Triptorelin monograph

Triptorelin

Overview

Triptorelin is a long-acting synthetic GnRH agonist used clinically to suppress pituitary gonadotropin release and downstream sex-steroid production. In men, that means medical castration for advanced prostate cancer; in pediatrics, it is used for central precocious puberty; outside approved medicine it is sometimes discussed for fertility/endocrine suppression, but that use is not evidence-based for bodybuilding. It is a depot peptide drug with a predictable initial flare followed by pituitary downregulation and sustained suppression.

Pharmacokinetics & Mechanism

• Class: Synthetic gonadotropin-releasing hormone (GnRH/LHRH) agonist peptide
• Mechanism of action: Triptorelin binds GnRH receptors on anterior pituitary gonadotrophs and initially stimulates LH/FSH release. With continuous exposure, receptor desensitization and downregulation occur, suppressing LH/FSH secretion and thereby reducing gonadal testosterone or estradiol production. The early flare can transiently worsen hormone-driven symptoms before suppression is established.
• Target(s): GnRH receptor (pituitary GnRHR); downstream hypothalamic-pituitary-gonadal axis; suppresses LH and FSH, secondarily lowering testicular testosterone and ovarian estradiol. Continuous agonism rather than antagonism is the key pathway.
• Route(s) of administration: Intramuscular depot injection (approved human products); some non-US/nonstandard formulations also exist in other markets. Not an oral drug. Animal-product triptorelin formulations also exist and should not be confused with human prescription products.
• Onset: Pharmacodynamic suppression is not immediate. There is an initial gonadotropin/testosterone flare after first dose, then suppression over days to a few weeks; clinical castration is generally reached by about 2-4 weeks in prostate-cancer use.
• Half-life: Depot formulations have a clinically relevant duration of action of 4, 12, or 24 weeks depending on product strength (e.g., 3.75 mg q4wk, 11.25 mg q12wk, 22.5 mg q24wk). The true terminal elimination half-life is not consistently stated in the accessible label text and is formulation-dependent; label and review sources emphasize duration of depot effect more than a single terminal half-life. Not well established from the sources accessed here for a single human value.
• Metabolism / clearance: Peptide degraded by tissue/proteolytic metabolism into fragments; label text indicates C-terminal fragments from tissue degradation. Clearance is via peptide catabolism with renal and hepatic contribution for fragments; unchanged parent drug is not the main clearance route. No meaningful CYP-mediated metabolism is expected.