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Thyroid Test: Is Fasting Required For it and Other Questions Answered



Thyroid Test:

Thyroid tests are a set of examinations done by doctors or other healthcare professionals to check whether your Thyroid gland is functioning appropriately. These test results help them to identify the root cause behind the conditions of Hyperthyroidism and Hypothyroidism. 

The thyroid gland is a small, butterfly-shaped gland in front of your neck that produces two major hormones, the Thyroxine (T4) hormone and Triiodothyronine (T3). These hormones play the primary role in controlling the energy usage in our body and hence impact most of the vital organs, including the Heart.

Having a healthy level of thyroid hormones helps your body perform metabolic functions optimally. Book a thyroid test and know about your thyroid gland health. 

What Imaging Tests Do Doctors Use to Diagnose and Find the Cause of Thyroid Disease?

Several imaging tests are required to get to the root cause of any disease associated with the thyroid gland and diagnose it. A trained technician should conduct these imaging tests in the doctor's office, outpatient centre, or hospital. Later, the reports of these tests are examined by the Radiologist and forwarded to your doctor for further diagnosis.


Doctors prescribe an ultrasound test to detect the presence of thyroid nodules. These nodules are lumped in your neck, which can also be cancerous. 

An ultrasound test typically lasts for thirty minutes. First, it requires you to lie down on the examination table. At the same time, a trained technician runs a device called a transducer over your neck. This device converts the mechanical waves running down your neck into ultrasound waves, which produce an image of your throat on an ultrasound film. 

Thyroid Scan

A thyroid scan helps the doctor to examine the shape, size, and position of your thyroid gland. A minimal amount of radioactive Iodine is used to detect the presence of thyroid nodules in your neck. As a result, doctors generally advise their patients to avoid food with high Iodine concentrations for at least one week before the test. 

For the test, you must either swallow the radioactive iodine capsule or inject it directly into your veins. Once your thyroid gland has absorbed the appropriate amount of radioactive Iodine, a special camera captures images of your thyroid. 

If the radioactive Iodine is seen to spread throughout your thyroid, it indicates that you are suffering from Grave's disease. 

You are advised to avoid a thyroid scan if you are pregnant or breastfeeding.

Radioactive Iodine Uptake Test

This test is used to detect the causes of Hyperthyroidism. Your doctor will advise you to avoid food with high Iodine concentrations for one week before the test. You must swallow a small amount of radioactive Iodine during the testing procedure. The technician then places a gamma probe in front of your neck, which measures the amount of radioactive Iodine taken up by your thyroid. 

Different Types of Thyroid Blood Tests?

To check whether your thyroid gland works correctly, your doctor might suggest some thyroid blood tests. These tests include the TSH test, T3 test, T4 test, etc.

These tests require you to let your health care professional take your blood sample, which your doctor will examine later. 

TSH Test 

Thyroid Stimulating Hormone (TSH) is a pituitary hormone that controls the secretion of T4 and T3 hormones in our body. The TSH test measures the amount of TSH in your blood. A high TSH level in your blood indicates hypothyroidism or a less active thyroid. It means that your thyroid is not secreting enough hormones. 

A low TSH level in your blood is a symptom of Hyperthyroidism or an overactive thyroid. It indicates that your thyroid is secreting too many hormones.

T3 Test

A high T4 and T3 levels indicate Hyperthyroidism, but sometimes, the T4 level in your blood can be average, but the T3 level is high. That's why the doctor suggests you sign up for both the T4 and the T3 tests. The T3 test measures the amount of T3 hormone, while the T4 test measures the amount of T4 hormone in your blood.

T4 Test

The T4 test measures the amount of T4 hormone in your blood to check your thyroid functionality. 

A high concentration of T4 in your blood suggests you are suffering from Hyperthyroidism. In contrast, a low concentration of the same is a likely symptom of hypothyroidism. Although, that's not always the case. Pregnant women or those who have taken oral contraceptives generally have high levels of thyroid hormones in their blood. 

Patients who generally intake corticosteroids for diagnostic purposes have low T4 concentrations in the blood. 

Certain illnesses and drugs alter the number of blood proteins that "bind" or connect to T4. Until required, bound T4 is stored in reserve in the blood. T4 that is "free" and unbound to these proteins can penetrate body tissues. Many medical practitioners prefer to evaluate free T4 levels because changes in binding protein levels do not impact them.

If you're experiencing any symptoms of thyroid disease, it's important to talk to your doctor and get a thyroid test. There are a few different types of thyroid tests, which may include an ultrasound, thyroid scan, or radioactive iodine uptake test. Your doctor will likely also recommend some blood tests to check the levels of thyroid hormones in your body.

These tests can help to identify the root cause of the problem and ensure that you receive the proper treatment. If you are diagnosed with a thyroid disorder, there are treatments available that can help you manage your condition and feel your best.

If you think you may have a thyroid disorder, it's important to talk to your doctor and get a thyroid test.

When Do I Need a Thyroid Test?

One may need a thyroid test if you think you have symptoms of underactive or overactive thyroid gland. Having excessive thyroid hormones in your blood is called hyperthyroidism and insufficient thyroid hormones is known as hypothyroidism.

Symptoms of Hypothyroidism Include following:

  • Weight gain
  • Tiredness
  • Low tolerance for cold temperatures
  • Irregular menstruation
  • Constipation
  • Hair loss

Symptoms of Hyperthyroidism Include following:

  • Weight loss
  • Tremors in the hands
  • Increased heart rate
  • Puffiness
  • Bulging of the eyes
  • Anxiety
  • Diarrhea

Is Fasting Required for Thyroid Test?

Usually,no special precautions including fasting need to be followed before taking a thyroid test. However, your pathologist can guide you better. For example, if you have to undergo some other health tests along with thyroid hormone levels, you may be asked to fast for 8-10 hours. Drinking water doesn’t come under violation of fasting. 

Should I Take Thyroid Tablets Before Thyroid Test?

If you are taking medicines for thyroid conditions (thyroxine) to treat your thyroid disease, it is recommended that your blood sample be taken before you take your dose for that day. Have your medicine post the tsh test. Always consult your doctor for such suggestions as they know your health condition best and might advise otherwise too.

Is There Any Common Medicine That Interferes With Thyroid Function Tests?

Biotin (Vitamin B7) is a commonly taken over-the-counter supplement that can lead to some aberrancy in your thyroid function tests even when the values are actually normal. Avoid taking biotin 2 days before a thyroid function testing.

Normal Reference Range for Thyroid Function Tests?

Reference ranges for each value under thyroid hormone is not consistent for everyone. It differs based on certain parameters such as age, health condition, and the laboratory that performs the testing.
Common reference ranges for the thyroid panel are enlisted here:

  • TSH: 0.4 to 4.5 mIU/L (may be as high as 7.5 mU/L in 70 year olds)
  • Free T4: Often falls between 0.8 and 1.5 ng/dL in adults.
  • Total T3: 75 to 195 ng/dL (1.1 to 3 nmol/L)

Check your tsh test report or ask your doctor for the normal/reference range. Most laboratory reports mention the reference ranges applied to your thyroid test, however, consult an expert to interpret the results. Also, since it is a panel test, values are generally interpreted together and not seen as individual numbers.


What Should I Take Care of After Getting Tested for Thyroid Hormones?

Once the blood sample for thyroid test is drawn, you can return to normal activities, including driving. A simple thing that you can follow is to avoid strenuous activity with the arm from where the sample was taken for a few hours after the tsh test. If you experience any pain or bleeding, apply (and do not rub) ice packs

Can I Take Thyroid Tests During Pregnancy?

Yes, you can if need be.In fact,it is not uncommon to have thyroid changes during pregnancy. While overactive thyroid affects about one in every 500 pregnancies, underactive thyroid happens in around one in every 250 pregnancies. If you have a pre-existing thyroid condition or develop a thyroid condition during pregnancy, your doctor will monitor your condition and ask for blood tests too. Most likely, your thyroid hormone levels will be checked every 4 to 6 weeks during the first half of your conception, and at least once after 30 weeks.

A thyroid panel test can help identify various conditions including hypothyroidism, hyperthyroidism, Graves' disease, and thyroid cancer. For all your lab test related needs, visit Metropolis.

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