Exploring the bidirectional association between thyrotropin and thyroid hormones in type 2 diabetes: a systematic...

Type 2 diabetes mellitus (T2DM) and thyroid dysfunction are some of the most prevalent endocrine disorders globally. Previous studies on the association and effect of thyroid hormones in patients with diabetes have yielded contradictory results. Therefore, this meta-analysis comprehensively examined the latest evidence regarding the bilateral association between thyrotropin and thyroid hormone levels in T2DM.

A thorough search across multiple databases was conducted to investigate the bidirectional relationship between thyroid hormones and T2DM. Two researchers independently performed data extraction and study quality was assessed using the Newcastle-Ottawa scale, with prevalence, odds ratios, and hazard ratios calculated using a random-effects model.

After screening 4159 studies, 36 were deemed eligible based on the inclusion criteria. A one-unit increase in serum thyroid-stimulating hormone (TSH) level was associated with a 2.49-fold increased odds of T2DM (OR: 2.49, 95%CI: 1.97-3.0). Similarly, a one-unit increase in Triiodothyronine (FT3) levels was associated with a 17% (HR:1.17,95%CI: 1.07-1.26) increased risk of T2DM. The pooled risk estimates of T2DM were 3.63 (95%CI: 1.63-8.09) for hypothyroidism, and 16.33 (95%CI: 7.59-35.12) for overt hypothyroidism. Individuals with thyroid dysfunction exhibited significantly higher HbA1c levels (Hedges'g: - 0.26, 95% CI: - 0.47 to - 0.06) and fasting plasma glucose (FPG) levels (Hedges'g: - 0.33, 95% CI: - 0.61 to - 0.05) compared to those with normal thyroid function.

Thyroid dysfunction, including both overt and subclinical hypo- and hyperthyroidism, significantly increases the risk of T2DM. Elevated TSH and FT3 levels are linked to higher diabetes risk, highlighting the need for regular thyroid screening and integrated clinical management.

The online version contains supplementary material available at 10.1007/s40200-025-01612-w.