Introduction: The estimated number of transgender youth in the United States has nearly doubled since 2017, leading to an increased need for gender-affirming care for transgender youth. Puberty suppression, with medications known as puberty “blockers,” can be an important component of medical care for young transgender patients. Currently, histrelin acetate implants are approved for precocious puberty treatment for one year. They have been shown to be effective in suppressing endogenous puberty in transgender youth, though the effective duration of these implants has not been assessed. Our clinical evidence suggests that a single implant may be effective for longer than one year in most patients, and at least 2 years for many patients.
Methods: A retrospective cohort study was conducted. We included transgender patients presenting for histrelin implants at Cincinnati Children’s Hospital between January 2015 and December 2021. Baseline, 3-month, and12-month follow-up values of LH, FSH, and the appropriate sex steroid: testosterone for patients assigned male at birth (AMAB) or estradiol in patients assigned female at birth (AFAB) were collected. Baseline and follow-up bone age data, Tanner staging, and patient-reported symptoms were also collected. The duration of each implant was measured as the time of implant use prior to replacement or until the initiation of gender-affirming hormone therapy (GAHT). Patients with an additional diagnosis of central precocious puberty or who had received other puberty-suppressing medication (typically leuprolide acetate) prior to histrelin implant were excluded. Discreet variables were summarized with frequency and percentages. Continuous variables were summarized with descriptive statistics. Comparisons were made using two-sided t-tests and correlations were calculated using Pearson correlations.
Results: 42 total patients received histrelin implants. 19 (45.2%) were AFAB and 23 (54.8%) were AMAB. More than half (n=26, 54.2%) of the patients received implants in the latter 2 years of data collection, between January 2020 and December 2021. The average implant duration for AMAB patients was 514 ± 252 days (range 153 – 1310 days). AFAB patients had an average duration of 637 ± 221 days (range 354 – 1282 days). There was no statistical significance in the difference between duration and sex assigned at birth (p=0.071). Lab values showed pubertal suppression. FSH levels decreased significantly from 3.76 ± 2.88 mUI/mL at baseline to 1.09 ± 0.80 mUI/mL at follow-up (p= 1.03E-06). Similarly, LH levels decreased significantly, from 2.80 ± 5.95 to 0.66 ± 0.68 (p=0.043). Bone age z-scores decreased from 1.41 ± 1.24 to 0.24 ± 0.95 (p=0.00067).
Conclusion: Histrelin acetate implants are effective in most patients for at least two years for suppressing puberty. For some patients, a single implant may be effective for as long as three years. Longer implant duration can reduce recurrent clinic visits and the number of invasive procedures needed for gender-affirming care.
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