Indian Pediatrics 2001; 38: 1331-1333  

Reply

We thank Dr. Kapil for giving us the opportunity to provide more details regarding our work. The writer has questioned the age group and size of the sample (Baroda) in study group and advised to follow the guideline recommended by WHO/UNICEF/ICCIDD. In this context, we have the following response to offer:

1. We have followed the guidelines given by WHO/UNICEF/ICCIDD for selecting the target group(1). According to WHO/UNICEF/ICCIDD a variety of target groups, including neonates, infants, pre-school-age children, school-age children and certain groups of adults might serve as a focus for IDD surveillance. Selecting the optimal group or groups depends on a number of considerations, including their vulnerability, repesentativeness, access-ibility, and potential usefulness for surveillance of multiple health problems. Three aspects for vulnerability are: (i) Extent of exposure to the deficiency; (ii) Severity of health consequences due to a deficiency; and (iii) Degree of clinical or biochemical responsiveness to the deficiency.

WHO/UNICEF/ICCIDD(1) has pub-lished a table that is framework for considering target groups for surveillance (Table I).

The epidemiological assessment of the severity of iodine defieincy largely rests with determination of urinary iodine status and of thyroid size in specified population groups(2). The assessment of IDD is difficult since it combines indirect measures of current iodine intake, urinary iodine, with that of past iodine intake, specifically thyroid size. Thyroid gland size is largely assessed in children, in part because of the easy availability of these subjects, and also because it reduce the confounding effect of duration of iodine deficiency on thyroid gland responsive-ness to changes in iodine status. The currency of the ultrasonography appears to diminish with age in adult population, but there has been no definitive study demonstrating the lack of utility of measuring thyroid size in an endemic goiter population.

2. The projected population of Baroda in 2001 would be 15,00,000(3). We assessed IDD biochemically in the rural population of two small villages (Muval and Tentalav) having a population of 10000 to 25000. Before this we had an idea of the goiter prevalence rate (TGR) in these villages(4). In the past, thyroid palpation was the preferred method for estimation of thyroid size but our previous study has shown that thyroid ultrasonography (US) is the best indicator for prevalence of IDD in 6-15 year schoold-age children(4). Thus thyroid size by ultrasound was measured for the first time in Gujarat children and adults as reported by us(4,5). The TGR was almost 100% in school-age children (529/530) when compared to WHO international reference (thyroid volume for BSA) based on 3474 European school children in 6-15 year age group. All other countries have reported these values as much higher due to persistent residual effect of past IDD in Europe(6,7). As thyroid size depends upon age, height and body weight, one would expect Indian children to have smaller thyroids in comparison to European children. We were compelled to compare our results (biochemical and thyroid size) with international references because Indian normative values are not established so far for any of these parameters. We have also shown an impact of malnutrition(8). We are trying to establish a normative ultrasound thyroid volume data. Future study is needed in field of IDD. Universal TSH screening is not a common place in India.

3. We have in fact given the distribution of urinary iodine and blood TSH in these children. Urinary iodine estimation (UIE) distribution is given in the ranges of severe (<20 µg/1), moderate (21-50 µg/I), and mild (51-100 µg/1) iodine deficiency. UIE in the range of 101-300 µg/1 is considered as adequate iodine intake.

WHO recommendations and guidelines are based on the research in each particular area. It is according to their recommendation that "as an IDD preven-tion program progresses, goiter rates become progressively less useful, and urinary iodine levels progressively more useful, as elimination criteria", Hence this present work on ‘Biochemical assessment of IDD" was carried out. WHO has advised for a sample size of 200 specimens that would give a relative precision of 20%, e.g., 50 ± 10% below 100 µg/1. Smaller sample sizes are adequate to establish an outset that iodine deficiency is the cause of the endemic goiter(1).

S.R. Brahmbhatt,
R.M. Brahmbhatt,
C.J. Eastman,
S.C. Boyages,
Westmead Hospital and Institute of Clincial Pathology and Medical Research,
Westmead NSW 2145, Australia.

1. WHO/UNICEF/ICCIDD. Chapter 2: Selecting target groups and Chapter 5: Selecting appropriate indicators: Biochemical indicators. In: Indicators for Assessing Iodine Deficiency Disorders and their Control Through Salt Iodination. Geneva. World Health Organization, WHO/NUT/94.6, 1994.

2. Dunn JT. Indicators for assessing IDD. ICCIDD USA IDD Newsletter 1999; 15: 3.

3. Baroda online at http//www.baroda.com

4. Brahmbhatt SR, Brahambhatt RM, Boyages SC. Thyroid ultrasound is the best prevalence indicator for the assessment of Iodine Deficiency Disorders: A study in rural/trial school children from Gujarat (Western India) Eur J Endocrinol 2000; 143: 37-46.

5. Brahmbhatt SR. Thyroid ultrasonography consistently identifies goiter in adults over the age of 30 years despite a diminished response with aging of the thyroid gland to the effects of goitrogenesis. Scientific World J 2001; 1: 239-249.

6. Xu F, Sullivan K, Houston R, Zhao J, May W, Maberly G. Thyroid volumes in US and Bangladesh schoolchildren: Comparison with European school chilren. Eur J Endocrinol 1999; 140: 498-504.

7. Hess S, Zimmermann M. Thyroid Volumes in a national sample of iodine sufficient Swiss schoolchildren: Comparison to the WHO/ICCIDD normative thyroid volume criteria. Eur J Endocrinol 2000; 142: 599-603.

8. Brahambhatt SR, Brahambhatt RM, Boyages SC. Impact of protein energy malnutrition (PEM) on thyroid size in an iodine deficient population of Gujarat (India): Is it an etiological factor for goiter? Eur J Endocrinol 2001; 145: 11-17.