COMPOUND

Compounds / TRT and hormones

Triptorelin

Triptorelin (Triptorelin Pamoate / Acetate)

TRT and hormones SubQ · IM Restricted (FDA Cat. 2)

Synthetic decapeptide GnRH agonist. FDA-approved as Trelstar (triptorelin pamoate; NDA 020715, 2000) for palliative treatment of advanced prostate cancer in 3.75mg / 11.25mg / 22.5mg depot IM formulations: continuous exposure produces paradoxical pituitary downregulation and chemical castration. Off-label bodybuilding use is the OPPOSITE pattern: a SINGLE low-dose (100-200mcg) SubQ injection causes a 1-2 week LH/FSH/T flare without downregulation: used as one-shot PCT to restart HPTA after AAS cycles. The two indications are mutually exclusive: dose, frequency, and intent must be captured precisely. COMPOUND defaults to the bolus PCT pattern.

At a glance

Half-life
~3 h Free peptide three-compartment model: 6 min / 45 min / 3h terminal. Depot pamoate formulation releases over months: Trelstar 22.5mg covers ~24 weeks. The flare effect (LH/FSH elevation) lasts 7-14 days regardless of plasma t½, because it reflects pituitary stored-pool depletion and recovery.
Routes
SubQ · IM
Vial sizes
0.1 mg · 0.2 mg · 2 mg
Evidence base
3 studies 2 human · 1 review

Mechanism

GnRH receptor (GnRHR) agonist on pituitary gonadotrophs. Acute exposure triggers stored LH and FSH release (the 'flare effect'): useful for HPTA restart. Continuous or repeat exposure causes GnRHR internalization and downregulation → suppressed LH/FSH → castrate-level T (the prostate cancer mechanism). Single bolus uses the flare; depot uses the downregulation. Bolus and depot are pharmacologically opposite uses of the same molecule.

Dosing

Any amounts shown here are reported from published studies only. 2 of 3 catalogued studies involved human subjects. COMPOUND does not publish its own dosing guidance.

Published evidence

  1. Human RCT 2003

    Comparative efficacy of triptorelin pamoate and leuprolide acetate in men with advanced prostate cancer

    Heyns CF, Simonin MP, Grosgurin P, Schall R, Porchet HC BJU Int

    Triptorelin vs leuprolide depot equivalence in prostate cancer: castrate T achieved at month 1 in both arms.

    PMID 12887472

  2. Human pilot 2015

    Single-dose triptorelin diagnostic test for HPG axis function

    Lunenfeld B, Akagbosu F, Afoutou JM, et al. Aging Male

    Single-dose triptorelin diagnostic test characterizes HPG axis responsiveness: supports the bolus flare pattern for HPTA assessment.

  3. Review 2018

    Trelstar (triptorelin pamoate) Prescribing Information: NDA 020715

    FDA / Allergan FDA Drug Label

    Depot PK, T suppression to castrate levels by week 3-4, prostate cancer outcomes. Primary regulatory source for triptorelin pharmacology.

Reported side effects

Injection site pain
Common Mild · Depot IM more painful than bolus SubQ. Pamoate suspension is viscous.
Hot flashes (continuous use)
Very common Moderate · Hypogonadal symptom of chronic exposure / depot: castrate T levels. Not seen with bolus PCT use.
Decreased libido / ED (continuous use)
Very common Moderate · Continuous exposure only; reverses with bolus pattern. Bolus PCT users typically experience the OPPOSITE: libido surge during T flare.
Bone density loss (chronic use)
Common Serious · Chronic depot use only: months of castrate T. Not a bolus PCT concern.
Paradoxical T surge in first 2 weeks of continuous use
Very common Moderate · Clinical 'flare': protect with bicalutamide in prostate cancer. Same phenomenon is the DESIRED effect in PCT bolus use. Same drug, opposite framing.
Mood changes
Common Moderate · Hypogonadal mood symptoms with chronic use; transient elevation/agitation possible during PCT flare.
Fatigue
Common Mild · Continuous depot use.
Anaphylaxis / hypersensitivity
Rare Serious · Rare peptide allergy: discontinue immediately if angioedema or systemic reaction.

Interactions

  • Test Cypionate Contraindicated

    Exogenous testosterone overrides the LH/FSH flare via negative feedback. Defeats the PCT mechanism: the entire point is to restart endogenous T production.

  • Anastrozole Synergy

    Pair with PCT bolus to control E2 spike from T flare: endogenous T 800-1500 ng/dL at day 7-14 aromatizes proportionally.

  • Tamoxifen Synergy

    SERM blocks ER at hypothalamus, complementing pituitary stimulation by triptorelin: common PCT stack.

  • HCG Redundant

    HCG mimics LH at the testicular level: redundant with triptorelin's pituitary LH release. Combination provides no PCT benefit and complicates lab interpretation.

  • Triptorelin Contraindicated

    Repeat bolus dosing within months risks shifting from flare-pattern to downregulation-pattern: chemical castration is the failure mode. Cumulative >1mg/year is the documented threshold.

Reconstitution and storage

Research acetate vials (100mcg or 2mg lyophilised): reconstitute with 1-2mL bacteriostatic water. Trelstar depot uses kit-supplied diluent only; IM ONLY, do not reconstitute with anything else.

Lyophilised acetate: -20°C long-term, refrigerated for use. Reconstituted: refrigerate 2-8°C, use within 30 days. Trelstar depot kit: room temperature, prepare immediately before injection.

Open the reconstitution calculator for Triptorelin