Thyroid Dysfunction and Its Association with Glycemic Control in Patients with Type 2 Diabetes Mellitus (T2DM): A Systematic Review and Meta-Analysis.

BACKGROUND

Diabetes mellitus (DM) is characterized by metabolic anomalies, such as hyperglycemia, resulting from pancreatic β-cell dysfunction. In this context, thyroid dysfunction is the second most prevalent endocrine disorder after DM, and the interaction with glycemic control in type 2 diabetes mellitus (T2DM) remains a topic of debate. Therefore, this meta-analysis aimed to evaluate the impact of thyroid dysfunction on glycemic control in T2DM patients.

METHODS

A systematic literature search was conducted using ScienceDirect, the Cochrane Library, and PubMed up to December 8, 2024, under PRISMA guidelines. Research evaluating the effect of thyroid dysfunction on glycemic control in T2DM was included, with Glycated hemoglobin (HbA1c) levels as the primary outcome measure. Furthermore, research lacking relevant outcome data, full-text availability, or appropriate design was excluded. Data extraction and quality assessment were performed collaboratively, using the STROBE checklist. Meta-analysis was conducted using Review Manager 5.4, with mean difference (MD) and 95% confidence intervals (CI) as the effect size. Random-effects models were used to account for anticipated clinical heterogeneity, assessed by Higgins' I-squared (I²) statistic.

RESULTS

The initial search identified 1,397 research studies, with only 3 papers meeting the inclusion criteria. A pooled analysis reported a significant increase in HbA1c levels in T2DM patients with thyroid dysfunction (MD: 1.94, 95% CI: 0.73 - 3.14; p < 0.000001) with high heterogeneity (I² = 98%).

CONCLUSION

Thyroid dysfunction was prevalent in T2DM patients and was associated with poorer glycemic control. Routine thyroid function assessment could also be integrated into T2DM management to optimize metabolic outcomes.