TRH (Thyrotropin-Releasing Hormone)

Hormonal / Thyroid

Also known as: Thyrotropin-Releasing Hormone, Protirelin, Thyroliberin, pGlu-His-Pro-NH2

Hypothalamic Releasing HormonesResearch phase: Endogenous hormone (well characterized)Regulatory: Endogenous peptide. Synthetic form (protirelin) was previously FDA-approved as a diagnostic agent for thyroid function.

Mechanism

TRH is the smallest hypothalamic releasing hormone — just three amino acids. Released from the hypothalamus, it stimulates the pituitary to release TSH (thyroid-stimulating hormone), which in turn drives the thyroid gland to produce T3 and T4. TRH also stimulates prolactin release and has neuromodulatory effects including analeptic (arousal) properties.

Technical detail

TRH (pGlu-His-Pro-NH2) is a hypothalamic tripeptide that binds TRH receptors (TRHR1/TRHR2), Gq-coupled GPCRs on anterior pituitary thyrotrophs and lactotrophs. Activation stimulates PLC-IP3-DAG signaling, releasing TSH and prolactin. TSH then drives thyroid follicular cells to synthesize T3/T4 via the TSH receptor-cAMP-PKA axis. TRH is also widely distributed in CNS (brainstem, spinal cord) with neuromodulatory roles including arousal, thermoregulation, and gastric motility. Rapidly degraded by pyroglutamyl peptidase II (PPII).

Evidence

  • Thyrotropin-releasing hormone has stimulatory effects on ventilation in humans.

    Nink M, Krause U, Lehnert H, Heuberger W, Huber I, Schulz R (1991) — Acta physiologica Scandinavica — PMID: 1907074

    Healthy human study found IV TRH rapidly increased minute ventilation and ventilatory airflow under basal and CO2-stimulated conditions, with associated CNS arousal-type effects and transient adverse effects like nausea, dizziness, and palpitations.

    moderate

  • Oral thyrotropin-releasing hormone treatment in inherited ataxias.

    Bonuccelli U, Nuti A, Cei G, Rossi G, Grasso L, Martino E (1988) — Clinical neuropharmacology — PMID: 3148366

    Placebo-controlled oral TRH study in hereditary ataxias found mild but significant improvement in manual dexterity and some eye-movement abnormalities, with limited effect on broader disability scores and no notable side effects.

    moderate

  • Controlled trial of thyrotropin releasing hormone in amyotrophic lateral sclerosis.

    Brooke MH, Florence JM, Heller SL, Kaiser KK, Phillips D, Gruber A (1986) — Neurology — PMID: 3080694

    Double-blind controlled ALS trial (30 patients) using IM TRH for 2 months found only temporary muscle strength improvement in some muscles without meaningful functional benefit and without altering disease course.

    moderate
Build a personalized protocol with TRH (Thyrotropin-Releasing Hormone) →