Correction of iodine deficiency in Macedonia

Universal salt iodization potentially contributes to health equity: socio-economic status of children does not affect iodine status

OBJECTIVES

Many studies have shown that socio-economic status (SES) contributes to health inequalities, with nutrition as one of the major risk factors. Iodine intake entirely depends on external sources, and deficiencies are known to be more prevalent in lower social groups, especially in countries with limited access to iodized salt. This study aimed to determine the influence of SES on iodine status and iodine availability from household salt in North Macedonia.

METHODS

Using cluster sampling, 1,200 children were recruited, and 1,191 children participated (response rate: 99.2%). Iodine status was assessed through urinary iodine concentration (UIC), and iodine availability through iodine content in household salt requested from participants. SES was assessed using standardized Family Affluence Score (FAS).

RESULTS

No statistically significant correlation was found between FAS and iodine in salt. Median regression revealed no significant associations of middle vs. low FAS (β=0.00; 95%-confidence interval (CI)=[-0.61, 0.62]; p=0.999) or high vs. low affluence (β=0.48; 95% CI=[-1.37, 0.41]; p=0.291) with iodine content in household salt. UIC levels were significantly lower in middle FAS children compared to low FAS children (β=-16.4; 95% CI=[-32.3, -0.5]; p=0.043). No statistically significant differences in UIC were found between children with high and low affluence (β=-12.5; 95% CI=[-35.5, 10.5]; p=0.287), possibly due to lowered statistical power for this comparison.

CONCLUSIONS

Universal salt iodization (USI) proves to be a cost-effective measure for appropriate iodine intake in healthy children and adults, irrespective of their social status. It can thus be concluded that USI contributes to reducing health inequalities related to iodine status among population of different social strata.

Modelling the contribution of iodised salt in industrially processed foods to iodine intake in Macedonia

Evidence from the 1950s showed that Macedonia was iodine deficient. After the introduction of mandatory universal salt iodisation, the country saw a steady increase in iodine intake and decline in goitre prevalence, earning iodine-deficiency free status in 2003. Iodine status assessments in 2007 and 2016 showed adequate iodine intake among school age children (median urinary iodine concentration of 241 μg/L and 236 μg/L respectively). Macedonia participated in piloting the Iodine Global Network Programme Guidance on the use of iodised salt in industrially processed foods to better understand potential iodised salt intake from processed foods. One objective of implementation was to identify the need, opportunities, and required actions to strengthen the processed food component of the national salt iodisation policy. Data from the 2017 Household Consumption and Expenditure Survey (HCES) was used to determine household salt consumption, to identify widely-consumed, salt-containing industrially processed foods, and estimate typical daily intake of these foods. Their estimated contribution to iodine intake was estimated based on their salt content and the percentage of food industry salt that is iodised. Although the study has limitations, including a relatively small selection of foods, the results indicate potential iodine intake from iodised household salt and iodised salt in the selected foods of nearly 300% of the Estimated Average Requirement and over 220% of the Recommended Nutrient Intake for adults. This was approximately 50% of the tolerable safe Upper Level for iodine intake. The study confirmed high daily salt intake (11.2 grams from household salt only). Successful salt reduction would be expected to reduce iodine intake, however, modelling with 10% and 30% reduction implied this is unlikely to put any population group at risk of deficiency. It is recommended that implementation of salt iodisation and salt reduction policies are harmonized, alongside continued regular iodine status monitoring for different population groups.

Schoolchildren thyroid volume in North Macedonia: data from a national survey in an iodine-sufficient country

PURPOSE

North Macedonia is historically iodine deficient, but due to the longstanding and effective preventive measures, it has been considered iodine replete since 2003. The aim of the recent national survey was to re-evaluate iodine status and to measure thyroid volume (TVol) by ultrasound in schoolchildren as a representative of the general population.

METHODS

A stratified probability proportionate to size cluster sampling was used to obtain a representative national sample of school children aged 7-10 years between the 28th of March and 4th of October 2016. Thyroid volume (TVol) was measured using ultrasonography in 1188 children. All TVol measurements were done by a single operator and their medians were compared with an international reference standard.

RESULTS

Significant positive correlation was found between Tvol and age, height, weight, body surface area (BSA), body mass index (BMI) in both girls and boys (p < 0.001), but not between TVol and urinary ioidine concentration (UIC). The most important predictors for Tvol in all children were age, height, weight, BMI, and BSA ( all p < 0.001). In multivariate regression, independent predictors for TVol were only BSA (p < 0.001) and age (p = 0.004) after being adjusted for sex, BMI, and UIC (R² = 0.291). The 97th percentile of Tvol in our survey was generally higher than in the reference study and goiter prevalence of 18.3% in boys and 15.6% in girls was found compared to the international standard.

CONCLUSION

In our survey, Tvol of schoolchildren was larger than in the international reference study, although iodine nutritional status of the country has been considered sufficient for many years. In countries and regions with long and effective, well-documented iodine prophylaxis, the optimal way to have realistic normative TVol would be to create their TVol reference limits. Therefore, the provided data for TVol measured in our survey could be proposed as the national reference TVol for schoolchildren aged 7-10 years.

Newborn Screening for Thyroid-stimulating Hormone as an Indicator for Assessment of Iodine Status in the Republic of Macedonia

BACKGROUND

Iodine deficiency is associated with goiter and impaired brain function leading to cretinism. An increased frequency of thyroid-stimulating hormone (TSH) measurements above 5 mlU/L on newborn screening points toward an impaired iodine status of the population.

METHODS

A 13-year retrospective analysis was performed in 228,266 newborns participating in the national thyroid newborn screening program. The TSH concentration was measured in dry blood spots collected by heel stick on filter paper, 48 hours after birth, using fluoroimmunometric DELFIA method.

RESULTS

Out of 236,378 live-born infants, 228,266 (96.6%) have been screened for TSH, of which 198,213 (86.8%) were retrospectively evaluated for TSH levels above 5 mlU/L. Neonates with congenital hypothyroidism, prematurity, and low birth weight were excluded from the evaluation, as well as the inadequately sampled neonates (13.2%). A national prevalence of 3.08% newborns (n=6,105) with TSH > 5 mIU/L was found. Higher percentages were noted in two regions of the country, indicating possible mild iodine deficiency in these regions and shifting the overall average to above 3%.

CONCLUSIONS

Our results indicate overall iodine sufficiency in the Macedonian population. Additional assessment of the iodine intake in the regions with suspected mild iodine deficiency is needed to prevent suboptimal cognitive and psychomotor outcomes.

High incidence of congenital hypothyroidism in one region of the republic of macedonia

Congenital hypothyroidism (CH) is the most common preventable cause of mental retardation in children. Diagnosis is difficult at birth without neonatal screening. Neonatal thyroid screening was established in Prilep, Republic of Macedonia as an integral part of the nationwide screening program. To estimate the prevalence of CH in this region, neonatal thyroid screening was performed on 9757 newborns, during the period 2002–2011. The DELFIA method was applied to measure the thyroid-stimulating hormone (TSH) concentration in dried blood spot samples on standard filter paper taken 48 hours after birth by heel-stick. The TSH cut-off level was 10 mU/L.

The neonatal thyroid screening coverage was 93.4%. Eight newborns with CH were detected, with an incidence of 1:1220 live births, significantly higher compared to the nationwide results 1:2602. The TSH level was not significantly dependent on the gender of the newborn. There was a statistically significant difference between the TSH level and the timing of newborn screening sampling (p <0.05) and between the TSH level and the newborn birth weight (p = 0.01). One point ninety-two percent of newborns with TSH levels above 5 mU/L indicated an iodine sufficiency in Prilep. The incidence of CH in Prilep, which is higher when compared with that reported in surrounding countries, might be a consequence of the higher percentage of the Romany population in this region. Further analysis of this population in other regions is warranted.