LETTER TO THE EDITOR
Year : 2014 | Volume
: 3 | Issue : 4 | Page : 293--294
Reply: Iodized salt, a boon or bane?: A retrospective study
Seshaiah Venkata Kurada1, Srinivasa Rao Dana1, Eswar Ganti2, Srijana Pakalapati1, Madhavi Pothukuchi3,
1 Department of Medicine, Government Siddhartha Medical College, Vijayawada, Andhra Pradesh, India
2 Pinnamaneni Siddhartha Institute of Medical Sciences and Research Foundation, Chinnavutapalli, Andhra Pradesh, India
3 Department of Community Medicine, Government Siddhartha Medical College, Vijayawada, Andhra Pradesh, India
Seshaiah Venkata Kurada
Department of Medicine, Government Siddhartha Medical College, Vijayawada - 520 008, Andhra Pradesh
|How to cite this article:|
Kurada SV, Dana SR, Ganti E, Pakalapati S, Pothukuchi M. Reply: Iodized salt, a boon or bane?: A retrospective study.J NTR Univ Health Sci 2014;3:293-294
|How to cite this URL:|
Kurada SV, Dana SR, Ganti E, Pakalapati S, Pothukuchi M. Reply: Iodized salt, a boon or bane?: A retrospective study. J NTR Univ Health Sci [serial online] 2014 [cited 2023 Feb 8 ];3:293-294
Available from: https://www.jdrntruhs.org/text.asp?2014/3/4/293/146669
We are extremely thankful for the learned reader for making valuable comments on our study. , I would like to clarify certain issues in relation to the comments made.
Upper safe limit is different from recommended daily intake of iodine. While recommended daily intake is essential, upper safe limit varies from region to region, due to varying concentrations of iodine in water, soil, plants as well as due to heterogeneous dietary habits. Hence, the definition of the upper safety levels of iodine intake should be region specific and should be more precise for iodine-sensitive individuals relative to those with normal thyroid function, because disturbed thyroid gland activity can take place due to excessive Iodine. 
Iodized salt is the major source of iodine consumption in many areas and so used as an important parameter in our study. Estimation of iodine intake by every individual in a family, from sources other than iodized salt, is a difficult task and not practicable. Instead, urinary iodine estimation reflects iodine intake.
In our study, we concluded that hypertension and diabetes are more frequent in the hypothyroid group than in nonhypothyroid group. Hypothyroidism is a metabolic disorder and leads to insulin resistant state, which is also a feature of sub-clinical hypothyroidism. Insulin resistance is an important factor in the pathogenesis of type 2 diabetes mellitus. 
Hypothyroidism is one of the important factors documented to cause secondary hypertension by increasing the peripheral vascular resistance as well as through renal dysfunction, volume changes, hormonal changes, and endothelial dysfunction.  Excessive usage of salt is only additive factor for hypertension. Hence hypothyroidism de novo, can cause hypertension and diabetes.
As rightly pointed by the reader, universal iodization of salt is a successful strategy and >170 countries committed to the implementation. However, the problem is a lack of monitoring, which is essential to identify the areas that reached the saturation stage and to exclude those areas from universal iodization programme.
Once started, iodization programme has become permanent in many countries. Studies in China, Srilanka, Greece, Turkey, and Brazil experienced auto-immune thyroiditis and hypothyroidism with prolonged usage of excessive iodine.  Periodic urinary iodine estimation surveys are essential to identify the areas of iodine saturation.
Though as per the report of National Rural Health Mission (Iodine Deficiency Disorder and Nutrition Cell) of India of 2006, only 263 out of 324 districts of India were endemic to iodine deficiency, studies in successive years identified decreased endemicity in many regions of India and increased prevalence of hypothyroidism.
Ever since India adopted the universal salt iodization programme in 1983, there has been a decline in goiter prevalence in several parts of the country, which were previously endemic. India is supposedly undergoing a transition from iodine deficiency to sufficiency state. In general India is now considered to be in postiodization phase. Nationwide prevalence of hypothyroidism is very high in this era.  All the districts except two of Andhra Pradesh were found to be having >100 μg/l of urinary iodine excretion levels.  A study on school children of Delhi documented increased prevalence of goiter and auto-immune thyroiditis, after two decades of salt iodization.  The reports of all studies reveal that the endemicity is not uniform.
Iodized salt coverage study 2010 of India revealed that 47.3% of rural households were consuming iodized salt, as against 27% which was reported in National Family Health Survey-3 of 2005-2006, indicating 20% increase. 
Our study is a retrospective study. Reference range of Serum thyrotropin level (0.3-4.8 μIU/ml) of our study is mentioned in materials and methods section of our article. 
Daily consumption of salt by each individual was calculated from total consumption of salt by the family and number of family members.
Data on family history and hormonal parameters mentioned in materials and methods, have been used for the diagnosis of hypothyroidism, which was the main focus of our study.
The main groups of our study were hypothyroid and nonhypothyroid. We excluded children and pregnant who will have increased demands for iodine. We did not consider age and gender in our study.
As pointed by the reader, there is a simplification error in calculating Chi-square value and P value, while comparing hypothyroidism with diabetes. The revised values are χ2 = 5.135, P ≤ 0.05, which are still statistically significant.
As already quoted in our article, further population-based studies are required to focus much information on this issue. In view of reports of recent studies, in the postiodization phase in India, it is essential to realize that saving iodine sufficient areas from iodine toxicity is as important as protecting the areas of iodine deficiency with supplementation. We are also planning to conduct large sample surveys with estimation of urinary iodine excretion levels, which is a limitation in our present study.
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