Thyroid-stimulating hormone (TSH) test

What’s covered?

What is thyroid hormone?

The thyroid gland is a butterfly-shaped endocrine gland found in the lower front of the neck that produces the thyroid hormone. Thyroid hormone enters the circulation and travels to all tissues throughout the body. It helps the body consume energy, remain warm, and keep the brain, heart, muscles, and other organs operating normally.

Thyroid hormone comes in two varieties: thyroxine (T4) and triiodothyronine (T3) (T3). T4 is the most prevalent thyroid hormone present in the blood, accounting for about 95% of all thyroid hormones. T4 is converted to T3 by removing an iodine atom to exert its effects; this occurs mostly in the liver and specific tissues where T3 acts, such as the brain. T3 is responsible for around 5% of thyroid hormone circulating in the blood. The vast majority of thyroid hormone in the blood is bound by protein, leaving just a trace "free" to reach tissues and have an effect. Thyroid testing may be used to determine total protein-bound and free hormone levels.

What is a TSH test?

TSH is an abbreviation for thyroid-stimulating hormone; TSH testing is a blood test that detects this hormone. In addition, the thyroid-stimulating hormone is produced in the pituitary gland of the brain; if the pituitary gland is not functioning properly, it may produce too little TSH. When the thyroid gland does not generate enough thyroid hormone it causes a condition known as hypothyroidism. When the thyroid gland generates too much thyroid hormone it causes hyperthyroidism.

Why do I need a TSH test?

A TSH test may be required if you experience symptoms of either too much or too little thyroid hormone in your blood (hyperthyroidism) (hypothyroidism).

Hyperthyroidism, often known as an overactive thyroid, causes the following symptoms:

• Anxiety
• Loss of weight
• Hands trembling
• Increased heart rate
• Puffiness
• Eyelid enlargement
• Sleeping problems

Hypothyroidism, commonly known as underactive thyroid, causes the following symptoms:

• Gaining weight
• Tiredness
• Loss of hair
• Cold temperature tolerance is low
• Irregular menstrual cycles
• Constipation

What happens during a TSH test?

A small blood sample will be collected in a test tube or vial following needle insertion. You can feel a sting as the needle goes in or out. This usually takes around five minutes.

There is no need to prepare for a TSH blood test. If your physician has ordered further blood tests, you may need to fast and refrain from eating or drinking for several hours prior to the test. If there are any special instructions to follow, your health provider will let you know.

Is there any risk in taking the test?

A blood test is not very dangerous. You may have some soreness or bruising where the needle was placed, but most symptoms will go quickly.

What do the findings imply?

High TSH levels may imply that your thyroid is not producing enough thyroid hormones, known as hypothyroidism. Low TSH levels may imply that your thyroid is producing too many hormones, a condition known as hyperthyroidism. A TSH test does not reveal why TSH levels are abnormally high or low. If your test results are abnormal, your physician will most likely prescribe more tests to discover the source of your thyroid issue.

Among these tests are:

• T4 thyroid hormone levels testing
• T3 thyroid hormone levels testing
• Tests to diagnose Graves' disease, an autoimmune disease that causes hyperthyroidism
• Tests to diagnose Hashimoto's thyroiditis, an autoimmune disease that causes hypothyroidism

What is a T4 test?

The quantity of bound and free thyroxine (T4) hormone in the blood is determined by total T4 testing. A Free T4 test identifies what is not bound and can freely enter and modify human tissues.

Significantly, medicines and medical conditions that modify thyroid hormone-binding proteins influence Total T4 levels. Oestrogen, oral contraceptives, pregnancy, liver disease, and hepatitis C virus infection are common reasons for higher thyroid hormone-binding proteins and a high Total T4. Testosterone or androgens and anabolic medications are vital contributors to low thyroid hormone-binding proteins and hence low Total T4.

In certain cases, such as pregnancy, a person may have normal thyroid function but Total T4 levels higher than the typical reference range. In these conditions, tests measuring free T4, either a free T4 (FT4) or a free T4 index (FTI), may be a better indication of how the thyroid gland is working. When thyroid illness is present in the setting of aberrant thyroid-binding proteins, an endocrinologist may diagnose it.

What is a T3 test?

T3 tests measure the concentrations of triiodothyronine (T3) in the blood. A Total T3 test determines the bound and free fractions of triiodothyronine. Total T3 levels are typically elevated in hyperthyroid people. T3 tests may be used to confirm a hyperthyroidism diagnosis and to determine hyperthyroidism severity.

The ratios of T3 and T4 in the blood alter in several thyroid illnesses and may give diagnostic information. An elevation in T3 vs. T4 distinguishes Graves' illness. Medication such as steroids and amiodarone and severe sickness may reduce the amount of thyroid hormone the body converts from T4 to T3 (active form), resulting in a reduced percentage of T3. T3 levels decline late in hypothyroidism and are therefore not regularly used to assess individuals with underactive or surgically missing thyroid glands. Moreover, free T3 measurement is feasible; however, it is often unreliable and may be ineffective. For more information and our comprehensive guide to blood tests, click here.

Is there anything more I should know about TSH testing?

Thyroid alterations are possible during pregnancy. These changes are typically minor, but some pregnant women might develop thyroid illness. Hyperthyroidism affects roughly one in every 500 pregnancies, whereas hypothyroidism affects about one in every 250 pregnancies. After pregnancy, hyperthyroidism and, less often, hypothyroidism may persist. If you acquire a thyroid issue while pregnant, your physician will keep an eye on you after your baby is delivered. If you have a family history of thyroid problems, see your doctor if you are pregnant or want to get pregnant.

Welzo is a digital healthcare platform that aims to make you feel your best. Moreover, it aids in reducing any inefficiencies in the healthcare system, improves the standard of care, and reduces healthcare costs. We provide a variety of tests to meet your health requirements. You can order with delivery the next day to avoid waiting at a doctor's office or clinic, initiate your test, and collect your sample the next morning. In addition, you can return the sample the same day. A simple finger prick collection approach that takes around 5 minutes is used to get samples. You will also receive GP-reviewed findings and individualized suggestions for improvement.

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