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Free Alpha-Subunit, Serum/Plasma — Concentration

Published: August 9, 2026Updated: August 16, 2026

A blood test measuring the free alpha-subunit portion of pituitary and other glycoprotein hormones, often used when evaluating possible pituitary disorders.

Quick summary

["This test measures a hormone component in blood and is usually interpreted alongside other pituitary hormone results."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
100833-3
Short code
Alpha subunit free sp4 p chal SerPl-aCnc
Synonyms
Alpha subunit free sp4 p chal SerPl-aCnc
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
44
Ref high
147
Critical range
— – 100 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84075
SNOMED
27550007
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test?

This test measures the free alpha-subunit of glycoprotein hormones such as follicle-stimulating hormone, luteinizing hormone, and thyroid-stimulating hormone. A blood sample is analyzed to determine the concentration of this hormone component.

Why might I need this test?

A clinician may order this test when symptoms or other laboratory findings suggest a pituitary or hypothalamic disorder. It may be used to help evaluate certain pituitary tumors and is generally reviewed with related hormone tests.

How is the test performed?

A blood sample is collected, usually from a vein, and sent to a laboratory. The free alpha-subunit is measured using laboratory methods designed to detect its concentration in serum or plasma.

How do I prepare for the test?

Special preparation is usually not required unless your clinician gives specific instructions. Tell the laboratory if you are pregnant or taking hormone medicines, because these can affect hormone-related results.

Reference range

Adult: 44-147 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Alpha-Subunit

Frequently asked questions

Is fasting required for this test?
Fasting is generally not required, but your clinician or laboratory may provide different instructions for a specific clinical situation.
Does this test diagnose a pituitary tumor by itself?
No. This test is one part of an evaluation and is typically interpreted together with other hormone tests, symptoms, and imaging studies.
Can hormone medicines affect the result?
Yes. Medicines that stimulate or suppress pituitary hormones can change hormone-related measurements, so tell your clinician about all medicines and supplements you use.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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 16, 2026. · Read our editorial policy