Thyroid function tests are blood tests that assess how well the thyroid gland in the neck produces thyroid hormone and how much it needs to be stimulated.
What is TSH?
Thyroid Stimulating Hormone (TSH), a key player in thyroid function, is produced in the pituitary gland, located in the head. TSH levels can indicate how well the thyroid is functioning:
- High TSH Levels: This can indicate that the thyroid gland is having difficulty producing enough thyroid hormone and, therefore, requires higher levels of TSH to stimulate it.
- Low TSH Levels: This can indicate high thyroid hormone levels, which turn off the pituitary function of producing TSH.
A thyroid screening test generally measures only TSH because it is a very sensitive marker for hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid). If TSH levels are abnormal, a free T4 test may be ordered separately, or it may be a “reflex” test, automatically done if TSH levels are abnormal.
What is Free T4?
A free T4 test measures the amount of thyroid hormone in the blood.
- Low Free T4 Levels (Hypothyroidism): This can result in symptoms such as fatigue, weight gain, cold intolerance, hair thinning, poor concentration, constipation, and dry skin.
- High Free T4 Levels (Hyperthyroidism): This can result in symptoms such as heat intolerance, fast heartbeat, nervousness, and unexplained weight loss.
What Are Normal Ranges for Thyroid Function Test Results?
- Normal TSH: 0.5 to 5.0 milli-international units per liter (mIU/L)
- Normal Free T4: 5.0 to 12.0 micrograms per deciliter (µg/dL)
Where Can I Order a Thyroid Test?
You can order your own thyroid function test online through QuickMD. The test can be collected at any LabCorp location in the US, and one of the QuickMD doctors will contact you with the results.
Get Professional Advice on Thyroid Tests with QuickMD
For personalized medical advice and to order a thyroid function test, QuickMD’s telemedicine urgent care services are here to help. Consult with a QuickMD provider.
