What is the normal range for thyroid-stimulating hormone (TSH)?

Thyroid-stimulating hormone (TSH) is a key marker used to assess thyroid function. If the thyroid gland fails to secrete adequate thyroid hormones, it results in thyroid hormone deficiency—commonly known as hypothyroidism. So, what is the normal reference range for TSH?

What Is the Normal Reference Range for Thyroid-Stimulating Hormone (TSH)?

The standard reference range for serum TSH is 0.3–5.0 mIU/L. TSH is a hormone secreted by the anterior pituitary gland and plays a critical role in regulating thyroid cell proliferation, thyroid blood supply, and the synthesis and secretion of thyroid hormones—thereby maintaining normal thyroid function. TSH levels exhibit an inverse (negative feedback) relationship with circulating thyroid hormone levels. In patients with primary hypothyroidism, serum T3 and T4 levels decrease while TSH levels increase; conversely, in those with primary hyperthyroidism, T3 and T4 levels rise while TSH levels fall. When T3 and T4 levels remain within normal limits but TSH is either elevated or suppressed, the condition is termed subclinical hypothyroidism or subclinical hyperthyroidism, respectively.

TSH is one of the most commonly used clinical indicators for diagnosing hyperthyroidism or hypothyroidism. However, TSH reference ranges vary with age. For instance, in infants under one year old, the normal range may be 1.7–9.1 mIU/L; in children and adolescents, it is typically 0.7–5.7 mIU/L; and in adults and middle-aged individuals, the normal reference range is generally 0.4–4.2 mIU/L.

If you suspect you may have hypothyroidism or hyperthyroidism, it is essential to visit a healthcare facility for comprehensive thyroid function testing to confirm the diagnosis. We hope this information has been helpful!