What Is TSH 3 Generation Test Used For?

TSH, or thyroid stimulating hormone, is the common name used for thyrotropin. This is the hormone secreted by the thyroid and regulated by the pituitary gland. When a doctor suspects thyroid disease, third-generation TSH testing is the most commonly used because of its accuracy compared with first- and second-generation testing -- thus cutting down on the need to do follow-up blood work.

First-generation and Second-generation Tests

• First-generation thyroid tests are no longer used because their detection rate of thyroid hormone is 5 to 10 mU/L, and they often miss mild hypothyroidism. First-Generation tests were never used for hyperthyroidism because TSH levels are much lower than the test detects.

  Second-generation is still used as of 2010 to detect a properly working thyroid gland.

Third-generation Testing

• Third-generation tests are the most commonly used as of 2010 because of lower detection limits of TSH in the blood. Third-generation tests are used, with accuracy, to detect both hyperthyroidism and hypothyroidism and is used to detect thyroid problems in newborns. This testing is also used by doctors to determine the amount of replacement levothyroxine to prescribe.

Other Diagonostic Testing

• There are additional tests that a doctor may use to help determine thyroid disease, how bad it is, and what is causing it. Often doctors will order a complete thyroid panel that includes all follow-up blood work.

  Free thyroxine T4 is the active form of thyroxine and gives a bigger picture of how the body is using the hormone than a third-generation TSH test. Free T4 testing is ordered when an abnormal third-generation TSH test comes back abnormal.

  Free T3 is used to diagnose hyperthyroidism as well as monitoring hyperthyroid patients and their medication. If hyperthyroidism is diagnosed, radioactive iodine imaging will be done.