Anti-Thyroid Peroxidase Antibodies and Thyroid-Stimulating Hormone for Risk Stratification of Subclinical Thyroid Dysfunction in Patients With Type 2 Diabetes Mellitus

Background Thyroid dysfunction and autoimmune thyroid disease frequently coexist with type 2 diabetes mellitus (T2DM), yet optimal screening strategies remain uncertain. Anti-thyroid peroxidase antibodies (anti-TPO) may help identify patients at increased risk of thyroid dysfunction before overt biochemical abnormalities occur. This study evaluated the clinical decision-support utility of anti-TPO and thyroid-stimulating hormone (TSH) for risk stratification of subclinical thyroid dysfunction in T2DM. Methods In this matched case–control study, 200 adults with T2DM and 100 age- and sex-matched healthy controls were recruited. Clinical, glycemic, lipid, and thyroid parameters were assessed. Subclinical hypothyroidism was defined as elevated TSH with normal free thyroxine. Multivariable logistic regression, receiver operating characteristic analysis, net reclassification improvement, and decision curve analysis were used to evaluate discriminative performance and clinical utility. Results Subclinical hypothyroidism was more prevalent in patients with T2DM than controls (27.5% vs 3.0%, P < 0.001). Anti-TPO positivity was higher among diabetics and independently associated with subclinical hypothyroidism. The combined anti-TPO and TSH model demonstrated superior discrimination (area under the curve 0.88) and improved clinical utility compared with TSH alone. Conclusion Anti-TPO and TSH are independently associated with thyroid dysfunction (subclinical hypothyroidism) in T2DM. Their combined use significantly improves risk discrimination and clinical utility. Screening for thyroid autoimmunity in diabetics, especially women and those with poor glycemic control, may enhance early detection and improve long-term outcomes. These findings support a targeted, risk-stratified screening approach, rather than universal thyroid autoimmunity testing in all patients with T2DM.