Thyroid functions test or TFT is a term used to describe a series of blood tests that are conducted to test the functionality of the thyroid gland.
The thyroid gland is situated just aver Adam’s apple in the neck. The gland is instrumental in the secretion of thyroid hormones that are vital to several body processes such as metabolism and growth. Any issues with the effective functioning of the thyroid gland can result in several health problems. The secretion of thyroid hormones that is lower than normal levels is termed as hypothyroidism and excess secretion of thyroid hormones is known as hyperthyroidism.
A doctor may request for a thyroid function test, in case an individual shows the symptoms of either an overactive thyroid gland or an underactive thyroid gland. It may also be conducted to determine the effectiveness of thyroid replacement or thyroid suppression therapies, or to check for the presence of thyroid related ailments such as anxiety disorder and atrial fibrillation.
Depending on the policies of the local laboratories, a thyroid function test panel usually consists of thyroid hormones such as thyroid-stimulating hormone or TSH, triiodothyronine or T3 and thyroxine or T4.
The thyroid stimulating hormone or TSH blood test involves a simple blood test. The thyroid gland secretes the thyroid hormones as a result of stimulation from TSH. This thyroid stimulating hormone is produced by the pituitary gland, which is a critical organ of the endocrine system and is located at the lower end of the brain. It is the pituitary gland that instructs the thyroid gland to manufacture and release the essential hormones such as triiodothyronine or T3 and thyroxine or T4.
Therefore, the thyroid functions tests are ordered by health care providers to monitor thyroid problems. Individuals who have under thyroid function tests or are about to undergo such tests, would certainly like to know the meaning of the test results.
Provided below is a detailed explanation of the thyroid function tests, the measurements and the respective meanings that they convey.
Explanation of thyroid function test
A thyroid stimulating hormone blood test assists in the measurement of the quantity of TSH that is available in the blood. Provided below are the test details, that will allows individuals to effective prepare for the thyroid function test and also understand the results that follow.
Preparation for TSH blood test
The blood test can be conducted at any time of the day and hence one does not need to fast before undergoing a thyroid function test. There are certain medications that may interfere with the test and hence the physician may also you to temporarily stop their consumption. Some such drugs that affect the test results include lithium, amiodarone, potassium iodide, antithyroid medications, prednisone and dopamine.
The procedure of TSH blood test
The process for TSH blood test used to determine problems of the thyroid varies for adults and children. A sharp device known as lancet is used to pierce the skin in order to draw blood from children and infants. The blood is then collected either in a pipette, which is a tiny glass tube or onto a test strip. The piercing is then covered with a bandage to prevent any bleeding.
In adults, blood for a TSH blood test is taken from a vein that is generally present at the back of the hand or within the elbow. An elastic band is wrapped on the arm by the physician, before he/she inserts the needle into the vein. The elastic band exerts pressure on the area making the aforesaid vein to swell with blood. Once the blood is drawn, the needle is taken out and the elastic band is removed from the arm. The blood thus collected is stored in an airtight vial. Also, the punctured site is bandaged to stop any bleeding.
TSH Normal range
A thyroid function test will reveal the TSH levels among other things. The normal range of TSH levels tends to vary from one laboratory to another. As a rule, though, the general range is understood to be between 0.4 – 4.0 mIU/L. Any individual, who does not elicit any symptoms or signs of an underactive thyroid gland but has a reading of over 2.0 mIU/L in the TSH test, is likely to develop hypothyroidism in the future. The reading can be considered as an early phase of hypothyroidism.
Individuals, who have such TSH values or TSH levels in the range between 0.5 to 3.0 mIU/L, have to be treated for potential thyroid disorder and their health should be close monitored. It is important for such individuals to discuss the results with their doctor to come up with a recovery plan.
Abnormal TSH levels interpretation
Low TSH levels indicate:
- The presence of hypothyroidism
- Insufficient levels of TSH in the body
- Individuals who intake medications such as glucocorticoids, dopamine agonists and bexarotene may also have lower than normal TSH values.
High TSH levels indicate:
- Resistance to the thyroid hormone
- The affected individual has TSH-dependent hyperthyroidism
- Presence of primary hypothyroidism
- Exposure to mice can also lead to high TSH levels.
- Cretinism can also indicate higher than normal TSH levels
In case, a thyroid function test yields abnormal results, then it is essential to consult the doctor and come up with a plan to effectively treat the condition.