Thyroid-Stimulating Hormone (TSH)

What is TSH?

TSH, also sometimes called thyrotropin, is produced by the pituitary gland and stimulates the thyroid to produce the hormones thyroxine (T4) and triiodothyronine (T3). The thyroid is a butterfly shaped gland that is found near your throat. It produces hormones that are needed to regulate your body’s energy usage. These hormones are also involved in managing your weight and keeping your temperature at a normal level. They also affect your mood and muscle strength. When too much or too little TSH is produced, it impacts the levels of other thyroid hormones. The TSH test can help detect if you have a thyroid disorder like hyperthyroidism or hypothyroidism. A TSH test is a simple blood test that measures how much thyroid hormone is present in your blood.

Why take a TSH test?

The American Thyroid Association (ATA) recognizes TSH as the first test used to screen for and help detect thyroid conditions, such as hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid). TSH tests are also used to monitor existing thyroid conditions and the effectiveness of the treatments chosen. There are several different thyroid tests, including individual T3 tests and T4 tests, and it's important to ensure your testing includes both measurements to be a comprehensive thyroid hormone levels screening.

According to the American Thyroid Association, about 12 percent of people in the US have a thyroid condition, and half of them are unaware. Thyroid conditions can affect anyone but are more common in women. Roughly one in eight women will develop a thyroid problem at some point in their life. Thyroid conditions are sometimes mistaken for symptoms of menopause, therefore women who think they may be entering into menopause should consider getting a TSH test.

What are the symptoms of thyroid disfunction?

Most people get their thyroid hormone levels tested in relation to their experience of the symptoms of thyroid dysfunction. The symptoms of thyroid dysfunction are different depending upon whether the thyroid is under- or overactive.

Hyperthyroidism is marked by an excess of T3 and T4 in the blood. The symptoms of hyperthyroidism (an overactive thyroid) can include:

• Elevated heart rate or palpitations
• Anxiety, irritability, and restlessness
• Excess sweating
• Increased sensitivity to heat
• Weight loss
• Fatigue
• Increased bowel movements
• Sleep disturbances

The most common cause of hyperthyroidism is Graves' disease, which is a genetic thyroid disease that is most common in women. Other causes, such as inflammation of the thyroid (thyroiditis) or nodules on the thyroid can result in the production of excess thyroid hormones.

Hypothyroidism, on the other hand, is marked by insufficient levels of T3 and T4 in the blood. The symptoms of hypothyroidism (an underactive thyroid) can include:

• Depressed heart rate
• Fatigue muscle weakness
• Muscle pain and aches
• Joint pain
• Hair loss
• Weight gain
• Strained bowel movements
• Irregular menstruation
• Depression
• Increased sensitivity to cold
• Swelling of the thyroid, also known as a "goiter"

The most common causes of hypothyroidism is Hashimoto's thyroiditis, an autoimmune disease that can cause the immune system to attack the thyroid. Treatment for thyroid cancer can also result in suppression of thyroid hormone production. Other causes for hypothyroidism include pituitary gland dysfunction, pregnancy, certain congenital diseases, and more.

What do your TSH test results mean?

Normally, your TSH value should range between 1.4 and 4.0 milli-international units per liter (abbreviated mIU/L). If you have a thyroid condition and you are following a course of treatment recommended by your physician or endocrinologist (gland specialist); then your normal ranges would be between 0.3 and 3.0. Values above this range indicate an underactive gland while values below this reference range suggest an overactive gland.

Some medications and medical conditions can lead to inaccurate readings of the amount of TSH present in your blood sample. For instance, large doses of biotin (a drug commonly used to curb hair loss in men) can skew readings of thyroid hormone levels, elevating T3 and T4 levels while leading to low levels of TSH. And just as low TSH levels can be due to medications, high TSH levels can also be falsely influenced by illnesses and medications. As such, you may want to ensure that you are not ill before taking the TSH test, and make sure to disclose all medications you're taking to your doctor.

How are thyroid conditions treated?

An underactive gland is normally treated by taking synthetic thyroid hormones, daily, which will bring the blood levels back to normal. As a result, you feel more energetic and can lose the weight may have you gained. In that case, your TSH levels will be tested every two months to make sure you are receiving the right treatment. If the results come back within normal ranges, your TSH will typically be checked once a year.

An overreactive thyroid is treated in various ways such as using radioactive iodine, anti-thyroid medications, beta blockers, or by surgically removing the gland. If you are diagnosed with an overactive thyroid you will need periodic TSH testing with your healthcare provider to monitor your levels.

Where can I get a TSH test near me?

Please use our Lab Locator to find find a convenient thyroid testing location.

References

American Thyroid Association. Thyroid Function Tests. Available at: https://www.thyroid.org/thyroid-function-tests/. American Thyroid Association. General Information/About Hypothyroidism. Available at: https://www.thyroid.org/hypothyroidism/.

Reviewed By: Dr. Kurt Kloss, MD
Last Reviewed Date: Mar 12, 2020