Is TSH useful for blood sugar?

TSH (thyroid-stimulating hormone) is a marker of thyroid function, not directly of blood sugar. However, thyroid hormones influence glucose metabolism: hypothyroidism can reduce insulin sensitivity and raise fasting glucose; hyperthyroidism can increase hepatic glucose output. Observational studies show modest associations between TSH levels and insulin resistance, but TSH alone is not a reliable predictor of dysglycemia. Evidence is human-observational, not from interventional trials. For blood sugar assessment, established markers like HbA1c, fasting glucose, and OGTT are far more informative. TSH may be considered as a secondary risk factor when thyroid dysfunction is suspected, but it is not a primary tool for glucose management. The clinical utility of TSH for blood sugar is limited; routine screening for thyroid function in diabetes is recommended by some guidelines, but not for diagnosing or monitoring glucose control. Caveat: TSH reference ranges vary, and subclinical abnormalities often have unclear significance.