Doctors can diagnose thyroid disorders much earlier than in the past — often before you experience symptoms. Because the TSH test is the best screening test, your doctor will likely check TSH first and follow with a thyroid hormone test if needed. TSH tests also play an important role in managing hypothyroidism.

Which thyroid test is the most accurate?

Assessment of TSH is the single most useful test of thyroid function in the vast majority of patients. Primary care providers should seldom need to order any other biochemical thyroid test. In most cases the TSH will be within the normal range, and no further testing is indicated.

Is TSH or T4 more important?

T4 is produced in large quantities by the thyroid. However, TSH is a far superior screening test because small changes in T4 cause large TSH spikes.