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Thyroid function tests – What are they and what do the tests mean?

THYROID FUNCTION TESTS

Before we get into the details of the tests involved first let's understand the details about the thyroid gland itself.

WHERE IS THE THYROID GLAND?

The thyroid gland is a small, butterfly-shaped gland situated at the base of the front of your neck, just below your Adam's apple. Hormones produced by the thyroid gland — triiodothyronine (T3) and thyroxine (T4) — have an enormous impact on your health, affecting all aspects of your metabolism.  They maintain the rate at which your body uses fats and carbohydrates, help control your body temperature, influence your heart rate, and help regulate the production of proteins.

WHAT DOES THE THYROID GLAND DO?

The major thyroid hormone secreted by the thyroid gland is thyroxine, also called T4 because it contains four iodine atoms. To exert its effects, T4 is converted to triiodothyronine (T3) by the removal of an iodine atom. This occurs mainly in the liver and in certain tissues where T3 acts, such as in the brain. The amount of T4 produced by the thyroid gland is controlled by another hormone, which is made in the pituitary gland located at the base of the brain, called thyroid-stimulating hormone. The amount of TSH that the pituitary sends into the bloodstream depends on the amount of T4 that the pituitary sees. If the pituitary sees very little T4, then it produces more TSH to tell the thyroid gland to produce more T4. Once the T4 in the bloodstream goes above a certain level, the pituitary’s production of TSH is shut off. In fact, the thyroid and pituitary act in many ways like a heater and a thermostat

WHAT IS THE THYROID FUNCTION TEST?

(TFTs) is a collective term for blood tests used to check the function of the thyroid.

A TFT panel typically includes thyroid hormones such as thyroid-stimulating hormone (TSH, thyrotropin) and thyroxine (T4), and triiodothyronine (T3), free T3 and free T4.

WHEN IS A THYROID FUNCTION TEST DONE?

We advise TFTs to be done if a patient is thought to suffer from hyperthyroidism (overactive thyroid) or hypothyroidism (underactive thyroid) or to monitor the effectiveness of either thyroid-suppression or hormone replacement therapy. It is also requested routinely in conditions linked to thyroid diseases, such as atrial fibrillation and anxiety disorder.

WHAT IS TSH?

TSH stands for Thyroid-stimulating hormone. The best way to initially test thyroid function is to measure the TSH level in a blood sample. A high TSH level indicates that the thyroid gland is failing because of a problem that is directly affecting the thyroid (primary hypothyroidism). The opposite situation, in which the TSH level is low, usually indicates that the person has an overactive thyroid that is producing too much thyroid hormone (hyperthyroidism). Occasionally, a low TSH may result from an abnormality in the pituitary gland, which prevents it from making enough TSH to stimulate the thyroid (secondary hypothyroidism). In most healthy individuals, a normal TSH value means that the thyroid is functioning normally.

WHAT IS THE T4 TEST: -

Your thyroid produces a hormone, thyroxine, which is known as T4. This hormone plays a role in several of your body’s functions, including growth and metabolism. Some of your T4 is called free T4.

This means that it has not bonded to protein in your blood. Most of the T4 in your body bond with the protein. There are two kinds of T4 tests. The first, known as a total T4 test, measures both kinds of T4 (the T4 that has bonded to protein and the free T4) in your blood. The second, a free T4 test, measures only the free T4 in your blood.

WHAT IS THE T3 TEST:-

Most of the T3 in your body binds to protein. The T3 that does not do so is called free T3 and circulates unbound in your blood. The most common kind of T3 test, known as the T3 total test, measures both kinds of T3 in your blood. By measuring the T3 in your blood, your doctor may be able to determine if you have a thyroid problem.

WHAT IS HYPOTHYROIDISM:-

Hypothyroidism is a common endocrine disorder in which the thyroid gland does not produce enough thyroid hormone.

The signs and symptoms of hypothyroidism vary, depending on the severity of the hormone deficiency. Hypothyroidism signs and symptoms may include

WHAT IS HYPERTHYROIDISM:-

Hyperthyroidism, also known as overactive thyroid and hyperthyreosis, is the condition that occurs due to excessive production of thyroid hormone by the thyroid gland. Hyperthyroidism can mimic other health problems, which may make it difficult for your doctor to diagnose.

It can also cause a wide variety of signs and symptoms, including:

If you have any of these symptoms, we advise you to get your thyroid levels checked and confirm with the thyroid function test.


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