Thyroxine - Total

Also known as Total Thyroxine, Total T4

You need to provide

Blood

This test is for

Male, Female

Test Preparation

No special preparation is required.

Understanding Thyroxine - Total

What is Thyroxine - Total?

A Thyroxine - Total is a blood test that measures the level of total thyroxine (T4) hormone in the blood. This test helps assess overall thyroid function and detect possible thyroid disorders. It is also performed in combination with total T3 and TSH tests as part of a thyroid profile total test.

Thyroxine, also known as T4, is a hormone produced by the thyroid gland. The thyroid is a small, butterfly-shaped gland located at the front of your neck. It helps regulate helps regulate the body’s metabolism, normal temperature, blood pressure, and heart rate. T4 along with triiodothyronine (T3), another hormone produced by the thyroid gland, plays an important role in the growth and development of the nervous system and the brain. T4 exists in the blood in two forms: bound (attached to proteins) and free (not attached to proteins).

A Thyroxine - Total measures the total level (both free and bound forms) of the T4 hormone. Deranged levels of T4 can result in either hyperthyroidism (the thyroid gland produces too much T4) or hypothyroidism (the thyroid gland produces less T4). Your doctor may suggest this test if you show symptoms of hyperthyroidism, like increased appetite, weight loss, sweating, anxiety, tremors, etc., or hypothyroidism, like fatigue, weight gain, dry skin, constipation, etc.

No special preparations are needed for a Thyroxine - Total test. However, do let your doctor know about all the medications you take as some of those can affect thyroid function. Biotin (Vitamin B7) is a commonly taken over-the-counter supplement that can lead to some aberrancy in your thyroid function test values even if they are normal. Therefore, avoid taking biotin 2 days before this test.

Test result ranges are approximate and may differ slightly between different labs depending on the methodology and laboratory guidelines. Talk to your doctor about your specific results. The test results will help them determine your medical condition, make recommendations for lifestyle modifications such as diet and exercise, evaluate whether or not medication will be required to manage your condition, and formulate your overall treatment plan.

What is Thyroxine - Total used for?

A Thyroxine - Total is done:

To measure the levels of total T4 hormone in the body.
As part of a thyroid profile total test along with total T3 and TSH tests.
To evaluate symptoms suggestive of an imbalance in thyroid hormone levels, such as fatigue, weight loss, hair loss, and changes to heart rate.
To diagnose and monitor the treatment of hypothyroidism or hyperthyroidism.
To detect an underactive thyroid gland in newborn babies.
To evaluate disorders such as thyroid nodules, goiters, and pituitary or hypothalamus gland disorders.

What does Thyroxine - Total measure?

A Thyroxine - Total measures both the bound and unbound/free form of thyroxine (T4) hormone in the blood. T4 exists in the blood in two forms: bound (attached to proteins) and free (not attached to proteins). Most of the T4 circulating in the blood is bound to proteins and only a small part is free. It is necessary to maintain a fine balance of these forms to ensure the proper functioning of the body.

Interpreting Thyroxine - Total results

Interpretations

Values higher than normal reference range are seen in hyperthyroidism and patients with acute thyroiditis.

Values lower than normal reference range are seen in hypothyroidism, myxedema, cretinism, chronic thyroiditis, and occasionally, subacute thyroiditis.

Answers to Patient Concerns & Frequently Asked Questions (FAQs) about Thyroxine - Total

Frequently Asked Questions about Thyroxine - Total

Q. Why is a Thyroxine - Total test done?

A Thyroxine - Total test is done to measure the level of T4 in the body and evaluate symptoms suggestive of an imbalance in this hormone, such as weight gain/loss, fatigue, dry skin, hair thinning, slow heart rate, or depression, muscle weakness, anxiety, trouble sleeping, or frequent bowel movement.

Q. Can I take a Total T4 test during pregnancy?

Yes, you can take a Total T4 test during pregnancy. This test along with others is usually recommended during pregnancy to measure the levels of thyroid hormones, as thyroid disorders can complicate pregnancy.

Q. What happens when Total T4 levels are high?

High Total T4 levels can lead to a condition called hyperthyroidism in which the thyroid gland produces too much thyroid hormone. Some of the common symptoms of hyperthyroidism include weight loss, nervousness, irritability, increased sweating, and rapid heartbeat.

Q. What happens when Total T4 levels are low?

When Total T4 levels are low, it can lead to a condition called hypothyroidism. Some of the common symptoms of hypothyroidism are fatigue and weakness, weight gain, cold intolerance, and constipation.

Q. Is fasting required for a Total T4 test?

No, fasting is not needed before taking this test. However, your doctor will guide you if any special preparation is required.

Q. What is Hyperthyroidism?

Hyperthyroidism is a condition in which the thyroid gland is overactive and there is an increased production of thyroid hormones by the thyroid gland. Causes of Hyperthyroidism include Graves’ disease, multinodular goiter, thyroid nodules, toxic adenoma, inflammation of the thyroid, eating too much iodine, and too much synthetic thyroid hormone. Diagnosis of this condition can help to relieve the symptoms and prevent long-term complications.

Q. What are the symptoms of Hyperthyroidism?

Symptoms of Hyperthyroidism include: Rapid heartbeat (tachycardia) — commonly more than 100 beats/minute — irregular heartbeat (arrhythmia) or pounding of your heart (palpitations), sudden weight loss, nervousness, anxiety, irritability, tremor (usually a fine trembling in your hands and fingers), changes in menstrual patterns, increased sensitivity towards heat, changes in bowel patterns (especially more frequent bowel movements), an enlarged thyroid gland (goiter) which may appear as a swelling at the base of your neck, increased appetite, sweating, fatigue, muscle weakness, sleep disturbances, skin thinning, fine and brittle hair.

Q. What is Hypothyroidism?

Hypothyroidism, also called underactive thyroid or low thyroid is a condition in which the thyroid gland does not produce enough thyroid hormones. It can be commonly caused by intake of low iodine diet or Hashimoto's thyroiditis (an autoimmune disease). Less common causes include previous treatment with radioactive iodine, injury to the pituitary gland which secretes TSH, intake of certain medicines, previous thyroid surgery, or a lack of a functioning thyroid gland at birth.

Q. What are the symptoms of Hypothyroidism?

Hypothyroidism can cause symptoms such as tiredness (fatigue), hoarseness, constipation, feeling cold, dry skin, dry and thin hair, puffy face, weight gain, and muscle weakness. Along with that, one may experience decreased sweating, depression, slowed heart rate, increased blood cholesterol levels, pain, and stiffness in your joints, impaired memory, problems of infertility or menstrual changes, muscle stiffness, aches, and tenderness.

Q. Is there any risk associated with this test?

There is usually no risk associated with this test. However, some people may feel a slight sting while the needle is pricked and may experience some bleeding that is normal and usually not bothersome. Rarely some people may experience slight swelling or bruising at the site of the needle prick. Applying ice 3-4 times a day for about a week may help reduce swelling and bruising. If it does not get better, consult your doctor.

Q. How can hyperthyroidism affect a pregnant woman and her baby?

An untreated hyperthyroidism during pregnancy can lead to miscarriage, premature birth, low birth weight of the baby, preeclampsia (a very high rise in blood pressure in late pregnancy), thyroid storm (a sudden, severe worsening of symptoms of hyperthyroidism) and congestive heart failure.

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