TSH stands for thyroid stimulating hormone, which is a hormone produced by the pituitary gland in the brain that prompts the thyroid gland to produce and release its own hormones, thyroxine (T4) and triiodothyronine (T3) . A TSH test is a blood test that measures the amount of TSH in the blood. The test is used to find out how well the thyroid is working and can tell if a person has hyperthyroidism (too much thyroid hormone) or hypothyroidism (too little thyroid hormone) in their blood. The test can also detect a thyroid disorder before a person has any symptoms. TSH levels that are too high or too low may be a sign of a thyroid problem. The normal range for TSH levels may vary slightly among different laboratories, and a healthcare provider can explain the meaning of specific test results.