The relationship between iron status and thyroid hormones in adolescents living in an iodine deficient area

Celiac Disease and the Thyroid: Highlighting the Roles of Vitamin D and Iron

Celiac disease (CD) and autoimmune thyroid diseases (AITD) like Hashimoto’s thyroiditis (HT) and Graves’ disease (GD) frequently coexist, entailing numerous potential impacts on diagnostic and therapeutic approaches. Possible correlations might exist through gut microbiota, regulating the immune system and inflammatory responses, promoting autoimmune diseases, as well as shared cytokines in pathogenesis pathways, cross-reacting antibodies or malabsorption of micronutrients that are essential for the thyroid like iron or vitamin D. Vitamin D deficiency is a common finding in patients with AITD, but might protect from autoimmunity by wielding immunoregulatory and tolerogenic impacts. Additionally, vitamin D is assumed to be involved in the onset and progression of CD, presumably plays a substantial protective role for intestinal mucosa and affects the thyroid via its immunomodulatory effects. Iron is an essential micronutrient for the thyroid gland needed for effective iodine utilization by the iron-dependent enzyme thyroid iodine peroxidase (TPO). Despite being crucial for thyroid hormone synthesis, iron deficiency (ID) is a common finding in patients with hypothyroidism like HT and is frequently found in patients with CD. A literature research was conducted to examine the interplay between CD, AITD, vitamin D and iron deficiency. This narrative review highlights the relevant correlation of the two disease entities CD and AITD, their reciprocal impact and possible therapeutic options that should be further explored by future studies.

The Influence of Iron Depletion and Chronic Energy Deficiency on the Risk of Hypothyroidism in Pregnant Women Living in Iodine Deficiency Disorders Endemic Areas in Badegan Ponorogo District East Java, Indonesia

Several minerals are needed for thyroid hormone to work properly, such as iodine and iron. Iron is one of important essential trace elements that serves as co-factor for thyroid peroxidase (TPO). Those with iron deficiency have lower ferritin serum level than those who are normal. In particular, pregnant women with chronic energy deficiency (CED) have higher anemia risk than the otherwise. The study aimed to measure ferritin level, CED and hypothyroidism among pregnant women living in iodine deficiency disorders (IDD) endemic areas. A total of 37 pregnant women aged 18-45 y-oldwith pregnancy of 2 to 8 mo living in ID Dendemic of Dayakan and Watu Bonang Villages of Ponorogo District were include dinthestudy. Two different measurements were taken namely, anthropometric measurement of mid-upper arm circumference (MUAC) or upper circumference (UAC) which is more correct term to use, and blood markers of iodine and iron status were assessed using thyroid stimulating hormone (TSH), free thyroxine (fT4), and bloodferritin. Among pregnant women, 27% had hypothyroidism and 54.05% had iron depletion, with 30% had both conditions. The hypothyroidism was higher in pregnant women had CED than those non-CED, 50% vs. 18.5%. No significant correlation (p≥0.05) between hypothyroidism and both ferritin and CED, but adjusted odds ratio (AOR) was found at 7.7 (95% CI: 1.2-52.9), indicated more than four times higher risk of hypothyroidism in pregnant women with CED than the otherwise. Hypothyroidism in pregnant women living in Ponorogo was not caused by iron deficiency, but allegedly by lack of other nutritional intake. Conclusion: Integrated and sustainable efforts to improve nutritional status is needed since pre-conception and throughout pregnancy.

Micronutrients, iodine status and concentrations of thyroid hormones: a systematic review

Context

The metabolism of thyroid hormones, which are essential for normal development, involves many proteins and enzymes. It requires iodine as a key component but is also influenced by several other micronutrients, including selenium, zinc, iron, and vitamin A.

Objective

This systematic review was designed to investigate the effect of micronutrient status and supplementation on iodine status and thyroid hormone concentrations.

Data Sources

Using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guidelines, electronic databases were searched from their inception to April 2016.

Study Selection

Human studies published in English and reporting data on micronutrient status and iodine status and/or thyroid hormone concentrations were included. Studies that examined the effect of micronutrient supplementation on iodine status and/or thyroid hormone concentrations were also included.

Data Extraction

A predesigned and piloted data extraction form was used to compile data from individual studies.

Results

A total of 57 studies were included: 20 intervention studies and 37 observational studies. Although observational evidence suggests that concentrations of selenium, zinc, and iron are positively associated with iodine status, data from randomized controlled trials fail to confirm this relationship.

Conclusions

Further studies are needed to provide greater understanding of the role of micronutrient status in iodine nutrition and thyroid function to ascertain the public health implications for populations worldwide.

Association of exposure to multiple metals with papillary thyroid cancer risk in China

Papillary thyroid cancer (PTC) has inflicted huge threats to the health of mankind. Metal pollution could be a potential risk factor of PTC occurrence, but existing relevant epidemiological researches are limited. The current case-control study was designed to evaluate the relationships between exposure to multiple metals and the risk of PTC. A total of 262 histologically confirmed PTC cases were recruited. Age- and gender-matched controls were enrolled at the same time. Urine samples were used as biomarkers to reflect the levels of environmental exposure to 13 metals. Conditional logistic regression models were adopted to assess the potential association. Single-metal and multi-metal models were separately conducted to evaluate the impacts of single and co-exposure to 13 metals. The increased concentration of urinary Cd, Cu, Fe, and Pb quartiles was found significant correlated with PTC risk. We also found the decreased trends of urinary Se, Zn, and Mn quartiles with the ORs for PTC. These dose-response associations between Pb and PTC were observed in the single-metal model and remained significant in the multi-metal model (OR_25-50th=1.39, OR_50-75th=3.32, OR_>75th=7.62, p for trend <0.001). Our study suggested that PTC was positively associated with urinary levels of Cd, Cu, Fe, Pb, and inversely associated with Se, Zn, and Mn. Targeted public health policies should be made to improve the environment and the recognition of potential risk factors. These findings need additional studies to confirm in other population.

Multiple Nutritional Factors and the Risk of Hashimoto's Thyroiditis

BACKGROUND

Hashimoto's thyroiditis (HT) is considered to be the most common autoimmune disease. It is currently accepted that genetic susceptibility, environmental factors, and immune disorders contribute to its development. With regard to nutritional factors, evidence implicates high iodine intake and deficiencies of selenium and iron with a potential relevance of vitamin D status. To elucidate the role of nutritional factors in the risk, pathogenesis, and treatment of HT, PubMed and the Cochrane Library were searched for publications on iodine, iron, selenium, and vitamin D and risk/treatment of HT.

SUMMARY

Chronic exposure to excess iodine intake induces autoimmune thyroiditis, partly because highly iodinated thyroglobulin (Tg) is more immunogenic. Recent introduction of universal salt iodization can have a similar, though transient, effect. Selenoproteins are essential to thyroid action. In particular, the glutathione peroxidases protect the thyroid by removing excessive hydrogen peroxide produced for Tg iodination. Genetic data implicate the anti-inflammatory selenoprotein S in HT risk. There is evidence from observational studies and randomized controlled trials that selenium/selenoproteins can reduce thyroid peroxidase (TPO)-antibody titers, hypothyroidism, and postpartum thyroiditis. Iron deficiency impairs thyroid metabolism. TPO, the enzyme responsible for the production of thyroid hormones, is a heme (iron-containing) enzyme which becomes active at the apical surface of thyrocytes only after binding heme. HT patients are frequently iron deficient, since autoimmune gastritis, which impairs iron absorption, is a common co-morbidity. Treatment of anemic women with impaired thyroid function with iron improves thyroid-hormone concentrations, while thyroxine and iron together are more effective in improving iron status. Lower vitamin D status has been found in HT patients than in controls, and inverse relationships of serum vitamin D with TPO/Tg antibodies have been reported. However, other data and the lack of trial evidence suggest that low vitamin D status is more likely the result of autoimmune disease processes that include vitamin D receptor dysfunction.

CONCLUSIONS

Clinicians should check patients' iron (particularly in menstruating women) and vitamin D status to correct any deficiency. Adequate selenium intake is vital in areas of iodine deficiency/excess, and in regions of low selenium intake a supplement of 50-100 μg/day of selenium may be appropriate.

Association between iron status and thyroid function in Nepalese children

Background

Deficiencies of iodine and iron may have adverse effect on thyroid function. This study was undertaken to investigate the association between iron status and thyroid function in Nepalese children living in hilly regions.

Methods

A cross-sectional study was conducted among 227 school children aged 6–12 years living in hilly regions of eastern Nepal. Urine and blood samples were analyzed for urinary iodine concentration, free thyroxine, free triiodothyronine, thyroid stimulating hormone, hemoglobin, serum iron and total iron binding capacity, and percentage transferrin saturation was calculated.

Results

The cohort comprised euthyroid (80.6 %, n = 183), overt hypothyroid (1.3 %, n = 3), subclinical hypothyroid (16.3 %, n = 37) and subclinical hyperthyroid (1.8 %, n = 4) children respectively. About 35.2 % (n = 80) children were anemic, 43.6 % (n = 99) were iron deficient and 19.8 % (n = 45) had urinary iodine excretion < 100 μg/L. Hypothyroidism (overt and subclinical) was common in anemic and iron deficient children. The relative risk of having hypothyroidism (overt and subclinical) in anemic and iron deficient children was 5.513 (95 % CI: 2.844−10.685, p < 0.001) and 1.939 (95 % CI: 1.091-3.449, p = 0.023) respectively as compared to non-anemic and iron sufficient children. Thyroid stimulating hormone had significant negative correlation with hemoglobin (r = −0.337, p < 0.001) and transferrin saturation (r = −0.204, p = 0.002).

Conclusions

Thyroid dysfunction, iron deficiency and anemia are common among Nepalese children. In this cohort, anemic and iron deficient children had poor thyroid function.

The Influence of Iron Status on Iodine Utilization and Thyroid Function

Despite significant progress, deficiencies of iron and iodine remain major public health problems affecting > or =30% of the global population. These deficiencies often coexist in children. Recent studies have demonstrated that a high prevalence of iron deficiency among children in areas of endemic goiter may reduce the effectiveness of iodized salt programs. These findings argue strongly for improving iron status in areas of overlapping deficiency, not only to combat anemia but also to increase the efficacy of iodine prophylaxis. The dual fortification of salt with iodine and iron may prove to be an effective and sustainable method to accomplish these important goals.

Iron deficiency in goitrous schoolchildren of Semirom, Iran

BACKGROUND

Iodine deficiency produces the spectrum of iodine deficiency disorders (IDDs): endemic goiter, hypothyroidism, cretinism, and congenital anomalies. Other factors, including goitrogens and micronutrient deficiencies, may influence the prevalence and severity of IDDs and response to iodine supplementation. This cross-sectional, descriptive study was performed in 2003 on elementary school children of Semirom, a mountainous region of Iran, where goiter was hyper-endemic in 1994, but the goiter prevalence had not decreased as expected many years after salt iodization and iodine injection. Some possible risk factors associated with goiter in that area were evaluated, and the results of iron study are presented here.

METHODS

1,869 cases were selected by a multistage cluster sampling procedure. Grade 2 goitrous children were compared with equal number of nongoitrous children for serum iron, ferritin, transferrin, thyroxin, TSH and urine iodine concentrations (UIC).

RESULTS

210 children (105 goiter grade 0 and 105 goiter grade 2) entered this sub-study. Of 210 participants, 70 children had low transferrin saturation, 13 had low serum ferritin and 9 children had both problems. There was no significant difference in goiter rate between children with low iron indices and others. There was no significant correlation between serum iron, ferritin or transferrin saturation with other variables including T4, UIC and goiter stage.

CONCLUSION

The present study reveals that in the area studied, iron deficiency cannot explain the high prevalence of goiter, so other responsible factors should be investigated.

Risk factors for goiter in primary school girls in Qom city of Iran

OBJECTIVE

Goiter is endemic in Iran. The iodine deficiency disorders program was begun a few years ago in Iran, and the coverage of iodized salt is sufficient now. But, in a periodic yearly medical examination of primary school girls in Qom, the prevalence of goiter was above 30% in 2002. This survey was designed to study the risk factors of goiter in those students.

DESIGN

The study was a randomized (multistage, proportional simple random sampling) case-control study.

SUBJECTS AND INTERVENTIONS

We selected and performed thyroid examinations in 1050 girl students in primary schools in Qom city of Iran in 2002. We found 284 cases: girls in primary schools had goiter in accordance with the clinical exam of World Health Organization classification. Among students who did not present with goiter in the clinical exam, we randomly selected 288 students as the control group. We used a questionnaire to evaluate them for the risk factors of goiter.

RESULTS

The mean+/-s.d. ages of cases and controls were 8.7+/-1.3 and 8.9+/-1.3 years, respectively. There is no significant difference between the two groups regarding history of soya, kale, turnip, fish, daily iodized salt usage, education and job of mothers, monthly family income, nationality, immigration and residential situation. By using multinomial logistic regression, we found that storage of iodized salt in open containers, odds ratio (OR): 2.201 (1.412-3.428); P-value <0.0001, medium socioeconomic situation (SES) of family, OR: 2.099 (1.029-4.282), P-value=0.041, district 2 of Qom city, OR: 2.880 (1.376-6.027), P-value=0.005, and district 3 of Qom city, OR: 2.051(1.032-4.078), P-value=0.041, were the major risk factors for goiter in this population.

CONCLUSIONS

In this study, the main risk factors for goiter were storage of iodized salt in open containers, medium SES and also living in specific districts of Qom city. As the coverage of iodinized salt is over 95% in Iran, we advise the education of the family about storage of iodized salt in closed containers. We also recommend the study of the other risk factors of goiter in the different geographical areas of Iran, because of differences in the SES and nutritional habits.

SPONSORSHIP

This study was supported by issuing permission letters for our activities: (not funding support) Qom Health Network and Medical Services, Qom Medical University, Qom Primary School Education Office, Fathemieh Medical University.