Thyroid Lab Tests


12 Items

Set Descending Direction
per page

Have you noticed any of the following symptoms?

- Feeling tired all the time, even after a full night of sleep or a nap

- You feel "fuzzy", like there is wool in your brain

- Feeling moody or depressed

- Your sex drive has tanked

- Nerves, anxiety, the "jitters"

- Your digestive system isn't working properly

- You've lost your appetite, or your sense of smell or taste has changed

These are just a few symptoms of thyroid problems.

What is the Thyroid Gland?

The thyroid is a butterfly-shaped endocrine gland that is approximately two inches long and is located at the front of your neck below your Adam's apple. The thyroid plays a major role in growth and metabolism by releasing the hormones thyroxine or T4 and triiodothyronine or T3, which regulate your body's ability to convert calories and oxygen into energy. The hypothalamus in your brain produces thyrotropin-releasing hormone or TRH, which stimulates the release of thyroid stimulating hormone or TSH from your pituitary gland. TSH then travels to your thyroid and prompts the release of T4 and T3 into your bloodstream. Under normal conditions, your thyroid produces approximately 80% T4 and 20% T3, with T3 being four times more potent than T4.

Every cell in your body has receptors for thyroid hormones affecting your cardiovascular system, bone metabolism, protein synthesis, body temperature regulation, cholesterol production, glucose metabolism, cognitive function, and your gastrointestinal tract. An estimated 20 million Americans have some form of thyroid disorder with women being impacted more often than men.

What is Hypothyroidism and What Thyroid Tests Diagnose it?

Hypothyroidism is the most common thyroid disorder characterized by fatigue, weight gain, constipation, hair loss, dry skin, cold intolerance, irregular menstruation, depression, muscle pain, and cognitive impairment. Hypothyroidism is an underactive thyroid gland producing an insufficient amount of hormones necessary for optimal metabolic function. The most common cause of hypothyroidism is Hashimoto's thyroiditis, which is an autoimmune disorder where the body produces antibodies that attack and destroy thyroid gland tissue.

Other causes of hypothyroidism include an iodine deficiency, a pituitary tumor, radiation therapy on your face, neck or chest, pregnancy and childbirth, the aging process, and an under conversion of T4 to T3 due to inflammation, stress, a selenium deficiency, and overexposure to fluoride, chlorine or mercury. If you're experiencing any of the symptoms of hypothyroidism, you should request that your family physician order blood tests that include thyroid stimulating hormone, free T4, free T3, reverse T3, and thyroid antibodies, if he or she suspects Hashimoto's. When interpreted correctly, lab results can help to determine the root cause of your thyroid dysfunction and the appropriate clinical interventions.

Why Is It Important to Understand Your Thyroid Tests?

With so many different symptoms and so many different organ systems potentially affected by thyroid system dysfunction, one might think that a diagnosis would be easy. However, in spite of the available blood tests for thyroid/pituitary/liver/adrenal function, the diagnosis is often missed. One of the most common misconceptions regarding thyroid function is the assumption that any reliance on the requirement that the diagnosis of hypothyroidism depends on an elevated TSH level. Normally, the pituitary gland will secrete Thyroid stimulating hormone (hence TSH) in response to a low circulating thyroid hormone level.

This is thought to reflect the pituitary's sensing of inadequate thyroid hormone levels in the blood that would be consistent with hypothyroidism. There is no question that an elevated TSH can confirm the diagnosis of hypothyroidism, but it is far too insensitive a measure, in other words, the vast majority of patients who have hypothyroidism do not have an elevated TSH level. Some have suggested that perhaps the upper limit of what is considered normal is too high, instead of the normal TSH range being from 1.0-4.5, the range of normal for TSH should be 0.5-2.5. In that way, more patients would be considered hypothyroid.

Furthermore, the lab level of TSH tends to vary throughout different times during the day making it less useful to rely on as the average level. MSG (monosodium glutamate) and stress tend to lower the TSH level, for example.

The most commonly used tests of thyroid hormone levels (note that I use the term level rather than function because the two are not always equal) are the T4 (or total T4), T3-uptake, FTI (also called the T7 or Free Thyroxine Index), and total T3 (sometimes called the T3-by-RIA). These tests are also unreliable because they do not reflect the hormone level that is actually available for action. Only the free T4 and free T3 are available to act on the cells. The total T4 and total T3 (as is most commonly measured) is a mixture of protein-bound T4 and T3 (and therefore not available to the cells) and the free T4 and T3. A large percentage of patients have low levels of the free T4 and free T3 even when all the other more commonly used tests are normal. Complicating the problem is the fact that these symptoms may present themselves while all the usual blood tests (TSH, FI, Total T3, etc) appear to be normal. When patients with Free T4 and Free T3 hormone levels below normal with or without an elevated TSH are given appropriate therapy, many report a tremendous improvement in the symptoms classically associated with hypothyroidism. Even when the lab work does not indicate low thyroid levels, many patients appear to fit the profile for low thyroid action. In fact, many of the best thyroidologists use the response to therapy as the major determinant of whether or not the patient was in fact hypothyroid. The diagnosis was confirmed by the response to the proper therapy. Even many of the most prestigious textbooks validate this approach.



1-     Go to the "Find a Location" page to find the closest lab location. Please only go to “Quest Diagnostics” locations.

2-     Go to "Choose a Test" and add your selection (s) in the shopping cart. You can also save money by buying bundled lab test panels.

3-     If you have a discount coupon code, add it to your cart.

4-     Pay using a credit card.

5-     You will receive three emails: an order confirmation, detailed instructions, and a lab requisition form by email during business hours (Monday-Friday 9-5 PM Central).

6-     Print the lab requisition form (PDF file).

7-     Take that form to the closest Quest Diagnostics location with a picture ID. Get your blood drawn.  

8-     Your results will be ready within 5-7 business days (depending on the test). You will received them by email.