The impact of common micronutrient deficiencies on iodine and thyroid metabolism: the evidence from human studies
Program in International and Community Nutrition, Department of Nutrition, University of California, Davis, CA, USA.Best Practice & Research: Clinical Endocrinology & Metabolism (Impact Factor: 4.6). 02/2010; 24(1):117-32. DOI: 10.1016/j.beem.2009.08.012
Deficiencies of micronutrients are highly prevalent in low-income countries. Inadequate intake of iodine impairs thyroid function and results in a spectrum of disorders. Other common deficiencies of micronutrients such as iron, selenium, vitamin A, and possibly zinc may interact with iodine nutrition and thyroid function. Randomised controlled intervention trials in iodine- and iron-deficient populations have shown that providing iron along with iodine results in greater improvements in thyroid function and volume than providing iodine alone. Vitamin A supplementation given alone or in combination with iodised salt can have a beneficial impact on thyroid function and thyroid size. Despite numerous studies of the effect of selenium on iodine and thyroid metabolism in animals, most published randomised controlled intervention trials in human populations failed to confirm an impact of selenium supplementation on thyroid metabolism. Little evidence is available on interactions between iodine and zinc metabolism.
- "Adequate levels of thyroid hormones are especially important for myelination, cell migration, differentiation and maturation of the fetal brain   . IDD are caused primarily by insufficient dietary iodine intake and/or inadequate iodine utilization due to, for example , the presence of goitrogens  . "
Article: Iodine in autism spectrum disorders
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- "Several micronutrients deficiency interacting with nutritional iodine may affect thyroid function in low income countries, and even occur in well-nourished elderly population [43,44]. Both chronic iodine deficiency and iodine excess may increase thyroid cancer risk . "
ABSTRACT: In the past few decades, the incidence of thyroid cancer has rapidly increased worldwide. Thyroid cancer incidence is relatively high in regions where the population's daily iodine intake is insufficient. While low dietary iodine has been considered as a risk factor for thyroid cancer development, previous studies found controversial results across different food types. Among different ethnic groups, dietary factors are influenced by various dietary patterns, eating habits, life-styles, nutrition, and other environmental factors. This review reports the association between dietary factors and thyroid cancer risk among ethnic groups living in different geologic regions. Iodine-rich food such as fish and shellfish may provide a protective role in populations with insufficient daily iodine intake. The consumption of goitrogenic food, such as cruciferous vegetables, showed a positive association with risk. While considered to be a risk factor for other cancers, alcohol intake showed a protective role against thyroid cancer. High consumption of meat such as chicken, pork, and poultry showed a positive association with the risk, but dairy products showed no significant association. Regular use of multivitamins and dietary nitrate and nitrite also showed a positive association with thyroid cancer risk. However, the study results are inconsistent and investigations into the mechanism for how dietary factors change thyroid hormone levels and influence thyroid function are required.
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- "Although substantial progress has been made over the last several decades, iodine deficiency (ID) remains a significant public health problem worldwide, including in developed nations. Inadequate intake of iodine impairs thyroid function and results in a wide variety of clinical manifestations, including goiter, impaired cognitive development and congenital abnormalities, collectively referred to as iodine-deficiency disorders. ID is the most common cause of preventable mental impairment worldwide. "
ABSTRACT: Background: Some studies have shown the possible role of protein-energy malnutrition (PEM) in persistence of endemic goiter in iodine replenished areas. The present study was conducted to assess the association between PEM and goiter in schoolchildren of Isfahan, Iran. Methods: In a cross-sectional study using multistage cluster random-sampling, 2331 schoolchildren with age ranged from 6-13 years old with a female to male ratio of 1.60 were enrolled. Thyroid size was examined by two endocrinologists for goiter detection. Children were considered goitrous if they had palpable or visible goiters according to World Health Organization (WHO)/United Nations children's Fund/International Council for the Control of Iodine Deficiency criteria. Weight and standing height were measured using the standard tools and anthropometric indices were calculated using the WHO AnthroPlus software developed by the World Health Organization. Height-for-age Z-scores (HAZ), weight-for-age Z-scores (WAZ) and body mass index (BMI) for age were calculated for each child. Children with a HAZ, WAZ or BMI-for-age of Z-score < –2.0 were classified as stunted, underweight or thin, respectively. Blood samples were drowned to measure serum thyroid hormones. Results: Overall, 32.9% of subjects were classified as goitrous. Weight, height, BMI, WAZ and BMI-for-age Z-score were significantly lower in children with goiter than in children who did not have goiter (P < 0.05). The prevalence of goiter in thin children was higher than that in non-thin ones (48.4 vs. 31.6%, odds ratio [OR]: 2.02, 95% confidence interval [CI]: 1.52-2.69, P < 0.001). Although 33.4% of non-stunted children were goitrous, 31% of stunted ones had goiter (P = 0.5). According to the logistic regression model taking sex and age as covariates, the only significant parameter affecting palpable goiter detection was thinness (OR = 2.13, 95% CI: 1.22-3.69, P < 0.001). Conclusions: In the present study, we found a high prevalence of goiter in children who were malnourished. It seems that PEM may play a role in the still high prevalence of goiter in this region.
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