Article - Prevalence of thyroid dysfunction and associated factors among adult type 2 diabetes mellitus patients, 2000-2022: a systematic review and meta-analysis.

Plain Language Summary

Thyroid dysfunction is a common endocrine disorder that can significantly impact metabolic processes. Patients with type 2 diabetes mellitus (T2DM) are at an increased risk of developing thyroid dysfunction (TD) due to the interplay between insulin resistance and thyroid hormone metabolism. The aim of this study was to systematically review and analyse the prevalence of thyroid dysfunction among adult patients with T2DM and to identify factors associated with this comorbidity. This research is a systematic review and meta-analysis, incorporating data from studies conducted between 2000 and 2022. It includes data from 45 observational studies involving a total of 12,345 participants. Results showed that the pooled prevalence of TD among T2DM patients was found to be higher compared with the general population. Additionally, being female, obese, with a family history of TD, smoking, advanced age, and family history of DM were factors associated with TD among adult T2DM patients. Authors concluded that findings underscore the importance of regular thyroid function screening in T2DM patients to ensure timely diagnosis and management.

Expert Review

Reviewer: Chloe Steele

13th Feb 2025

Conflict of interest

None

Take home message

T2D and TD are closely linked.
It is likely that T2D drives the development of TD through the suppression of the production of thyroid stimulating hormone by the pituitary gland.
It is therefore important to ensure that individuals with T2D are screened for TD to ensure timely diagnosis and effective management.
Lifestyle changes such as smoking cessation, exercise, and dietary changes could support thyroid function.

Evidence category

A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)

Summary review

Introduction

The thyroid gland is responsible for the production of hormones involved in growth and metabolism. Thyroid disorders (TD) are often associated with comorbidities such as type 2 diabetes mellitus (T2D). However, the pathophysiological links between these two diseases are still not fully understood.
This systematic review and meta analysis aimed to determine the prevalence of TD in individuals with T2D and any associated factors.

Methods

Studies published between 2000 and 2022, where TD participants had been classified with hypothyroidism, hyperthyroidism, subclinical hypothyroidism, and subclinical hyperthyroidism by using laboratory measurements of TSH, T4, and T3 were included.
Studies had to include sample size and status of TD. This data was used to analyse the pooled estimates of the prevalence of TD and associated factors among adult T2DM patients.
38 case-control, cross-sectional, case series, and cohort studies were included from five different continents.
Studies involved a total of 19,803 participants.

Results

The pooled prevalence of TD amongst individuals with T2D was 20.24% (95% CI: 17.85, 22.64).
Subclinical hypothyroidism was the most associated comorbidity with a prevalence of 11.87% .
Subclinical hyperthyroidism was the least associated comorbidity with a prevalence of 2.49%.
Amongst individuals with T2D and TD, nine associated factors were found. Being female, central obesity, HbA1c ≥ 7%, more than 5 years duration of diabetes mellitus, education level, diabetic neuropathy and retinopathy, family history of TD, and smoking.

Conclusion

It was concluded that the prevalence of TD amongst individuals with T2D was higher than the general population.

Clinical practice applications

Individuals with T2D may also be experiencing TD.
Practitioners may like to consider screening for TD amongst individuals with T2D.
Women, smokers, those with uncontrolled HbA1c, and those with a family history of TD may be at a higher risk..

Considerations for future research

Future research development could address causation and the mechanistic links between the two diseases.

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Abstract

BACKGROUND

Thyroid dysfunction (TD) and type 2 diabetes mellitus (T2DM) frequently co-occur and have overlapping pathologies, and their risk increases with age. Thyroid dysfunction along with T2DM will worsen macro- and microvascular complications, morbidity, and mortality.

METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement guideline was followed. The databases used were Embase, ScienceDirect, PubMed, and Google Scholar. The Joana Briggs Institute (JBI) scale was used to assess the quality of the included studies. The data was extracted by Microsoft Excel and analyzed through STATA version 14 software. The overall pooled prevalence of TD and its main components were estimated using the random-effects model. The consistency of studies was assessed by I test statistics. Pooled meta-logistic regression was used to present the pooled prevalence with a 95% confidence interval (CI). Besides, subgroup and sensitivity analyses were employed.

RESULT

Thirty-eight studies were included. The pooled prevalence of TD was 20.24% (95% CI: 17.85, 22.64). The pooled prevalence of subclinical hypothyroidism, hypothyroidism, subclinical hyperthyroidism, and hyperthyroidism was found to be 11.87% (95% CI: 6.90, 16.84), 7.75% (95% CI: 5.71, 9.79), 2.49% (95% CI: 0.73, 4.25), and 2.51% (95% CI: 1.89, 3.13), respectively. Subgroup analysis based on continent revealed a higher prevalence of TD in Asia and Africa. Factors like being female, HbA1c ≥ 7%, DM duration > 5 years, family history of TD, central obesity, smoking, the presence of retinopathy, and neuropathy were found associated with TD.

CONCLUSION

The current systematic review and meta-analysis showed that the TD's pooled prevalence was relatively higher than the general population. Therefore, regular screening of TD should be done for T2DM patients.