Selenium deficiency as a possible contributor of goiter in schoolchildren of Isfahan, Iran

The relationship between maternal thyroid volume, TSH levels, and Healthy Eating Index scores in BMI-matched pregnant women with hyperemesis gravidarum

OBJECTIVE

The aim is to investigate the relationship between thyroid volume measurement and healthy nutrition questionnaire scoring in pregnant women diagnosed with hyperemesis gravidarum (HEG).

METHODS

One hundred and fifty pregnant women with a BMI of 15-25 kg/m² and between the ages of 17 and 42 who were diagnosed with HEG at 11-14 weeks of gestation were included in the study. Patients with a history of any disease, drug use, and previously diagnosed eating disorders were excluded. All patients were subjected to the Healthy Eating Index (HEI) questionnaire. The cutoff value for HEI score was determined as 80 points. Patients were evaluated in two groups: group 1 (HEI <80 score) and group 2 (HEI ≥80 score). Complete urine analysis including ketonuria, and thyroid function tests including TSH, T3, and T4 levels were performed for all patients. In addition, the thyroid gland volume of every patient was measured by the same radiologist.

RESULTS

Increased thyroid gland volume was significantly associated with lower TSH levels (p = .02) and lower HEI scores (p < .001). On the other hand, it was not significantly associated with ketonuria (p = .47), and parity status (p = .82).

CONCLUSIONS

In our study, we found that there may be an increase in thyroid volume in pregnant women with HEG with lower TSH levels and eating scores. Thyroid volume may predict the patients with probable eating disorders and further studies on thyroid volume in patients with HEG may contribute to the literature.

Selenium inadequacy hampers thyroid response of young children after iodine repletion

Selenium (Se) is an integral component of iodothyronine deiodinase, glutathione peroxidase and thioredoxin reductase enzymes and thus is important for normal thyroid function. This study investigated the influence of Se inadequacy on thyroid response of iodine-replete young children. Serum thyroxine (T₄), triiodothyronine (T₃), thyroglobulin (Tg), thyroid stimulating hormone (TSH), and Se were analyzed in 54-60 mo old children (n = 628) from the Amhara region of Ethiopia before salt iodization was commenced; analyses were repeated (n = 555) 15 mo after iodized salt became available. Iodized salt coverage increased from 12.2% to 91.6% of households. Median urinary iodine concentration (UIC) among children increased from 9 μg/l to 167 μg/l (p < 0.001). In addition, all thyroid indices except T₃ showed significant improvement (p < 0.05). Nearly, half of the study children (49.1%) had Se inadequacy (serum Se < 70 μg/l). Serum Se was significantly correlated with T₃ (r = 0.38, p < 0.001), T₄ (r = 0.15, p < 0.001), TSH (r=-0.205, p < 0.001) and Tg (r= -0.11, p < 0.01) concentrations 15 mo after iodine repletion; baseline serum Se and T₄(r= -0.22, p < 0.01) were inversely correlated. Despite adequate iodine status, children with low serum Se had lower serum T₄ (p = 0.003) and T₃(p < 0.001) but higher TSH concentration (p = 0.003). In the partial least square regression model, Se was among the latent variables significantly explaining T₄ and T₃. Results of the present study suggest that Se inadequacy negatively affects the thyroid metabolism of iodine-replete children and may present a substantial public health concern thus emphasize the need to consider correction of Se status for normal thyroid function as well as for benefits from its diverse biological roles.

Association of serum selenium with thyroxin in severely iodine-deficient young children from the Amhara region of Ethiopia

BACKGROUND/OBJECTIVES

Selenium (Se) as part of glutathione peroxidase and iodothyronine deiodinase enzymes influences thyroid metabolism. This study investigated the association of serum Se levels with thyroid metabolism of severely iodine-deficient young children from the Amhara region of Ethiopia.

SUBJECTS/METHODS

In a cross-sectional study, Se, thyroid-stimulating hormone, total thyroxin, total triiodothyronine and thyroglobulin in serum of children (N=628) 54-60 months of age from the Amhara region, Ethiopia, were analyzed. In addition, iodine in urine and household salt was analyzed, and the presence of goiter was assessed.

RESULTS

The median serum Se concentration was 61.4 μg/l (10.7-290.9 μg/l). Selenium deficiency (serum Se <70 μg/l) was detected in 57.8% (N=349) of the children. The median urinary iodine concentration (UIC) was 9.8 μg/l. The majority (86.6%, N=449) of children had UIC below the recommended value (100 μg/l). In addition, 59.8% (N=310) of children were severely iodine deficient (UIC<20 μg/l). Only 12.7% of salt samples had iodine. Goiter was present in 44.6% (N=280) of the children. Selenium-deficient children had higher serum thyroxin (T4) than children with normal serum Se concentration (P<0.001).

CONCLUSIONS

Serum Se was negatively associated with T4 level in young children from the Amhara region of Ethiopia and may endanger the effectiveness of the salt iodization program.

Selenium and its relationship with selenoprotein P and glutathione peroxidase in children and adolescents with Hashimoto's thyroiditis and hypothyroidism

The essential trace element selenium (Se) is required for thyroid hormone synthesis and metabolism. Selenoproteins contain selenocysteine and are responsible for biological functions of selenium. Glutathione peroxidase (GPx) is one of the major selenoproteins which protects the thyroid cells from oxidative damage. Selenoprotein P (SePP) is considered as the plasma selenium transporter to tissues. The aim of this study was to evaluate serum Se and SePP levels, and GPx activity in erythrocytes of children and adolescents with treated Hashimoto's thyroiditis, hypothyroidism, and normal subjects. Blood samples were collected from 32 patients with Hashimoto's thyroiditis, 20 with hypothyroidism, and 25 matched normal subjects. All the patients were under treatment with levothyroxine and at the time of analysis all of the thyroid function tests were normal. GPx enzyme activity was measured by spectrophotometry at 340 nm. Serum selenium levels were measured by high-resolution continuum source graphite furnace atomic absorption. SePP, TPOAb (anti-thyroid peroxidase antibody), and TgAb (anti-thyroglobulin antibody) were determined by ELISA kits. T4, T3, T3 uptake and TSH were also measured. Neither GPx activity nor SePP levels were significantly different in patients with Hashimoto's thyroiditis or hypothyroidism compared to normal subjects. Although GPx and SePP were both lower in patients with hypothyroidism compared to those with Hashimoto's thyroiditis and normal subjects but the difference was not significant. Serum Se levels also did not differ significantly in patients and normal subjects. We did not find any correlation between GPx or SePP with TPOAb or TgAb but SePP was significantly correlated with Se. Results show that in patients with Hashimoto's thyroiditis or hypothyroidism who have been under treatment with levothyroxine and have normal thyroid function tests, the GPx, SePP and Se levels are not significantly different.

Iodine, copper, zinc, selenium and molybdenum levels in children aged between 6 and 12 years in the rural area with iodine deficiency and in the city center without iodine deficiency in Hatay

AIM

Thyroid diseases related with iodine deficiency are observed commonly in our country and in the world. In this study, we aimed to investigate iodine deficiency in urine and selenium, zinc, copper or molybdenum deficiency which may accompany this in children aged between 6 and 12 years in two schools in the province of Hatay (endemic goitre region).

MATERIAL AND METHODS

This study is a case-control field-study in which students aged between 6 and 12 years were included. One hundred fourteen subjects from the village of Tanışma related to the center of our province and 100 subjects from the city center of Hatay (Antakya) were included in the study. Iodine, selenium, zinc, copper and molybdenum levels were measured in the urine samples of the students included in the study.

RESULTS

Iodine deficiency was found with a severe (5%), moderate (18.4%) and mild degree (43%), respectively in the village of Tanışma. Mild iodine deficiency (7%) was found in the center of Hatay. No moderate and severe iodine deficiency was found in the control group. A significant difference was found between the groups in terms of urine iodine excretion (p<0.001). A significant correlation was found between the levels of iodine, selenium, zinc and molybdenum (p<0.05). A moderately positive correlation was found between iodine and selenium (p<0.001). A moderately positive correlation was found between iodine and zinc levels (p<0.001) and a weak correlation was found between iodine and molybdenum (p<0.01). No significant correlation was found between iodine level and copper level (p>0.05).

CONCLUSIONS

Selenium and zinc deficiency may accompany iodine deficiency. Selenium and zinc deficiency should be considered in individuals who are found to have iodine deficiency especially in endemic goitre regions.

Selenium supplementation in thyroid associated ophthalmopathy: an update

The therapeutic effect of selenium (Se) has already been proven in thyroid disease and thyroid associated ophthalmopathy (TAO). In spite of clear scientific proof of its benefits in TAO, there appears to be no clear agreement among the clinicians regarding its optimum dose, duration of the treatment, efficacy and safety to date. In this review, the author summarises the findings of 135 English language articles published on this subject over the past four decades from 1973 to 2013. The regulation and metabolism of thyroid hormones require a steady supply of Se and recent studies have revealed several possible mechanisms by which Se improves the severity of thyroid disease and TAO. These mechanisms include 1) inhibitory effect of HLA-DR molecule expression on thyrocytes; 2) profound reductions of thyroid stimulating hormone (TSH) receptor antibodies (TSHR-Ab) and TPO antibodies (TPO-Ab); 3) prevention of dysregulation of cell-mediated immunity and B cell function; 4) neutralising reactive oxygen species (ROS) and inhibition of redox control processes required for the activation, differentiation and action of lymphocytes, macrophages, neutrophils, natural killer cells involved in both acute and chronic orbital inflammation in TAO; 5) inhibition of expression of pro-inflammatory cytokines and 6) inhibition of prostaglandin and leukotriene synthesis. An increased oxidative stress has been observed in both acute and chronic phases of thyroid disease with raised tissue concentrations of ROS. The benefits of Se supplementation in individuals with TAO appear to be proportionate to the degree of systemic activity of the thyroid disease. The maximal benefit of Se supplementation is therefore seen in the subjects who are hyperthyroid. Restoration of euthyroidism is one of the main goals in the management of TAO and when anti-thyroid drugs are combined with Se, the patients with Graves' disease (GD) and autoimmune thyroiditis (AIT) achieved euthyroidism faster than those treated with anti-thyroid drugs alone. Se status of normal adult humans can vary widely and Se supplementation may confer benefit only if serum Se levels are insufficient. The author recommends that serum Se levels of patients with TAO to be assessed prior to and during Se supplementation at regular intervals to avoid potential iatrogenic chronic Se overdose.

Thyroid volume, goiter prevalence, and selenium levels in an iodine-sufficient area: a cross-sectional study

Background

Selenium (Se) is a necessary element for the biosynthesis of thyroid hormones. We investigated the relationship between selenium status, thyroid volume, and goiter in a cross-sectional study in an iodine-sufficient area.

Methods

We selected residents of Chengdu (over 18 years old and living in the city for more than 5 years) using a stratified cluster sampling technique. Fifteen hundred subjects were selected for the study, which involved a questionnaire survey, physical examination, thyroid ultrasound, serum thyroid function test, and determination of serum selenium level. Thyroid volume was calculated from the thickness, width, length, and a corrective factor for each lobe. Ultimately, 1,205 subjects completed the investigation and were included in our study. Additionally, 80 school-age children were selected to provide urine samples for urinary iodine analysis. We analyzed the data using appropriate nonparametric and parametric statistical tests.

Results

The median urinary iodine value was 184 μg/L in school-age children, indicating iodine sufficiency. The median serum selenium level of the 1,205 subjects was 52.63 (interquartile range [IQR] : 40.40-67.00) μg/L. The median thyroid volume was 9.93 (IQR: 7.71-12.57) mL; both log-transformed serum selenium and log-transformed thyroid volume were Gaussian distributions (P = .638 and P = .046, respectively). The prevalences of goiter and thyroid nodules were 8.8% and 18.6%. The prevalences of positive thyroid autoantibodies, thyroperoxidase autoantibodies and thyroglobulin autoantibodies were 16.7%, 12.0%, and 11.1%, respectively. In the general linear regression model, there were positive associations between serum selenium and age, and body mass index. We found no association between serum selenium and thyroid-stimulating hormone. In simple linear regression analyses, we found no association between thyroid volume and serum selenium. There were no significant differences in serum selenium between persons with or without goiter. Serum selenium was not a risk factor for goiter.

Conclusion

In our study population, serum selenium was neither associated with thyroid volume nor with goiter in an iodine-sufficient area. More studies should be conducted by following non-goitrous persons over time and monitoring their selenium status.

The role of thyroid autoantibodies in the etiology of endemic goiter in schoolchildren of Isfahan, Iran

BACKGROUND

Eleven years after the initiation of universal salt iodization program in Iran, the prevalence of goiter is still high in some areas.

AIM

To investigate the role of thyroid autoimmunity in the etiology of residual goiter in schoolchildren of Isfahan, Iran.

MATERIAL AND METHODS

In a cross-sectional study, 2331 schoolchildren were selected by multi-stage random cluster sampling. Thyroid size was estimated in each child by inspection and palpation. Urinary iodine concentration (UIC), serum anti-thyroperoxidase antibody (anti-TPO Ab), and anti-thyroglobulin antibody (Anti-Tg Ab) were measured.

RESULTS

Overall, 32.9% of children had goiter. The median UIC was 1955.5 microg/dl. There was significant difference in prevalence of positive anti-TPO Ab in goitrous (grade 2) and non-goitrous children (9.7 vs 3.7%, p= 0.02). Goitrous children had higher prevalence of positive anti-Tg Ab than non-goitrous ones (15.1 vs 3.1%, p<0.001).

CONCLUSIONS

According to the present study, goiter is still a public health problem in this region. This study suggests that thyroid autoimmunity is among the contributors of goiter persistence after elimination of iodine deficiency in Isfahan.