What is the T4 (Thyroxine) Test?

Frequently Asked Questions:

What is the T4 test used for?

The T4 hormone is secreted in the human body in two forms - free T4 and bound T4. The total T4 test measures both the free and the bound T4 levels. A free T4 test checks the free T4 levels and is considered more accurate than the total T4 test. It helps to diagnose thyroid disease and will give an insight into the functioning of the thyroid gland.

Understanding the test results of the T4 (thyroxine) test

The T4 test results are necessary to understand the proper functioning of the thyroid gland in an individual. Doctors prefer free T4 levels tests to check the functioning of the gland as it measures the level of thyroxine available for the body to use. If the test results fall outside the normal range, please talk to your doctor.

Why do I need a T4 (thyroxine) test?

Your doctor will ask you to take a T4 test if you have symptoms like dryness, irritation, puffiness, watering eyes, skin dryness, hair fall, or hand tremors. Doctors will recommend a T4 test for other symptoms like unexplained weight changes, insomnia or difficulty in sleeping, fatigue, anxiety, mood swings, and menstrual irregularity. This test is also helpful to check on signs of improvement in thyroid functions among existing patients. 

What happens during the T4 (thyroxine) test?

A T4 test is similar to any other blood test. A healthcare professional will collect a blood sample from a vein by piercing a thin needle. You might feel a pricking sensation as the needle pierces your skin. However, the pain will not last long. This test has absolutely no side effects. The entire procedure of collecting the test takes about 5 minutes.

What does it mean if thyroxine (T4) is high?

High levels of T4 are indicative of an overactive thyroid gland. Thyroxine secretion is regulated by the hypothalamus and pituitary gland as well. An abnormal thyroxine level could be indicating an issue with either of these glands. High levels of T4 will cause anxiety, weight loss, an increased appetite, irregular heart rate, and irritability, along with erratic mood swings. 

What is a normal free T4 level for a woman?

Women, especially those under 40, are more susceptible to suffer from irregular functioning of the thyroid gland. As a result, women need to check their thyroxine levels if they develop any symptoms. The free T4 level tests are more accurate as it is not affected by bound proteins. For women who are not pregnant, normal free T4 levels fall under the range of 0.7 - 1.9 nanograms per deciliter (ng/dL).

What happens when T4 is low?

Production of less thyroxine by the thyroid gland is called hypothyroidism. It is often the result of poor iodine intake, the use of certain drugs and medicines, or some autoimmune diseases. The causes can also remain unknown sometimes. Hypothyroidism often results in weight gain, reduced appetite, depression, poor memory, and fatigue. Thyroxine is necessary for physical and mental development. If left untreated, hypothyroidism could cause impairment and stunted growth.

Is the T4 test necessary?

Problems with the proper functioning of the thyroid gland are usually hereditary. You should get a thyroxine test if a family member has ever had thyroid disease. This test is a must if you have the symptoms of either hypothyroidism or hyperthyroidism. It is very vital for women aged under 40 to undergo this test, as they are more prone to thyroid-related diseases. 

What does it mean if thyroxine (T4) is high?

High levels of T4 could be indicating an overactive thyroid, also called hyperthyroidism. It is also indicative of other problems like multinodular goitre or thyroiditis. The release of excessive thyroxine is called thyrotoxicosis, which can be spotted by swelling around the throat. High levels of T4 cause weight loss, increased appetite, irritability, irregular menstrual cycles, and heart palpitations. 

What is the normal range of T4?

The normal free T4 level of adults ranges from 0.8 - 1.8 nanograms per deciliter (ng/dl) of blood. For pregnant women, it is slightly different, as thyroid changes may occur during pregnancy. For children, the range varies depending on their age. Please consult your pediatrician regarding your child’s T4.

Book your appointment at Yashoda Hospitals and get your T4 (Thyroxine) checked today. You can request and  Get a free second opinion from experts at Yashoda Hospitals.