GnRH agonist · prostate cancer, puberty
A synthetic version of gonadotropin-releasing hormone (GnRH), the brain signal that tells the pituitary gland to drive the testes and ovaries. Given as a long-acting injection into muscle, it is used in the US to lower testosterone in advanced prostate cancer (Trelstar) and to pause early puberty in children (Triptodur).
Triptorelin is a ten-amino-acid peptide built on the natural GnRH sequence, with a D-tryptophan at position six1. In lab and animal studies it was many times more active than native GnRH at releasing pituitary hormones1. As a result, the first exposure acts as a strong 'go' signal: LH, FSH, testosterone and estradiol rise for a short time. With continued exposure the pituitary stops responding, LH and FSH output falls, and within about two to four weeks testosterone in men drops to levels like those seen after surgical castration1.
In children with central precocious puberty, the same shutdown brings sex hormones back toward prepubertal levels2. The label notes these effects are usually reversible after treatment stops1. The long-acting products carry the peptide in biodegradable microgranules injected into muscle1.
The evidence comes from trials in people. In a randomized trial of 284 men with advanced prostate cancer, triptorelin was compared with leuprolide, another GnRH agonist, over nine months. Fewer men on triptorelin reached castrate testosterone levels by day 29 (91.2% vs 99.3%), but rates were equivalent by day 57 (97.7% vs 97.1%) and castration was maintained as well through the study; nine-month survival was higher with triptorelin (97.0% vs 90.5%), though this was a secondary outcome3. The FDA label reports similar hormone results for its longer-acting versions1.
In a single-arm, open-label phase 3 study of 44 previously untreated children aged 2 to 9 with central precocious puberty, 93.2% had LH suppressed to prepubertal levels at month 6, and suppression held through month 124; 95% showed no further advance in bone age relative to chronological age by month 122. That study had no control group and lasted about a year, so it could not show effects on adult height4.
Approved by the FDA as Trelstar (2000) for advanced prostate cancer and as Triptodur (2017) for central precocious puberty in children 2 years and older.
Per the FDA labels, men treated for prostate cancer most often report hot flushes, skeletal pain, headache, erectile dysfunction and testicular shrinkage. A temporary testosterone surge in the first weeks can worsen disease, including spinal cord compression or urinary blockage. Warnings cover allergic reactions, metabolic changes such as high blood sugar, heart attack and stroke, seizures, severe skin reactions, QT prolongation and fetal harm.
In children, injection-site reactions, vaginal bleeding, hot flush and headache are common; mood changes and raised pressure inside the skull have been reported.
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