Pregnancy iodine deficiency

Iodine Deficiency in Pregnancy Iodine Deficiency and Supplementation in Pregnancy... 

In the cerebral hemispheres, there was little change in weight or cell number (as measured by the DNA content) but in the visual cortex area an increase in neuronal density was apparent in the granular band in the second pregnancy iodine-deficient newborns. Synaptic counts also were reduced in the visual cortex (Table 2). 

A deficiency of iodine results iu insufficient synthesis of thyroxine and a low plasma level, so that secretion of TSH is increased in an attempt to stimulate synthesis but this results in enlargement of the thyroid gland (goitre). Iodine deficiency in pregnancy impairs brain development in the foetus, causing mental retardation (known as cretinism). Indeed iodine deficiency is one of the major public health issues worldwide an estimated 200 million people are affected. 

WHO/UNICEF/ICCIDD. Iodized oil during pregnancy. Safe use of iodized oil to prevent iodine deficiency in pregnant women. Geneva (Switzerland) World Health Organization 1996. (WHO/NUT/96.5). 

Glinoer, D. (1997). The regulation of thyroid function in pregnancy Pathways of endocrine adaptation from physiology to pathology, f.tiiiocr. Ken JB, 404-433-Hetzcl, B. S., and Dunn, J, Y. (1989). The iodine deficiency disorders. Ari/iu, Rm Nutr, 9, 21-38. 

Sheep and cattle developed the same symptoms of iodine deficiency. Abortion rate, length of pregnancy (4 days longer) and mortality of the lambs were significantly increased (Groppel 1986, Groppel and Korber 1982, Groppel etal. 1983). Cows with an iodine intake of 70 pg kg feed DM produced 19% less milk than con-... 

Pharoah POD, Butteield IH and Hetzel BS (1971) Neurological damage to the fetus resulting from severe iodine deficiency during pregnancy. Lancet 1 308-310. 

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. 

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. 

Note-. The thyroid function tests change in iodine-deficient women during pregnancy. 

Transplacental passage of maternal T4 Physiological changes in pregnancy in iodine-deficient women... 

In mild and moderate iodine deficiency, endemic cretinism is not observed. However, in a population there is a certain spread of iodine intake, and women at the lower end of the range of iodine intake may still be at risk of insufficient iodine intake during pregnancy. Deficiency of other nutrients and intake of goitrogens from food or from tobacco smoking may increase the risk. 

This chapter will discuss the physiology of iodine deficiency in pregnancy, in addition to outlining the magnitude of the problem and its assessment in clinical practice. 

The realization that iodine deficiency in pregnancy has a pronounced effect on fetal, neonatal and childhood brain function has resulted in a large body of knowledge on the effects of thyroid hormone on brain and nervous-system development (see Grave, 1977 DeLong et ai, 1989 Stanbury, 1994 Bemal, 2002). 

The observations relating to iodine deficiency in pregnancy are firstly those concerned with maternal thyroid function and maternal goiter. Maternal urinary iodine (UI) excretion is the usual method of assessing iodine status in the population at risk or the individual, and is discussed below. Neonatal indicators of maternal iodine deficiency are goiter and neurointellectual impairment. 

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. 

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