Triptorelin
FDA ApprovedTriptorelin
A GnRH agonist that initially stimulates and then suppresses testosterone production. Used clinically for prostate cancer and researched for post-cycle testosterone restoration.
Dose
100-500 mcg
Route
SubQ injection, Intramuscular
Cycle
Single administration for HPTA axis restart; several months to years for sustained suppression protocols
Storage
Store at 2-8°C (refrigerated), protected from light
What is Triptorelin?
Triptorelin is a synthetic decapeptide analog of gonadotropin-releasing hormone (GnRH). It functions as a GnRH receptor agonist. Initially, it stimulates the pituitary gland, leading to a surge in gonadotropin release (LH and FSH), which in turn increases testosterone and estradiol levels. However, continuous or repeated administration of Triptorelin, especially in depot formulations, causes desensitization and down-regulation of GnRH receptors in the pituitary. This leads to a profound and sustained suppression of gonadotropin release, and consequently, a reduction in sex hormone production (testosterone in males, estradiol in females). In research, its biphasic action is leveraged for different purposes, including the study of prostate cancer treatment and the investigation of hypothalamic-pituitary-gonadal (HPG) axis restoration protocols.
Key Benefits
- Testosterone axis restart research
- Post-cycle recovery
- Hormonal regulation research
Mechanism of Action
- GnRH agonist - initially stimulates, then desensitizes pituitary
- Single pulse can restart HPTA axis
- Sustained use suppresses testosterone
Best For
- Advanced hormonal research
- Post-cycle research
Body Systems
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Molecular Information
Molecular weight
1311.45 g/mol
Length
10 amino acids
Type
Peptide, GnRH agonist
Amino acid sequence
pGlu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH2
pyroglutamyl at N-terminus, D-tryptophan at position 6, and a C-terminal amide
Pharmacokinetics
Time to peak
1-3 hours (for short-acting formulations)
Half-life
3 h
Time to clear
Elimination half-life for short-acting formulations is approximately 3 hours; depot formulations can have effective half-lives of several weeks to months.
Clinical pharmacology data from pharmaceutical dossiers and peer-reviewed studies.
Research Indications
Hypothalamic-Pituitary-Gonadal (HPG) Axis Restart
Researched for its ability to stimulate endogenous testosterone production, particularly in contexts of post-cycle therapy or secondary hypogonadism where a 'reset' of the HPG axis is desired.
Prostate Cancer Research
Widely studied and clinically used to induce chemical castration in males with advanced prostate cancer by suppressing testosterone production.
Research Protocols
| Goal | Dose | Frequency | Route |
|---|---|---|---|
| HPTA Axis Restart (Short-Term Pulsatile Stimulation) | 100-500 mcg | Single subcutaneous (SubQ) injection | Subcutaneous |
| Prostate Cancer Suppression (Long-Term) | 3.75 mg or 11.25 mg (depot formulation) | Once a month or once every three months | Intramuscular |
| Precocious Puberty (Long-Term Suppression) | 3.75 mg (depot formulation) | Once every 28 days | Intramuscular |
| Endometriosis/Uterine Fibroids (Long-Term Suppression) | 3.75 mg (depot formulation) | Once a month for up to 6 months | Intramuscular |
For HPTA restart research, a single, short-acting dose is typically discussed. For sustained suppression, long-acting depot formulations are used in clinical contexts, but this is less common in acute research protocols for HPTA restart.
Peptide Interactions
- Use Caution
Androgens/Anabolic Steroids
Concurrent use of androgens will suppress the HPTA axis, counteracting Triptorelin's role in HPTA restart protocols. For prostate cancer, androgen use is contraindicated.
- Avoid
Other GnRH Agonists/Antagonists
Combining Triptorelin with other GnRH agonists or antagonists may lead to unpredictable hormonal responses and is generally not recommended in research protocols due to redundant or conflicting mechanisms of action.
- Monitor Combination
Drugs affecting bone metabolism (e.g., corticosteroids)
Long-term Triptorelin use can affect bone mineral density. Concomitant use with other medications known to impact bone health may exacerbate risks, requiring careful monitoring.
- Use Caution
Drugs that prolong the QT interval
Some GnRH agonists have been associated with QT interval prolongation. Caution is advised when co-administering with other drugs known to prolong the QT interval.
- Avoid
Testosterone Replacement Therapy (TRT)
TRT provides exogenous testosterone and suppresses endogenous production, directly opposing the goal of HPTA axis restart using Triptorelin. For prostate cancer, TRT would counteract the suppressive effects of Triptorelin.
How to Reconstitute
- 1Gather supplies: Triptorelin lyophilized powder vial, bacteriostatic water for injection (BWFI), sterile syringes, and alcohol wipes.
- 2Clean the rubber stopper of the Triptorelin vial and the BWFI vial with alcohol wipes.
- 3Draw the desired amount of BWFI into a sterile syringe. A common reconstitution ratio is 1 mL of BWFI per 100-500 mcg vial of Triptorelin, resulting in a manageable concentration.
- 4Slowly inject the BWFI into the Triptorelin vial, aiming the stream at the side of the vial to avoid direct impact on the powder.
- 5Do not shake the vial. Gently swirl the vial to facilitate complete dissolution of the powder. This may take a few minutes.
- 6Visually inspect the solution to ensure all powder has dissolved and there are no particulates. The solution should be clear and colorless.
Use bacteriostatic water for injection (BWFI) for reconstitution to ensure sterility and stability for multi-dose vials if applicable. For single-use vials, sterile water for injection (SWFI) is also appropriate.
What to Expect
- Within 1-3 days (single dose for HPTA restart): An initial surge in LH, FSH, and testosterone levels, often referred to as a 'flare-up' effect.
- Within 1-2 weeks (single dose for HPTA restart): A subsequent decrease in testosterone levels after the initial surge, as the pituitary begins to desensitize.
- Within 2-4 weeks (single dose for HPTA restart): Gradual normalization or upward trend of endogenous testosterone production as the HPTA axis responds to the initial stimulation and subsequent withdrawal of GnRH agonist effects.
- Within 4-8 weeks (single dose for HPTA restart): Continued monitoring of hormonal parameters is commonly discussed to assess the full extent of HPTA axis recovery.
- Months (for sustained suppression protocols): Significant and sustained suppression of testosterone levels in contexts such as prostate cancer research.
Side Effects & Safety
| Effect | Frequency | Severity |
|---|---|---|
| Hot flashes | Common | Mild |
| Temporary testosterone suppression | With repeated use | Serious |
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