Disclaimer: I am not a medical professional and this is not medical advice.
GnRH agonists are a class of medications that reversibly block the progression of natal puberty both in cis youth with precocious (early) puberty and in trans adolescents, allowing trans youth time for decision-making about whether to proceed with more permanent medical transition or discontinue blockers and resume their natal puberty. These drugs work at the pituitary gland to halt the release of LH and FSH which stimulate the production and release of sex hormones, meaning that trans girls on GnRH agonists will temporarily stop producing testosterone and trans boys will stop producing estrogen. If trans youth wish to go on to transition, they can continue taking blockers while receiving cross-sex hormones for the induction of their desired puberty.
These long-acting drugs, such as leuprolide (Lupron), triptorelin (Decapeptyl), or goserelin (Zoladex), are typically given as a depot injection every month or every three months. A more recently developed route of administration is a once-yearly implant of histrelin acetate, intended for the treatment of central precocious puberty or as part of androgen deprivation therapy in prostate cancer. This medication, marketed as Supprelin LA for precocious puberty and Vantas for prostate cancer, allows for continuous treatment without the need for more frequent injections or monitoring. As such, it has also entered wider usage as a puberty-blocking implant for transgender adolescents.
Two issues arise when histrelin implants are used in trans youth: these implants are very expensive, and in the United States they are usually not covered by insurance for the treatment of trans adolescents. Supprelin LA has a listed price of $37,300, while Vantas costs $4,400 (these implants are clinically equivalent in their effects). Reportedly, fewer than 20% of puberty-blocking implants for trans youth at the Gender Multispecialty Service at Boston Children’s Hospital were covered by insurance, and copays and deductibles can be a prohibitive expense even when this is covered, depriving trans youth of access to these crucial and medically necessary treatments (Stevens, Gomez-Lobo, & Pine-Twaddell, 2015). Dowshen, Christensen, & Gruschow (2019) found that numerous insurance plans still exclude coverage of puberty blockers for trans adolescents.
However, one factor may help to mitigate these costs: some patients have been found to achieve continued suppression of puberty with a single histrelin implant for two years or more, beyond the intended lifetime of one implant. Kanj, Wellenstein, & Cipres (2020), studying trans adolescents receiving medical transition treatment at Cincinnati Children’s Hospital Medical Center, reported that 16 of 17 patients used the less expensive Vantas rather than Supprelin LA, and 11 patients had an implant for long enough for it to be removed and possibly replaced with a new one. Those 11 patients kept a single implant in place for an average of 25.6 months, much longer than the listed duration of histrelin implants. The authors stated that one patient had been using a single implant for 33 months without any observed progression of puberty. When implants were removed, this was most frequently because of a provider’s recommendation to do so after 18-24 months, and less frequently due to observed progression of puberty and the need for a new implant.
Longer-term viability of one-year histrelin implants has been previously reported in the literature: Lewis et al. (2013) found that a single implant was equally effective for 12 months or 24 months in 33 youth with precocious puberty, and a study of prostate cancer patients found that one implant could in some cases maintain suppression of testosterone for 21 to 30 months (Chertin et al., 2000). One case report showed that a single implant had remained effective in treating precocious puberty for 4 years, although the implant had “deteriorated” with the surrounding tissue growing into it, making it difficult to remove (Mitchell & Tapiador, 2016). With appropriate monitoring, use of the less-expensive Vantas implant for a period longer than a year may represent a useful cost-saving measure that could increase access to this treatment for transgender youth. ■
