What are Thyroid Function tests?
Thyroid function tests (TFTs) are tests that are used to measure the working capacity of thyroid gland. Thyroid gland is a small endocrine gland that is located just above the collarbone. It produces two hormones: triiodothyronine (free T3) and thyroxine (free T4).
TFTs are used to diagnose various thyroid disorders such as hyperthyroidism (increase in thyroxine hormone) and hypothyroidism (decrease in thyroid hormones).
Hormones that are included in TFTs are thyroid-stimulating hormone (TSH), triiodothyronine (T3) and thyroxine (T4) along with a few antibodies.
- TSH test: It is done to check the amount of TSH in blood. TSH is a hormone produced in the pituitary gland, which instructs the thyroid gland to produce the right amount of T3 and T4 hormones. TSH is continuously produced and released in blood by pituitary gland.
- T4 test: This test checks the amount of T4 in blood. Pregnancy and oral contraceptives can result in an increase in the levels of this hormone. Some illnesses and medications (for the treatment of arthritis, asthma or other health problems) can cause a drop in T4 levels.
- T3 test: If an individual has hyperthyroidism despite a normal level of T4, then they need to undergo a T3 test to confirm the diagnosis.
- Thyroid antibody test: Thyroid antibodies are produced when the immune system starts to attack the thyroid gland. Measuring thyroid antibodies can be useful for diagnosing autoimmune disorders such as Graves’ disease and Hashimoto’s disease.