Safe use of iodized oil to prevent iodine deficiency in pregnant women. A statement by the World Health Organization

The risks and expected benefits from iodized oil, given orally or by injection, to pregnant women in areas of severe iodine deficiency where iodized salt is not available were evaluated. The conclusions, which were approved by the International Council for Control of Iodine Deficiency Disorders (ICCIDD), showed that for preventing and controlling moderate and severe iodine deficiency, the giving of iodized oil is safe at any time during pregnancy. Maximum protection against endemic cretinism and neonatal hypothyroidism will be achieved when iodized oil is given before conception. The potential benefits greatly outweigh the potential risks in areas of moderate and severe iodine deficiency disorders, where iodized salt is not available and is unlikely to be made available in the short term (1-2 years).

Role of goitrogens in iodine deficiency disorders & brain development

Although iodine deficiency has primarily been implicated in the causation of goitre, the significant role played by food goitrogens in the etiology of iodine deficiency disorder (IDD) is being increasingly recognized. Impaired brain development is the major cause of concern in IDD. Detailed experimental studies were undertaken to ascertain various biochemical changes associated with developing brain in response to treatment with a goitrogens--thiocyanate. Addition of thiocyanate to food deprived of KI brought down significantly the circulating levels of thyroxine (T4) in rats. Nucleic acids and protein content in different regions of brain were significantly lowered in rat pups exposed to thiocyanate. The rate of microtubule assembly, which is detrimental for neurite growth was considerably lowered, thereby influencing both myelin deposition and synaptogenesis in developing brain. Goitrogen intake not only caused an adaptive increase in the activity of type II 5'-deiodinase, which governs availability of triiodothyronine (T3) in brain, it also increased the latter's binding to brain nuclear receptors under conditions of thiocyanate induced hypothyroid state. Addition of adequate quantities of KI mitigated thiocyanate induced alterations by restoring circulating level of thyroxine. These investigations suggest that goitrogens play a significant role in influencing biochemical events unique to developing brain.

Towards the elimination of iodine deficiency disorders in India

Iodine deficiency disorders (IDD) are an important public health problem in India with an estimated 270 million people at risk of IDD. India has adopted the strategy of salt iodization for control of IDD and has the goal of "Universal iodization of salt by 1995 and elimination of IDD by 2000". There is a high degree of political commitment which need to continue if the goal is to be achieved. Currently the ban on ale of un-iodized salt is only applicable to salt on human consumption. There is a need for extending the ban to include salt for animal consumption as IDD affects livestock as well. India has the installed capacity to produce its requirement of 5 million tonnes iodised salt. Communication strategies have to be strengthened especially to educate people who have concerns about of iodine toxicity. The success to a large extent depends on the quality control and monitoring of iodine content of salt at all stages from production to consumption. NGO's and the community have to be encouraged to participate in this process. To sustain the elimination of IDD, a partnership of various stakeholders IDD elimination is essential.

Maternal hypothyroxinaemia during the first half of gestation in an iodine deficient area with endemic cretinism and related disorders

OBJECTIVE

Iodine deficiency is well known as the cause of several disorders such as endemic goitre and cretinism, along with a wide spectrum of psychoneurological development disorders including endemic mental deficiency and endemic cognitive deficiency, which are generally correlated to damage to the fetus. Such damage is, by inference, deemed a consequence either directly of iodine deficiency or of insufficient availability of thyroxine at the feto-placental unit level. Early pregnancy represents the crucial period for neurogenesis in the embryo. Several experimental studies have emphasized the direct role of maternal T4 in neurological embryogenesis, before the onset of fetal thyroid function and, therefore, its protective role in fetal thyroid failure. The objective of this study was to evaluate whether iodine deficiency may influence thyroid status of pregnant women throughout the first half of pregnancy.

DESIGN

Thyroid function tests including total and free T4 and T3, TBG and TSH along with urinary iodine excretion were measured in the serum of pregnant women from an iodine deficient endemic goitre area in north-eastern Sicily, at 8, 13 and 20 weeks of gestation. The times of sampling were chosen to correspond approximately to a period prior to, coincident with and after the onset of fetal thyroid function, respectively.

SUBJECTS

The longitudinal study was undertaken in 16 euthyroid pregnant women from the iodine deficient area in which major iodine deficiency disorders such as endemic cretinism and endemic cognitive deficiency in schoolchildren still persist (area A) and in 7 age matched volunteer pregnant women from a marginally iodine sufficient area (area B).

MEASUREMENTS

Hormones and TBG were measured using commercial kits. Urinary iodine was measured by an automated method.

RESULTS

The divergent changes in serum T4 and TBG with pregnancy progression induced a progressive TBG desaturation by T4 during the whole study period (from 22 to 17% in area A, ANOVA two-way F = 18.9, P < 0.0001; from 33 to 20% in area B, F = 20.7, P < 0.0005) in both areas. At 20 weeks, average FT4 levels were lower in area A than in area B (11.5 +/- 2.5 vs 14.3 +/- 2.4 pmol/l, t = 2.7 P < 0.01) and were below the normal range in 2/16 and borderline-low in 6/16 pregnant women. FT4 serum levels were inversely related to TSH concentrations (r = -0.54, P < 0.0001) which progressively increased, in area A, during the whole study period (F = 6.0, P < 0.01) and were abnormally high in the two women with low FT4, but not in area B. Also in area A (F = 3.4, P < 0.05) a significant T3/T4 molar ratio increase was observed.

CONCLUSIONS

Iodine deficiency induces in early pregnancy a series of events (reduced synthesis of maternal T4, TBG desaturation by T4, critical decrease of FT4 levels with consequent TSH increase) responsible for overt or marginal biochemical hypothyroidism in about 50% of pregnant women. It is hypothesized that the imbalance of maternal thyroid hormone homeostasis during pregnancy as a consequence of endemic iodine deficiency may be responsible for the impaired psychoneurological development observed in children from that area so appropriate iodine and/or thyroxine prophylaxis to women in that region may prevent the neurobehavioural, cognitive and motor compromise of the population.

Timing of vulnerability of the brain to iodine deficiency in endemic cretinism

BACKGROUND

Endemic cretinism, caused by severe iodine deficiency during pregnancy, is the world's most common preventable cause of mental retardation. It can be prevented by iodine treatment before conception, but whether it can be prevented or ameliorated by treatment during pregnancy or after delivery is not known.

METHODS

In a severely iodine-deficient area of the Xinjiang region of China, we systematically administered iodine to groups of children from birth to three years of age (n = 689) and women at each trimester of pregnancy (n = 295); we then followed the treated children and the babies born to the treated women for two years. We used three independent measures of neural development: the results of the neurologic examination, the head circumference (which correlates with brain weight in the first postnatal year), and indexes of cognitive and motor development. Untreated children one to three years of age, who were studied when first seen, served as control subjects.

RESULTS

The prevalence of moderate or severe neurologic abnormalities among the 120 infants whose mothers received iodine in the first or second trimester was 2 percent, as compared with 9 percent among the 752 infants who received iodine during the third trimester (through the treatment of their mothers) or after birth (P = 0.008). The prevalence of microcephaly (defined as a head circumference more than 3 SD below U.S. norms) decreased from 27 percent in the untreated children to 11 percent in the treated children (P = 0.006), and the mean (+/- SD) developmental quotient at two years of age increased (90 +/- 14, vs. 75 +/- 18 in the untreated children; P < 0.001). Treatment in the third trimester of pregnancy or after delivery did not improve neurologic status, but head growth and developmental quotients improved slightly. Treatment during the first trimester, which was technically problematic, improved the neurologic outcome.

CONCLUSIONS

Up to the end of the second trimester, iodine treatment protects the fetal brain from the effects of iodine deficiency. Treatment later in pregnancy or after delivery may improve brain growth and developmental achievement slightly, but it does not improve neurologic status.

Iodine deficiency disorders: contemporary scientific issues

Iodine deficiency is the leading cause of preventable intellectual impairment and is associated with a spectrum of neurologic and developmental pathology. More than one billion people are at risk. The developing fetus, newborn, and young child are the most susceptible to the effects of an iodine-deficient diet. If intervention is not initiated in a timely fashion, the pathophysiologic abnormalities become resistant to treatment and permanent intellectual, neurologic, and somatic deficits result. The technology of iodine deficiency intervention is well established. Iodized salt, the preferred method, is easy to produce, administer in physiologic doses, and is cost effective. The distribution of iodized salt and social marketing are key to a successful iodine deficiency elimination program. In remote regions, iodized oil is a useful interim intervention. However, it is clear that technology is not enough. Any national effort to eliminate iodine deficiency must extend far beyond the Ministry of Health. The program will require the full participation of a range of national government ministries and agencies and the full support and participation of local or regional governments.

Prevention of iodine deficiency disorders by oral administration of lipiodol during pregnancy

The prevalence of iodine deficiency disorders and the thyroid status of the population were studied in an endemic goitre area in Algeria. After oral administration of lipiodol (0.5 ml), three treated groups of mother-newborn couples were compared to an untreated group: group A, mothers treated 1-3 months before conception; group B, mothers treated during the first month of pregnancy; group C, mothers treated during the third month of pregnancy. Untreated mothers were used as a control (group D). After lipiodol treatment, all newborn babies and mothers were clinically euthyroid. All tested newborn babies were full term and no goitre was observed in the four groups. In the mothers, goitre prevalence and thyrotrophin levels decreased significantly, whereas maternal milk and urinary iodine and serum-free thyroxine levels were significantly higher after treatment. The rate of prematurity, stillbirths and abortions in the treated groups was reduced when compared to the untreated group, whereas placental and birth weights were significantly higher. In group D two cases of neonatal hypothyroidism were detected. Their re-evaluation confirmed that hypothyroidism was transient. Groups A, B and C were statistically different from group D with regard to neonatal thyrotrophin and thyroxine. Positive correlations were found between neonatal thyroxine and birth weights and placental weights on the one hand, and maternal urinary iodine and free thyroxine on the other. Consequently, these data indicate that oral administration of lipiodol before or during the first trimester of pregnancy normalizes thyroid function in newborn babies and mothers, increases placental and birth weight and reduces the frequency of iodine deficiency disorders.(ABSTRACT TRUNCATED AT 250 WORDS)

Endemic goitre and cretinism in the Simbai and Tep-Tep areas of Madang Province, Papua New Guinea

In the late 1960s and early 1970s a mass campaign of iodized oil injections was carried out in Papua New Guinea as an interim measure to improve iodine status in the population and to prevent endemic goitre and endemic cretinism. Following informal reports of children with neurological abnormalities resembling endemic cretinism in two areas of Madang Province, the Simbai and Tep-Tep Subdistricts, surveys were conducted in these areas in 1985 to establish prevalence rates of goitre and cretinism in order to determine whether they had returned as public health problems. 42% of the Simbai population and 38% of the Tep-Tep population attended for examination. Amongst those surveyed, the visible goitre rate was low: 0.1% in the Simbai and 2.5% in the Tep-Tep area. Although the iodized oil patrols were carried out a decade previously, goitre does not seem to have re-emerged in the area to the levels reported previously. In the Simbai villages surveyed, there were nine individuals diagnosed as suffering from cretinism, three of whom were thought to have been born after the last iodized oil patrol in the area. In the Tep-Tep villages, eight subjects were diagnosed as suffering from cretinism, all of whom were thought to have been born before the iodized oil patrols. A number of younger children with neurological abnormalities which did not fulfil criteria for endemic cretinism were also seen in both areas. Because of the difficulties in diagnosing endemic cretinism in young children, it is not possible to conclude that endemic cretinism is no longer a problem in these areas. More work is needed to confirm the results of these studies. This will enable a rational control program to be designed and implemented.

[Molecular genetics of congenital isolated thyrotropin deficiency]

In 1971, the first case of congenital isolated thyrotropin (TSH) deficiency was reported by Miyai et al. Subsequently, the same group reported that the disease was caused by a missense mutation in the CAGYC region of the TSH-beta gene (substitution from G to A in exon 2 which altered the Gly29 [GGA] to Arg29 [AGA]). At present the same mutation was reported in 6 patients in 5 Japanese families. Dacou-Voutetakis reported 3 patients with a nonsense mutation in exon 2 (Glu12 [GAA] to Ter [TAA]) and Rajan reported 3 patients with bioinactive TSH caused by a frameshift mutation in exon 3 (Cys105 [TGT] to Val105 [*GTA] and Val114 [GTA] to Ter [TAG]). Significance of C-X-G-X-C motif for biosynthesis of glycoprotein hormones and mass screening for early diagnosis of this disease were discussed.

Clinical study of endemic cretinism in south Sikkim

One hundred individuals suffering from Endemic Cretinism were studied. There were 55 males and 45 females. 62% of the cretins had visible goitre. Thirty nine (62.9%) goitrous cretins had grade II goitre. Neurological cretinism was the predominant type encountered (99%) and Myxoedematous cretinism was seen in only one patient. The most salient neurological feature was deaf-mutism seen in 74%. Findings in the motor system were, apart from deaf-mutism, the most characteristic feature of the condition on clinical examination. 58% had exaggerated deep tendon reflexes and 31% had extensor plantar response. Squint was noticed in 29%. Familial aggregation was noticed and was striking. Endemic cretinism is a distinctive and easily identifiable clinical entity and is an important indicator of the severity of iodine deficiency in a community.

Iodine supplementation and the prevention of cretinism

Normal development of the CNS requires adequate thyroid hormone exposure. Since iodine is an essential component of the thyroid hormone molecule, its deficiency during fetal development can cause hypothyroidism and irreversible mental retardation. The full-blown syndrome, called cretinism, includes deaf-mutism, short stature, spasticity, and profound mental retardation. The clinical spectrum can vary in degree and combination of these features. Screening programs in iodine-deficient countries show that up to 10% of neonates have elevated serum TSH levels, putting them at theoretical risk for permanent brain damage. About one billion people worldwide risk the consequences of iodine deficiency, all of which can be prevented by adequate maternal and infant iodine nutrition. Iodized salt is usually the preferred prophylactic vehicle, but iodized vegetable oil, iodized water, and iodine tablets are also occasionally used. The United Nations and the heads of state of most countries have pledged the virtual elimination of iodine deficiency by the year 2000. This goal is technically feasible if pursued with sufficient vigor and resources.

Iodine-supplementation trials

Iodine deficiency as a major determinant of endemic goiter has been recognized for several decades. The evidence is also strong that iodine supplementation is effective in preventing both varieties of endemic cretinism, provided it is given before conception; early fetal and infant death may also be prevented. However, the reason for the variation in prevalence of the different types of cretinism is still a matter of conjecture. Iodine supplementation may improve motor and cognitive performance, but the evidence needs to be evaluated in light of the difficulty in transposing tests of intellectual and motor ability developed in one culture to another very different one.

Endemic cretinism: toward a unifying hypothesis

Based on our data, the clinical picture of endemic cretinism results from the product of two pathophysiological events. Both events share a common feature, namely iodine deficiency, but act at different points in time. The first event occurs in all cretins and represents the prenatal action of thyroid hormone deficiency on brain development, transmitted vertically from mother to fetus, resulting in the neurological disorder of endemic cretinism. A consistent pattern and intensity of neurological, intellectual, and audiometric deficit is common to and equally present in all types of endemic cretin. The nature of these deficits points to an intrauterine insult to the developing fetal nervous system around the time of the midtrimester. The second event represents the postnatal action of thyroid hormone deficiency on somatic as well as brain development. Whereas previous workers had attributed the differences in the clinical presentation of endemic cretinism to the presence or absence of neurological features (i.e. prenatal hypothyroidism), the distinction between the types of endemic cretin can be related to the length and severity of postnatal thyroid hormone deficiency. Endemic cretins with predominant neurological features have had only transient hypothyroidism in the postnatal period, evidenced by their near normal thyroid function and by a lack of hypothyroid clinical features. By contrast, cretins with marked myxedematous features were characterized by permanent and severe postnatal thyroid hormone deficiency. These cretins, in addition to signs of neurological damage, were typically dwarfed, sexually immature, with marked clinical features of myxedema. This second event, influenced by the thyroid gland's morphologic response to its environment (goiter or thyroid atrophy), dictates the final clinical outcome. In conclusion, our hypothesis states that the clinical expression of endemic cretinism is determined by the sum of two pathophysiologic processes. The first process is fetal hypothyroidism which results in the neurological damage of the disorder and the second process is the duration and magnitude of postnatal hypothyroidism which dictates the final clinical appearance.

[Iodine supplementation in the province of Styria]

As far back as 1898 the Austrian Nobel price winner Wagner von Jauregg was the first to recommend iodination of salt as prophylaxis against endemic goitre (prevalence 48%) and cretinism (greater than 10%). In 1923 he achieved in a voluntary iodine supplementation of 5 mg KJ/kg table salt, which only lasted for a number of years. It was in 1963 when finally a mandatory iodized salt prophylaxis was introduced at the rate of 10 mg KJ/kg. In this study the effect of 25 years of iodine supplementation is investigated: Endemic cretinism, hypothyroidism, and goitre in newborns disappeared generally and endemic goitre in pupils was significantly reduced. However, due to epidemiological studies at elementary and secondary schools and army recruitment examinations we still found out endemic goitre grade I (according to WHO) mainly in female juveniles. Examinations were done by palpation, ultrasonography and urinary iodine excretion. In the above as well as in the urine of newborns and in mother's milk the iodine content was significantly lower than in iodine rich countries. Consequently a higher iodination of salt at the rate of 20 mg KJ/kg was recommended by the Austrian Society of Nuclear Medicine in 1985. This suggestion was taken up by the Austrian authorities and it will finally be instituted by law in May 1990 for the benefit of coming generations.

On goiters and the stupidity which in some countries accompanies them. Endeavours of Vincenzo Malacarne, from Saluzzo

Two hundred years ago, V. Malacarne, pathologist and surgeon, published a booklet entitled "Su i gozzi e sulla stupidità che in alcuni paesi gli accompagna". Malacarne was born at Saluzzo, a town at the foot of the Cottian Alps, in Western Piedmont. Goiter and endemic cretinism were prevalent at the time (1789) in the countryside. In 1940-45 goiter epidemics spread through these still endemic regions. On the basis of his own observations on autoptic material, he suggested that the main cause of cretinism was brain damage due to impeding of the blood circulation by the neck swelling, and invited the pathologists of the Po and Aosta valleys to send him the head and the neck of these goitrous idiots for his researches. Today, too, we believe the thyroid and the brain to contain crucial factors of cretinism and assume that iodine deficiency is the main cause of the disease. Yet we do not know either the factor which damages and prevents in the myxoedematous cretin postnatal thyroid growth, or the pathogenesis of deaf-mutism, spastic paraplegia and severe mental deficiency of the neurological, non-hypothyroid cretin. While these questions remain unanswered, ample evidence has been gathered during the last two centuries regarding the practical importance of iodine prophylaxis to prevent these scourges, today referred to as "iodine deficiency disorders".

Iodine deficiency disorders in Zimbabwe. No change in prevalence of endemic goitre in Wedza District, as shown by school surveys carried out 18 years apart

Goitre prevalence surveys were carried out in 1986 in five primary schools in Wedza District and the results compared with those obtained from the same schools in 1968. Overall, goitre prevalence was 73 percent and there had been no significant change since 1968. In 1986 the visible goitre rate was 14 percent. Goitre was more common in girls on both occasions. Evidence (though not conclusive) of milder forms of endemic cretinism was found. The need for a nationwide iodination programme is emphasised.

["Goiters and the associated idiocy in several countries. Attempts of Vincenzo Malacarne from Saluzzo". Current interpretation of endemic cretinism]

Two hundred years ago V. Malacarne pathologist and surgeon, born in Saluzzo, a town on the foot of the Cottian Alps, published a booklet about goiter and endemic cretinism being diseases prevalent at that time in the countryside. In 1940-45 goiter epidemics spread through these still endemic regions. On the basis of his own observations on autoptic specimens he suggested that the main cause of cretinism was brain damage due to impeded blood circulation by the neck swelling, and invited the pathologists of the Po and Aosta Valleys to send him "il capo ed il collo (the head and the neck)" of these goitrous idiots for a control. Also today we believe the thyroid and the brain to contain crucial factors of cretinism, both sporadic and endemic, and we assume that iodine deficiency is the causal link between the two diseases. Yet we do not know either the factors which damage and prevent, in the myxedematous cretin, postnatal thyroid growth, or the aetiopathogenesis of the deaf-mutism, spastic paraplegia and severe mental deficiency of the neurological non hypothyroid cretin. While these questions remain unanswered, ample evidence has matured during the last two centuries regarding the practical importance of iodine prophylaxis to prevent these scourges, today referred to as "iodine deficiency disorders". Some recent findings on diencephalon inflammation in human and canine goitre are quoted.