Effects Of Selenium Yeast On Antibodies Of Autoimmune Thyroiditis

ObjectiveAutoimmune thyroiditis (AIT) is an organ specific autoimmune disorder, which characterized by lymphocytic infiltration, high thyroid peroxidase and/or thyroglobulin antibody titres. The thyroid status includes euthyroid, subclinical hypothyroidism and overt hypothyroidism. Subclinical autoimmune thyroiditis refers to positive thyroid peroxidase antibodies and with or without subclinical hypothyroidism. Subclinical autoimmune thyroiditis is hazard,as follow:①Every year about 2-4 percent asymptomatic persons progress to overt hypothyroidism who needs life-long treatment of thyroid hormones.②60-70 percent pregnant women with positive thyroid peroxidase antibodies grow in to postpartum thyroiditis,and 20-30 percent postpartum thyroiditis persons develop to permanent hypothyroidism.③Positive thyroid peroxidase antibodies or subclinical hypothyroidism during pregnancy can affect fetal neuropsychological development. Moreover, neuropsychological development maybe delayed if the timely treatments are not given.④Increase the risk of abortion and artificial fertilization. Until now, no treatment has shown efficacy on autoimmune thyroiditis. Only the hypothyroidism can accepted thyroid hormone replacement therapy. Recent evidence has shown that hypothyroidism is significantly correlated with oxidative damage of thyroid. Therefore, supplementation of selenium become an alternative method to treat AIT because selenium has antioxygenation effect. Some investigators reported that the combination of selenium and levothyroxine become an effcetive method to treat autoimmune thyroiditis.We objective to whether selenium supplementation on subclinical autoimmune thyroiditis patients can prevent and delay the progress of hypothyroidism. The present study aimed to explore effects of selenium yeast on antibodies of autoimmune thyroiditis and further investigation on its machanism.Subjects and MethodsThis is a prospective, randomized, double blind, controlled study (the rigistration number is ChiCTR-TRC-00000155). Onehundred and thirty-four patients (range 15-70yrs) with known AIT and elevated serum TPOAb (>300IU/ml) were included and their informed consent to participate in the study was obtained. Patients were randomized into three groups according to their thyroid status,namely euthyroid group, subclinical hypothyroidism group and overt hypothyroidism group.Patients then received either 200μg/d selenium yeast,orally or placebo for 6 months. Serum TSH, free serum T4(FT4), TPOAb, serum Se, IgG subtypes of TPOAb, activities of TSBAb and TSAb were measured at baseline and at the end of each 3-months period during the study.Results1. The median urinary iodine in our study was 182μg/l, indicating the iodine intake in our study was appropriate.2. Basal serum concentrations of Se were found to be within the reference range in all patients,87.79±22.29 (μg/1) of euthyroid group,93.61±23.21 (μ/1) of subclinical hypothyroidism group,92.39±19.87 (μg/1) of overt hypothyroidism group.Se levels increased greatly in all three groups after selenium supplementation and there was no change in placebo groups.3. In euthyroid group, TPOAb levels showed an overall decrease of 4.3% at 3 months and of 12.6% at 6 months after Se supplementation. In overt hypothyroidism group TPOAb values found an overall decrease of 21.9% at 3 months and of 20.4% at 6 months after treatment with selenium yeast plus L-T4. Moreover,2 patients in euthyroid group became negative for TPOAb, as opposed to none in placebo groups.4. The predominant TPOAb IgG subclasses in sera from patients with AIT were IgG1, IgG3, IgG4 and the positive percentage were 72%,41%,72% respectively. The positive rate and concentrations of IgG3 in patients with hypothyroidism and subclinical hypothyroidism were significantly higher than that of euthyroidism (p< 0.05).The concentrations of IgG2 in patients with euthyroidism were significantly higher than those of hypothyroidism. A significant decrease in IgG1 and IgG3 levels were noted in euthyroidism group at 6 months after Se supplementation (p<0.05). Concentrations of IgG3 in subclinical hypothyroidism and IgGl levels in overt hypothyroidism were also reduced significantly compared with that before Se supplementation (p<0.05). There were no changes in levels of IgG4 and the ratio of IgG1/IgG4 in any group after selenium supplementation. In all patients with Se supplementation (n=77),52 patients'TPOAb levels decreased at 6 months, while others' increased or showed no change. The positive percentage and concentrations of IgG1 in patients whose TPOAb levels decreased at 6 months after Se supplementation were greatly higher than those of patients whose TPOAb levels increased (p<0.05).5. The positive rate of TSBAb and TSAb in euthyroid group were 18.8%(12/64), 3.1%(2/64), in subclinical hypothyroidism group were 20%(5/25),4%(1/25) and overt hypothyroidism group were 48.9%(22/45),4.4%(2/45). Activities of TSBAb and TSAb in each group were as follows:(13.94±48.98)% and (92.48±36.30)%, (18.34±43.64)% and (82.87±33.54)%, (41.18±35.17)% and (55.52±55.01)%. The positive rate and activities of TSBAb were statistically higher in overt hypothyroidism group than euthyroid and subclinical hypothyroidism group.After Se supplementation, there was a significant decrease in activities of TSBAb in euthyroid group (p<0.05). The activities of TSBAb were also descent in subclinical hypothyroidism patients, but there was no statistic significance. There was no change in serum TSAb activities in either group.Conclusions1. It appears to be useful as adjunctive therapy with L-T4 in the treatment of AIT. More importantly, our study proves that selenium can influence the natural course of autoimmune thyroiditis by reducing autoantibody titres, especially for subclinical AIT.2. After Se supplementation, the predominant decrease of TPOAb IgG subclasses are IgG1 and IgG3. However, high levels of TPOAb IgGl subclasses may be a factor in the difficulty of TPOAb decline.3. Se may slow the process of subclinical autoimmune thyroiditis to overt hypothyroidism by decreasing the activities of TSBAb in early autoimmune thyroiditis patients.4. In conclusion, Se is beneficial for AIT patients.