Thyroid is a 20 g gland that lies at the base of the neck on either side of the windpipe. It secretes thyroxine hormone that regulates metabolism and is vital to humans. Thyroid function tests are performed if there is a suspicion of an underactive or overactive thyroid. A detailed description and the reference values in thyroid function tests are provided below.
- Underactive thyroid (hypothyroidism). Hypothyroidism is a condition in which the thyroid gland does not make enough thyroxine or stops secreting it entirely.
- Overactive thyroid (hyperthyroidism). In hyperthyroidism, the gland produces too much thyroxine.
Name and abbreviation of test: THYROTROPIN P -TSH
Thyrotropin is a pituitary hormone that regulates thyroid gland function. The abbreviation TSH stands for thyroid-stimulating hormone. Thyrotropin is essential to thyroxine (thyroid hormone) production. The test is a standard test to screen suspected hypothyroidism, which is indicated by high TSH levels. In P-TSH, the typical range of reference in adults of age 20 or older is between 0.27 and 4.2 mU/l.
Name and abbreviation of test: THYROXINE, FREE P -T4-V
This test is a standard test performed if there is a suspicion of an underactive or overactive thyroid. Decreased free thyroxine levels indicate hypothyroidism and elevated levels hyperthyroidism. Some drugs, such as heparin, and large doses of salicylate may also induce increase in thyroxine levels. Elevated levels can also be seen in patients with certain systemic diseases. In P-T4-V, the typical range of reference in adults of age 20 or older is between 11.0 and 22.0 mU/l.
- Adults of age 20 or older: 0.27 – 4.2 mU/l
- Adults of age 20 or older 11.0 – 22.0 pmol/l
About the test
The sample should be collected between 7 a.m. and 2 p.m., and if on medication, before the next dose. In the event of a control sample, due to diurnal variation in TSH, sampling should be performed around the same time of the day, if possible, to ensure the comparability of the results.
Who will interpret my test results?
Please note that the doctor treating you is always responsible for interpreting the results. Consult your doctor if you have any questions regarding the results.