Thyroid Function Panel (TSH, T3, and T4): Blood Test Overview, Clinical Context, and Why Your Doctor May Order It
This blood test measures three important amino acid substances in your blood to help evaluate your metabolism and nervous system function.
{"Measures beta-alanine, beta-aminoisobutyrate (BAIB), and gamma-aminobutyrate (GABA) in blood","Helps diagnose metabolic disorders and evaluate liver or neurological conditions","Sample is collected from a vein in your arm","Results are interpreted by your healthcare provider in context of your overall health","No special preparation is typically needed, but follow your doctor's instructions"}
Key facts at a glance
- LOINC
- 79638-3
- Short code
- AAB-PAT
- Synonyms
- B-Alanine + B-AIB + GABA patt SerPl-Imp
- Category
- chemistry
- Sample
- serum
- Container
- Red-top serum tube (no anticoagulant) or SST (serum separator tube); alternatively lithium-heparin plasma tube
- Units
- N/A
- Ref low
- 0
- Ref high
- 10
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) with ion-exchange chromatography
- CPT
- 82139
- SNOMED
- 395790006
- Specimen volume
- 1-2 mL of serum or plasma
- Stability
- Stable for 24 hours at 2-8°C; for longer storage, freeze at -20°C or below. Avoid repeated freeze-thaw cycles. Stable up to 7 days when refrigerated.
- Hemolysis max
- 100
- Lipemia max
- 50
- Icterus max
- 25
- TAT
- 48–168 hours
- Order
- routine
What is a thyroid function panel and what does it measure in your blood?
This test measures the levels of three substances in your blood: beta-alanine, beta-aminoisobutyrate (BAIB), and gamma-aminobutyrate (GABA). These are amino acid metabolites that your body produces during normal metabolism. The test provides an interpretation pattern rather than individual measurements, helping healthcare providers understand how these substances relate to each other in your body.
What do the thyroid-related substances TSH, T3, and T4 do in your body?
Beta-alanine is an amino acid that helps build carnosine, which protects muscles during exercise. Beta-aminoisobutyrate (BAIB) is produced when your body breaks down certain DNA components. GABA is an important neurotransmitter that helps regulate brain activity and promotes calmness. All three substances are processed by your liver and provide important information about your metabolic health.
How is the thyroid function panel performed during a routine office visit?
A healthcare professional will draw a small blood sample from a vein in your arm. The blood is collected into a tube and sent to a laboratory for analysis. The test requires serum (the liquid part of blood after it clots), so your sample will be processed to separate the serum from blood cells before testing.
Do I need to fast, stop medications, or take other steps to prepare for the test?
Follow any specific instructions given by your healthcare provider. You may need to fast (not eat) for a certain period before the test. Inform your doctor about all medications, vitamins, and supplements you are taking, as some substances may affect test results. Stay well-hydrated and wear a shirt with sleeves that can be easily rolled up for the blood draw.
Reference range
Interpretation provided as narrative report. Beta-alanine: typically <10 µmol/L; Beta-aminoisobutyrate: typically <5 µmol/L; Gamma-aminobutyrate (GABA): typically <0.5 µmol/L in plasma. Elevated levels of beta-aminoisobutyrate may indicate renal tubular dysfunction; elevated GABA may suggest neurotransmitter metabolism disorders.N/A
No special preparation required. Patient should be well-hydrated. For accurate amino acid profiling, avoid high-protein meals within 4 hours of collection if clinically feasible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test helps healthcare providers evaluate metabolic function and detect certain disorders. Abnormal levels may indicate liver disease, since the liver processes these amino acid metabolites. The test can also help assess neurological conditions, as GABA is a key brain neurotransmitter. Patterns in these three substances can help distinguish between different types of metabolic disorders. Your doctor will interpret the results along with your symptoms, medical history, and other test findings to make a diagnosis or monitor your health condition.
Frequently asked questions
Why do I need this specific test?
Are the results immediate?
What do abnormal results mean?
Is the test safe?
Sources
- 1
- 2
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 14, 2026. · Read our editorial policy