Triptorelin

What is triptorelin?

Triptorelin is a synthetic version of gonadotropin-releasing hormone (GnRH), the brain signal that controls the reproductive hormones. It belongs to the class of drugs called GnRH agonists, alongside leuprolide, goserelin and buserelin. It has been in clinical use since the 1980s.

In the US, triptorelin is sold as Trelstar for the palliative treatment of advanced prostate cancer, and as Triptodur for central precocious puberty in children. In Europe and elsewhere it is widely sold as Decapeptyl and used for prostate cancer, endometriosis, fibroids, early puberty and in fertility treatment. It comes mostly as long-acting depot injections lasting one, three or six months.¹

Triptorelin also has a niche off-label following among bodybuilders, who use a single small dose to try to restart their own testosterone production after a steroid cycle. That use has almost no formal evidence and works in the opposite direction from how the drug is used in medicine.

How triptorelin works

Normally the brain releases GnRH in short pulses. Each pulse tells the pituitary gland to release LH and FSH, which in turn drive the testes to make testosterone and the ovaries to make estrogen and release eggs. The pulsing is essential.

Triptorelin behaves very differently depending on how it is given. A single dose acts like a big GnRH pulse, so LH, FSH and sex hormones surge for a few days. This is called the flare. Continuous exposure from a depot injection does the opposite. The pituitary stops responding, LH and FSH fall, and testosterone or estrogen drop to very low levels within a few weeks. Medicine uses that shutdown to treat hormone-driven diseases.

In more precise terms, triptorelin is a decapeptide in which the glycine at position 6 of native GnRH is replaced by D-tryptophan. That change increases receptor binding and resistance to enzymatic breakdown. Sustained occupancy of pituitary GnRH receptors leads to receptor desensitization and downregulation, suppressing gonadotropin secretion. In men with prostate cancer given a six-month depot, testosterone rose briefly and then fell to castrate levels in a mean of about 19 days.¹

What the research shows on triptorelin

For prostate cancer, the evidence is robust. In the pivotal trial of the six-month formulation in 120 men with advanced prostate cancer, 97.5% reached castrate testosterone levels by day 29, and about 93% stayed suppressed from months 2 to 12. Side effects such as hot flushes matched the drug's hormonal action.¹

For endometriosis, GnRH agonists including triptorelin relieve pain by inducing a temporary menopause-like state.⁴ A detailed review concluded that triptorelin improves endometriosis pain and shrinks endometriotic nodules during treatment.³ GnRH agonists also carry more side effects than some other options.⁴

In fertility medicine, a single dose of a GnRH agonist can replace or join hCG to trigger final egg maturation in IVF. A network meta-analysis found that a GnRH agonist trigger lowered the risk of ovarian hyperstimulation syndrome compared with hCG, without improving pregnancy rates.⁵ Combining the two, a dual trigger, was associated with higher live birth rates than hCG alone in another meta-analysis.⁸ GnRH agonist pretreatment before frozen embryo transfer in polycystic ovary syndrome was linked to higher pregnancy rates overall, though the effect disappeared when only randomized trials were analyzed.⁶ In women with adenomyosis, a recent randomized trial found low-dose letrozole performed similarly to a GnRH agonist before embryo transfer.²

For restarting testosterone after anabolic steroid use, there are no controlled trials. The practice rests on the flare effect, case reports and anecdote. Whether it speeds recovery more than time alone is unknown.

Studied for: Advanced prostate cancer, Endometriosis, Central precocious puberty, HPTA restart research.

Triptorelin reference data

Triptorelin dosage in published research

How triptorelin is used in practice

In medicine, triptorelin is given by a clinician as an intramuscular depot injection. In prostate cancer it is often combined with an anti-androgen at the start to block the effects of the initial testosterone flare. In children with early puberty, it pauses puberty until an appropriate age. In IVF clinics, short-acting triptorelin is used both to suppress natural cycles and as a one-off trigger shot.

In bodybuilding circles, triptorelin is bought from overseas pharmacies or research-chemical vendors and injected once at a low dose after a steroid cycle. Some telehealth men's health clinics have offered it as an alternative to hCG or clomiphene. Gray-market supply carries the usual risks of wrong dose and contamination, and with this drug the dose matters a lot. Too much or repeated dosing could suppress rather than stimulate the hormonal axis. Triptorelin is prohibited in male athletes under anti-doping rules.

Triptorelin risks and side effects

With long-term suppression, side effects come from low sex hormones: hot flushes, reduced libido, erectile dysfunction, fatigue, mood changes and, over months to years, loss of bone density. Androgen deprivation in men is also associated with weight gain, insulin resistance and higher cardiovascular risk. Injection-site reactions occurred in about 7% of men in the six-month depot trial.¹

The initial flare can briefly worsen symptoms. In advanced prostate cancer this can mean increased bone pain or, rarely, spinal cord compression or urinary obstruction, which is why clinicians monitor high-risk patients closely.

Triptorelin must not be used in pregnancy. It can blunt the effects of hCG or gonadorelin if given around the same time. For off-label restart use, the main risk is that it simply does not work, or that an incorrect dose or repeated use prolongs suppression rather than ending it.

Reported side effects

Alternatives to triptorelin

For prostate cancer, other GnRH agonists include leuprolide and goserelin. GnRH antagonists such as degarelix and oral relugolix suppress testosterone without a flare. For endometriosis pain, the levonorgestrel intrauterine system and laparoscopic surgery also have evidence of benefit.⁴ Other options include hormonal contraceptives, progestins, and oral GnRH antagonists such as elagolix and relugolix combination therapy.

For recovering natural testosterone after steroid use, clinicians more often use hCG, clomiphene or enclomiphene, or simply time and monitoring. Men with persistent low testosterone should be evaluated for hypogonadism rather than relying on a one-off dose.

Questions for a clinician

• What evidence applies to my situation, and at what level?
• What established alternatives should I consider first?
• What monitoring would be necessary, and how often?