The thyroid gland is responsible for determining how the body uses energy. TSH stands for thyroid stimulating hormone, according to LabTestsOnline. A blood test can measure the amount of TSH to help a doctor diagnose a disease or to monitor the blood of a patient who is taking medicines to correct thyroid problems. A TSH can be drawn, or in conjunction with other thyroid tests. TSH levels are important pieces of data essential to an accurate diagnosis. While TSH levels can indicate illness or dysfunction, the lab test cannot pinpoint the cause of illness.
Uses
The doctor may order a TSH blood test if the patient has symptoms of a thyroid disorder or as a screen for thyroid dysfunction in patients who don't display any symptoms. This test is also used to screen newborns for under-active thyroids and to monitor those patients engaged in thyroid replacement therapy to treat hypothyroidism. A TSH can also diagnose and monitor women with infertility problems and help evaluate pituitary gland function.
Function
The pituitary gland creates thyroid stimulating hormones. TSH directs the thyroid gland to produce and release other hormones, such as T3 and T4. A high TSH indicates the thyroid is being over-stimulated and creating excessive hormones, whereas a low TSH means the thyroid does not excrete enough hormones. These hormones travel through the body in the blood, telling the cells how fast they should use energy and create proteins.
Lab Tests
The patient can eat and drink normally before having a TSH level drawn unless the need for other tests, like blood sugar, require the patient to fast. The test measures the amount of thyroid stimulating hormone in the patient's blood. Additional thyroid tests may be done in conjunction with a TSH, such as a T3 and a T4. The doctor may order a thyroid profile which includes all those tests to give the physician a better understanding of the patient's thyroid function. At least 5ml of blood is drawn into a special tube that separates blood serum from the blood cells and the TSH is performed on the serum. Test results are usually available in 1 to 3 days.
Considerations
Certain drugs, like aspirin, lithium and prednisone can affect TSH levels. The patient should review medications with his physician before having TSH levels drawn to ascertain whether the medicines might give abnormal TSH results. The patient taking thyroid medications should wait about 2 months after adjusting dosages before having a TSH level drawn to allow for adjustment to this new dose. MedlinePlus describes normal TSH results as between 0.4 and 4.0 mlU/L, but suggests that patients discuss test results with her physician as each laboratory may have its own limits.
Results
Abnormal TSH results can indicate disease, like thyroid cancer or dysfunction such as hyperthyroidism. A high TSH result because of Hashimoto's Disease, the most common cause of hypothyroidism in the United States, according to MayoClinic.com. Rarely, a high level of TSH can help diagnose a problem in the pituitary gland, such as a tumor. Acute stress and extreme illness can also affect TSH levels. Additionally, low TSH levels may occur in women during the first trimester of pregnancy.
