Written By: Dr Anitha Anchan | Updated : April 8, 2016 12:13 AM IST
The thyroid gland is a ductless gland in your neck. It secretes hormones which regulate your growth and development by controlling your food metabolism, energy usage, sleep patterns, etc. The thyroid stimulating hormone (TSH) is produced by the pituitary gland. It stimulates the thyroid gland to produce the two important hormones -thyroxine (T4) and triiodothyronine (T3). The two thyroid hormones circulate in the blood in two forms - bound to a carrier protein and unbound or freely circulating. The cells of the body use only the unbound T3 and T4. The T3 hormone is crucial in maintaining the metabolism and other functions of the body. Increase (hyperthyroidism) or decrease (hypothyroidism) in thyroid hormone production can cause health issues.
Thyroid function tests what are they?
Thyroid function tests are blood tests that check how well your thyroid gland is functioning. They measure the levels of thyroid-stimulating hormone (TSH), triiodothyronine (T3) and thyroxine (T4).
When is it recommended?
Thyroid function tests are recommended when you have symptoms of overactive or underactive thyroid and to monitor the treatment of thyroid diseases. They are also prescribed to screen thyroid dysfunction if you are at an increased risk of thyroid dysfunction. Ideally, you should get TFT done every five years after you turn 35 and if you have risk factors like a family history of thyroid disease, type 1 diabetes, stressful life, have had thyroid surgery or suffer from Down s or Turner s syndrome. Women are at an increased risk during periods of hormonal changes like during pregnancy and menopause.While there are medications to help treat thyroid problems, yoga can help relieve symptoms.
Reading your thyroid function test report
1. Thyroid Stimulating Hormone (TSH) Measuring the TSH is the most important test for early detection of thyroid dysfunction. Lower TSH levels indicate overactive thyroid (hyperthyroidism). Rarely, an abnormality in the pituitary gland can cause low TSH levels. Higher TSH values indicate underactive thyroid (hypothyroidism) or thyroid tumor. The reference values and measurement units vary from lab to lab. Results above or below the normal range indicate the need for T4 and T3 tests. Excess free T3 or free T4 in the blood suppress TSH levels.
Normal range: 0.4 to 4.0 milli-international units per liter of blood (mIU/L)
2. Free T4 T4 or thyroxine test measures the T4 hormone level in the blood. Bound hormone molecules cannot be used by the cells. Only the ones that freely circulate in the blood are taken up by the cells. Hence, measurement of free T4 (FT4) levels is preferred over total T4 to determine how the thyroid is functioning. A low T4 indicates hypothyroidism and a high T4 level indicates hyperthyroidism.
Normal range: 9 - 25 picomoles/litre
3. Free T3 The T3 hormone is ten times stronger than T4 in its action. Measuring T3 levels is useful for diagnosing and determining the severity of thyroid dysfunction. Just like the free T4, measurement of free T3 levels is preferred over total T3. A low T3 level indicates hypothyroidism and a high T3 level indicates hyperthyroidism.
Normal range: 3.5 to 7.8 pmol/litres
Image source: Shutterstock
