Cretinism, endemic development

Ermans AM, Nbulamoko NM, Delange F, et al., eds. 1980. Role of cassava in the etiology of endemic goitre and cretinism. Ottawa, Canada International Development Research Centre, 1-182. 

Perhaps the most striking illustration of the pervasive developmental effects of thyroid hormones is provided by children with severe thyroid hormone deficiency from early childhood, a condition termed cretinism. This may either be endemic in regions of severe iodine deficiency or sporadic due to failure of the thyroid to develop normally or defects in the synthesis of thyroid hormone. Affected children are dwarfed with short extremities, have mental retardation, and are inactive and listless. Other manifestations include facial puffiness, enlarged tongue, dry and doughy skin, slow heart rate, and decreased body temperature. Eor full recovery, treatment of patients with cretinism must be initiated before these florid features are apparent. Thus, pregnant women in areas of endemic cretinism due to iodine deficiency are supplemented with iodine and aU newborns are screened for thyroid hormone deficiency in many developed nations. 

In 1966, iodized oil was injected in residents of Papua New Guinea, where the severity of endemic goiter and cretinism was high. A follow-up study showed that cretinism disappeared almost completely from the offspring of mothers who received iodized oil. The effect of iodine supplementation on the survival of the fetus and on their brain development was established. 

The method of detecting iodine supply levels and the evaluation of the effect of the lack or oversupply (Boyages, 1993) of iodine on the condition of the thyroid gland (its size, function and the impact on the autoimmunity process) and the resulting evaluation of the overall condition of health of an entire population (from the occurrence of endemic cretinism due to significant lack of iodine to mild occurrence of brain dysfunction due to lack of iodine during intrauterine development) problems in the development of the somatic. 

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.

Ramirez, L, Fierro-Benitez, R. and Estrella, E. (1972). In (eds J.B. Stanbury and R.L. Kroc), Human Development and the Thyroid Gland Relation to Endemic Cretinism. Plenum Press, NewYork, NY, p. 223. 

At the most severe end of the spectrum this manifests as endemic cretinism, but even mild iodine deficiency can affect cognitive development and subsequent intellectual abifi-ties, as well as, causing deficits in hearing and reproduction (Bleichrodt and Born, 1994 Dunn, 1996 Hetzel, 2004). Detailed consideration of the effects of iodine deficiency on brain function can be found in the chapter in the handbook entitled Iodine Deficiency and the Brain by Basil Hetzel. 

We conclude that iodine is essential for normal fetal brain development because of the critical role of the thyroid hormones, investigations are required into the postnatal period before the pathogenesis of endemic cretinism can be elucidated. 

The term endemic cretinism applies to individuals bom and living in areas of severe iodine deficiency and endemic goiter exhibiting irreversible anomalies of intellectual and physical development not explained by other causes than the environmental factors responsible for goiter. The prevalence of the disorder can reach 10 % of the whole population in severely affected areas and cretinism constitutes the most serious complication of endemic goiter. 

We need more information on the structure and ultrastructure of the thyroid in the two types of cretinism. We need to know whether there are specific aspects of thyroid morphology in hypothyroid newborns and stillbirths in endemic areas. We also need to know whether there are age-related changes in the thyroid of hypothyroid infants and children. In other words, how valid is the hypothesis that only progressive atrophy of the thyroid will result in permanent hypothyroidism and myxedematous cretinism in some individuals while the development of compensatory thyroid hyperplasia explains the transient character of hypothyroidism in others (5). Finally, is there any morphological evidence of an autoimmune process within the thyroid ... 

B.S. Hetzel and A. Querido, Iodine deficiency, thyroid function, and brain development, "Endemic goiter and endemic cretinism", J.B. Stanbury and B.S. Hetzel eds., John Wiley Publ., New York (1980), pp. 461-472. 

I. Ramirez, M. Cruz and J. Varea, Endemic cretinism in the Andean region New methodological approaches, "Cassava toxicity and thyroid research and public health issues", F. Delange, R. Ahluwalia eds.. International Development Research Center Publ., Ottawa (1983),... 

Studies of the antithyroid effects of cassava and of thiocyanate in rats, "Role of cassava in the etiology of endemic goitre and cretinism", A.M. Ermans, N.M. Mbulamoko, F. Delange and R. Ahluwalia eds.. International Development Research Centre Publ., Ottawa (1980), pp. 93-110. 

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

In Human development and the thyroid gland relation to endemic cretinism. Stanbury JB and Kroc RL (eds). New York, Plenum Press, 1972, pp 325-333. 

Although the materials studied in the present paper and the above mentioned differences were relatively small, the morphometric changes in the brains of certain iodine deficient fetuses are definite. The results suggest that prenatal iodine deficiency exhibits certainly a depressive influence on the brain in some of the fetuses in the endemic goiter and cretinism areas retarding its development. This might account for the neurological deficit of cretinism or cretinoid syndrome. 

Recently a series of non-verbal tests has been developed. Dr. Collin measured the intelligence of some school children in an endemic area in China using the Hiskey-Nebraska Test to avoid the language interference. Dr. DeLong and Dr. Lu L. had measured the intelligence of some cretin patients using the Beery test of visuomotor integration which has been considered free of cultural interference. 

The Role of Iodine in intellectual Development in an Area of Endemic Goiter. In J.T. Dunn and G.A. Medeiros-Neto(eds.), Endemic Goiter and Cretinism Continuing Threats to World Health. Pan American Health Organization Sci. Publ., Washington, D.C., pp. 135-140. 

---