Results of a Second Year of Therapy with the 12-Month Histrelin Implant for the Treatment of Central Precocious Puberty

Diagnosis, Treatment, and Outcomes of Males with Central Precocious Puberty

Central precocious puberty (CPP) among males is less frequent than among females but more likely to have an underlying pathologic cause. Diagnosis of CPP is often straightforward among males because increased testicular volume, the first sign of puberty, can be verified although careful central nervous system (CNS) assessment is generally necessary. Treatment with gonadotropin-releasing hormone agonist (GnRHa) is indicated, given in conjunction with any therapy needed for CNS lesions. Monitoring of treatment usually can consist of evaluating growth and physical puberty and with testosterone levels as the only lab data. Short-term and long-term outcome data indicate efficacy and safety, although data are limited. Such data need to be reported.

Trends in Histrelin Implantation at a Pediatric Tertiary Care Center

INTRODUCTION

Determine procedural outcomes and identify changing trends of utilization among patients undergoing histrelin implantation at a large pediatric tertiary care center over 15 y.

METHODS

Retrospective review of all patients undergoing histrelin implantation between January 2008 and April 2022.

RESULTS

A total of 746 patients underwent 1794 unique procedures (1364 placements/replacements, 430 removals). Procedures were performed in the clinic (1071, 60%), sedation unit (630, 35%), and operating room (93, 5%). A total of 14 (0.8%) complications were identified, including two patients that required early implant removal and one patient requiring antibiotics. Implants were placed for central precocious puberty (CPP, 579) or gender dysphoria (GD, 167). Cohort included 25.9% males and 74.1% females with mean age of implantation of 9.48 y (SD: 2.34, range: 1.05-17.34). The GD group is comprised of 52.4% males and 47.6% females, compared to 18.3% males and 81.7% females in the CPP. Significant difference was identified for mean age at placement by indication (CPP 8.65 y versus GD 12.34, P < 0.001). New patient referrals and implant procedures increased significantly over 14 y. Yearly frequency of patients receiving implants for CPP and GD increased significantly (P < 0.001), with proportion of GD patients increasing from 7% to 32%.

CONCLUSIONS

Histrelin procedures have increased in frequency overall with the greater increase noted in the GD cohort. The development of a streamlined process and a dedicated team have enabled histrelin procedures to be safely performed in the clinic setting for most, with a very low complication rate.

Approach to the Patient: Central Precocious Puberty

Central precocious puberty (CPP) classically refers to premature activation of the hypothalamic-pituitary-gonadal axis with onset of sexual development before the age of 8 years in girls and 9 years in boys. A decrease in the age of thelarche has been reported over the past several decades; however, the tempo of pubertal progression can be slower and adult height may not be adversely affected in many of the girls who experience thelarche at 6-8 years. Outside of this secular trend in the development itself, the past several decades have also brought about advances in diagnosis and management. This includes the widespread use of an ultrasensitive luteinizing hormone assay, decreasing the need for stimulation testing and a better understanding of the genetics that govern the onset of puberty. Additionally, management of CPP using gonadotropin-releasing hormone analogs (GnRHas) has changed with the advent of new longer-acting formulations. Emerging long-term outcomes of GnRHa administration with regards to obesity, cardiovascular risk factors and fertility are reassuring. Despite these advancements, clinical care in CPP is hampered by the lack of well-designed controlled studies, and management decisions are frequently not supported by clear practice guidelines. Data in boys with CPP are limited and this article focuses on the diagnosis and management of CPP in girls, particularly, in those who present with thelarche at the age of 6-8 years.

Long-term experience with the use of a single histrelin implant beyond one year in patients with central precocious puberty

OBJECTIVES

The histrelin implant has been used to treat central precocious puberty (CPP) for more than 15 years. Although approved for annual use, limited published reports suggest that a single implant is efficacious well beyond a year. Our objective was to report our long-term experience using a single histrelin implant for more than 12 months in children with CPP.

METHODS

We performed a retrospective study of 170 children with central precocious puberty treated with a single histrelin implant for more than 1 year.

RESULTS

Implants were left in situ for an average of 24 months. Pubertal development regressed or remained stable in the vast majority of patients and biochemical suppression was maintained. No correlation between time since an implant was placed and complications such as implant breakage or a second incision was seen.

CONCLUSIONS

A single histrelin implant provides excellent pubertal suppression well beyond a year. Extended use of a single histrelin implant should be considered standard of care in children with CPP.

Gonadotropin-releasing hormone analog therapies for children with central precocious puberty in the United States

Gonadotropin-releasing hormone agonists (GnRHa's) are the standard treatment for children with central precocious puberty (CPP). We aim to present data on available GnRHa options with an easy-to-review table and discuss factors that influence treatment selection. Five GnRHa's are currently FDA-approved and prescribed in the US and published data suggest similar safety and efficacy profiles over the first year of treatment. One- and 3-month intramuscular (IM) leuprolide acetate (LA) have long-term safety and efficacy data and allow for flexible dosing. Six-month IM triptorelin pamoate offers a longer duration of treatment, but without long-term efficacy and outcome data. Six-month subcutaneous (SQ) LA combines a SQ route of injection and long duration of action but lacks long-term efficacy and outcome data. The 12-month SQ histrelin acetate implant avoids injections and offers the longest duration of action, but requires a minor surgical procedure with local or general anesthesia. Factors in treatment selection include route of administration, needle size, injection volume, duration of action, and cost. The current GnRHa landscape provides options with varying benefits and risks, allowing physicians and caregivers to select the most appropriate therapy based on the specific needs and concerns of the child and the caregiver. Agents have different advantages and disadvantages for use, with no one agent displaying superiority.

Clinical characteristics and treatment patterns with histrelin acetate subcutaneous implants vs. leuprolide injections in children with precocious puberty: a real-world study using a US claims database

OBJECTIVES

Gonadotropin-releasing hormone analogs are the treatment of choice for central precocious puberty (CPP). This study characterizes patients treated with histrelin implant or leuprolide injection.

METHODS

A US claims database was used to identify patients aged ≤20 years with ≥1 histrelin or leuprolide claim (index treatment) between April 2010 and November 2017 and continuous enrollment ≥3 months before and ≥12 months after the index treatment date.

RESULTS

Overall, 4,217 patients (histrelin, n=1,001; leuprolide, n=3,216) were identified. The percentage of patients with CPP diagnosis was greater in the histrelin (96.5%) vs. leuprolide (68.8%; p<0.0001) cohort. In patients with CPP (histrelin, n=966; leuprolide, n=2,214), mean age at treatment initiation was similar for histrelin (9.0 ± 2.0 years) and leuprolide (9.1 ± 2.3 years), with >50% of patients aged 6-9 years. Mean treatment duration was significantly longer for histrelin (26.7 ± 14.8 months) vs. leuprolide (14.1 ± 12.1 months; p<0.0001), and was longer in younger patient groups. More patients switched from leuprolide to histrelin (12.3%) than vice versa (3.6%; p<0.0001). Median annual total treatment costs were slightly lower for the histrelin cohort ($23,071 [interquartile range, $16,833-$31,050]) than the leuprolide cohort ($27,021 [interquartile range, $18,314-$34,995]; p<0.0001).

CONCLUSIONS

Patients with CPP treated with histrelin had a longer duration of treatment, lower rates of index treatment discontinuation, and lower annual treatment costs vs. those treated with leuprolide.

Growth, growth potential, and influences on adult height in the transgender and gender-diverse population

The sexually dimorphic trait of height is one aspect of the experience of transgender and gender‐diverse (TGD) individuals that may influence their gender dysphoria and satisfaction with their transition. In this article, we have reviewed the current knowledge of the factors that contribute to one's final adult height and how it might be affected in TGD youth who have not experienced their gonadal puberty in the setting of receiving gonadotropin‐releasing hormone analog (GnRHa) and gender‐affirming hormonal treatment. Additional research is needed to characterize the influence of growth and final adult height on the lived experience of TGD youth and adults and how to best assess their growth, predict their final adult height, and how medical transition can be potentially modified to help them meet their goals.

Use of Gonadotropin-Releasing Hormone Analogs in Children: Update by an International Consortium

This update, written by authors designated by multiple pediatric endocrinology societies (see List of Participating Societies) from around the globe, concisely addresses topics related to changes in GnRHa usage in children and adolescents over the last decade. Topics related to the use of GnRHa in precocious puberty include diagnostic criteria, globally available formulations, considerations of benefit of treatment, monitoring of therapy, adverse events, and long-term outcome data. Additional sections review use in transgender individuals and other pediatric endocrine related conditions. Although there have been many significant changes in GnRHa usage, there is a definite paucity of evidence-based publications to support them. Therefore, this paper is explicitly not intended to evaluate what is recommended in terms of the best use of GnRHa, based on evidence and expert opinion, but rather to describe how these drugs are used, irrespective of any qualitative evaluation. Thus, this paper should be considered a narrative review on GnRHa utilization in precocious puberty and other clinical situations. These changes are reviewed not only to point out deficiencies in the literature but also to stimulate future studies and publications in this area.

Changes in body mass index in children on gonadotropin-releasing hormone agonist therapy with precocious puberty, early puberty or short stature

Background The use of gonadotropin-releasing hormone agonists (GnRHa) for pubertal suppression has been associated with increased body mass index (BMI) in female subjects with central precocious puberty (CPP), although results have been so far conflicting. This study examined the effects of GnRHa therapy in both genders and in subjects treated for CPP, early puberty or short stature. Methods This was a longitudinal retrospective study of subjects followed at outpatient pediatric endocrinology clinics of an academic medical center from 2005 to 2014 receiving GnRHa therapy. Results At 12 months, subjects on depot GnRHa had a statistically significant increase in BMI standard deviation score (SDS) from baseline (0.13 ± 0.35, p < 0.02). Subjects with short stature (0.17 ± 0.34, p < 0.02) but not early or precocious puberty, and subjects with normal baseline BMI (0.18 ± 0.38, p < 0.02) had significant increases in BMI SDS; no significance was noted at 24 months. Male subjects did not have a significant increase in BMI SDS, whereas female subjects did (0.11 ± 0.36, p < 0.01). Conclusions Subjects with short stature, normal BMI at baseline and female sex had significant increases in BMI SDS at 12 months. This is the first study to show an increase in BMI SDS in children treated with GnRHa for short stature, and is one of the few studies to assess BMI changes in males.

Predictors of bone maturation, growth rate and adult height in children with central precocious puberty treated with depot leuprolide acetate

BACKGROUND

Children with central precocious puberty (CPP) are treated with gonadotropin-releasing hormone agonists (GnRHa) to suppress puberty. Optimizing treatment outcomes continues to be studied. The relationships between growth, rate of bone maturation (bone age/chronological age [ΔBA/ΔCA]), luteinizing hormone (LH), predicted adult stature (PAS), as well as variables influencing these outcomes, were studied in children treated with depot leuprolide (LA Depot) Methods: Subjects (64 girls, seven boys) with CPP received LA Depot every 3 months for up to 42 months. Multivariate regression analyses were conducted to examine the predictors affecting ΔBA/ΔCA, PAS and growth rate.

RESULTS

Ninety percent of subjects (18 of 20) were suppressed (LH levels <4 IU/L) at 42 months. Over 42 months, the mean growth rate declined 2 cm/year, the mean BA/CA ratio decreased 0.21 and PAS increased 8.90 cm for girls (n=64). PAS improved to mid-parental height (MPH) in 46.2% of children by 30 months of treatment. Regression analysis showed that only the Body Mass Index Standardized Score (BMI SDS) was significantly associated (β+0.378 and +0.367, p≤0.05) with growth rate. For PAS, significant correlations were with MPH (β+0.808 and +0.791, p<0.001) and ΔBA/ΔCA (β+0.808 and +0.791, p<0.001). For ΔBA/ΔCA, a significant association was found only with BA at onset of treatment (β-0.098 and -0.103, p≤0.05). Peak-stimulated or basal LH showed no significant influence on growth rate, ΔBA/ΔCA or PAS.

CONCLUSIONS

Growth rate and bone maturation rate normalized on treatment with LA Depot. LH levels were not significantly correlated with growth rate, ΔBA/ΔCA or PAS, suggesting that suppression was adequate and variations in gonadotropin levels were below the threshold affecting outcomes.

Central Precocious Puberty: Update on Diagnosis and Treatment

Central precocious puberty (CPP) is characterized by the same biochemical and physical features as normally timed puberty but occurs at an abnormally early age. Most cases of CPP are seen in girls, in whom it is usually idiopathic. In contrast, ~50% of boys with CPP have an identifiable cause. The diagnosis of CPP relies on clinical, biochemical, and radiographic features. Untreated, CPP has the potential to result in early epiphyseal fusion and a significant compromise in adult height. Thus, the main goal of therapy is preservation of height potential. The gold-standard treatment for CPP is gonadotropin-releasing hormone (GnRH) analogs (GnRHa). Numerous preparations with a range of delivery systems and durations of action are commercially available. While the outcomes of patients treated for CPP have generally been favorable, more research about the psychological aspects, optimal monitoring, and long-term effects of all forms of GnRHa treatment is needed. Several potential therapeutic alternatives to GnRHa exist and await additional investigation.

Long-Term Continuous Suppression With Once-Yearly Histrelin Subcutaneous Implants for the Treatment of Central Precocious Puberty: A Final Report of a Phase 3 Multicenter Trial

CONTEXT AND OBJECTIVE

The histrelin implant has proven to be an effective method of delivering GnRH analog (GnRHa) therapy to children with central precocious puberty (CPP), yet there are limited data available regarding hormonal suppression and auxological changes during an extended course of therapy.

DESIGN

This was a phase 3, prospective, open-label study.

SETTING AND PARTICIPANTS

Thirty-six children with CPP who participated in a phase 3, open-label study and required further GnRHa therapy were eligible to continue treatment receiving a new implant upon removal of the prior 12-month histrelin implant during a long-term extension phase.

OUTCOME MEASURES

Hormone levels and auxologic parameters were measured periodically for up to 6 years of treatment and up to 1 year of posttreatment follow-up.

RESULTS

Hormonal suppression was maintained throughout the study in patients who had prior GnRHa therapy (n = 16) and in treatment-naive patients (n = 20). Bone age to chronological age ratio decreased from 1.417 (n = 20) at baseline to 1.18 (n = 8) at 48 months in treatment-naive children (P < .01). Predicted adult height in girls increased from 151.9 cm at baseline to 166.5 cm at month 60 (n = 6; P < .05), with a 10.7-cm height gain observed among treatment-naive children (n = 5). No adverse effect on growth or recovery of the hypothalamic-pituitary-gonadal axis was observed with hormonal suppression. The histrelin implant was generally well tolerated during long-term therapy.

CONCLUSIONS

Long-term histrelin implant therapy provided sustained gonadotropin suppression safely and effectively and improved predicted adult height in children with CPP.

Novel approaches to short stature therapy

Besides growth hormone, several pharmaceutical products have been investigated for efficacy and safety in increasing short term growth or adult height. Short-term treatment with testosterone esters in boys with constitutional delay of growth and puberty is efficacious in generating secondary sex characteristics and growth acceleration. The addition of oxandrolone to growth hormone (GH) in Turner syndrome has an additive effect on adult height gain. Treatment with GnRH analogs is the established treatment of central precocious puberty, and its addition to GH therapy appears effective in increasing adult height in GH deficient children, and possibly short children born SGA or with SHOX deficiency, who are still short at pubertal onset. Aromatase inhibitors appear effective in several rare disorders, but their value in increasing adult height in early pubertal boys with GH deficiency or idiopathic short stature is uncertain. A trial with a C-natriuretic peptide analog offers hope for children with achondroplasia.

Precocious puberty

PURPOSE OF REVIEW

Precocious puberty continues to elicit great interest and concern among medical practitioners, as well as the public.

RECENT FINDINGS

Studies have elucidated neural regulation of puberty by kisspeptin, neurokinin B, and other factors. Cohort studies from the North America and Europe suggest that the age of thelarche may be earlier than determined 2 decades ago, and menarche may be slightly earlier, but the causes are unclear. Long-term outcomes of gonadotropin-releasing hormone analog therapy demonstrate increases in final height in the youngest treated patients, with no apparent adverse bone or reproductive consequences.

SUMMARY

Although the appropriate threshold age of onset of central puberty remains uncertain, gonadotropin-releasing hormone analog therapy is well tolerated and effective in suppressing luteinizing hormone pulses and ovarian activity.

Surgical and anesthetic considerations in histrelin capsule implantation for the treatment of precocious puberty

BACKGROUND

Precocious puberty treatment traditionally meant anxiety-provoking monthly depot injections until the advent of the annually implanted histrelin capsule. This study is the first to evaluate the surgical and anesthetic aspects of histrelin implantation for precocious puberty.

METHODS

All cases from one surgeon at a tertiary pediatric hospital were reviewed for patient age, anesthetic type, technical difficulties, and complications.

RESULTS

From 12/2007 to 3/2013, 114 cases (49% implantations, 25% removals/re-implantations, 25% removals) were performed. Local anesthesia was employed in 100% of non-general anesthesia cases (n=109, 96%), augmented by inhaled N2O in 49%. Five patients (4%) underwent general anesthesia: three neurologically-impaired and two coordinated with scheduled MRIs. Procedural difficulties (n=18, 16%) included implant fracture during removal (n=16/58 removals, 28%). Fracture never occurred during implantation. Three children (3%) suffered complications. One infection was treated with antibiotics, and two implants were removed for systemic allergic reaction. Six children (5%) had unscheduled post-operative checks for pain (n=3, 3%), allergy to elastic dressing (n=2, 2%), or rash (n=1, 1%). Mean charges for general anesthesia were $10,188±1292 versus $528±147 for N2O or local alone (p<0.0001).

CONCLUSION

While histrelin implantation is straightforward, removal presents technical challenges. Local anesthesia, with possible N2O supplementation, is well-tolerated and introduces substantial resource and cost savings.

Resumption of puberty in girls and boys following removal of the histrelin implant

OBJECTIVES

To determine time to menarche in girls and testicular volume increase in boys after removal of a histrelin implant, which causes profound hypothalamic-pituitary-gonadal axis suppression.

STUDY DESIGN

Medical records of patients treated with a histrelin implant were reviewed. Seventy-one patients (56 girls) treated with the histrelin implant were identified, of these patients, 37 explanted girls (68% naïve) and 6 explanted boys (83% naïve) were included in the analysis. Time to menarche after explantation in girls and time to testicular volume increase after explantation in boys were determined. Additional variables investigated included indication for and duration of treatment, history of menarche (girls), previous therapy, and age at beginning and end of histrelin treatment.

RESULTS

Of the girls, 30 were treated for central precocious puberty (CPP), 26 had menarche at an average of 12.75 months after explantation. Of the 30, 7 were treated for other indications, of whom 6 had reached menarche. In girls with CPP, older age at explantation correlated with sooner menarche (P = .04). All boys achieved spontaneous testicular enlargement within 1 year of explantation.

CONCLUSIONS

This study documented resumption of puberty after histrelin explantation in treatment naïve and non-naïve boys and girls with and without CPP. Menarche in girls with CPP occurs within a similar timeframe to that observed after other treatment approaches.

Random unstimulated pediatric luteinizing hormone levels are not reliable in the assessment of pubertal suppression during histrelin implant therapy

Background

Gonadotropin-releasing hormone agonist (GnRHa)-stimulated luteinizing hormone (LH) is the standard hormonal assessment for both diagnosis and therapeutic monitoring of children with central precocious puberty (CPP). Use of unstimulated (random) LH levels may be helpful in diagnosis and has gained popularity in monitoring GnRHa therapy despite lack of validation against stimulated values. The objective of this investigation was to assess the suitability of random LH for monitoring pubertal suppression during GnRHa treatment.

Methods

Data from a multi-year, multicenter, open-label trial of annual histrelin implants for CPP was used for our analysis. Children meeting clinical and hormonal criteria for CPP, either naïve to GnRHa therapy or previously treated with another GnRHa for at least 6 months who were being treated at academic pediatric centers were included in the study. Subjects received a single 50-mg subcutaneous histrelin implant annually until final explant at an age determined at the discretion of each investigator. Monitoring visits for physical examination and GnRHa-stimulation testing were performed at regular intervals. The main outcome measure was pubertal suppression during treatment defined by peak LH < 4 mIU/mL after GnRHa stimulation.

Results

During histrelin treatment, 36 children underwent a total of 308 monitoring GnRHa stimulation tests. Unstimulated and peak LH levels were positively correlated (r = 0.798), and both declined from the first to second year of treatment. Mean ± SD peak LH level during therapy was 0.62 ± 0.43 mIU/mL (range, 0.06–2.3), well below the normal prepubertal mean. Mean random LH was 0.35 ± 0.25 mIU/mL (range, 0.04–1.5), 10-fold higher than the normal prepubertal mean. The random LH levels were above the prepubertal upper threshold (<0.3 mIU/mL) in 48.4% of all tests and in 88.9% of subjects at some point during therapy.

Conclusions

In contrast with GnRHa-stimulated LH, unstimulated LH values frequently fail to demonstrate suppression to prepubertal values during GnRHa therapy for CPP, despite otherwise apparent pubertal suppression, and are thus unsuitable for therapeutic monitoring.

Trial registration

ClinicalTrial.gov NCT00779103.

A single histrelin implant is effective for 2 years for treatment of central precocious puberty

We investigated whether a "yearly" histrelin implant would provide pubertal suppression when left in place for 2 years. Equivalent suppression was observed when comparing 12 and 24 months in 33 children with central precocious puberty. A single implant for 2 years reduces cost and number of implant procedures.

Current pharmacotherapy of central precocious puberty by GnRH analogs: certainties and uncertainties

INTRODUCTION

GnRH analogs represent the drug of choice for medical treatment of central precocious puberty (CPP). They provided prompt and reversible suppression of reproductive axis and several reports have shown that adult height is preserved in treated children.

AREAS COVERED

This review updates GnRH analog treatment in CPP by a search of the literature published on the topic since 1980.

EXPERT OPINION

Monthly GnRH analogs are currently considered the 'gold standard' for the medical treatment of CPP, since a lot of experience is accumulated on their use in children. Differences in long-term outcome (in terms of adult height) are reported and they may be due to differences in selection criteria, treatment monitoring, criteria to stop of therapy, different biological activity of the various drugs and different genetic background of treated patients; altogether, these items remain poorly evaluated. Psychological indications for treatment and long-term psychological outcome of treated children should be better addressed. Comparative trials among the various GnRH analogs are very scarce. New very long-acting GnRH analogs (quarterly or yearly formulations) may improve compliance with therapy, but longer follow-up studies are needed. Medical treatment of CPP should be close to pediatric endocrinologists or tertiary pediatric endocrinology centers with documented experience in this field.

Treatment and outcomes of precocious puberty: an update

Precocious puberty is a common problem affecting up to 29 per 100,000 girls per year. The earliest identified neuroendocrine change in early puberty thus far is increased kisspeptin secretion from the arcuate nucleus and the anteroventral paraventricular nucleus of the hypothalamus. The regulation of kisspeptin secretion is not well understood, but neurokinin B and dynorphin provide autocrine regulation. The etiologies of precocious puberty may be subdivided into GnRH-dependent and GnRH-independent causes. GnRH-dependent precocious puberty, often called central precocious puberty (CPP), is usually treated with GnRH analogs. Newer developments in the treatment of CPP include expanded data on the safety and efficacy of the subdermal histrelin implant, which is useful for long-term treatment, although removal may be difficult in some cases. Preliminary data suggest that the implant may be left in place for up to 2 years without loss of biochemical suppression. In the last 2 years, more data have been published concerning extended-release leuprolide acetate injections that indicate that the 11.25-mg dose may not provide full biochemical suppression but may clinically suppress signs of puberty, including the accelerated growth velocity and advanced skeletal maturation seen in CPP. Treatment options for familial male-limited precocious puberty and McCune-Albright syndrome are expanding as well, although data are preliminary. Long-term outcome studies of CPP indicate overall good menstrual and reproductive function, but the prevalence of polycystic ovary syndrome may be higher than in the general population. Remarkably few studies have evaluated the behavioral and psychological outcomes of precocious puberty, in contrast to early normal maturation. Additional outcome studies of endocrine, metabolic, and psychological effects of CPP are clearly needed.

Free alpha-subunit is the most sensitive marker of gonadotropin recovery after treatment of central precocious puberty with the histrelin implant

BACKGROUND

Gonadotropin free alpha-subunit (FAS) levels paradoxically increase during GnRH agonist (GnRHa) treatment of central precocious puberty (CPP). The histrelin implant suppresses gonadotropins and estradiol (E(2)) levels for 1 yr, but effects on FAS have not been described.

OBJECTIVES

We aimed to determine whether FAS levels remain elevated during treatment with the implant, to assess the dynamics of FAS after removal, and to ascertain the reliability of FAS for monitoring gonadotropin secretion.

METHODS

Ten girls with CPP were studied. In eight, monthly im GnRHa preparations were given until implant insertion. Two naive girls did not receive prior GnRHa. Duration of implant treatment ranged from 18-63 months with repeated implant removals and insertions of new implants. LH, FSH, E(2), and FAS were measured before implant insertion in the two naive patients and during treatment, and in all girls before and after implant removal.

RESULTS

FAS levels were 0.2 and 0.4 ng/ml (normal, <0.6 ng/ml) in the two naive girls and increased to 2.4 and 5.1 ng/ml within 2-5 d of insertion. FAS level (mean +/- SD) in all 10 girls during histrelin implant treatment was 1.19 +/- 0.49 ng/ml and rapidly decreased to 0.31 +/- 0.12 ng/ml within 1 wk of implant removal (P < 0.03). In contrast, significant increases in LH (P < 0.05) and FSH (P < 0.02) were observed at 3 wk and E(2) (P < 0.05) at 6 wk after implant removal.

CONCLUSIONS

Compared to LH, FSH, and E(2), FAS responds more rapidly to implant removal and represents the most sensitive indicator of gonadotropin recovery after histrelin implant treatment.