TRH (Protirelin)_Dosage, benefits & legal status
Also known as TRH, protirelin, thyrotropin-releasing hormone, Thyrel TRH, protirelin tartrate, Hirtonin, Thyrotropin TRH, TRH Thyrotropin
The brain hormone behind a discontinued thyroid test, often sold under the wrong name.
What is TRH (Protirelin)?
Plain language first. The technical label stays, but it never stands alone.Overview
A tiny hormone from the brain that switches on the thyroid chain. Doctors once injected it a single time to test that chain, and in Japan it is still used for a movement disorder.
Protirelin (5-oxo-L-prolyl-L-histidyl-L-prolinamide, pGlu-His-Pro-NH2) is the synthetic form of thyrotropin-releasing hormone. It stimulates TSH and prolactin release from the anterior pituitary. It was FDA-approved as Thyrel TRH, 500 mcg for intravenous use as an adjunct in the diagnostic assessment of thyroid function; US production stopped in 2002 and the product is listed as discontinued. Protirelin tartrate injection remains approved in Japan for ataxia in spinocerebellar degeneration and for prolonged impaired consciousness.
What it's used for
Its approved uses are a one-off pituitary and thyroid test in the US, now discontinued, and treatment of spinocerebellar degeneration in Japan. Peptide vendors sell it as a research chemical.
How does TRH (Protirelin) work?
What it does in the body, and where.TRH sits at the top of the chain that runs the thyroid.
- 01The brain releases itNeurons in the hypothalamus release TRH into the small blood supply that feeds the pituitary gland.
- 02The pituitary answers with TSHTRH binds receptors on pituitary cells, which release TSH and also prolactin. TSH then tells the thyroid to make thyroid hormone.
- 03The test used that responseAfter a single injection, TSH normally peaks 20 to 30 minutes later. A flat or exaggerated rise pointed to where in the chain a problem sat.
- 04It is cleared in minutesThe label gives a half-life of about five minutes, and the response weakens when doses are repeated close together.
What else is it used for?
Each group carries its own evidence level.Approved means regulators have cleared it for that purpose. Investigational means it is in trials. Early research means it is being studied and is not established.
Thyroid and pituitary testing
FDA-approved- RegulatoryThe US label used a single 500 mcg injection into a vein. TSH peaks 20 to 30 minutes later and returns to baseline in about three hours.
- RegulatoryProduction stopped in 2002. The American Thyroid Association noted at the time that sensitive TSH blood tests had already made the TRH test rarely necessary.
Depression
Early research- Human trialEight inpatients with treatment-resistant depression received 500 mcg into the spinal fluid and a sham procedure a week apart. Five of the eight responded, quickly but briefly.
Vendor listings often call it "Thyrotropin TRH". Thyrotropin is another name for TSH, the hormone TRH tells the pituitary to release, and it is sold as a separate prescription drug, thyrotropin alfa, for thyroid cancer follow-up. The two are not interchangeable. A 25 mg vial also holds as much protirelin as fifty of the label's 500 mcg test doses.
The published record
Papers about TRH (Protirelin) · this compound only
Searched: protirelin, TRH stimulation test, TRH test, thyrotropin-releasing hormone administration, intravenous TRH, Thyrel TRH, Hirtonin.
Left out: TRH (the endogenous hormone in general, tens of thousands of physiology papers); thyrotropin-releasing hormone (the endogenous hormone in general); Thyrotropin (a different hormone (TSH); the vendor label is a misnomer).
382 papers tagged human · 342 not reviews or lab · 45 clinical trial publications
How the compound was given: 131 applied to skin · 130 injected · 33 by mouth or rectal · 2 intranasal · 231 route not stated in the abstract
Read from each paper's indexing terms and abstract, by rule. A paper that mentions a cream studied a cream, not necessarily the product being sold.
15 registered trials · 4 with posted results
Furthest stage reached: Approved in the US, no longer sold
Counted from Europe PMC indexing, not read by a person; a human tag can land on reviews, commentary or lab papers; clinical trial publications is the narrower count. A preprint and its journal version count once. 463 papers and 15 trials held here.
At a glance
Four things to know about TRH (Protirelin)
Evidence
FDA-approved
Category
Sexual and hormonal
Common vial
25 mg
Half-life
About 5 minutes in the blood
How much, and do you cycle it?
The range, and whether you take breaks.Set by the label, once, for a test. A single test dose Discontinued
The label describes one injection per test. It notes that the TSH response shrinks when TRH is repeated, and recommends seven days between tests.
How long does it stay in the body?
The half-life, and where the figure comes from.About 5 minutes in the bloodDiscontinued label
Measured after an injection into a vein. The TSH it releases lasts much longer, returning to baseline after about three hours.
Source: TRH (protirelin) labeling, clinical pharmacology section, DailyMed setid af5da799-76bf-415a-9dc7-99c7ddc62bc4
You can compare this against the whole library to see where it sits.
How do I dose and price it?
Enter your vial and your dose. Pick a mix. We show the draw and the cost.The vial holds a fixed amount of drug. Adding more water does not make more drug, it just spreads it thinner, so you draw a bigger number on the syringe for the same dose.
Choose your mix
Measuring the water1 mL = one full 100-unit syringe.
TRH (Protirelin) starts at $73.00 across 3 vendors, typically $2.92 – $4.75 per mg.
4 listings, last read Nov 15, 2026. Shipping and card fees are not included.
How do you store it?
Before mixing, and after.Follow the label that came with it.
This is an approved product, and its own label sets how long it keeps once mixed. Those windows vary enormously between products, from use-immediately to about a month, so the label is the only thing worth following here. Vials of the same compound sold by peptide vendors arrive with no label and no established holding time.
What are the side effects and cautions?
Known cautions and warnings for this compound.Who should avoid it
- A known pituitary tumor, since bleeding into the pituitary has been reported after testing in people with large adenomas
- Pregnancy or breastfeeding, without medical advice
Stop and get help
- Chest pressure, throat tightness or trouble breathing
- A sudden severe headache or a change in vision
Common effects
- Flushing
- An urge to urinate
- Nausea
- Headache
- Lightheadedness
- A strange taste or a dry mouth
Where this page says nothing is established, that means nobody has studied it, not that a compound is safe.
Is TRH (Protirelin) approved?
And where the numbers on this page come from.Approved, but no longer sold in the United States. TRH (Protirelin) was approved by the FDA, and the US product has since been discontinued. It is also approved in Japan.
- Approval statusFDA-approved
- RouteInto a vein, as a single test dose
- Checked29 September 2026
- Approved outside the USJapan: Approved in Japan as protirelin tartrate injection, sold as Hirtonin and as generics, for ataxia in spinocerebellar degeneration and for prolonged impaired consciousness. Not currently marketed in the US.This does not change the United States position above.
- DoseFrom a discontinued product or program. No current label supports this dose.
- Vial sizeFrom what vendors typically list; not a recommendation.
- SourcesTRH (protirelin) labelling, DailyMed (compounded product; text follows the Thyrel TRH label)American Thyroid Association. Thyrel TRH temporarily removed from marketPMDA. Protirelin tartrate injection 2 mg package insert (Japan)Marangell LB, et al. Effects of intrathecal thyrotropin-releasing hormone (protirelin) in refractory depressed patients. Arch Gen Psychiatry
What has happened recently
FDA-approved as Thyrel TRH for thyroid and pituitary testing. The manufacturer halted production in 2002 and the product is listed as discontinued in the US. Labeling for compounded TRH still appears on DailyMed, marked as not approved by FDA. Approved in Japan as protirelin tartrate injection.
You can compare this against the whole library, or read how to check a seller.
What else is like TRH (Protirelin)?
Others in Sexual and hormonal, side by side.If you're weighing TRH (Protirelin), it's worth reading Cabergoline, Toremifene, and Angiotensin II (Giapreza) in the same class.
The brain hormone behind a discontinued thyroid test, often sold under the wrong name.
- Dose
- Set by the label
- How often
- Once, for a test
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- Dose
- 0.25 up to 1 mg per dose, twice a week
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- Dose
- 60 mg per day
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- Dose
- 20 ng/kg/min to start, adjusted every 5 minutes (label)
- How often
- Continuous infusion, adjusted to blood pressure
Guides for this compound
- How to Reconstitute a Peptide
Mix peptide powder with bacteriostatic water, step by step.
- How to Read an Insulin Syringe
Read the units, convert to millilitres, and draw the exact dose.
- mcg vs mg: The Peptide Dosing Mistake to Avoid
Your vial says mg and your protocol says mcg. Here is the conversion and how to check it.
Sources
- TRH (protirelin) labelling, DailyMed (compounded product; text follows the Thyrel TRH label)500 mcg intravenous dose for adults, plasma half-life about five minutes, TSH peak at 20 to 30 minutes, seven days between repeat tests.
- American Thyroid Association. Thyrel TRH temporarily removed from market(2002)Production halted in July 2002; the test had become rarely needed after sensitive TSH assays.
- PMDA. Protirelin tartrate injection 2 mg package insert (Japan)(2025)Approved in Japan for prolonged impaired consciousness and for spinocerebellar degeneration.
- Marangell LB, et al. Effects of intrathecal thyrotropin-releasing hormone (protirelin) in refractory depressed patients. Arch Gen Psychiatry(1997)Five of eight patients responded to 500 mcg given into the spinal fluid; responses were rapid but short-lived.
Beyond these, 478 records are indexed for this compound. Browse the records