Library / Hormonal

Triptorelin

Also known as Diphereline, Trelstar, Triptodur, Decapeptyl

Approved medicine

Long acting gonadotrophin releasing hormone agonist that suppresses sex hormones with ongoing use. Approved for prostate cancer, endometriosis, precocious puberty and used in IVF protocols.

Prescription medicine. Only a prescriber can decide whether a medicine suits you and at what dose. This page is information, not a recommendation.

Background

Synthetic analogue of gonadotrophin releasing hormone (GnRH) with one amino acid swapped (D-tryptophan at position 6) to make it far more potent and longer lasting. It came from GnRH research in the 1970s and is sold as Diphereline, Decapeptyl, Trelstar and Triptodur.

How it is thought to work

At first it stimulates the pituitary, briefly raising sex hormones (a 'flare'). With continued use the pituitary becomes desensitised, so testosterone or oestrogen falls to very low levels.

What is claimed, and the evidence

Claim	Evidence	Notes
Advanced prostate cancer	Approved use	Trelstar label (US) and Diphereline (Australia).
Central precocious puberty in children aged 2 and over	Approved use	Triptodur label.
Endometriosis	Approved use	Approved in several countries; reviews show pain relief.
Ovarian suppression with hormone therapy in premenopausal early breast cancer	Approved use	EU approval for Decapeptyl based on the SOFT and TEXT trials.
Pituitary suppression in IVF	Approved use	Used in IVF protocols in several countries; approval varies by country and product.
Restarting natural testosterone after steroid use ('PCT')	No published evidence	Promoted online as a single low dose; no controlled trials support this and it can suppress hormones.

Side effects

Effect	How often	Notes
Hot flushes	Common	Most common reaction on the Trelstar label.
Erectile dysfunction, loss of libido and testicular shrinkage	Common	Label, from testosterone suppression.
Bone and skeletal pain, headache, leg swelling	Common	Label.
Temporary worsening of symptoms (tumour flare) Serious	Common	Label warning; in prostate cancer this can cause spinal cord compression or urinary blockage in the first weeks.
Bone loss with long term use Serious	Common	Expected with sex hormone suppression.
Metabolic changes: high blood sugar, diabetes, high lipids Serious	Uncommon	Label warning for GnRH agonists.
Heart attack, sudden cardiac death and stroke Serious	Uncommon	Label warning of increased risk in men.
Mood changes, seizures and severe skin reactions Serious	Rare	Label warnings.
Raised pressure in the skull in children Serious	Rare	Triptodur label warning.
Injection site reactions and vaginal bleeding in children	Common	Triptodur label.

Warnings

Causes an early surge in hormones before suppression, which can temporarily worsen symptoms.
Long term hormone suppression affects bones, heart, metabolism and mood.
May cause fetal harm and must not be used in pregnancy.
Prescription only (Schedule 4); unregulated products sold for hormone restart may be contaminated or mislabelled.

Regulatory status

Australia: Approved (ARTG, Diphereline). Schedule 4.
United States: FDA approved (Trelstar for advanced prostate cancer; Triptodur for central precocious puberty).

Sources

Also in Hormonal

From the VialOwl library, reviewed 26 September 2026. For education and general information. It is not medical advice and not a recommendation to use Triptorelin.