| The Thyroid Stimulating Hormone (TSH) blood test is | | | | the thyrotropin-releasing hormone (TRH) that in turn |
| often performed to determine how the thyroid gland is | | | | causes the pituitary gland to produce TSH. It is TSH |
| performing through the measurement of the amount | | | | that controls the production of T3 and T4 by the |
| of TSH in the blood. A common reason for ordering a | | | | thyroid gland. Normally, if the pituitary gland senses a |
| TSH blood test is to determine whether a patient has | | | | low level of T3 and T4 in the blood, it releases TSH to |
| hyperthyroidism or hypothyroidism. Hyperthyroidism | | | | cause the thyroid to release more of these hormones. |
| means that the thyroid gland, which is found in front of | | | | To help in the interpretation of the results of the TSH |
| the windpipe, produces too much of the thyroid | | | | blood test, a physician usually requires also the |
| hormones such as triiodothyronine (T3) and thyroxine | | | | measurement of the levels of T3 and T4 in the |
| (T4). Hypothyroidism means that there is a lack of | | | | patient's blood. Thus, if the patient has unusually high |
| these hormones in the body. A person with | | | | levels of TSH but has low quantities of the T3 and T4 |
| hypothyroidism usually has symptoms such as weight | | | | hormones and vice versa, it can be determined that it |
| gain, frequent menstruation, constipation, fatigue and | | | | is a thyroid problem. However, if both the thyroid |
| dry skin. On the other hand, hyperthyroidism can cause | | | | hormones and TSH are too high or both are too low, |
| a person to have symptoms like weight loss, fast | | | | then it is the pituitary gland that may be diseased. |
| heart beats, irregular menstruation, nervousness, and | | | | However, some medication or drugs, such as aspirin, |
| diarrhea. | | | | can affect the level of TSH in the blood. During the |
| The TSH blood test may be ordered for people who | | | | first stages of pregnancy, TSH levels may also be low. |
| have goiter or an enlarged thyroid gland and those | | | | Other conditions, such as too much stress, exposure |
| who have symptoms indicative of hyperthyroidism or | | | | to radioactive materials or an x-ray using iodine dye, |
| hypothyroidism. It is the hypothalamus that produces | | | | can also influence the amount of TSH in the blood. |