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PeptideHormone

Thyrotropin-releasing hormoneTRH

The hypothalamic trigger for the thyroid axis.

EndogenousEstablishedWithdrawn

A tripeptide at the top of the thyroid axis — the shortest sentence in the catalog, and among the most consequential.

Identity

Class
Tripeptide (3 aa) — the smallest peptide hormone here
Source
Hypothalamus
Receptor
TRH receptor (TRHR), a class A GPCR

Key properties

Evidence floorClinicalREF1CLIN1
Molecular weight
~362.4 Da
REF
Half-life (native)
~2–5 min
CLIN
Model dosing

Approximate values for the native hormone; engineered analogs are often deliberately larger and far longer-acting. Each figure carries its own provenance tier, and the floor is the weakest of them - the Standard.

Mechanism

TRH stimulates the anterior pituitary to release TSH (and prolactin), setting the tone of the thyroid axis. At just three residues it is among the smallest peptide hormones, showing that potency does not require length.

Reference notes

  • TRH is only three amino acids — minimal size, full hormonal activity.
  • It drives both TSH and prolactin secretion.
  • It sits atop the hypothalamic–pituitary–thyroid axis.

Regulatory status

United States · reviewed September 2026
WithdrawnTRH is a formerly approved product that is no longer marketed.
Basis
Protirelin (Thyrel TRH) was approved as a diagnostic and later discontinued in the US.

Status describes the molecule as a drug substance under US law and is an editorial reading of the public record — approvals, trial registrations, and the FDA 503A bulk-substances list. It is not legal advice and it changes; the review date above is the last time the table was checked. Other jurisdictions are noted only where they differ materially.

Common questions

What is Thyrotropin-releasing hormone (TRH)?
The hypothalamic trigger for the thyroid axis. Structurally it is Tripeptide (3 aa) — the smallest peptide hormone here.
How does TRH work?
TRH stimulates the anterior pituitary to release TSH (and prolactin), setting the tone of the thyroid axis. At just three residues it is among the smallest peptide hormones, showing that potency does not require length.
How strong is the evidence for TRH?
PeptideHormone grades TRH at the "Established" evidence tier — its mechanism and core effects are settled across the peer-reviewed literature. It is catalogued as an endogenous signal the body produces itself, and the tier is an editorial judgment about the public literature that can change as the science does.
What is the half-life of TRH?
The reported circulating half-life of TRH is ~2–5 min.
Is TRH FDA-approved?
No — as of September 2026, TRH is a formerly approved product that is no longer marketed. Protirelin (Thyrel TRH) was approved as a diagnostic and later discontinued in the US. Status is US-centric and can change; check the FDA record for the current position.

In the literature

Live registry counts · retrieved
Registered trialsREF
183 recruiting
  • Ph 11
  • Ph 25
  • Ph 34
  • Ph 40
Open on ClinicalTrials.gov
PubMed recordsREF
13,978
Since 2022583 · 4%
Open on PubMed

Searched as Thyrotropin-releasing hormone, TRH. Counts are search hits from the primary registries, not a curated set and not a grade – a measure of how much work exists on TRH, not how it turned out.

Selected literature

Curated peer-reviewed reviews, sourced from PubMed. Selected for relevance, not exhaustive — open any entry on PubMed for the full record and its primary citations.

  1. 1.Thyrotropin-releasing hormone analogs · Mini reviews in medicinal chemistry, 2006 · PMID 16472189
  2. 2.Thyrotropin-releasing hormone · The New England journal of medicine, 1982 · PMID 6798440

External references

TRH in the public knowledge graph — the same entity resolved across the authoritative chemistry and protein databases.