Thyroid Stimulating Hormone (TSH)
Hypothalamus produces a substance called Thyrotropin-Releasing Hormone (TRH). Pituitary gland is stimulated by TRH and produces Thyroid Stimulating Hormone (TSH). Thyroid gland in turn is stimulated by TSH to produce two hormones: thyroxine (T4) and triiodothyronine (T3). These two hormones help in controlling metabolism in the body. Thyroid Stimulating Hormone Test measures the levels of TSH in blood.
Why the test is ordered?
The test may be ordered to determine whether thyroid gland is working properly or not. The test may also be recommended to determine the cause of hypothyroidism and monitor its treatment and also to monitor thyroid gland function in people who are being treated for hyperthyroidism. The test can be used for new-born babies to determine underactive thyroid gland.
How is the sample collected?
A blood sample from the arm is collected.
How to prepare for the test?
There is no test preparation required, but it is better to inform the doctor about all the medicines or supplements one is taking before getting the test done. For those who are on thyroid hormone therapy, their blood would be drawn before they take the dose for that day. It is better to inform the doctor if the person who would be undergoing the test has done X-ray by taking radioactive material or iodine dye during the four to six weeks before the test date. Results of the Thyroid Stimulating Hormone Test may not be accurate for a person who had iodine contrast prior to the test.