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Are probiotics, prebiotics, and synbiotics beneficial in primary thyroid diseases? A systematic review with meta-analysis.
Zawadzka, K, Kałuzińska, K, Świerz, MJ, Sawiec, Z, Antonowicz, E, Leończyk-Spórna, M, Abadi, AK, Trofimiuk-Müldner, M, Bała, MM
Annals of agricultural and environmental medicine : AAEM. 2023;30(2):217-223
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Plain language summary
Irregularities in intestinal microbial composition are thought to be correlated with thyroid dysfunction. Supplementation of prebiotics, probiotics and synbiotics are gaining momentum in recent times in improving health in general. This systematic review of randomised controlled trials was conducted to summarise the up-to-date evidence on the therapeutic potential of prebiotics, probiotics and synbiotics in the treatment of thyroid disease. The meta-analysis did not show beneficial effects on thyroid hormone balance, BMI or levothyroxine dosage reduction. Supplementation with Lactobacillus and Bifidobacterium resulted in improvement in constipation and a statistically non-significant reduction in thyroid-stimulating hormone in adult participants with hypothyroidism. Further robust long-term studies are required to evaluate the efficacy of prebiotics, probiotics and synbiotics in thyroid disease treatment as the availability of the number of studies included in this systematic review was limited. However, healthcare professionals can use the review to understand the current evidence in this area and the correlation between gut microbial alterations and thyroid disease.
Abstract
INTRODUCTION AND OBJECTIVE A number of studies indicate the presence of a thyroid-gut axis and the important influence of the gut microbiota on thyroid function. As prebiotics, probiotics and synbiotics show therapeutic potential in the treatment of intestinal dysbiosis, the aim of this review is to evaluate the efficacy of their supplementation in primary thyroid diseases. REVIEW METHODS Electronic databases (Ovid MEDLINE, Embase, CENTRAL), registers of clinical trials, and grey literature up to 6 October 2022 were searched for randomised controlled trials (RCTs) meeting pre-specified inclusion criteria. The protocol was registered in PROSPERO (CRD42021235054). BRIEF DESCRIPTION OF THE STATE OF KNOWLEDGE After screening 1,721 references, two RCTs were identified, which included 136 hypothyroid participants in total. Meta-analysis of the results after eight weeks of supplementation with predominantly Lactobacillus and Bifidobacterium strains indicated a clinically and statistically nonsignificant decrease in TSH (MD -0.19 mIU/L; 95% CI -0.43 to 0.06; I2= 0%), and no effect on fT3 levels (MD 0.01 pg/mL; 95% CI-0.16 to 0.18; I2= 0%). Data from single studies indicated no significant change in the levels of fT4, thyroid auto-antibodies, BMI, levothyroxine doses, and severity of symptoms measured with validated scales. Only constipation scores showed significant improvement (MD -8.71 points in the Faecal Incontinence Questionnaire; 95% CI -15.85 to -1.57; I2= 0%). SUMMARY Low-certainty evidence from two randomised trials, suggests that routine administration of probiotics, prebiotics or synbiotics may result in little to no benefit in patients with primary hypothyroidism.
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The correlation between selenium levels and autoimmune thyroid disease: a systematic review and meta-analysis.
Zuo, Y, Li, Y, Gu, X, Lei, Z
Annals of palliative medicine. 2021;10(4):4398-4408
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Autoimmune thyroid disease (AITD) encompasses several autoimmune conditions affecting the thyroid gland. Genetics, environmental and lifestyle factors influence the condition. Part of the clinical presentation is an abnormal function of the thyroid and the presence of antibodies against thyroid proteins, such as antithyroglobulin antibody (TGAb) and anti-thyroid peroxidase antibody (TPOAb). Selenium is a trace mineral essential to the human body and an important building block for a particular family of proteins called Selenoproteins. This protein family exerts enzymatic functions and plays a major role in thyroid health, furthermore, also in hormone synthesis and managing oxidative stress. Previous research noted that supplemental selenium had beneficial effects on thyroid hormones and antibodies. This systematic review and meta-analysis sought to collectively examine the effect of selenium supplementation on hormone and antibody levels in people with AITD. Blood values investigated were TSH (thyroid stimulating hormone), FT3 (free triiodothyronine), FT4 (Thyroxine), TPOAb, and TGAb. The review included 17 randomised controlled trials, with a total of 1,095 subjects with AITD, plus controls. The cumulated results demonstrated that selenium can notably decrease blood levels of FT3, FT4, and TPOAb in patients with AITD. However, levels of TSH and TGAb seemed not to be significantly affected by selenium supplementation. The authors highlighted that the review was not specific to a particular AITD and that there was limited literature available concerning TGAb levels. More research is needed to clarify the benefits of selenium in AITD.
Abstract
BACKGROUND This investigation systematically evaluated the selenium levels and the effects of selenium supplementation in patients with autoimmune thyroid disease (AITD). METHODS Randomized controlled trials (RCTs) related to selenium supplementation in patients with AITD were selected from the PubMed, Medline, Web of Sciences, Embase, Cochrane Library, and Spring databases. All related literature published between January 2000 and November 2020 were included. The RCT bias risk assessment was conducted according to the Cochrane Handbook 5.0.2. The Review Manager 5.3 software was applied for meta-analysis of the included literature. RESULTS A total of 17 articles meeting the requirements were selected, including a total of 1,911 subjects. Meta-analysis results showed that the serum free triiodothyronine (FT3) levels in patients was greatly reduced after selenium supplementation compared to placebo treatment (MD =-0.40; 95% confidential interval (CI): -0.70--0.10; Z=2.61; P=0.009). Serum free thyroxine (FT4) levels and anti-thyroid peroxidase antibody (TPOAb) levels were also significantly reduced (MD = -0.76; 95% CI: -1.58--0.07; Z=1.79; P=0.07), and anti-thyroid peroxidase antibody (TPOAb) level was decreased observably (MD =-150.25; 95% CI: -04.06--96.43; Z=5.47; P<0.00001). The thyroid stimulating hormone (TSH) levels (MD =0.06; 95% CI: -0.53-0.66; Z=0.21; P=0.83) and anti-thyroglobulin antibody (TGAb) levels (MD =17.19; 95% CI: -254.86-289.25; Z=0.12; P=0.90) were not significantly different between the experimental group and the control group. CONCLUSIONS Selenium-containing drugs were effective in treating AITD patients, and greatly reduced the levels of FT3, FT4, and TPOAb in AITD patients. These results suggested that selenium level had a great effect on AITD and selenium supplementation showed a very important effect on AITD.