what is tsh and t4
A T4 test is a blood test that helps your doctor identify problems with your thyroid. Itâs a low-risk procedure thatâs often used with other blood tests, including a T3 test and a TSH test. If youâre preparing for a T4 test, make sure to tell your doctor about any medications youâre taking.
1 T4 is a hormone that plays a role in several body functions, including growth and metabolism. 2  There are two kinds of T4 tests: a total T4 test and a free T4 test.  A number of drugs can interfere with your T4 levels, so tell your doctor what medications youâre taking before a T4 test.
Sometimes, your doctor may also order a test for T3 and/or TSH. The TSH, or thyroid-stimulating hormone, stimulates your thyroid to release both T3 and T4. Performing one or both of these other tests may help your doctor gain a better understanding of your thyroid problem.
The pituitary gland produces the TSH hormone, which triggers the thyroid to make T3 and T4, states WebMD. Low TSH values indicate possible hyperthyroidism, damage to the pituitary gland, a first-trimester pregnancy or an excess of thyroid-stimulating medication.