Thyroxine Free T4 Free
Also Known As: Free Thyroxine, Free T4, Thyroxine Screen, Free T4 Concentration
What Is A T4 Free (FT4) Test?
A free T4 test help diagnose different disorders of the thyroid gland. The term T4 here is short for Thyroxine which is one of the most integral hormones made by your hormone glands. Your body produces two different types of Thyroxine hormone, i.e., free T4 that flows through the bloodstream independently and bound T4, which travels through your bloodstream after attaching to the proteins. Doctors usually order a total T4 test to measure the concentration of free and bound T4 in your blood. Sometimes, they only order a free T4 test that does not involve results related to bound T4. It is mainly because of the accuracy issues encircling the bound T4 results.
While the primary reason for a free T4 test is to check your thyroid, it is also often used to notify your doctor regarding medical issues affecting your pituitary gland.
What Is The Test Used For?
The T4 Free (FT4) Test serves as an indicator of free T4 free Thyroxine level in your bloodstream. It is also used to determine how efficiently and appropriately your thyroid gland is working. You might need to undergo this test if your health care provider or doctor wants to figure out whether you have a thyroid-related problem such as hyperthyroidism or hypothyroidism. If you do have any of these conditions, you might also need to take this test to analyze the changes and the effectiveness of the treatment plan.
Your provider will recommend you for a T4 Free (FT4) Test if you are showing signs and symptoms of thyroid disorders, including:
- Inability to become pregnant
- Abnormal findings of other thyroid-related blood tests like TSH or T3
- Symptoms of underactive Thyroid
- Signs and symptoms of an overactive thyroid
- Lump or nodule in the thyroid
- Hypopituitarism, a condition where your pituitary gland is unable to produce enough hormones
- A regular or enlarged thyroid gland
Why And When Do You Need A T4 Free (FT4) Test?
Thyroid diseases are much more common in females and most often occur at 40 years of age or above. It also tends to run in families; however, there are so many reasons you need to take a T4 Free (FT4) Test. Your doctor or practitioner will ask for this test if they suspect your thyroid is overactive or underactive, i.e., hyperthyroidism or hypothyroidism. If your thyroid is underactive, it becomes unable to generate adequate Thyroxine, which ultimately decreases your metabolism and slows down your body. Signs and symptoms of an underactive thyroid or hypothyroidism include the following:
- Dry skin
- Being constipated all the times
- Feeling depressed
- Feeling cold
- Unexplained weight gain
- Constant tiredness and fatigue
- Heaving weak muscles
- Irregular periods
- Thinning of hair
People with an overactive thyroid (where the thyroid gland makes excessive Thyroxine) may have a fast metabolism and high energy levels along with the following symptoms:
- Feeling hungry all the time (feeling hungrier than usual)
- Feeling of nervousness
- Feeling hot
- Having diarrhea
- Losing weight unintentionally
- Difficulty in sleeping
- Shaky hands
- Thinning of hair
- Dry and puffy eyes
Sometimes, your doctor will order other related tests like T3 or TSH test along with FT4 test to analyze an ongoing problem or assess your improvement through the treatment plan.
What Kind Of Sample Is Required For The Test?
During the procedure, your doctor or healthcare provider will collect blood in a tube or vial and then send it to the lab for further analysis. They usually take the sample by inserting a small needle into a vein in your arm. After inserting a needle, a small amount of blood is collected per the doctor's recommendation. You might feel a little sting when the needle goes in or out, but the overall process is straightforward and usually takes about five minutes or less.
Do You Need To Prepare For The Test?
You don't need to do anything special before undergoing the Free T4 test. If your doctor has ordered some additional tests along with it, you might need to fast, i.e., stop eating and drinking (except water) for at least 8-10 hours. As for the medications, vitamins, and supplements you are taking, only your doctor or care provider can consult you regarding their use before the test. Usually, the free T4 test remains unaffected by any medicine, but some supplements like biotin or Vitamin B7 can alter the result and normal ranges. Also, pregnancy and kidney or liver disorders can modify the test results.
Are There Any Risks To This Test?
A free T4 test shows more specific risks, but in rare cases, you may experience the following complications:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma or build-up of blood under the skin
- Multiple punctures to locate means
- Infection at the injection site
More commonly, you may experience slight discomfort or pain during the blood draw. You are also likely to bleed negligibly after the needle is removed. In some cases, people also develop a small bruise near the puncture site.
What Do The Test Results Mean?
The test results may differ depending on your gender, age, health history, and the method used for the testing. A typical normal range for the ft4 test is 0.9- 2.3 ng/dl. These normal values may vary slightly among different laboratories because some use different measurements to attest different specimens according to their standards. It is wise to talk to your provider about the true interpretation of your specific test results.
To fully understand the free T4 test results, other thyroid-related tests like T3 and TSH are required. Your results can be affected by estrogen level, pregnancy, liver problems, inherited protein changes that bind to t4, and other body-wide diseases. A higher than normal ft4 level can be due to a condition that includes overactive thyroid like:
- Tumors of testes and ovaries
- Graves disease
- Eating food that contains iodine
- Taking too much thyroid hormone medicine
- Medical imaging test with contrast dye containing iodine
- Toxic thyroid nodules or toxic goiter
Lower than normal level of FT4 indicates:
- Severe acute illness
- Hypothyroidism in conditions like Hashimoto's disease and those involving an underactive thyroid
- Use of certain medications
- Fasting or malnutrition
Related Tests: Non-Protein Bound Tetraiodothyronine Test, Thyroid Function Cascade, TSH Test, T3 Test, Total Thyroid Test
Frequently ordered together
Thyroid Peroxidase TPO Antibody
Triiodothyronine Free T3 Free
Triiodothyronine Total T3 Total
Thyroxine T4 Total
Thyroid Stimulating Hormone TSH With Reflex to Free T4
Thyroid Stimulating Hormone TSH
Ultrasound Thyroid Gland
THYROID PANEL WITH TSH (Thyroid Stimulating Hormone)
Thyroid Stimulating Hormone TSH-Reflex
T3 Uptake Reflex
Thyroid Screening Test
TSI (Thyroid Stimulating Immunoglobulin)
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