Iodine supplementation in Austria: methods and results.

Until 1963 Austria was an extremely iodine-deficient area with low iodine intake and high goiter prevalence. Therefore, for the first time in 1963, salt iodination with 10 mg of potassium iodide per kilogram of salt was introduced by federal law. Twenty years after this salt iodination, however, investigations in schoolchildren demonstrated iodine deficiency grade I to II according to the World Health Organization (WHO) (urinary iodine excretion, 42-75 microg/g Crea) and goiter prevalence of far more than 10%. In 1990, salt iodination was increased to 20 mg of potassium iodide per kilogram of salt. In 1994, further investigations in schoolchildren demonstrated an increase of urinary iodine excretion (121 microg/g Crea) and a reduction of goiter prevalence below 5%, with the exception of pupils ages 14-19 (12%). In the year 2000, 10 years after the increase of salt iodination in Austria, 430 nonselected adult inhabitants of three communities in Carinthia (a county of Austria) were investigated for iodine excretion, goiter prevalence, and prevalence of thyroid autoantibodies. This study demonstrated that although iodine supply is sufficient now in Austria (males, 163.7 microg of Crea; females, 183.3 microg of iodine per gram of Crea), goiter prevalence is still high in the elderly, who lived for a longer period of iodine deficiency (34.3% in women and 21.3% in men), whereas goiter prevalence in younger people up to age 40 years is below 5%. It could also be shown that the percentage of thyroid autoantibodies is now as high as in other countries with sufficient iodine supply (3.19% in males, 5.17% in females). In addition to the changes of urinary iodine excretion and goiter prevalence because of salt iodination, changes of incidence in hyperthyroidism and histologic types of thyroid cancer are discussed in this paper. In conclusion, the introduction of salt iodination led to an improvement in iodine supply with a marked reduction of goiter prevalence in people who were born after 1963, but also to an increase in hyperthyroidism and autoimmune thyroid diseases as well as changes in histologic types of thyroid cancer.     

Thyroid volume and urinary iodine excretion in the schoolchild population of a Northwestern Italian sub-Alp metropolitan area

Iodine deficiency is recognised as a major preventable public-health worldwide problem. The aim of this study is to assess local reference values for thyroid volume, and give a snapshot of the epidemiology of goiter and iodine nutritional status of the Turin schoolchild population. Sonographic thyroid volume and median urinary iodine excretion were obtained in 1067 schoolchildren aged 11-15 yr resident in Turin for more than 5 yr to assess both goiter prevalence and iodine intake. All the subjects were asked to fill in a questionnaire about their life habits. Anamnestic and anthropometric data, thyroid volume by both bimanual palpation and ultrasonography were assessed, and spot urinary iodine samples were collected. The results show that the median urinary iodine concentration is 113.1 microg/l and the prevalence of goiter <5%, indicating this area as iodine-sufficient. Nevertheless, 40.5% of the schoolchild population has urinary iodine levels lower than the cut-off level recommended as iodine-sufficiency. Interestingly, the high relative prevalence of ultrasound features of autoimmune thyroid disease suggests autoimmune-thyroiditis as a frequent thyroid disease in Turin schoolchildren. As no active programs of salt, milk or water iodisation have ever been carried out, a silent iodine prophylaxis has probably occurred in the city. Despite a sufficient median urinary iodine excretion, a focused program of iodine prophylaxis should be developed due to the presence of a large rate of iodine-deficient population.     

Goiter prevalence and urinary iodine status in urban and rural/mountain areas of Piedmont region

Piedmont region was reported in the 70s as a mild iodine-deficient area with a goiter prevalence > 10%. This study aimed at characterizing the current status of iodine deficiency in Piedmont, with special attention to putative differences between urban and rural/mountain areas. A cross-sectional, observational study was performed according to the surveillance methods for iodine deficiency disorders recommended by the World Health Organization (WHO). Ultrasound local thyroid volume reference values and median urinary iodine concentration were obtained in 2178 schoolchildren aged 11-15 yr, resident in Piedmont region for more than 5 yr to assess both goiter prevalence and iodine intake. Anamnestic and anthropometric data, thyroid volume by both bimanual palpation and ultrasound were assessed, and spot urinary iodine samples were collected. The median urinary iodine concentration was 115.8 microg/l and the prevalence of goiter 3.1%, indicating this area as iodine-sufficient. Nevertheless, 39% of the schoolchild population had urinary iodine levels < 100 microg/l and 6.8% < 50 microg/l. No differences in goiter prevalence and median urinary iodine excretion were observed between urban and rural/ mountain populations. In conclusion, Piedmont is now an iodine-sufficient region. As no programs of salt iodization have been carried out in the last 30 yr, a silent iodine replacement has occurred. Despite a sufficient median urinary iodine excretion, a program of iodine prophylaxis is strongly recommended due to a large part of iodine-deficient population.     

Iodine nutrition, nodular thyroid disease, and urinary iodine excretion in a German university study population.

We determined the influence of different nutritional factors on the urinary iodine excretion in an East German university population. First, we assessed iodine excretion in spot urine samples. Second, we measured iodine content in the university canteen meals, where approximately 20% of the probands had regular meals. Third, we used a special food questionnaire to assess for other sources of nutritional iodine intake, namely iodine tablets, fish consumption, etc. Fourth, we determined the actual prevalence of goiter and thyroid nodules in our probands by high-resolution ultrasonography. The mean urinary iodine excretion in our cohort was 109 +/- 81 microg/g level indicating a borderline adequate iodine intake (100-200). The frequency of thyroid nodules was 30% and the frequency of goiter 11%. Thyroid volumes greater than 18 mL and 25 mL were considered to be enlarged in adult women and men respectively. Urinary iodine excretion was not related to the presence of goiter or thyroid nodules. In addition urinary iodine excretion did not vary with regular consumption of canteen meals, which contained approximately 50% of the daily recommended iodine intake. In contrast probands with regular supplementary intake of iodine tablets had significantly higher values of urinary iodine excretion (169 +/- 130 microg/g) compared to participants without (103 +/- 87 microg/g). No other single nutritional factor (e.g., salt, milk, or bread) had a statistically significant impact on urinary iodine excretion or was able to raise the urinary iodine excretion above the level of marginal iodine deficiency. In summary, the nutritional iodine intake in a Saxonian study population was found to be close to the margin of iodine deficiency. This shows insufficient supplementation of iodine through iodized salt/industrialized food production.     

Chronic iodine excess does not increase the incidence of hyperthyroidism: a prospective community-based epidemiological survey in China

OBJECTIVE: An increasing incidence of hyperthyroidism has been observed when iodine supplementation has been introduced to an iodine-deficient population. Moreover, the influence of chronic more than adequate or excessive iodine intake on the epidemiological features of hyperthyroidism has not been widely and thoroughly described. To investigate the influences of different iodine intake levels on the incidence of hyperthyroidism, we conducted a prospective community-based survey in three communities with mild-deficient, more than adequate (previously mild deficient iodine intake), and excessive iodine intake. SUBJECTS AND METHODS: In three rural Chinese communities, a total of 3761 unselected inhabitants aged above 13 years participated in the original investigation and 3018 of them received identical examinations after 5 years. Thyroid function, levels of thyroid peroxidase antibody (TPOAb), thyroglobulin antibody and urinary iodine excretion were measured and thyroid ultrasound examination was also performed. RESULTS: In three communities, median urinary iodine excretion was 88, 214, and 634 microg/l (P<0.05) respectively. The cumulative incidence of hyperthyroidism was 1.4, 0.9, and 0.8% (P>0.05) respectively. Autoimmune hyperthyroidism was predominant in thyroid hyperfunction in all the three cohorts. Either positive TPOAb (>50 U/ml) or goiter in original healthy participants was associated with the occurrence of unsuspected hyperthyroidism in 5 years (logistic regression, OR=4.2 (95% CI 1.7-8.8) for positive TPOAb, OR=3.1 (95% CI 1.4-6.8) for goiter). CONCLUSION: Iodine supplementation may not induce an increase in hyperthyroidism in a previously mildly iodine-deficient population. Chronic iodine excess does not apparently increase the risk of autoimmune hyperthyroidism, suggesting that excessive iodine intake may not be an environmental factor involved in the occurrence of autoimmune hyperthyroidism.     

Variations in urinary iodine excretion and thyroid function. A 1-year study in healthy men

OBJECTIVE: The iodine intake level in a population is determined in cross-sectional studies. A fraction of samples with iodine content below a certain level, e.g. 25 microg/l, may suggest iodine deficiency in part of the population. However, urinary iodine varies considerably from day to day and the fraction of low samples caused by dispersion remains unsettled. DESIGN: A longitudinal study of 16 healthy men living in an area of mild to moderate iodine deficiency. METHODS: We measured urinary iodine and creatinine concentrations, and serum TSH, total thyroxine (T4), free T4 index and total tri-iodothyronine (T3) in samples collected monthly for 1 year. RESULTS: Average urinary iodine excretion was 57.0 microg/l (49.1 microg/24 h (corrected for creatinine excretion)) and varied from 29 to 81 microg/l (28 to 81 microg/24 h) between participants. Individual samples varied between 10 and 260 microg/l, and the variation around the mean was 2.4 times larger when calculated for the 180 individual samples compared with the 15 average annual values (1.7 times larger for estimated 24 h iodine excretion values). The fraction of individual samples below 25 microg/l was 6.7% (7.2% < 25 microg/24 h), whereas none of the participants had average iodine excretion below 25 microg/l or 25 microg/24 h. Participants with average annual iodine excretion below 50 microg/24 h had a negative correlation between iodine excretion and TSH, whereas a positive correlation was observed when average annual iodine excretion was above this level. CONCLUSIONS: Seven per cent of individual urine samples indicated severe iodine deficiency without this being present in the group studied. Dispersion was reduced by 24% when using estimated 24 h urinary iodine excretion rather than urinary iodine concentration. Participants with moderate iodine deficiency (average annual urinary iodine excretion 25-50 microg/24 h) showed clear signs of substrate deficiency for thyroid hormone synthesis while participants with mild iodine deficiency (50-100 microg/24 h) did not.     

Thyroid autoimmunity is associated with higher urinary iodine concentrations in an iodine-deficient area of Northwestern Greece.

Northwestern Greece was identified in the 1960s for its high prevalence of endemic goiter and iodine deficiency. Although iodized salt has been commercially available since then, a recent epidemiological survey of 3916 schoolchildren found that low-grade goiter is still prevalent in endemic proportions (21%). The aim of this study was to further assess the cause of goiter and the severity of iodine deficiency in children from this endemic area of Greece. Of the 800 children with clinically detectable goiter, 97 children (60 girls and 37 boys, 8-15 years) were recruited for determination of urinary iodine excretion, as well as assessment of thyroid volume and function and detection of antithyroid antibodies. The median urinary iodine concentration was 8.4 microg/dL, indicative of a mild iodine deficiency. Thyroid function was normal in all but 11 children who had subclinical hypothyroidism. Sixteen children (16.5%), including all those with subclinical hypothyroidism, were positive for antithyroid antibodies. Their median urinary iodine concentration (20.6 microg/dL) was higher compared to children who were negative for antibodies (7.4 microg/dL; p<0.001). The mean thyroid volume by ultrasonography (12.2+/-4.1 mL) was above the upper limit of normal for this age group. Thyroid volume was inversely related to the urinary iodine content in the children with negative antithyroid antibodies. Iodine deficiency is still prevalent in northwestern Greece although of mild severity and constitutes the primary cause of goiter among schoolchildren. However, it appears that autoimmune thyroiditis is emerging as a frequent cause of goiter in those children with sufficient iodine intake.     

Goiter prevalence and urinary iodide excretion in a formerly iodine-deficient region after introduction of statutory lodization of common salt.

The objective of this epidemiologic study was to determine the volume of the thyroid gland as well as urinary iodine excretion in dependence on age and gender in a population from an area of low natural iodine supply now receiving iodine prophylaxis. In 430 persons from three communities in the province of Carinthia, Austria, we determined thyroid volume via sonography as well as urinary iodide excretion. As in numerous other European countries, natural iodine supply is insufficient in Austria. Therefore, to reduce goiter incidence, iodization of common salt with 10 mg potassium iodide (KI) per kilogram of NaCl was made mandatory in Austria in 1963 by federal law. In 1990, the amount of iodine addition was increased to 20 mg KI per kilogram of NaCl. Our results show that mean urinary iodide excretion in the persons investigated was altogether satisfactory (males: 163.7 microg of iodine per gram of creatinine; females: 183.3 microg of iodine per gram of creatinine). Goiter prevalence was 34.3% in women and 21.3% in men. An increase in goiter occurrence with age was noted in both genders. The increase in goiter prevalence was particularly obvious in the age group older than 40, i.e., among those participants who had spent at least a certain span of their lives in an area of iodine deficiency. Thus, the most likely reason for the persistently high goiter prevalence is not current iodine deficit but rather the high number of goiters that had developed previously at the time of iodine deficiency and were unable to undergo regression in spite of today's comparatively good iodine supply situation.     

Iodine in drinking water varies by more than 100-fold in Denmark. Importance for iodine content of infant formulas

The iodine intake level of the population is of major importance for the occurrence of thyroid disorders in an area. The aim of the present study was to evaluate the importance of drinking water iodine content for the known regional differences in iodine intake in Denmark and for the iodine content of infant formulas. Iodine in tap water obtained from 55 different locations in Denmark varied from <1.0 to 139 microg/l. In general the iodine content was low in Jutland (median 4.1 microg/l) with higher values on Sealand (23 microg/l) and other islands. Preparation of coffee or tea did not reduce the iodine content of tap water with a high initial iodine concentration. A statistically significant correlation was found between tap water iodine content today and the urinary iodine excretion measured in 41 towns in 1967 (r=0.68, P<0.001). The correlation corresponded to a basic urinary iodine excretion in Denmark of 43 microg/24h excluding iodine in water and a daily water intake of 1.7 l. The iodine content of infant formulas prepared by addition of demineralized water varied from 37 to 138 microg/l (median 57 microg/l, n=18). Hence the final iodine content would depend heavily on the source of water used for preparation. We found that iodine in tap water was a major determinant of regional differences in iodine intake in Denmark. Changes in water supply and possibly water purification methods may influence the population iodine intake level and the occurrence of thyroid disorders.     

Thyroid disorders in mild iodine deficiency.

Comparative epidemiologic studies in areas with low and high iodine intake and controlled studies of iodine supplementation have demonstrated that the major consequence of mild-to-moderate iodine deficiency for the health of the population is an extraordinarily high occurrence of hyperthyroidism in elderly subjects, especially women, with risk of cardiac arrhythmias, osteoporosis, and muscle wasting. The hyperthyroidism is caused by autonomous nodular growth and function of the thyroid gland and it is accompanied by a high frequency of goiter. Pregnant women and small children are not immediately endangered but the consequences of severe iodine deficiency for brain development are grave and a considerable safety margin is advisable. Moreover, a shift toward less malignant types of thyroid cancer and a lower radiation dose to the thyroid in case of nuclear fallout support that mild-to-moderate iodine deficiency should be corrected. However, there is evidence that a high iodine intake may be associated with more autoimmune hypothyroidism, and that Graves' disease may manifest at a younger age and be more difficult to treat. Hence, the iodine intake should be brought to a level at which iodine deficiency disorders are avoided but not higher. Iodine supplementation programs should aim at relatively uniform iodine intake, avoiding deficient or excessive iodine intake in subpopulations. To adopt such a strategy, surveillance programs are needed.     

Urinary iodine and thyroid volume in a Swedish population

OBJECTIVE: To evaluate the present efficacy of an iodine supplementation programme working in Sweden since 1936 by studying the iodine excretion in urine and determining the thyroid volume in a population in a semi-rural community. DESIGN: A cross-sectional population screening comprising three age groups with randomly selected individuals: group 1 (children): 7-9 years, n = 61 (invited 70); group 2 (teenagers): 15-17 years, n = 61 (invited 63), and group 3 (adults): 60-65 years; n = 57 (invited 73). MAIN MEASUREMENTS: Urinary iodine was measured spectrophotometrically; thyroid volume by ultrasonography. RESULTS: The median values for urinary iodine concentration in the three age groups were 194 microg L(-1), 246 microg L(-1) and 190 microg L(-1), respectively, indicating an adequate iodine intake. In the 7-9 year olds, the median value of the thyroid volume was 4.7 mL, which coincides with the recently established upper limit of normal children of that age, 4.0-4.8 mL (ICCIDD, International Council for control iodine deficiency disorders). One eight-year-old boy had a pronounced goiter. Four teenagers and one adult were found to have an enlarged thyroid gland according to earlier established reference volumes (15 years >16 mL; adults > 25 mL). CONCLUSION: We conclude that the iodine intake in our region is sufficient in age groups ranging from young children to pre-retirement adults.     

Assessment of goiter in an area of endemic iodine deficiency.

Urinary iodone (UI) excretion and sonographically measured thyroid volume were investigated in 195 subjects living in 6 separate villages in the Casamance region of southeastern Senegal, West Africa. A comparison of goiter prevalence using thyroid palpation and volume measurement and of iodine excretion expressed as micrograms per gram (microg/g) creatinine or micrograms per deciliter (microg/dl) urine was undertaken, and possible pathogenetic factors were investigated. Ultrasound measured thyroid volumes were above the recommended upper limit of the reference range for an area replete in iodine in 83.1% or females, 52.3% of males, and 80.0% of children aged 13 years or younger. Overall sensitivity and specificity for palpation compared to sonographically demonstrated thyroid enlargement was 51.7% and 91.5%, respectively. Thyroid enlargement was not associated with ethnic origin, thiocyanate ingestion, HLA DR/DQ phenotype frequency, or thyroid growth-stimulating immunoglobulin (TGI) positivity. Median UI was 32 microg/g creatinine with 65.0% having values consistent with iodine deficiency (< 50 microg/g). When results were expressed as micrograms per deciliter, the percentage having values consistent with iodine deficiency (< 5.0 microg/dl) increased to 95.7%. The findings suggest a primary role for iodine deficiency in goitrogenesis in the study population. They demonstrate that classification of the severity of the endemia in this or other study populations in areas of iodine deficiency is dependent on the methods used to determine goiter prevalence (palpation or ultrasound measured thyroid enlargement), or dietary iodine status (iodine excretion expressed as micrograms per gram creatinine or micrograms per deciliter urine).     

A survey of iodine intake and thyroid volume in Dutch schoolchildren: reference values in an iodine-sufficient area and the effect of puberty

BACKGROUND: Iodine deficiency and endemic goiter have been reported in the past in The Netherlands, especially in the southeast. OBJECTIVE: To evaluate iodine intake and thyroid size in Dutch schoolchildren, contrasting those living in a formerly iodine-deficient region in the east (Doetinchem) with those living in an iodine-sufficient region in the west (Amsterdam area). DESIGN: Cross-sectional survey of 937 Dutch schoolchildren aged 6--18 years, of whom 390 lived in the eastern and 547 in the western part of the country. METHODS: Thyroid size was assessed by inspection and palpation as well as by ultrasound. Iodine intake was evaluated by questionnaires on dietary habits and by measurement of urinary iodine concentration. RESULTS: Eastern and western regions were similar with respect to median urinary iodine concentration (15.7 and 15.3 microg/dl, NS, Mann-Whitney U test), goiter prevalence by inspection and palpation (0.8 and 2.6%, P=0.08, chi-squared test), and thyroid volumes. The P97.5 values of thyroid volumes per age and body surface area group were all lower than the corresponding sex-specific normative WHO reference values. Iodized salt was not used by 45.7% of households. Daily bread consumption was five slices by boys and four slices by girls. Weekly milk consumption was 3 liters by boys and 2 liters by girls. Seafish was consumed once monthly. From these figures we calculated a mean daily iodine intake of 171 microg in boys and 143 microg in girls, in good agreement with the measured median urinary concentration of 16.7 microg/dl in boys and 14.5 microg/dl in girls. The sex difference in iodine excretion is fully accounted for by an extra daily consumption of one slice of bread (20 microg I) and one-seventh of a liter of milk (8.3 microg I) by boys. Thyroid volume increases with age, but a steep increase by 41% was observed in girls between 11 and 12 years, and by 55% in boys between 13 and 14 years, coinciding with peak height velocity. Girls have a larger thyroid volume at the ages of 12 and 13 years, but thyroid volume is larger in boys as of the age of 14 years. CONCLUSIONS: (1) Iodine deficiency disorders no longer exist in The Netherlands. (2) Bread consumption remains the main source of dietary iodine in The Netherlands; the contribution of iodized table salt and seafish is limited. (3) The earlier onset of puberty in girls renders their thyroid volume larger than in boys at the age of 12--13 years, but boys have a larger thyroid volume as of the age of 14 years.     

Epidemiological survey on the relationship between different iodine intakes and the prevalence of hyperthyroidism

OBJECTIVE: To investigate the effect of different levels of iodine intake on the prevalence of hyperthyroidism and the impact of universal salt iodization on the incidence of hyperthyroidism. DESIGN: A comparative cross-sectional and longitudinal survey was conducted in three areas with borderline iodine deficiency, mild iodine excess (previously mild iodine deficiency) and severe iodine excess. Universal salt iodization had been introduced 3 years previously except in the area with borderline iodine deficiency. METHODS: In total 16 287 inhabitants from three areas answered a questionnaire concerning the history of thyroid disease. Among them 3761 unselected subjects received further investigations including thyroid function, thyroid autoantibodies, thyroid ultrasonography and urinary iodine excretion. RESULTS: Among areas with median urinary iodine excretion of 103 microg/l, 375 microg/l and 615 microg/l (P<0.05), the prevalence of hyperthyroidism did not differ significantly (1.6%, 2% and 1.2%). The prevalence of subclinical hyperthyroidism was higher in areas with borderline iodine deficiency and mild iodine excess than in the area with severe excess iodine intake (3.7%, 3.9% and 1.1%, P<0.001). The prevalence of Graves' disease and its proportion in hyperthyroidism did not differ among areas. The incidence of hyperthyroidism did not significantly increase after the introduction of universal salt iodization. CONCLUSION: Different iodine intakes under a certain range do not affect the prevalence and type of hyperthyroidism. Subclinical hyperthyroidism is more prevalent in the iodine deficient area than in the severe iodine excessive area. In the area with mild iodine deficiency, the introduction of universal salt iodization may not be accompanied by an increased incidence of hyperthyroidism.     

Continuous rise of urinary iodine excretion and drop in thyroid gland size among adolescents in Mecklenburg-West-Pomerania from 1993 to 1997.

Improved legislation (1989, 1993), as well as education of the public, are likely to improve the iodine supply for the German population. Children and adolescents will be the first to profit. We investigated thyroid size and urinary iodine excretion in a total of 2906 students aged 10 to 18 in Mecklenburg-West-Pomerania in 1993, 1995, and 1997. The median urinary iodine excretion rose from 73 microg/g creatinine in 1993 to 133 microg/g in 1997. The prevalence of goiter, according to the reference range of Gutekunst, dropped from 33% to 10% over the same interval, and the median thyroid size declined from 11 ml to 6 ml. While only 6% of the test subjects excreted more than 150 microg iodine per g creatinine in 1993, this figure rose to 33% in 1997. The improved alimentary iodine supply is due to the increased use of iodine enriched salt by the food industry, food factories and in common food supply services.     

Sustainable control of iodinedeficiency in Iran: beneficial results of the implementation of the mandatory law on salt iodization

Iodine deficiency disorders (IDD) were prevalent in the Islamic Republic (IR) of IRAN before 1989, when the national salt iodization program with 40 mg l/k of salt was initiated. Despite a comprehensive IDD control program, less than 50% of the households in rural areas consumed iodized salt by 1994. A law for the mandatory production of iodized salt for households was passed in 1994. The purpose of this study was to evaluate goiter status and urinary iodine excretion 2 yr after this law was implemented. In each of 26 provinces, 30 groups of 40 schoolchildren, total 36,178, were examined for goiter and classified according to World Health Organization (WHO) classification. Urinary iodine excretion was measured in 2,917 children by digestion method. Goiter was endemic in all provinces, but the majority were small (grade 1) goiter. Median urinary iodine was 20.5 microg/dl 85.1% had urinary iodine > or =10 microg/dl. Median urinary iodine was above 13 microg/dl in all 26 provinces. In all provinces the percentage of schoolchildren with urinary iodine <5 microg/dl was less than 16%. In nine provinces the median urinary iodine was between 13 to 20 microg/dl; urinary iodine of their schoolchildren was <5 microg/dl in 10.8% and <2 microg/dl in 6-9%. No significant difference was observed between boys and girls or children of rural and urban regions in urinary iodine excretion. We conclude that 7 yr after the beginning of salt iodization and 2 yr following mandatory iodized salt consumption, urinary iodine excretion is adequate in schoolchildren; considering the data of the percent of households consuming iodized salt and programmatic setting of the IDD program, The IR of Iran has reached a sustainable control program for iodine deficiency.     

Effect of iodine supplementation on a pediatric population with mild iodine deficiency.

A cross-sectional study in two stages consisted of healthy children to assess the effect of iodine supplementation on a pediatric population with mild iodine deficiency in an ongoing program in the Province of Pontevedra, northwestern Spain. In the first survey (1984), 1565 schoolchildren and in the second survey (1995) 907 schoolchildren were randomly selected from the population. In January 1985, a mandatory consumption of iodized salt in our region was begun. In both surveys we studied prevalence of goiter, urinary iodine excretion, and prevalence of thyroid dysfunction. Similar prevalences of goiter were observed in both surveys, 3.7% versus 3.9%; however, significantly lower prevalence of Ib and II degree goiters were observed in the second survey. The mean iodine excretion was 88.6 +/- 73 microg/L (median 66.3) and 146.4 +/- 99 microg/L (median 115.7), p < 0.01 for the first and second surveys, respectively. Finally, the overall prevalence of thyroid dysfunction was similar in both surveys, 9.2% versus 7.0%; however, significantly lower prevalence of suppressed serum thyrotropin (TSH), considered as a marker of subclinical hyperthyroidism, was observed in the second survey when compared to the first, 0.1% versus 2%, p < 0.01. Our results are in agreement with the recent data from Denmark, where the prevention of subclinical hyperthyroidism occurring in the elderly as a consequence of longstanding mild iodine deficiency is the reason that the Danish finally started iodine supplementation on a national basis. In conclusion, long-term correction of mild iodine deficiency in a pediatric population has beneficial effects on the prevalence of high-degree goiters, and this correction reduces significantly the prevalence of subclinical hyperthyroidism. The present observation constitutes a strong argument for correcting even mild iodine deficiency.     

Prevalence of thyroid dysfunction in elderly subjects from the general population in an iodine deficiency area.

The prevalence of thyroid disorders was investigated in 466 (403 female, 63 male) subjects over the age of 60 years (79.2 +/- 7.5 years; mean +/- SD) from the general population in an area of iodine deficiency. In addition to thyroid hormone assays, thyroid antibodies and urinary iodine excretion were determined. In cases with thyroid dysfunction, ultrasound investigations were performed. Twenty-two of the 466 subjects (4.7%) showed hyper- or hypothyroidism; 7 subjects were hyperthyroid (1.5%), 5 had primary hypothyroidism (1.1%), and 10 showed "subclinical" hypothyroidism (2.2%). The latter constellation is defined as an elevation of thyrotropin (TSH) with normal values for thyroxine and triiodothyronine. Most subjects with hyperthyroidism had a goiter by palpation (6/7); thyroid volume by ultrasound (median) was 26.2 mL with an inhomogeneous echo pattern in 6 of the 7 subjects. In 4 cases, a rise in urinary iodine excretion was documented; none had TSH-receptor antibodies. Most subjects with overt or subclinical hypothyroidism had a homogeneous or low-echogenic pattern by ultrasound; thyroid volume (median) was 12.9 mL and 12.7 mL, respectively. By palpation, 8 of the 15 subjects had no goiter. In general, these persons had no rise in urinary iodine excretion (11/13), but most showed an elevation of antibodies against the microsomal antigen and/or thyroglobulin (11/15).(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of goiter endemia by ultrasound in schoolchildren in Val Sarmento (Italy).

Ultrasonography is an excellent and objective method for assessing thyroid volume, especially in children where clinical evaluation is inaccurate. The aim of this study was to evaluate the presence of goiter by thyroid ultrasound and palpation in 244 schoolchildren, 6 to 14 years old, living in some rural villages of Val Sarmento, a mountain area of Basilicata, Italy. In 1996 we revealed the presence of endemic goiter in 25% of the schoolchildren evaluated by palpation, according to World Health Organization (WHO) criteria, and in 15.9% of the schoolchildren evaluated by ultrasonography (7.5 MHz linear probe). The median urinary iodine excretion, taken from an extemporaneous sample of the first urines in the morning, was 62.2 microg/l. This study includes Val Sarmento, an area with mild-moderate grade (Grade I) of iodine deficiency, suggesting the need for iodine prophylaxis. Furthermore, it proves that the measurement of thyroid volume by ultrasonography is an essential instrumental method for a correct epidemiological study of endemic goiter, particularly in areas where there is mild iodine deficiency.     

First beneficial results of the implementation of Croatian new law on salt iodination

Presented pilot-study on urinary iodine excretion among schoolchildren in main geographic regions of Croatia indicates a significant improvement in iodine excretion only 12 months after introduction of a new mandatory salt iodination with 25 mg KI/kg of salt. Measurements of urine iodine excretion in 663 schoolchildren of both sexes, aged 9-16 years, from Zagreb, Rude, Bednja, Osijek, Dakovo, Rijeka, Pazin and Dubrovnik showed that from 77.9% to 94.8% of subjects have had urinary iodine above 5 microg/dl. Also from 41.2% to 70.8% of children have had urinary iodine excretion above 10 microg/dl. Before introduction of a new law mostly borderline values of urinary iodine excretion were recorded; therefore recent values present significant positive shift and actually they are the best signs of almost adequate iodine intake in Croatian youth. Nevertheless, further measures for improvement of iodine intake are recommendable because still 31% of controlled table-salt samples from households and 15.7% of imported salt samples have had KI level below 20 mg/kg of NaCl. Salt produced in Croatia was (Pag and Nin salt plants) completely in accordance with iodination regulations. On the other hand, as recent increase in urinary iodine excretion could not be simultaneously followed by reduction in goiter prevalence, in the following years further epidemiological surveys of iodine deficiency disorders shall be warranted.