Cretinism, endemic maternal

Another example of a maternal condition that contributes to birth defects is low circulating iodine. Cretinism is one of the most profound, but completely preventable, syndromes of malformation known. Characteristic consequences of prenatal iodine deficiency include pervasive mental and physical retardation, deaf-mutism (due to primary malformation of the inner ear), lack of muscle tone with a spastic or rigid walk, and failure to attain a height at maturity of more than 1 m. Today, this condition (known as endemic cretinism) is most prevalent in impoverished areas of African and East Asian countries. Prior to implementation of a national program of iodized salt in the early part of the twentieth century, endemic cretinism was commonplace in Switzerland. After institution of iodized salt, deaf-mutism declined 50% within 8 years and no cretins have been born in that country since 1930. 

Endemic cretinism has been a common finding in the mountains or isolated regions, such as the Alps or the Himalayas and has been described or depicted in drawings over the centuries. McCarrison (1917) studied this condition in the Himalayas, describing two types of cretinism the nervous and myxedematous types. He already suspected the influence of the maternal thyroid function on the fetus. Early observations in the Alps (Hunziker-Shild, 1915) already reported that the fetus could receive the hormone from the mother, and proposed the prophylactic administration of iodine from conception. 

There are three types of TH deficiency known to impact fetal development, including (Figure 108.1) isolated fetal hypothyroidism (congenital hypothyroidism CH), combined maternal and fetal hypothyroidism (endemic cretinism EC), and isolated maternal hypothyroidism (primary maternal hypothyroidism). According to the review of CH (American Academy of Pediatrics, 2006), TH deficiency originates from birth and is mainly due to the failure of... 

Figure 108.1 Human fetal and neonatal hypothyroid syndromes iodine defioienoy and endemic cretinism. If environmental iodine deoreases, maternal iodine deficiency in early pregnancy will not provide the fetal thyroxine required for neural development. Insuffioient supply of iodine leads to fetal and neonatal hypothyroidism.

J.B.Stanbury, Cretinism and fetal-maternal relationship, "Human development and the thyroid gland. Relation to endemic cretinism",... 

The first 3 cases (serial nos 604, 638, 515) in the table had hormonal profiles entirely consistent with severe hypothyroidism although these women did not exhibit the clinical features of hypothyroidism In all three cases the pregnancy outcome was a stillblrth/early neonatal death In the succeeding 3 cases (serial nos 568, 245, 430) the maternal total and free thyroxine values were low but triiodothyronine values were within the normal range In one of these the outcome was a stillbirth/early neonatal death and one child has a hearing/speech defect but no other abnormality and, by our definition, cannot be labelled as an endemic cretin ... 

There is a spectrum of Impairment ranging from death through clinical endemic cretinism and subclinical deficits of motor and cognitive performance, to normality. This spectrum of effects appears to be associated with maternal thyroxine during pregnancy. No association with maternal triiodothyronine was found. 

The myxoedematous form of endemic cretinism, which is still prevalent in many parts of the world (CoNTEMPRE et al. 1991), is not only due to the lack of iodine, but also of selenium. The selenoprotein type 1 5 -deiodinase catalyses the deiodination of the prohormone L-thyroxine (3,3 ,5,5 -tetraiodo-L-thyronine, T4) to the biologically active form 3,3 ,5-triiodo-L-thyronine (L-T3). During fetal development the maternal organism contributes at least minimal amounts of thyroid hormone for the fetus. After birth, the baby then slowly reaches the condition of thyroid hormone deficiency, because contin-... 

Known genetic transmission Chromosomal aberration Environmental causes Ionizing radiations Therapeutic Infections Rubella virus Cytomegalovirus Herpes virus hominis Maternal metabolic imbalance Endemic cretinism Diabetes... 

Endemic Occurrence of a disease confined to a community Endemic Cretinism A state resulting from the loss of function of the maternal thyroid gland due to iodine deficiency during pregnancy characterised by mental defect, deaf-mutism and spastic paralysis in its fully developed form... 

Intramuscular iodine injections Numerous studies have confirmed that iodine supplementation by injection before a woman becomes pregnant can prevent endemic cretinism and that a single injection can prevent goitre for up to 3-4 years. Other documented benefits of maternal supplementation observed in several controlled studies include reduced infant and young-child mortality, improved birth weight, and better manual function in children born to iodine-supplemented mothers. 

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