Pregnancy iodine requirements

Delange F Iodine requirements during pregnancy, lactation and the neonatal period and indicators of optimal iodine nutrition. Public Health Nutr 2007 10 1571. [PMID 18053281]... 

When iodine requirements are not met, TH synthesis is reduced, resulting in enlargement of the thyroid gland to compensate for this reduction. In adults, mild iodine deficiency (ID) is associated with nontoxic nodular goiter and, less often, with toxic nodular goiter, due to increases in the constitutive (thyrotropin-independent) growth and functional potential of some clones of thyroid cells. In pregnancy, this can result in fetal neurodevelopmental deficits and mental retardation. 

For the maternal thyroid gland to meet the demands of pregnancy, it must have a sufficient supply of iodine. When increased iodine requirements are not met, TH synthesis is reduced. 

Recently, a WHO technical consultation group met to review the maternal iodine requirements during gestation (Benoist et al, 2007). Consideration was given to the fact that the amount recommended should be sufficient to prevent brain damage or thyroid function disorders due to iodine deficiency during pregnancy. There is a lack of data to indicate an optimal intake. Therefore, conclusions were reached after evaluation of the efficiency of gut absorption of iodine, the estimated metabolic needs, and the typical daily losses in the feces and urine. 

Iodine Nutrition in Pregnancy Meeting Iodine Requirements in the Diets of Pregnant Women... 

Other treatment options, besides thioamide therapy, involve RAI. The iodine 131 isotope is taken up by the thyroid gland and the radioactivity destroys the gland. RAI is safe, pain free, easy to administer, and very effective. RAI may result in euthyroidism but more frequently results in hypothyroidism requiring lifelong levothyroxine supplementation. RAI should never be given during pregnancy since it crosses the placenta. 

The daily requirement for iodine in adults is 1-2 /ag/kg body weight. In the U.S., recommended daily allowances for iodine range from 40 to 120 /xg for children, 150 fxg for adults, 220 fxg for pregnancy, and 270 p,g for lactation. Dairy products and fish have relatively high iodine contents. Because of concerns of iodine insufficiency, iodine supplementation has been widely used for prophylaxis and therapy. The most practical form of this supplementation has been addition of iodide or iodate (now preferred) to table salt. In the U.S., such supplementation is optional and iodized salt provides 100 fxg of iodine/g. 

Pregnant and lactating women are vulnerable to iodine deficiency if specialized enteral preparations are their sole source of nutrition. Only 9 out of 44 specialized enteral preparations for adults provide the current requirement of 200 pg/day. If the WHO technical consultation presently under review is accepted, then only two preparations will meet the proposed allowance of 250 pg/day. This has particular consequences for the brain development of the fetus and infant if the mother has an iodine deficiency during pregnancy and if she breast-feeds. Generally, standard infant formula are recommended for use by the manufacturers for up to 1 year, but as infants are weaned from approximately 6 months, estimation of iodine intakes can only be approximate as the mixed diet progresses. 

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