress has been made in efforts to eradicate iodine deficiency worldwide, this is still an important issue, as 2014 data show that greater than 50% of European countries have mild iodine deficiency (39), while in the most recent NHANES data (2007-2010), 26% of pregnant women in the US were found to have suboptimal iodine levels, with urinary iodine <100 μg/L (40). The implications of these findings are important, as iodine deficiency affects not only maternal but also fetal thyroid hormone production.…”

Section: Causes Of Imhmentioning

confidence: 99%

MANAGEMENT OF ENDOCRINE DISEASE: Isolated maternal hypothyroxinemia during pregnancy: knowns and unknowns

Dosiou

Medici

2017

European Journal of Endocrinology

View full text Add to dashboard Cite

Isolated maternal hypothyroxinemia (IMH) during pregnancy is defined as a low maternal T 4 in the absence of TSH elevation. As IMH is common, with a prevalence of 1-2% in iodine-sufficient populations, and early research has suggested adverse effects on fetal neurodevelopment, it has been the focus of many studies in the last decade. In the current review, we first discuss the significance of IMH based on data from animal models and recent discoveries regarding the role of thyroid hormone on neurodevelopment. We address issues surrounding the definition and prevalence of this entity and discuss new insights into the etiologies, clinical consequences and management of IMH. A number of large cohort studies have investigated the effects of IMH on the risk of various pregnancy complications and child neurodevelopment. We review these studies in detail and describe their limitations. We discuss the available research on management of IMH, including two recent randomized controlled trials (RCTs). Finally, we delineate the remaining uncertainties in this field and emphasize the need for a sufficiently powered, placebo-controlled RCT on the treatment of IMH early in the first trimester of pregnancy.

show abstract

Section: Causes Of Imhmentioning

confidence: 99%

MANAGEMENT OF ENDOCRINE DISEASE: Isolated maternal hypothyroxinemia during pregnancy: knowns and unknowns

Dosiou

Medici

2017

European Journal of Endocrinology

View full text Add to dashboard Cite

show abstract

“…Considering the increased iodine requirements during pregnancy, it has been recommended that pregnant women ingest at least 250 µg/day of this element (7). Studies conducted on iodine-sufficient populations such as those of the United States, United Kingdom and the northeastern region of the state of São Paulo, Brazil, have revealed iodine deficiency in pregnant women (13)(14)(15)(16). Iodine deficiency and excess can have different effects on thyroid function.…”

Section: A) Preanalytical Factorsmentioning

confidence: 99%

Are TSH normal reference ranges adequate for pregnant women?

Maciel

2016

Arch. Endocrinol. Metab.

View full text Add to dashboard Cite

A ccording to some investigators, pregnancy represents a "stress test" for the thyroid gland (1) since an intact gland and an appropriate iodine supply are needed for an adequate hormone supply for mother and fetus. Patients with mild underlying thyroid disease or inadequate dietary iodine may fail the test and become hypothyroid. Typically, thyroid hormone production and daily iodine intake increase by approximately 50% in the first few weeks of pregnancy (2). This greater demand on the thyroid gland is due to a series of physiological changes occurring during pregnancy. One of the important alterations is the elevated level of human chorionic gonadotropin (hCG) which, by being structurally similar to TSH, has a direct stimulating action on the thyroid gland through the TSH receptor. During pregnancy, the hCG peak occurs at the end of the 1 st trimester, followed by a reduction to a plateau during the second and third trimesters. The thyrotropic effect of hCG results in an increased production of thyroid hormones (TH) which is reflected on a transitory increase in free T4 (FT4) at the end of the 1 st trimester (3,4). Concomitantly, the increase in hCG results in a reduction of TSH; with the progression of pregnancy and the decline of hCG there is an elevation of TSH (5). Compared to pre-pregnancy concentrations, thyroxine binding globulin (TBG) increases 2-3 times by about the 20 th week of gestation. This is due to the estrogen-stimulated increase in the hepatic production of TBG and to a reduced clearance of the sialylated, heavier, forms of the molecule. This elevation causes, on average, a 1.5-fold increase of total tri-iodothyronine l (TT3) and thyroxine (TT4) around the 16 th week of gestation. Extra TH production is also necessary to cover the losses due to placental deiodination.During pregnancy, the maternal requirements of iodine increase due to several reasons (4,6). One of the mechanisms postulated is related to the greater renal loss of iodine, although its significance has been debated (7). At the same time, iodine is transported to the growing fetus through the placenta, being necessary in order to cover the increased maternal production of TH due to the increase in TBG.The diagnosis of hypothyroidism during pregnancy is fully dependent on thyroid function tests. Four guidelines have been recently published by experts' groups in North America, Europe and Brazil regarding the diagnosis and management of thyroid disease in pregnancy (1,6,8,9). For the interpretation of thyroid function tests, all guidelines similarly recommend 2.5 mUI/L as the upper normal limit for TSH in the 1 st trimester if the normal range has not been established for that region. All guidelines also warn about the use of FT4 in pregnancy. The ATA recommends the determination of TT4 and the calculation of the free T4 index (FTI) as preferable to FT4 by immunoassay, although some investigators have argued that this is a retrograde and misguided measure (10).

show abstract

“…In many populations the content of iodine in the diet tends to be below the recommended amount [2], and this may well lead to inadequate iodine intake among pregnant women because there is an increase in the need for iodine during pregnancy [3,4]. Thus, in recent years there has been much focus on the potential need for individual intake of iodine-containing supplements among pregnant women.…”

Section: Introductionmentioning

confidence: 99%

Iodine Supplementation in Pregnancy and the Dilemma of Ambiguous Recommendations

Andersen¹,

Laurberg²

2016

Eur Thyroid J

View full text Add to dashboard Cite

Iodine requirements are increased during pregnancy, predominantly caused by an increase in renal iodide clearance and in the use of iodine for thyroid hormone production. Because iodine deficiency (ID) in pregnancy may be associated with neurodevelopmental deficits in the offspring, a pertinent question is at what level of iodine intake pregnant women should be advised to take iodine-containing supplements. The consensus reached by the WHO/UNICEF/ICCIDD in 2007 was that pregnant women should not be recommended to take iodine-containing supplements if the population in general had been iodine sufficient for at least 2 years. However, guidance on this differs between scientific societies. This review discusses iodine supplementation in pregnancy. Based on current evidence, the recommendations given by WHO/UNICEF/ICCIDD in 2007 provide a valid guidance on the use of iodine supplements in pregnant women. Women living in a population with a median urinary iodine concentration (UIC) at or above 100 µg/l are not in need of iodine supplementation in pregnancy. On the other hand, if the population median UIC is below 100 µg/l, pregnant women should take iodine-containing supplements until the population in general has been iodine sufficient for at least 2 years by way of universal salt iodization.

show abstract

Iodine deficiency in pregnant women in Europe

Cited by 128 publications

References 10 publications

MANAGEMENT OF ENDOCRINE DISEASE: Isolated maternal hypothyroxinemia during pregnancy: knowns and unknowns

MANAGEMENT OF ENDOCRINE DISEASE: Isolated maternal hypothyroxinemia during pregnancy: knowns and unknowns

Are TSH normal reference ranges adequate for pregnant women?

Iodine Supplementation in Pregnancy and the Dilemma of Ambiguous Recommendations

Contact Info

Product

Resources

About