Thyroid Panel (TSH + Free T4)
A comprehensive thyroid screening test that measures TSH and Free T4 levels to evaluate thyroid function and help diagnose hypothyroidism or hyperthyroidism.
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What this test measures
This thyroid panel measures two essential markers that work together to evaluate thyroid function. Thyroid-stimulating hormone (TSH) is produced by the pituitary gland and triggers the thyroid to produce and release its hormones thyroxine (T4) and triiodothyronine (T3). Thyroxine (T4) is the main hormone released by the thyroid gland into the bloodstream, and Free T4 specifically measures the unbound, active portion that can enter tissues and affect the body.
These hormones are essential for maintaining the body's metabolic rate: the speed at which the body transforms food into energy. T3 and T4 help control how the body stores and uses energy to do its work (metabolism), and also help control many other body processes including heart rate, body temperature, nervous system function, and weight regulation. The TSH and Free T4 test combination provides a comprehensive picture of thyroid health, as T4 tests more accurately reflect thyroid function when combined with a TSH test.
What's included
Who should consider this test
You might consider this test if you are experiencing any of the following:
- Individuals experiencing unexplained fatigue, weight changes, or mood fluctuations that may indicate thyroid dysfunction
- Those with family history of thyroid disorders, autoimmune conditions, or endocrine problems
- People with symptoms of hypothyroidism such as cold intolerance, constipation, dry skin, or hair loss
- Individuals experiencing symptoms of hyperthyroidism including rapid heartbeat, anxiety, tremors, or unexplained weight loss
- Adults over 60 years old, as thyroid disorders become more common with age
- Those currently taking thyroid medication who want to monitor their treatment effectiveness independently
What to expect
Preparation
No special preparation is typically required for this test. Fasting is not necessary. However, individuals taking biotin supplements should discontinue use at least 72 hours before testing, as biotin can interfere with thyroid test results. Those taking thyroid medications should consult with their healthcare provider about timing, as some prefer testing before the daily dose.
Sample Type
A blood sample is collected from a vein in the arm using a standard blood draw procedure.
Collection
The blood draw typically takes less than 5 minutes. A healthcare professional will clean the arm, insert a small needle into a vein, and collect the sample into test tubes. Most people experience only minimal discomfort.
Turnaround
Results are typically available within 1-2 business days and will be accessible through the online patient portal with email notification when ready.
Understanding your results
Since TSH triggers the production of T4 and elevated T4 levels prevent the release of TSH, these hormones directly affect each other. TSH levels go in the opposite direction of thyroid hormones: when thyroid hormones are low (hypothyroidism), the body creates more TSH to produce more T3 and T4. Understanding this inverse relationship is key to interpreting results, as normal ranges can vary between laboratories and individual circumstances may affect optimal levels.
| Population | Reference Range | Notes |
|---|---|---|
| Adults (non-pregnant) | TSH: 0.4-4.5 mIU/L, Free T4: 0.8-1.8 ng/dL | Most common reference ranges, though some labs use slightly different intervals |
| Adults over 60 | TSH: May be slightly higher than standard adult ranges | Age-related changes are normal and don't necessarily indicate thyroid disease |
| Pregnant women | Trimester-specific ranges apply | Pregnancy causes changes in thyroid hormone levels requiring specialized interpretation |
Reference ranges shown are general guidelines. Your lab report will include the specific reference range used by the laboratory that processed your sample, which is the authoritative range for interpreting your results.
What does a “Low” result mean?
Low TSH levels are usually a sign of hyperthyroidism, with symptoms that may include rapid heartbeat (palpitations), feeling shaky and/or anxious, unexplained weight loss with increased appetite, diarrhea and more frequent bowel movements, and vision changes. Symptoms of hyperthyroidism include increased basal metabolic rate, weight loss, increased appetite, sweating, tremors, heat sensitivity, irritability, diarrhea, and insomnia. Low Free T4 levels typically suggest hypothyroidism and may occur alongside elevated TSH levels.
What does a “High” result mean?
High TSH levels are usually a sign of hypothyroidism, which occurs when the thyroid isn't making enough thyroid hormone, causing the condition called hypothyroidism or underactive thyroid. Symptoms may range from minimal to more pronounced and can include cold intolerance, fatigue, weight gain, dry skin, constipation, and voice changes. High Free T4 levels, conversely, may indicate thyrotoxicosis, which can result from hyperthyroidism (overactive thyroid), thyroid inflammation (thyroiditis), or taking excessive amounts of thyroid medication.
Privacy & confidentiality
All test orders are authorized and results reviewed by an independent, board-certified physician who is not the patient's personal doctor. Your thyroid test results are completely confidential and protected by strict privacy measures. Results are <u>not reported to your doctor</u> unless you choose to share them, and they are <u>not part of your medical records</u> with your primary care provider or health system. The test will <u>not appear on insurance statements</u> or explanation of benefits (EOB) forms, ensuring complete discretion. Your employer, insurance company, and other family members have no access to these results. All testing is conducted through CLIA-certified laboratories with secure, encrypted result delivery. This privacy protection allows individuals to monitor their thyroid health proactively, understand their hormone levels, and make informed decisions about their health without concerns about medical record documentation or insurance implications. With no doctor visit required, this test provides convenient, confidential access to important thyroid health information.
Frequently asked questions
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CPT Code: 84443, 84439
This test may not be available in: NY, NJ, RI
This page is for informational purposes only and does not constitute medical advice. Always consult with a healthcare provider regarding any health concerns. LevelPanel does not diagnose, treat, or prescribe.
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