TSH stands for thyroid stimulating hormone. A TSH test also called thyrotropin test is a blood test that measures this hormone. The thyroid is a small, butterfly-shaped gland located near your throat. Your thyroid makes hormones that regulate the way your body uses energy. It also plays an important role in regulating your weight, body temperature, muscle strength, and even your mood. TSH is made in a gland in the brain called the pituitary. When thyroid levels in your body are low, the pituitary gland makes more TSH. When thyroid levels are high, the pituitary gland makes less TSH. TSH levels that are too high or too low can indicate your thyroid isn’t working correctly.
You may need a TSH test if you have symptoms of too much thyroid hormone in your blood (hyperthyroidism), or too little thyroid hormone (hypothyroidism).
Symptoms of hyperthyroidism, also known as overactive thyroid, include:
Symptoms of hypothyroidism, also known as underactive thyroid, include:
The TSH test involves simply drawing some blood from your body. The blood will then be analyzed in a lab. It’s best to do this in the morning as your TSH levels can fluctuate throughout the day. No preparation is needed (such as overnight fasting). However, if you’re on certain medications, like dopamine and lithium, you may need to come off them beforehand. Check with your doctor to find out. You shouldn’t feel any pain beyond a small prick from the needle in your arm. You may have some slight bruising too.
Triiodothyronine (T3) is one of two major hormones produced by the thyroid gland, most of the T3 in your body binds to protein. The T3 that doesn’t bind to protein 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.
Your doctor will typically order a T3 test if they suspect a problem with your thyroid.
Potential thyroid disorders include:
Some medications that can affect your T3 levels include:
The T3 test simply involves having your blood drawn. The blood will then be tested in a laboratory. Typically, normal results range from 100 to 200 nanograms per deciliter (ng/dL). A normal T3 test result doesn’t necessarily mean that your thyroid is functioning perfectly. Measuring your T4 and TSH can help your doctor figure out if you have a thyroid problem despite a normal T3 result.
If you’re not pregnant or suffering from liver disease, elevated T3 levels might indicate thyroid issues, such as:
High T3 levels might also indicate high levels of protein in the blood. In rare cases, these elevated levels could indicate thyroid cancer or thyrotoxicosis.
Abnormally low levels of T3 may indicate hypothyroidism or starvation. It could also indicate that you have a long-term illness since T3 levels decrease when you’re sick. If you’re sick enough to be hospitalized, your T3 levels are likely to be low. This is one reason that doctors do not routinely use the T3 test as a thyroid test. Instead, they often use it along with the T4 and TSH test to get a more complete picture of how your thyroid is working.
Your thyroid produces a hormone called thyroxine, which is known as T4. This hormone plays a role in several of your body’s functions, including growth and metabolism.
Too much or too little T4 can indicate thyroid disease.
The T4 hormone comes in two forms:
A test that measures both free and bound T4 is called a total T4 test. Other tests measure just free T4. A free T4 test is considered more accurate than a total T4 test for checking thyroid function.
Purpose and Preparation for T4 test is same as T3, for this reason T3 and T4 are tested simultaneously, as the combined analysis of both T3 and T4 indicate the results. Typical results for the total T4 test in adults generally range from 4.5 to 11.2 micrograms per deciliter (μg/dL). Results for children vary based on age. So talk to your doctor about the normal ranges expected for your child. There may also be some variation between labs. Typical results in adults for the free T4 test generally range from 0.9 to 2.4 nanograms per deciliter (ng/dL). Like total T4 in adults, free T4 also varies in children according to age.
est results may also be affected by pregnancy, estrogen level, liver problems, more severe body-wide illnesses, and inherited changes in a protein that binds T4.
A higher than normal level of T4 may be due to conditions that involve an overactive thyroid, including:
A lower than normal level of T4 may be due to: