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Prolactin level measured after 1-hour intravenous administration of TRH (Thyrotropin-Releasing Hormone) via serum/plasma

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

This test evaluates how your body responds to TRH, a hormone that stimulates the release of prolactin, a hormone involved in milk production and regulating other reproductive functions.

Quick summary

["Assesses pituitary gland function and prolactin response to TRH stimulation for conditions like hyperprolactinemia or pituitary disorders."]

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

Key facts at a glance

LOINC
1611-3
Short code
Prolactin 1h p TRH IV SerPl-mCnc
Synonyms
Prolactin 1h p TRH IV SerPl-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
85610
SNOMED
396252006
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

Why This Test Is Done

Your doctor may order this test if they suspect a problem with your pituitary gland, such as a tumor, inflammation, or other conditions affecting hormone production. It can also help diagnose or monitor conditions like hyperprolactinemia, which is when prolactin levels are too high.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for a few hours before the blood draw. You’ll receive an injection of TRH, and your blood will be drawn 1 hour later to measure prolactin levels.

How the Test Works

A blood sample is taken before and after the TRH injection. The lab measures prolactin concentration in your serum or plasma using an immunoassay method, which detects the hormone’s presence and amount.

What the Results Mean

Results help determine if your pituitary gland is functioning normally in response to TRH. Abnormally high or low prolactin levels after stimulation may indicate underlying health issues requiring further evaluation.

Reference range

INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A

Specimen: serum

Inform your healthcare provider if you are taking blood thinners. No special preparation required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

TRH-Stimulated Prolactin Serum/Plasma

Frequently asked questions

What causes elevated prolactin levels after TRH stimulation?
Elevated prolactin levels after TRH stimulation may be caused by pituitary tumors (prolactinomas), medications that affect hormone levels, thyroid disorders, kidney problems, or other pituitary or brain conditions. Low response could indicate pituitary dysfunction or other neurological issues.
How often should I get this test?
The frequency depends on your medical condition and treatment. Your doctor may recommend follow-up tests if you have symptoms like infertility, menstrual irregularities, or unexplained headaches, or if you’re being monitored for a known pituitary disorder.
Can I take medications before this test?
Yes, but inform your doctor about all medications, including over-the-counter drugs or supplements, as some may affect prolactin levels. Avoid taking medications that influence hormone balance unless cleared by your provider.
  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