Case Report: Sustained pubertal suppression for 68 months with a single histrelin acetate implant in central precocious puberty

The subcutaneous histrelin acetate implant is FDA-approved for 12 months of continuous gonadotropin-releasing hormone (GnRH) agonist therapy in central precocious puberty (CPP). Published data demonstrated sustained suppression with a single implant for up to approximately 24 months; however, efficacy beyond this duration has not been reported. A 7 years 5 month old female patient presented with bilateral Tanner 2 breast development, a bone age of 10 years, and laboratory findings consistent with early central activation. Treatment was delayed 11 months due to disruptions in care during the COVID-19 pandemic, and a histrelin implant was placed at age 8 years 5 months. The patient was lost to follow-up and returned at nearly 14 years of age, approximately 68 months after the implant placement, with primary amenorrhea and pubertal arrest. Laboratory evaluation before implant removal showed suppressed but detectable gonadotropins with a prepubertal estradiol, consistent with sustained partial suppression of the hypothalamic-pituitary-gonadal (HPG) axis sufficient to arrest pubertal progression. Her predicted adult height (PAH) of 167.6 cm (66 inches) approximated her mid-parental height (MPH) of 166.4 cm (65.5 inches). This case demonstrates that a single histrelin acetate implant may maintain clinically meaningful pubertal suppression for at least 68 months. These findings support broader investigations into the pharmacokinetics of extended implant use, given implications for reducing surgical burden and healthcare costs in CPP management.