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Biol Trace Elem Res (2015) 167:194199 DOI 10.1007/s12011-015-0310-y
Plasma Selenium Levels in First Trimester Pregnant Women with Hyperthyroidism and the Relationship with Thyroid Hormone Status
Tugba Atilan Arikan1
Received: 21 January 2015 /Accepted: 10 March 2015 /Published online: 22 March 2015 # Springer Science+Business Media New York 2015
Abstract The thyroid gland has the highest selenium (Se) concentration per unit weight among all tissues. The aims of the present study were to evaluate the Se levels in the plasma of hyperthyroidic pregnant women and to investigate the association between maternal plasma Se concentrations and thyroid hormone levels. The study population consisted of 107 pregnant women, 70 healthy pregnant women (group 1) and 37 pregnant women with hyperthyroidism (group 2). The plasma free triiodothyronine (fT3) and free thyroxine (fT4) levels were significantly higher, and the plasma thyroid-stimulating hormone (TSH) and Se levels were significantly lower in group 2 than in group 1 (p<0.05). A correlation analysis showed a positive correlation between Se and fT4 in group 1 and with TSH in group 2 (p<0.05). Decreased maternal serum antioxidant trace element Se in hyperthyroidic pregnant women compared with normal pregnant women supported the hypothesis that hyperthyroidism was associated with decreased antioxidant response.
essential trace element that is important for human health [1]. Studies of Se typically begin with the characterization of the first mammalian enzyme containing the unusual amino acid selenocysteine (SeCys) in its catalytic center and cellular glutathione peroxidase (GPx) [2, 3]. The main selenoprotein families are the GPx genes (seven genes), the thioredoxin reductase (TRx) genes (three genes), and the iodothyronine deiodinases (IDIs) (three genes) [25]. After the identification of type-1 5-deiodinase (DI) as a SeCys-containing enzyme and the confirmation of the same connection in all three IDIs, Se was associated with thyroid functioning [6, 7]. During the iodination process and the conversion of thyroxine (T4) to triiodothyronine (T3), SeCys has a dominant role that underlines the dependency of DI activity on Se levels. The key step in the activation of thyroid hormones is the monodeiodination of T4 to 3,3,5-T3 by Se-containing DIs (DI-1, DI-2) [8, 9]. Based on the evidence, the pathological expression of DIs has been found in several severe disorders of thyroid hormone metabolism, such as Graves disease and hypothyroidism [10, 11].