Plain language summary
Hashimoto's thyroiditis (HT), also called chronic lymphocytic thyroiditis, is the most prevalent organ-specific autoimmune disorder as well as the most common cause of thyroid hypofunction. The main purpose of HT treatment is the control of hypothyroidism, including oral administration of a synthetic hormone to achieve normal circulating thyrotropin levels. The aim of this study was to review the association between vitamin D treatment in patients with HT by assessing patients’ serum circulating 25-hydroxyvitamin D - 25(OH)D - level to evaluate whether a change occurs in the course of disease. This study is a systematic review and meta-analysis of seven cohorts of patients from six studies (3 prospective cohort studies and 3 randomised controlled trials). Results show that vitamin D might significantly increase the serum 25(OH)D levels and produce changes in thyroid peroxidase antibodies titres. However, there wasn't a significant association between serum vitamin D supplementation and the levels of thyroid-stimulating hormone, thyroglobulin antibodies, free triiodothyronine and free thyroxine. Authors conclude that their findings suggest that vitamin D is not associated with the function of the thyroid in patients with HT. Thus, further well-designed randomised controlled trials with sufficient sample sizes investigating the effect of vitamin D on thyroid function are still warranted.
Abstract
INTRODUCTION Recent evidence suggested that vitamin D deficiency was associated with Hashimoto's thyroiditis (HT) pathogenesis and thyroid hypofunction. This study aimed to investigate whether vitamin D supplementation would be effective in the prevention and progression of hypothyroidism in patients with HT. METHODS PubMed, Embase and the Cochrane library were searched for randomized controlled trials (RCTs) and prospective cohort studies published from inception to August 2021. RESULTS A total of 7 cohorts of patients from six clinical trials with 258 patients with HT were included. Significant difference was found (WMD = 19.00, 95% CI: 12.43, 25.58, p < 0.001; I2 = 90.0%, pheterogeneity < 0.001) between the vitamin D group and control group in serum 25-hydroxyvitamin D level. And the combined results indicated vitamin D supplementation significantly reduced the level of thyroid peroxidase antibodies (TPO-Ab) compared to the control group (WMD = -158.18, 95% CI: -301.92, -14.45, p = 0.031; I2 = 68.8%, pheterogeneity = 0.007). Whereas no significant differences were found on the levels of thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), free thyroxine (FT4) compared to the control group (p > 0.05). WHAT IS NEW AND CONCLUSION Our study demonstrated that vitamin D treatment might significantly increase the serum 25(OH)D levels and produce changes in TPO-Ab titres. No significant association was found between serum vitamin D treatment and the levels of TG-Ab, TSH, FT3 and FT4, suggesting that vitamin D is not associated with the function of the thyroid in patients with HT.
Methodological quality
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