Extended Use of Histrelin Implant in Pediatric Patients

PURPOSE: Histrelin implant (HI) is a gonadotropin-releasing hormone agonist (GnRHa) used in pediatrics to treat central precocious puberty (CPP) and for pubertal suppression in transgender/non-binary (TG/NB) youth with gender dysphoria. HI is designed for annual removal/replacement; however, effectiveness has been reported beyond 1 year. No previous study has assessed prolonged HI use in TG/NB youth. We hypothesize that HI is effective >12 months in TG/NB youth as described in children with CPP. METHODS: This retrospective, two-center study included 49 subjects with 50 HI retained ≥17 months, in TG/NB (42) and CPP (7). Pubertal suppression was assessed biochemically and/or clinically (testicular/breast exams). Escape from pubertal suppression and HI removal is also characterized. RESULTS: Most implants (42/50) maintained clinical/biochemical suppression for the duration of the study. The average use of a single HI was 37.5±13.6 months. Pubertal suppression escape occurred in eight subjects at average 30.4 months from placement: five had only biochemical; two clinical; and one both clinical and biochemical escape. After an average of 32.9 months, only 3/23 HI removed had adverse effects (HI broken, difficult removal). CONCLUSION: Extended use of HI in our TG/NB and CPP subjects was efficacious, resulting in sustained biochemical and clinical pubertal suppression in most. Suppression escape occurred at 15–65 months. Complications at HI removal were infrequent. Keeping HI for extended time would improve cost and morbidity, while maintaining efficacy and safety for most patients.