Vitamin D, selenium in type 2 diabetes and Hashimoto's thyroiditis: Is it effective?

Abstract

The study by Feng et al, explores treatment approaches for these coexisting conditions. It emphasizes the potential advantages of selenium and vitamin D supplementation but also raises methodological and patient selection concerns. Findings indicate a complex interplay between interventions and disease markers, prompting the need for further research. Despite limitations, the study offers valuable insights into managing the intricate relationship between type 2 diabetes mellitus and Hashimoto's thyroiditis. The authors' contributions shed light on potential treatment avenues, although careful consideration of study design and patient characteristics is warranted for future investigations in this domain.

Key Words: Vitamin D; Selenium; Type 2 diabetes Mellitus; Hashimoto’s thyroiditis

Core Tip: A study on vitamin D, selenium, and antidiabetic drugs' role in managing type 2 diabetes mellitus with Hashimoto's thyroiditis: Highlights the potential benefits of selenium and vitamin D supplementation and it need to address concerns about methodology and patient selection. The study prompts further investigation into the relationship between interventions and disease markers, urging caution in interpreting findings. It acknowledges the study's valuable insights but underscores the need for clearer methodology and consideration of potential biases. Overall, it emphasizes the importance of rigorous research in understanding and managing these complex conditions.

TO THE EDITOR

We read with great interest recently published article entitled “Vitamin D, Selenium, and Antidiabetic Drugs in the Treatment of Type 2 Diabetes Mellitus with Hashimoto's Thyroiditis” authored by Feng et al[1]. We wish to express our heartfelt gratitude to the authors for their invaluable contribution through the publication of this retrospective case-control study in your esteemed journal. The study explores the treatment of Hashimoto's thyroiditis and type 2 diabetes mellitus (T2DM), addressing a significant medical challenge for which effective treatment modalities are not readily apparent in the near future.

This retrospective study, encompassing cases and controls across three groups, illuminates the potential benefits of selenium and vitamin D supplementation in individuals with Hashimoto’s thyroiditis (HT) and T2DM. The discussion presents existing knowledge regarding the role of selenium in the pathophysiology of T2DM, highlighting its association with insulin resistance and the deficiency of selenium in this context. Moreover, the established role of selenium in enzymes involved in thyroid hormone metabolism is explored within the context of this study.

This retrospective study, comprising cases and controls across three groups, illuminates the potential benefits of selenium and vitamin D supplementation in individuals with HT and T2DM. The discussion encompasses existing knowledge regarding the role of selenium in the pathophysiology of T2DM, highlighting its association with insulin resistance and the deficiency of selenium in this context. Moreover, the established role of selenium in enzymes involved in thyroid hormone metabolism is explored within the context of this study[2].

Findings from the CROHT Biobank indicate that, while no association between vitamin D levels and HT was observed, in cases of severe disease, vitamin D levels exhibit a slight elevation, albeit not reciprocally[3]. The role of vitamin D in diabetes mellitus remains inconclusive, with some studies suggesting a correlation while others contradict such findings[4]. In this retrospective study, patients in both control and intervention groups are appropriately matched and adjusted for sample size, age, gender, and body mass index, thereby mitigating selection bias and confounding factors.

Despite the thorough efforts made to mitigate potential biases, the article raises several concerns that require further clarification. Specifically, there is a lack of clarity regarding the low iodine diet prescribed and the extent of compliance with the advised diet, as this aspect is not addressed in the methodology. Additionally, the rationale for selecting saxagliptin as the oral antidiabetic drug for the control group is unclear. In test group A, while saxagliptin was mentioned, details regarding other specific oral antidiabetic drugs used and their respective doses were not provided. Furthermore, there is a need for special attention to adverse drug reactions associated with the intervention.

The inclusion criteria specify a thyroid stimulating hormone (TSH) level of < 10 uIU/mL, clearly indicating subclinical hypothyroidism. According to existing literature, the presence of HT and autoantibodies such as anti-thyroglobulin antibodies and anti-thyroid peroxidase antibodies does not necessarily warrant treatment. The natural course of HT typically progresses from a hyperthyroid state to a euthyroid state and then to a hypothyroid state, with the duration of each phase varying greatly among patients[5]. However, the article mentions that the average TSH levels in all three patient groups were 14.5 mIU/L, which contradicts the specified inclusion criteria.

In all three groups, a decrease in TSH values was observed alongside increases in Free T3 and Free T4 levels, although not in uniform proportions. Anti-Thyroid peroxidase antibody and anti-Thyroglobulin antibody titers decreased across all groups. Notably, in test group A, there was a disproportionate decrease in anti TPO antibody titers at the end of the third month, followed by an increase at 6 months. These fluctuations in antibody titers suggest a potential lack of association between treatment interventions and the elevation of free T3 and free T4 levels. Additionally, there is no mention of patients experiencing hypothyroid symptoms, for whom levothyroxine supplementation would represent an evidence-based guideline-recommended treatment modality.

The study would have been strengthened if selenium levels had been measured across the three patient groups for research purposes, as this could have facilitated the establishment of a causal relationship of hemoglobin A1c levels and disease activity in thyroiditis. Nonetheless, this study has provided valuable insights and raised pertinent research questions that serve as motivation for further investigation in this domain.

During the assessment of the intervention's effects on low density lipoproteins-cholesterol (LDL-C) levels, a consistent increase in LDL-C levels was noted across the three patient cohorts. Of particular interest, however, was the relatively subdued elevation of LDL-C levels in control group compared with both test groups A and B. Notably, group B exhibited the most significant increase compared with to both Group A and the control group. This unforeseen rise in LDL-C levels warrants thorough discussion, and further trials involving larger population samples are imperative before establishing a causal relationship or affirming the positive effects of vitamin D and selenium in T2DM.

In closing, we extend our heartfelt appreciation to the authors for generously sharing their expertise and research endeavors, particularly concerning interventions with nutritional supplements in the intricate landscape of T2DM and autoimmune conditions such as HT.