The data on thyroid volume measurements that determines prevalence of goitre in children is very important for public health consideration as the presence of goitre in children effectively reflects the status of iodine deficiency disorders (IDD) in the general population. Ultrasound is an excellent modality to evaluate thyroid size. Local experience in using a portable ultrasound machine to measure thyroid volume is presented. The thyroid anatomy and techniques of ultrasound assessment are highlighted. Proper training of public health doctors to perform thyroid gland ultrasonography is crucial to ensure that the thyroid volume data collected would be more accurate and reliable for the planning of health programmes to eliminate IDD in the particular areas.
Endemic iodine deficiency is largely an environmental problem affecting whole populations. Currently, thyroid volume data from a population are analyzed with the sole objective of obtaining an estimate of goitre prevalence using +97th percentile or +2 standard deviations of an appropriate reference as cut-off. This paper proposes an alternative approach to the analysis and presentation of thyroid volume data using Z-scores (standard deviation scores) of the thyroid volume indices such as thyroid volume-for-age or thyroid volume-for-body surface area. The calculation of the summary statistics of the Z-scores, such as mean or median, provides an alternative to the prevalence-based approach for expressing severity of iodine deficiency disorders (IDD). An advantage of the mean or median Z-score is that it describes the thyroid volume profile (and therefore the IDD status) of the entire population directly, unlike goitre prevalence which gives information only about the extremes of distribution. The frequency curve or histogram of the Z-scores provides a complete picture of the whole distribution. Although qualitatively similar conclusions on IDD severity can be drawn from both analytical approaches, only the Z-score system is able to capture adequately the trends or changes in thyroid size over time, and to establish whether a previously iodine-deficient community's thyroid volume profile has returned to 'normal' (as indicated by a distribution that is not significantly different from that of the reference) following intervention. As a continuous variable, Z-scores are particularly useful for the analysis of data from populations where the sample size is relatively small, or where many individuals lie outside the extreme percentiles of the reference population. In view of its advantages in the context of activities based on single and multiple measurements, the Z-score system is to be preferred for the reporting and use of thyroid volume indices. A desirable consequence of this preference is that national goals will be oriented towards an improvement of the overall thyroid volume profile of the population, rather than just a reduction of the number of individuals at the extremes.
Iodine deficiency is recognized as a public health problem. This paper assesses iodine status by socioeconomic factors in school children in Sarawak, East Malaysia. Kuching, Bau and Simunjan districts were chosen based on advice from the Sarawak's Medical and Health Authority. 803 school children, aged eight years, were selected from 19 schools via proportionate systematic sampling. About half the proportion of the school children were from Kuching, 24% from Simunjan and 22% from Bau. Almost all were equally distributed by sex. By mother's race, almost half were Malays, followed by Bidayuh, Iban, Chinese and other races. Mean urinary iodine concentration was 3.36 microg/ 100ml, mean creatinine level was 111.10 mg/100ml and mean creatinine/iodine ratio was 39.45 microg/ gram. Four female children (0.5%) were found to have enlarged thyroid. Urinary iodine levels were significantly different by district, mother's race and household income. It was highest in Kuching, among children with Malay mothers, and with household incomes more than RM500 per month. Conversely, it was lowest in Bau, among children of Iban/Dayak and Chinese mothers, and incomes of RM500 or less per month. Based on the WHO/UNICEF/ICCIDD classification, the Sarawak school children in the present study fall into the moderate IDD category. The low prevalence of goitre is a positive finding indicating that iodine deficiency is corrected over time.
Iodine deficiency endemia is defined by the goitre prevalence and the median urinary iodine concentration in a population. Lack of local thyroid volume reference data may bring many health workers to use the European-based WHO/International Council for Control of Iodine Deficiency Disorders (ICCIDD)-recommended reference for the assessment of goitre prevalence in children in different developing countries. The present study was conducted in non-iodine-deficient areas in Malaysia to obtain local children's normative thyroid volume reference data, and to compare their usefulness with those of the WHO/ICCIDD-recommended reference for the assessment of iodine-deficiency disorders (IDD) in Malaysia.
The study was conducted to compare the prevalence of goitre among Malays and Aborigines in remote inland rural areas to those in coastal areas. All subjects were examined thoroughly by an experienced endocrinologist for the presence of goitre. The overall goitre prevalence in coastal areas was 6.3%; 6.0% (4/67) of Aborigines and 6.7% (4/60) of Malays were affected. However, in remote inland areas, the prevalence of goitre was almost 5 times higher compared to coastal areas. The prevalence of goitre was 30.7% in Baling; 30.2% (19/63) Aborigines and 30.8% (92/299) Malays were affected. Iodine deficiency is the most likely cause for the high prevalence of goitre in the remote inland areas.
A total of 2,034 subjects aged 15 years and above from different parts of the State of Kelantan were studied to determine goiter size and urinary iodine excretion. The State was divided into 2 areas - area 1 consisting of localities in the districts near the coast and area 2 consisting of localities in the inland districts. There were 1,050 subjects in area 1 and 984 subjects in areas 2. The mean age (+/- SE) of subjects in areas 1 and 2 were 38.2 + 0.5 and 37.1 +/- 0.5 years, respectively. The prevalence of goiter was 31.4% in area 1 and 45.0% in area 2; the difference was statistically significant (p < 0.05). However, the prevalence of large and visible goiters (grades II and III) was only 2.0% in area 1 and 3.3% in area 2; the difference was not statistically significant. The mean (+/- SD) urinary iodine excretion in areas 1 and 2 was 57.1 +/- 2.1 and 56.8 +/- 2.1 micrograms I/g Cr, respectively. The values were below those recommended by WHO. There was no significant difference in urinary iodine excretion between those with and without goiters in both areas and also between the grades of goiters. There were significantly more females with goiters than males in both areas but there was no significant difference in the urinary iodine excretion between the 2 sexes. Thus based on urinary iodine excretion, the iodine intake of the population in this area, was suboptimal and this was associated with a high prevalence of goiter.
The effect of consuming large amounts of cassava leaves on thyroid function and urinary iodine was studied. Twenty volunteers were given 200 gm of boiled cassava leaves twice a day for 12 consecutive days. Thyroid hormones triiodothyronine and thyroxine were significantly lower by 9 days. Urinary iodine excretion was also significantly decreased. Cassava leaves, consumed in large amounts by aborigines, probably caused goitres by decreasing iodine absorption.
The urinary iodine excretions of women (15-40 y) and young children (< or = 6 y) from two longhouse villages in the iodine-deficient district of Lubok Antu, Sarawak, were compared. One longhouse (Mengkak) was provided with freshly produced iodized salt every two months (one kg per family) while the other (Menjiling) was provided with iodized water via fortification of the village piped-water supply. Spot urines were collected for iodine determination at baseline and at 6 and 12 months after the start of the study. Salt and water samples were collected at monthly intervals. Goiter assessment was performed on the women at the start and end of the one-year study. The mean iodine concentrations in the salt samples from Mengkak and Menjiling were, respectively, 47.1 +/- 9.7 mg/kg (n = 60) and 0.8 +/- 3.4 mg/kg (n = 60) while the mean iodine concentration in the water samples from Menjiling was 138.6 +/- 43.2 micrograms/L (n = 24); iodine could not be detected in the water samples from Mengkak. There were significant and sustained increases in median urinary iodine excretions of both women and young children in Menjiling; in Mengkak, however, significant and sustained increases in median urinary iodine excretions were observed only in women while the median urinary iodine excretions of children remained essentially unchanged throughout the study period. Goiter prevalences in the women were reduced in both longhouses. The above observations reveal the inadequacy of iodized salt as a vehicle for iodine delivery to young rural Sarawakian children and indicate the need for other means of delivering supplemental iodine to this age group in areas where salt iodization is the only strategy for IDD control. In contrast, iodization of village water supply by itself is adequate in delivering iodine uniformly to the whole community.
Thyroid cancer is the most common among all endocrine malignancies. The worldwide prevalence of goitre in the general population is estimated at 4-7 percent and the incidence of malignancy in goitrous thyroid is about ten percent. It is postulated that goitrous thyroid is a precursor lesion to the development of malignant thyroid diseases. As Sarawak is a state well known for endemic goitre, this study focused on establishing the incidence of thyroid malignancy among goitrous thyroid swellings.
A nationwide cross-sectional school-based survey was undertaken among children aged 8-10 years old to determine the current iodine deficiency status in the country. Determination of urinary iodine (UI) and palpation of the thyroid gland were carried out among 18,012 and 18,078 children respectively while iodine test of the salt samples was done using Rapid Test Kits and the iodometric method. The results showed that based on WHO/ ICCIDD/UNICEF criteria, the national median UI was 109 μg/L [25th, 75th percentile (67, 166)] showing borderline adequacy. The overall national prevalence of iodine deficiency disorders (IDD) with UI<100 μg/L was 48.2% (95% CI: 46.0, 50.4), higher among children residing in rural areas than in urban areas. The highest prevalence of UI<100 μg/L was noted among the aborigines [(81.4% (95% CI: 75.1, 86.4)]. The national total goitre rate (grade 1 and grade 2 goitre) was 2.1%. Of 17,888 salt samples brought by the school children, 28.2% (95% CI: 26.4, 30.2) were found to have iodine content. However, the overall proportion of the households in Malaysia using adequately iodised salt as recommended by Malaysian Food Act 1983 of 20-30 ppm was only 6.8% (95% CI: 5.1, 9.0). In conclusion, although a goitre endemic was not present in Malaysia, almost half of the states in Peninsular Malaysia still have large proportion of UI level <100 μg/L and warrant immediate action. The findings of this survey suggest that there is a need for review on the current approach of the national IDD prevention and control programme.