Objective: The World Health Organization (WHO) recently adopted thyroid volume ultrasonography results from European schoolchildren as the international reference for assessing iodine deficiency disorders. Our objective was to describe thyroid volumes measured by ultrasonography in US and Bangladeshi schoolchildren and compare these with European schoolchildren. Methods: Cross-sectional studies were performed in schoolchildren in the US (n = 302) and Bangladesh (n = 398). Data were collected on the following: thyroid size by palpation and ultrasonography; urinary iodine; age; sex; weight; and height. Results: Applying the new WHO thyroid volume references to the Bangladeshi children resulted in prevalence estimates of enlarged thyroid of 26% based on body surface area (BSA) and 7% based on age. In contrast, in the US children, the prevalence estimates were less than 1% for each reference. In the US children, the best single predictor of thyroid volume was BSA (R 2 = 0.32), followed by weight (R 2 = 0.31). Using linear regression, upper normal limits (97th percentile) of thyroid volume from US children were calculated for BSA, weight and age, and were found to be lower than the corresponding references based on BSA and age from European schoolchildren. Conclusions: In areas with malnutrition, such as Bangladesh, the BSA reference should be preferred to the reference based on age. Results from the US children indicated that a thyroid volume reference based on weight alone would perform as well as the one based on BSA. European schoolchildren had larger thyroids than US children, perhaps due to a residual effect of iodine deficiency in the recent past in some areas in Europe.
The measurement of urinary iodine in population-based surveys provides a biological indicator of the severity of iodine-deficiency disorders. We describe the steps performed to validate a simple, inexpensive, manual urinary iodine acid digestion method, and compare the results using this method with those of other urinary iodine methods. Initially, basic performance characteristics were evaluated: the average recovery of added iodine was 100.4 +/- 8.7% (mean +/- SD), within-assay precision (CV) over the assay range 0-0.95 mumol/L (0-12 micrograms/dL) was < 6%, between-assay precision over the same range was < 12%, and assay sensitivity was 0.05 mumol/L (0.6 microgram/dL). There were no apparent effects on the method by thiocyanate, a known interfering substance. In a comparison with five other methods performed in four different laboratories, samples were collected to test the method performance over a wide range of urinary iodine values (0.04-3.7 mumol/L, or 0.5-47 micrograms/dL). There was a high correlation between all methods and the interpretation of the results was consistent. We conclude that the simple, manual acid digestion method is suitable for urinary iodine analysis.
Iodine deficiency has traditionally been associated with goiter and cretinism. More recently, iodine deficiency has been recognized as the leading worldwide cause of preventable intellectual impairment. Intellectual and neurologic deficits occur because of a lack of thyroid hormone during critical phases of brain development. More sensitive biologic tests may be useful in determining the true extent of iodine deficiency in populations. Thyroid stimulating hormone (TSH) levels among urban newborns from countries with known iodine deficiency problems were determined using a sensitive whole-blood spot assay. Results found prevalences of high TSH (> 5 mU/L whole blood units using a sensitive monoclonal assay) ranging from 32-80% compared with a prevalence of 3% usually found in iodine-replete areas. These findings suggest that developing brains of newborns are at risk from the detrimental effects of iodine deficiency in these urban areas. The results presented suggest the need for effective intervention programs in urban areas as well.
Objectives: To compare thyroid-stimulating hormone (TSH) levels in neonatal cord blood between study sites in Bangladesh, Guatemala and the United States. Also, to compare neonatal TSH results with indicators of iodine deficiency in school children. Design: Consecutive births and, in school children, cross-sectional surveys. Setting: Savar, Bangladesh; San Pedro Sacatepequez, Guatemala; and Atlanta, United States. Subjects: In each study site, cord blood was spotted on to filter paper and TSH levels determined using a sensitive monoclonal assay. In the USA, heel stick blood specimens from newborns spotted on to filter paper were also obtained as well as exposure to iodine-containing antiseptics during the birthing process. Urine specimens were collected from mothers of newborns and tested for iodine concentration. School children in the same areas were surveyed for thyroid size by palpation and ultrasonography, and urine specimens collected for iodine concentration. Results: Between 141 and 243 cord blood specimens were collected from each study site. The prevalence of elevated cord blood TSH levels (. 5 mU l 21
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