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Low selenium intake may increase thyroid disease risk
The risk for thyroid disease is increased in areas of the world with low selenium intake, and increasing selenium intake may reduce this risk in these populations, according to recent findings.
In the cross-sectional, observational study, Bingyin Shi, MD, of The First Affiliated Hospital of Xi’an Jiaotong University Health Science Center in China, and colleagues evaluated data from 6,152 residents of two counties in Shaanxi province, China, to determine whether the prevalence of thyroid disease differed in the two areas. One of these counties, Ziyang (n = 3,038), had adequate soil selenium (Se) and the other, Ningshan (n = 3,114), had low soil Se.
Study participants from these counties were recruited between March and May 2013, and were stratified by soil-Se levels, township location and sex. All individuals aged 18 to 70 years who had lived in the same village for more than 5 years were eligible for inclusion.
The researchers interviewed participants using a 43-item questionnaire addressing demographic data, personal/family history of thyroid disease, medication history, and tobacco and alcohol consumption. Also included was a brief food-frequency questionnaire (FFQ). The FFQ asked about intake of tea, meat, eggs, salt (iodized or noniodized) and seaweed. Participants were clinically examined and underwent thyroid ultrasound and a fasting blood draw.
Participants were defined as having thyroid disease based on measured values of serum thyrotropin, thyroxine, thyroid peroxidase antibodies (TPOAb), thyrotropin-receptor antibody (TRab) concentrations, thyroid volume and thyroid nodule size. The researchers used logistic regression analysis to explore the association between selenium status, dietary factors and pathologic thyroid conditions.
Compared with the low-Se county (57.4 µg/L), the median serum Se concentration was nearly twice as high in the adequate-Se county (103.6 µg/L; P < .05). There was a significantly lower prevalence of pathologic thyroid conditions, including hypothyroidism, subclinical hypothyroidism, autoimmune thyroiditis and enlarged thyroid, in the adequate-Se county vs. the low-Se county (18% vs. 30.5%; P < .001). Higher blood concentrations of Se were correlated with decreased odds of the following: autoimmune thyroiditis (OR = 0.47; 95% CI, 0.35-0.65), subclinical hypothyroidism (OR = 0.68; 95% CI, 0.58-0.93), hypothyroidism (OR = 0.75; 95% CI, 0.63-0.9) and enlarged thyroid (OR = 0.75; 95% CI, 0.59-0.97).
The researchers noted that while these findings would suggest an association between low Se intake and thyroid disease, further analyses are needed to determine whether this link is causal.
“This study is the first large epidemiological investigation of populations that are similar with respect to genetics, culture, lifestyle and iodine status but who live in villages with very different soil-Se concentrations that are reflected in the Se content of local foodstuffs,” the researchers wrote. “As hypothesized, the prevalence of thyroid disease differed markedly between the adequate- and low-Se areas showing a significant association between Se deficiency and disease risk.” – by Jennifer Byrne
Disclosure: The study was funded in part by Mudanjiang Lingtai Pharmaceutical Co. Ltd. The researchers report no relevant disclosures.