[Screening for congenital hypothyroidism in neonates of Zhejiang Province during 1999-2004]

OBJECTIVE

To analyze the data of screening for congenital hypothyroidism (CH) newborns in Zhejiang Province during 1999-2004.

METHODS

The dried blood samples were collected on filter paper. The levels of thyroid-stimulating hormone (TSH) were measured by time-resolved fluoroimmunoassay, and the serum levels of TSH, triiodothyronine (T(3)) and thyroxine (T(4)) were detected by chemiluminescence. Infants with CH confirmed by neonatal screening were treated with levothyroxine (L-T(4)) initiated with 4-6 g/kg x d(-1 )for 2-3 years. Growth, development and intelligence status, scintigraphy or ultrasonography of thyroid, and bone age were investigated to evaluate the efficacy of therapy during follow-ups.

RESULT

A total of 1112784 neonates were screened for CH during 1999-2004 with a coverage rate of 63.5%. Of the 6750 suspected CH cases, 6335 (93.8%) were recalled. 764 cases of CH were confirmed with an average incidence rate of 1 case CH per 1457 newborns (1/1457). 244 of 764 patients were followed-up for more than 1.5-2 years. All of them received thyroid by scintigraphy or ultrasonography. Among them 189 cases were found with normal gland, 35 with hypogenetic gland, 11 with ectopic gland, and the remaining 9 didn't show any image of thyroid. The average score of development quotient (DQ) was 106. 9. Among them, the DQ score was less than 85 in 2 cases, less than 90 in 9 cases, less than 100 in 28 cases, and in 68 cases the DQ was greater than 100. The bone age of 122 CH infants was evaluated with the X-ray radiography. In 90 cases of them,the bone age was normal, and 32 cases had progressed from development delay to normal. The height and weigh measured in all 106 cases had reached the related age criteria. The evaluation indicated that 55 cases were found with primary CH, 169 with temporary CH and 20 with subclinical CH.

CONCLUSION

Neonatal screening for CH and regular treatment for CH patients are important for attaining normal body development and intelligence development of patients.

Thyroid disease in pregnancy and childhood

The subject of thyroid disease in pregnancy is receiving increasing attention from many scientific disciplines. Thyroid function in pregnancy is characterised by a T4 surge at 12 weeks declining thereafter. Serum thyroid hormone concentrations fall in the second half of pregnancy but there are few data on normal reference ranges. Fetal brain development depends on T4 transport into the fetus which in turn depends on sufficient maternal iodine supply. There is current concern that adequate iodisation is not present in large parts of Europe. There is increasing evidence that thyroid autoimmunity is associated with fetal loss but the mechanism is unclear and therapy requires carefully conducted studies. While hyperthyroidism in pregnancy is uncommon, effects on both mother and child are critical if untreated. The use of propylthiouracil is recommended together with measurement of TSH receptor antibodies at 36 weeks gestation. Women receiving thyroxine therapy for hypothyroidism or as suppressive therapy should have their dose increased by up to 50% during pregnancy. There are now substantial data to show deleterious effects on child IQ resulting from low maternal T4 (or high TSH) during gestation. Major advances in molecular biology have contributed to elucidation of many genetic causes of congenital hypothyroidism. However, the aetiology of the majority of cases is still unclear and further research is required. The presence of TPO antibodies in about 10% of pregnant women in early gestation is a predictor of an increased incidence of subclinical hypothyroidism during pregnancy and also of postpartum thyroid dysfunction. The latter condition occurs in 5-9% of women and 25-30% progress to permanent hypothyroidism. This review suggests that screening for thyroid function in early pregnancy and levothyroxine intervention therapy for maternal subclinical hypothyroidism should be considered but evidence is awaited. Screening for both thyroid dysfunction and thyroid antibodies ideally at a preconception clinic but certainly in early gestation is recommended.

[Real activity of Kraków endocrine group in Institute of Pediatrics CMUJ on the eradication of IDD in Polish children]

The authors present the investigations concerned the Iodine deficiency disorders (IDD) elimination in children living in South-East of Poland in last 15 years. To achieve the full success, what, as we know is possible, the monitoring and the exact control of the salt iodine supplementation according to the National Program of Iodine Deficiency Elimination (1999-2003) should be maintained. To avoid any negligence, the prompt education of the whole population is necessary, but yet especially the pregnant women. It is important to instruct them about the direct influence of iodine deficiency on the mental development of the fetus and the newborn.

Iodine supplementation for preventing iodine deficiency disorders in children

BACKGROUND

Iodine deficiency is the main cause of potentially preventable mental retardation in childhood, as well as causing goitre and hypothyroidism in people of all ages. It is still prevalent in large parts of the world.

OBJECTIVES

To assess the effects of iodine supplementation overall, and of different forms and dosages of iodine supplementation separately, in the prevention of iodine deficiency disorders in children.

SEARCH STRATEGY

The Cochrane Library, MEDLINE, EMBASE and reference lists, databases of ongoing trials and the Internet were searched. Date of latest search: October 2003.

SELECTION CRITERIA

We included randomised controlled trials and prospective controlled trials not using randomisation of iodine supplementation in children living in areas of iodine deficiency.

DATA COLLECTION AND ANALYSIS

Two reviewers did the initial data selection and quality assessment of trials independently. As the studies identified were not sufficiently similar and not of sufficient quality, we did not do a meta-analysis but summarised the data in a narrative format.

MAIN RESULTS

Twenty-six prospective controlled trials were related to our question, assessing a total of 29613 children. Twenty of them were classified as being of low quality, six of moderate quality. Most studies used iodised oil as a supplement, but other supplements were also used. The intervention groups were compared to a non-supplemented control group, different doses or different forms of iodine supplementation. There was a clear tendency towards goitre reduction with iodine supplementation; this was significant in several studies. Significant differences in physical development were not seen, except in one study. Results for differences in cognitive and psychomotor measures were mixed, with only few studies showing a positive intervention effect. One study suggested that infant mortality was lowered after iodine supplementation. Most studies showed a significant increase in urinary iodine excretion and levels recommended by the WHO were reached in most cases after supplementation. Thyroid-stimulating hormone (TSH) levels were significantly reduced in one study. In 1.8% of the children investigated, adverse effects were found, most of them were minor and transient.

REVIEWERS' CONCLUSIONS

Despite most of the included studies being of low quality, the results suggest that iodine supplementation, especially iodised oil, is an effective means of decreasing goitre rates and improving iodine status in children. Indications of positive effects on physical and mental development and mortality were seen, although results were not always significant. Adverse effects were generally minor and transient. Insufficient evidence was available on non-oil supplements. High quality controlled studies investigating relevant long term outcome measures are needed to address the question of the best form of iodine supplementation in different population groups and settings.

Iodine deficiency in Europe and its consequences: an update

This paper updates the information on the prevalence of the disorders induced by iodine deficiency (IDD) in Europe. Thirty-two European countries were still affected by mild to severe iodine deficiency in the late 1990s. The most severely affected countries were in Eastern Europe, including Central Asia, but Western Europe was also still affected. National surveys recently conducted in 11 of these countries show that, with the exception of the Netherlands, none has yet reached a state of iodine sufficiency, though very significant improvement in the situation has been evidenced in many of them, e.g. Poland, Bulgaria and Macedonia. The consequences of persisting iodine deficiency are goitre, hyperavidity of the thyroid for iodide (which increases the risk of thyroid irradiation in the event of a nuclear accident) and subclinical hypothyroidism during pregnancy and early infant (with a concomitant risk of minor brain damage and irreversible impairment of the neuropsychointellectual development of offspring). Access to iodised salt at the household level in European countries affected by IDD increased from 5%-10% in 1990 to 28% in 1999. This constitutes encouraging progress. However, in terms of access of iodine-deficient countries to iodised salt, Europe remains the worst region in the world, as shown by the fact that the mean figure worldwide in 1999 was 68%. In Latin America it even reached 90%. Salt iodisation has to be further implemented in Europe. Until that goal is achieved, iodine supplementation in those groups most sensitive to the effects of iodine deficiency (pregnant and lactating women and young infants) will have to be considered in the most severely affected areas.

[Iodine deficiency in the Russian Federation]

Epidemiological surveys for iodine deficiency (ID) were made in 30 regions of Russia in 1992 to 1999. A total of 40,999 individuals aged 7 to 17 years were examined. The advent of new assessments of the thyroid and new indicators of iodine deficiency has changed approaches to epidemiological surveys. The WHO standards for estimating the prevalence and severity of ID have been introduced into Russian practice. In Central Russia, the lowest (median 30-58 micrograms/l) iodine concentrations were found in rural dwellers; in more urbanized areas (cities, towns) the median was 50-78 micrograms/l. ID was more pronounced in the regions of East Russia where it was predominantly moderate (median 30-52 micrograms/l). In some areas, ID was severe (median 16-20 micrograms/l). As the severity of ID increases, the incidence of such conditions, as goiter, hypothyroidism, endemic cretinism is on the rise. Mild to moderate goiter endemia prevailed in Central Russia. The manifestations of goiter endemia were more pronounced in rural children (18-30%) than in urban ones (8-14%). East Russia was marked by moderate to severe goiter endemia (8-14%): the incidence of goiter ranged from 17 to 40%. There were only sporadic cases of goiter in some areas of the Sakhalin Region. In the Moscow and Voronezh Regions and the Republic of Kalmykia there were areas showing a high goiter incidence which did not correspond to the level of ID. An epidemiological analysis has indicated that dietary and water iodine intake is decreased in most regions of Russia. The actual dietary iodine intake was 40-80 micrograms/day, i.e. 2-3 times of the recommended allowance (150 micrograms). The Endocrinology Research Center has tested different models of preventive and therapeutical measures for eliminating iodine deficiency-caused diseases by using iodinated foodstuffs (salt, bread, butter) ad iodine medicaments.

[From gene to disease; POU1F1- and PROP1-mutations in pituitary hormone deficiency]

Multiple pituitary hormone deficiency can be caused by mutations in at least three pituitary transcription factors: POU1F1 (formerly called PIT1), PROP1 or HESX1. The role of the various pituitary transcription factors in pituitary ontogeny has been elucidated in part for the mouse. In humans, mutations in POU1F1 result in a total deficiency of growth hormone and prolactin, and a variable deficiency of TSH. Cases of mutations in PROP1 exhibit the same deficiencies, with additional deficiencies of gonadotrophins and a variable deficiency of ACTH. In the Netherlands, cases of multiple pituitary hormone deficiency are not only detected on the basis of the classical signs and symptoms of pituitary deficiency, but also by means of screening on congenital hypothyroidism with an incidence of approximately 1:20,000.

[The influence of iodine deficiency during pregnancy of fetal and neonatal development]

The iodine is fundamental substrate for thyroid hormones synthesis. Thyroxine and triiodothyronine play a crucial role in human brain development and maturation. It is well known, that not only fetal, but also maternal thyroid hormones are essential for normal prenatal central nervous system development. During pregnancy complex changes of maternal thyroid function occur and they are influenced by the maternal iodine supply. With decreasing iodine intake, maternal goiter and hypothyroxinemia as well as fetal and neonatal hypothyroidism become more prevalent. The severity of iodine deficiency and hypothyroidism in the mother during early and midgestation is related to the severity of the neural damage in the fetus. In severe iodine deficiency, central nervous system damage is already irreversible at birth and can only be prevented by correction of the maternal iodine deficiency early in pregnancy. Therefore iodine supplementation during pregnancy is now strongly recommended.

Iodine deficiency disorders in Europe

Iodine deficiency disorders (IDD) are related to the degree of iodine deficiency. In European countries, characterized by mild to moderate iodine deficiency, neurological deficits or minor neuropsychological impairments have been described. Urinary iodine excretion (UIE) ranged from 30 to 170 mcg/L, 141 millions of people were at risk of IDD, 97 millions were affected by goiter and 0.9 millions had an impaired mental development. Iodine prophylaxis is devoid of adverse reactions with the exception of sporadic cases of transitory hyperthyroidism, associated to the severity of iodine deficiency before the prophylaxis. The International Council for Control of IDD recommends an universal iodine prophylaxis, instituted gradually in severe iodine deficient countries. The total cost of universal iodine prophylaxis is very cheap compared to the social cost of goiter and cretinism. In conclusion, most European countries are still characterized by mild to moderate iodine deficiency. Iodine prophylaxis programs are already operating, its cost is irrelevant with respect to the undebatable beneficial impact on the health. Adverse effects are not observed except in severe iodine deficient areas where iodine intake was abruptly increased.

Endemic goiter and cretinism: an update on iodine status

Iodine deficiency is the most prevalent correctable cause of brain damage in the world. Over the past 15 years, great progress has been made towards the elimination of iodine deficiency, principally through universal salt iodization. Much more needs to be done for countries that are lagging in the effort or that have weak systems for sustaining it. The key to maintaining optimal iodine intake is regular monitoring, usually by the measurement of urinary iodine concentration, linked to a prompt response in the event of abnormal results. If the present momentum continues then global iodine sufficiency is possible and, in a landmark achievement, iodine deficiency will be the first major non-infectious disorder to be eliminated.

Iodine and neuropsychological development

The establishment of the essential link among iodine deficiency, thyroid function and brain development has emerged from a fascinating combination of clinical, epidemiologic and experimental studies. The central human phenomenon that focuses this relationship is the condition of endemic cretinism, described from the Middle Ages and characterized in its fully developed form by severe brain damage, deaf mutism and a spastic state of the hands and feet. The demonstration of the prevention of cretinism in a double-blind controlled trial with injections of iodized oil in Papua New Guinea (1966-1970) established the causal role of iodine deficiency in cretinism by an effect on the developing fetal brain. Cretinism could not be prevented unless the iodized oil was given before pregnancy. Iodine deficiency is now regarded by the WHO as the most common preventable cause of brain damage in the world today, with at least 30 million suffering from this preventable condition. Since 1986 the international NGO, the International Council for Control of Iodine Deficiency Disorders, has worked closely as an expert group with WHO and UNICEF in assisting countries with a program of universal salt iodization for the elimination of iodine deficiency as a cause of brain damage by the year 2000. In 1996, WHO reported that 56% of the population of 83 developing countries now had adequate access to iodized salt. This represents an increase of 750 million since 1990 with protection of 12 million children.

Maternal iodine supplements in areas of deficiency

BACKGROUND

Iodine deficiency is the leading preventable cause of intellectual impairment in the world. Although iodine supplementation is generally considered to be safe, there is a possibility of high doses of iodine suppressing maternal thyroid function.

OBJECTIVES

The objective of this review was to assess the effects of iodine supplementation before or during pregnancy in areas of iodine deficiency.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register.

SELECTION CRITERIA

All acceptably controlled trials of maternal iodine supplementation during pregnancy with clinical outcomes.

DATA COLLECTION AND ANALYSIS

Eligibility and trial quality were assessed by two reviewers.

MAIN RESULTS

Three trials involving 1551 women were included. In two trials, iodine supplementation was associated with a statistically significant reduction in deaths during infancy and early childhood (relative risk 0.71, 95% confidence interval 0. 56 to 0.90). Iodine supplementation was associated with decreased prevalence of endemic cretinism at the age of four years (relative risk 0.27, 95% confidence interval 0.12 to 0.60) and better psychomotor development scores between four to 25 months of age.

REVIEWER'S CONCLUSIONS

Iodine supplementation in a population with high levels of endemic cretinism results in an important reduction in the incidence of the condition with no apparent adverse effects.

Metabolic maladaptation: individual and social consequences of medical intervention in correcting endemic hypothyroidism

Endemic hypothyroidism has been studied in a Central African population in remote Congo (ex-Zaire) to investigate the prevalence, severity, causes, and potential control of this disorder, with questions as to why this disease is conserved, and whether it confers any adaptive advantage in this resource-constrained environment. Iodine deficiency, cassava goiterogens, and selenium deficiency were found to be the factors implicated in the severe hypothyroidism expressed in congenital cretinism and high goiter incidence in this isolated population, which continues to be under observation following medical intervention. Profound hypothyroidism was encountered in whole village populations as measured by serum thyrotropin determinations ranging from very high to over 1000 IU, and thyroxin levels ranging from low to undetectable; cretinism rates were as high as 11% and goiter incidence approached 100%. Assessment of endocrinologic status, caloric requirement, energy output, fertility, and ecologic factors was carried out before and during iodine repletion by depot injection. Hypothyroidism was corrected and cretinism eliminated in the treatment group, with goiters reduced in most instances (with regrowth exhibited in some who escaped control) and some symptomatic goiter patients were offered surgical treatment for respiratory obstruction. Individual patient benefits, including improved strength and increased energy output, were remarkable. The social and developmental consequences observed within the collective groups of treated patients were remarkable for an increase in caloric requirement and a dramatic increase in fertility that led to quantitative as well as qualitative increases in resource consumption. Micronutrient iodine repletion was not accompanied by any concomitant increase in macronutrient supply, and hunger and environmental degradation resulted. The highly prevalent disease of hypothyroidism is found in highest incidence in areas of greatest resource constraint. It may be that hypothyroidism is conserved in such areas because it may confer adaptive advantage in such marginal environments as an effect, as well as a cause, of underdevelopment. Hypothyroidism may limit energy requirements, fertility, and consumer population pressure in closed ecosystems that could otherwise be outstripped. Single factor intervention in a vertical health care program not sensitive to the fragile biologic balance and not part of a culture-sensitive development program might result in medical maladaptation.

Persistence of iodine deficiency 25 years after initial correction efforts in the Khumbu region of Nepal

AIMS

To assess the current status of, and understanding about iodine deficiency disorders among Sherpa residents of the Khumbu region of Nepal, 25 years after the introduction of iodised oil injections.

METHODS

Several groups of Khumbu Sherpas were studied and goitre rate, urinary iodine level and cretinism prevalence were measured as indicators of iodine deficiency. Subjects were also questioned in detail about their food consumption, with particular reference to salt use, and about their understanding of the causes and treatment of iodine deficiency disorders.

RESULTS

The prevalences of goitre, deaf-mutism and cretinism were 21%, 1.3% and 0.5% respectively (compared to 92%, 4.7% and 5.9% in 1966). No cretins had been born since 1966. The median urine iodine concentration was 35 microg/L. Most people preferred uniodised Tibetan rock salt, although 44% regularly consumed iodised salt. All granulated salt tested from the local market contained adequate amounts of iodine. Only 11% of those surveyed knew that goitre was caused by iodine deficiency

CONCLUSIONS

Although prevalences of iodine deficiency disorders are much less than 30 years ago, iodine deficiency continues to be a major problem in Khumbu and demands a clear control strategy, combining ongoing iodine supplementation and education. Iodised salt is usually the best approach to control of iodine deficiency disorders for most regions of the world but the Khumbu experience shows that local cultural and commercial factors can severely limit its impact. To be successful, control programme for iodine deficiency disorders also needs assessment of the salt trade, monitoring, education and occasional targeted interventions with iodised oil or other supplements.

[Efficacy and safety of iodine prophylaxis]

Iodine deficiency and iodine deficiency disorders (IDD) are still present in developing countries as well as in some European areas. It is well known that iodine deficiency correction prevents endemic goiter and other IDD. Iodized oil has been shown to reduce goiter prevalence and cretinism in African countries. In countries where iodine prophylaxis is performed since many years (USA, Switzerland, Scandinavian countries) IDD are dramatically reduced. One example of the efficacy of iodine prophylaxis through iodized salt was reported in a Tuscan village were urinary iodine excretion increased from 47 micrograms/l in 1981 to 130 micrograms/l in 1991. Goiter prevalence in schoolchildren dropped from 60% in 1981 to 8.1% in 1991. In the same children neuropsychological performances were evaluated showing a reduction of motor response to perceptive stimuli assessed by measurement of reaction times in children born before the beginning of iodine prophylaxis. Iodine prophylaxis has no side effects, although a transitory increase of hyperthyroidism has been reported in the past and recently in African countries. A reevaluation by the experts of the International Council for the Control of Iodine Deficiency Disorders (ICCIDD) has pointed out that this phenomenon is not relevant with respect to the efficacy of iodine prophylaxis. In conclusion, universal iodine prophylaxis prevents endemic goiter and other IDD, without side effects.

Alterations of neonatal thyroid function

Recent progress has been made in understanding the pathogenesis of neonatal thyroid disorders. Autosomal recessive inheritance of mutations of the thyroid peroxidase and thyroglobulin genes has been described in some patients with congenital hypothyroidism (CH) and a family history of CH. Autosomal recessive inheritance of mutations of the thyrotrophin (TSH) receptor gene has also been reported in patients with CH and thyroid hypoplasia, and autosomal dominant mutations of the PAX8 gene have been described in patients with different forms of thyroid dysgenesis. These discoveries are important for patients with CH diagnosed by neonatal screening, as these patients will have normal fertility. The molecular genetic analysis of mutations of the TSH gene in patients with familial and sporadic cases of isolated central CH, who are missed by TSH screening programmes, now enables rapid diagnosis and appropriate therapy in the neonate. In newborn infants with severe non-autoimmune hyperthyroidism, autosomal dominant gain-of-function mutations in the TSH receptor gene have been demonstrated. In these patients, molecular genetic studies are extremely helpful in therapeutic decision making, as early thyroid ablation is the only effective treatment that avoids the sequelae of long-term hyperthyroidism. Molecular genetic studies are therefore useful in the diagnostic work-up of neonatal thyroid alterations.

Newborn screening for certain treatable inborn errors of metabolism in Alexandria

The study was conducted on two groups of newborn infants: Group A; a random sample of 3000 infants attending different Health offices in Alexandria for BCG vaccination. Their ages ranged from 5-120 days with a mean age of 39.9 days. Group B; included all the infants born to high risk families attending the clinic of Human Genetics Department, Medical Research Institute (9 infants; 7 with family history of PKU and 2 with family history of congenital hypothyroidism). Their ages ranged from 7 to 60 days with a mean age of 18 days. The newborn infants of the two groups were screened for three treatable inborn errors of metabolism, phenylketonuria "PKU", galactosemia and congenital hypothyroidism with the aim of early detection and therapy to prevent mental retardation. In group A; one baby with transient hyperphenylalaninemia (HPA) (0.33%) and one presumptive case of galactosemia (0.33%) were found. Initial positive results were found in eleven infants they had high levels of thyroid stimulating hormone (TSH). On reevaluation of nine infants of them they were all euthyroids. In Group B, four infants were detected among the infants of PKU families. After confirmation of these results breast feeding was stopped at once and the infants started their dietary management and were kept on it with follow up and periodic evaluation of the adequacy of treatment.

Administration of iodized oil during pregnancy: a summary of the published evidence

This brief review of the available studies confirms that the administration of iodized oil before or during pregnancy prevents endemic cretinism and brain damage by correcting iodine deficiency and thyroid function in pregnant women, fetuses, neonates, infants and children. The potential benefits derived from using iodized oil immediately before or during pregnancy greatly outweigh the potential risks in areas of moderate and severe prevalence of iodine-deficiency disorders, where iodized salt is not yet available.