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Thyroid Testing: TSH, T3 & T4
Blog 4 min read
Thyroid Testing: TSH, T3 & T4
Mar 24, LabFinder Team

There are several blood tests connected to the function of the thyroid gland, which is located in the throat just below the Adam’s apple. The thyroid secretes several hormones throughout the body, including TSH, T4 and T3, which are essential to its function.

When the hypothalamus in the brain secretes thyrotropin-releasing hormone (TRH), it in turn prompts the pituitary gland to release TSH (Thyroid Stimulating Hormone)TSH then triggers the thyroid gland to make two hormones: triiodothyronine (T3) and thyroxine (T4), both of which help to control your body’s metabolism. According to WebMD, thyroid function and the resulting levels of each of these hormones are crucial to brain development during infancy and childhood, but there are many other thyroid conditions connected to the function of this small but powerful gland that can occur at all ages:

  • Hyperthyroidism: Characterized by increased heart rate, anxiety, weight loss, difficulty sleeping, tremors in the hands, weakness, diarrhea, light sensitivity, visual disturbances, including puffiness around the eyes, dryness, irritation, and, in some cases, bulging of the eyes.
  • Hypothyroidism: Characterized by weight gain, dry skin, constipation, cold intolerance, puffy skin, hair loss, fatigue, menstrual irregularity in women, or enlarged thyroid gland (goiter).
  • Goiter: An enlargement of the thyroid gland, potentially connected to many causes including hypothyroidism, hyperthyroidism, and in some cases even normal thyroid function.
  • Thyroid Nodules: Characterized by lumps or abnormal masses in the thyroid, which can be caused by a range of things including benign cysts or tumors, or, less frequently, thyroid cancer.
  • Thyroid Cancer: More common in women than men, thyroid cancer typically occurs in adulthood, often before the age of 55. While there are different kinds of thyroid cancer depending on the cell type that has become cancerous, most are treatable if detected early through blood tests.

Thyroid-Testing-ImageIf your doctor suspects you have any of the above symptoms, he or she may order blood work for you to get more information related to the different hormones connected to the function of your thyroid gland. There are several different thyroid tests your doctor could administer in this event.

The first is a Thyroid Stimulating Hormone Blood Test, used to determine the effectiveness of your thyroid’s function and diagnose potential thyroid disorders. This test is generally administered in cases where patients experiences symptoms related to hypothyroidism. The Mayo Clinic website points out how effective these tests are: “In the past, doctors weren’t able to detect hypothyroidism until symptoms were fairly advanced. But by using the sensitive TSH test, doctors are able to diagnose thyroid disorders much earlier — often before you experience symptoms.”

The T3, Total Test is another test that evaluates thyroid function, and a popular alternative to the THS test, particularly if your doctor suspects you have hyperthyroidism. This test is also used to detect thyroid disease.

Finally, The TSH w/ Reflex Free T4 Test is ordered when a patient has symptoms linked to hyperthyroidism or hypothyroidism, and is also often requested if there are abnormal or out of range results on the TSH test.

Your doctor may order only one of these tests, though they can all be administered simultaneously, so double check with your doctor to understand what he is prescribing and make sure you get the most out of your trip to the lab. According to the American Thyroid Association, these tests can be combined in different ways depending on your symptoms to more accurately determine how the thyroid gland is functioning.


LabFinder is a no-cost, online platform for people to easily schedule their medical tests and view results securely. The LabFinder team is passionate about improving the ‘patient and doctor experience’ through better communication, reduce out-of-pocket expenses and making everyone know more about their own medical tests. The mission of LabFinder is simple: we want to be solution to you and get you the test results you deserve so you can make right choices about your health.