The histrelin implant: a novel treatment for central precocious puberty.

OBJECTIVE: Standard treatment of central precocious puberty (CPP) consists of intramuscular or subcutaneous administration of a gonadotropin-releasing hormone (GnRH) agonist (GnRHa) at 3- to 4-week intervals. Although generally effective in suppressing clinical and laboratory parameters of puberty, GnRHa injections are painful, and the need for monthly clinic visits may contribute to poor compliance. Recently, a subcutaneous implant was developed that releases the GnRHa histrelin at an average rate of 65 microg/day. The aims of this study were to determine if a histrelin implant would suppress gonadotropin and estradiol (E2) in girls with CPP for 1 year and to compare the suppression to standard treatment.

METHODS: We studied 11 girls with CPP to determine if the histrelin implant can maintain long-term gonadotropin suppression. Mean age at diagnosis was 6 years (range: 2-9 years). GnRH (100 microg intravenously) stimulation tests (GnRH-STs) showed peak luteinizing hormone and follicle-stimulating hormone responses of 23 +/- 28 (mean +/- SD) and 20 +/- 25 mIU/mL, respectively. All subjects were initially treated with depot intramuscular GnRHa triptorelin embonate. Implants were inserted subcutaneously under local anesthesia, and depot GnRHa treatment was discontinued. Six girls were followed for 15 months after insertion (group A). For the remaining 5 girls, the implant was removed after 9 months, and a new implant was inserted at the same incision site (group B). GnRH-STs were performed before depot GnRHa treatment, immediately before implant insertion, at the 6- and 9-month visits for each patient and the 12- and 15-month visit for those girls followed for 15 months.

RESULTS: In all girls, breast development regressed, growth velocity decreased, and bone-age advancement was slowed. Basal gonadotropins and their responses to GnRH-STs and E2 levels were suppressed. Peak luteinizing hormone and follicle-stimulating hormone responses to GnRH-STs at preinsertion versus 9 months were 1.30 +/- 1.34 vs 0.25 +/- 0.08 and 1.68 +/- 1.08 vs 1.13 +/- 0.55 mIU/mL, respectively. Basal and stimulated gonadotropin levels and E2 level remained suppressed in all 6 patients followed for 15 months after implant insertion. Patients and parents reported less pain and discomfort and less interference with school activity and work with the implant compared with standard monthly injections.

CONCLUSIONS: The histrelin implant consistently suppresses clinical and laboratory parameters of puberty for 1 year and is a promising new technique for treating CPP without the pain and inconvenience of monthly injections.