Thyroid Panel

Why Get Tested?

To help evaluate thyroid gland function and to help diagnose thyroid disorders.

When to Get Tested?

As part of a health checkup or when symptoms suggest hypo- or hyperthyroidism due to a condition affecting the thyroid. A thyroid panel may be ordered as part of a health checkup or when symptoms suggest hypo- or hyperthyroidism due to a condition affecting the thyroid.

Signs and symptoms of hypothyroidism may include:

  • Weight gain
  • Dry skin
  • Constipation
  • Cold intolerance
  • Puffy skin
  • Hair loss
  • Fatigue
  • Menstrual irregularity in women

Signs and symptoms of hyperthyroidism may include:

  • Increased heart rate
  • Anxiety
  • Weight loss
  • Difficulty sleeping
  • Tremors in the hands
  • Weakness
  • Diarrhea
  • Puffiness around the eyes, dryness, irritation, or bulging of the eyes

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None needed; however, certain medications can interfere with the tests included in the panel, so tell your doctor about any drugs that you are taking.

What is being tested?

A thyroid panel is a group of tests that are often ordered together to help evaluate thyroid gland function and to help diagnose thyroid disorders. The tests included in a thyroid panel measure the amount of thyroid hormones in your blood. These hormones are chemical substances that travel through the bloodstream and control or regulate your body’smetabolism—how it functions and uses energy.

TSH is produced by the pituitary gland and is part of the body’s feedback system to maintain stable amounts of the thyroid hormones T4 and T3 in the blood. When concentrations decrease in the blood, the pituitary is stimulated to release TSH. The TSH in turn stimulates the production and release of T4 and T3 by the thyroid gland. When the system is functioning normally, thyroid production turns on and off to maintain constant blood thyroid hormone levels. The thyroid panel usually includes:

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and AnxietyTips on Blood TestingTips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed. Certain medications can interfere with the tests included in the panel, however, so tell your doctor about any drugs that you are taking.

How is it used?

A thyroid panel is used to screen for or help diagnose hypo– and hyperthyroidism due to various thyroid disorders.

The preferred test to screen for thyroid disorders is a TSH test. If your TSH level is abnormal, it will usually be followed up with a test for total T4 or free T4. Sometimes a total T3 or free T3 will also be performed. A thyroid panel may be requested by your doctor to have all three tests performed at the same time to get a more complete picture.

What does the test result mean?

If the feedback system involving the thyroid gland is not functioning properly due to one of a variety of disorders, then increased or decreased amounts of thyroid hormones may result. When TSH concentrations are increased, the thyroid will make and release inappropriate amounts of T4 and T3, and the person may experience symptoms associated with hyperthyroidism. If there is decreased production of thyroid hormones, the person may experience symptoms of hypothyroidism.

The following table summarizes test results and their potential meaning.

TSH

T4

T3

INTERPRETATION

High Normal Normal Mild (subclinical) hypothyroidism
High Low Low or normal Hypothyroidism
Low Normal Normal Mild (subclinical) hyperthyroidism
Low High or normal High or normal Hyperthyroidism
Low Low or normal Low or normal Nonthyroidal illness; rare pituitary (secondary) hypothyroidism

Is there anything else I should know?

1.  What conditions are associated with hypo- and hyperthyroidism?

The most common causes of thyroid dysfunction are autoimmune-related. Graves disease causes hyperthyroidism and Hashimoto thyroiditis causes hypothyroidism. Both hyper- and hypothyroidism can also be caused by thyroiditis, thyroid cancer, and excessive or deficient production of TSH.

2.  What other tests may be ordered in addition to a thyroid panel?

Blood tests that may be performed in addition to a thyroid panel may include:

  • Thyroid antibodies (Anti TPO & Anti Tg)- to help differentiate different types of thyroiditis and identify autoimmune thyroid conditions
  • Thyroglobulin – to monitor treatment of thyroid cancer