The importance of gynecological examination in adolescent girls and adult women with Prader-Willi syndrome.

Current published guidelines for routine care of women with Prader-Willi syndrome (PWS) do not include recommendations for gynecologic examinations. We describe our experience with gynecological examinations in women with PWS and offer recommendations for routine health care for these patients. Data were collected on all 41 PWS females ages ≥12 year, followed in our national Israeli multidisciplinary clinic between the years 2011 and 2022. Menstrual data and findings on external gynecological examination, including evaluation of the vulva and hymen were recorded at yearly visits. During the gynecological evaluation the topic of sexual education was discussed. Pelvic ultrasound, specifically for antral follicular count, was performed for those visiting the clinic during 2020-2022. Blood samples for luteinizing hormone (LH), follicular stimulating hormone (FSH), and estradiol were obtained routinely and DEXA scans for bone density were done when indicated. Of the 41 women, (median age at start of follow-up 17 years, range [12.3-39], BMI 30.4 kg/m2 [IQR 23.5-37.1]), 39 women agreed to external gynecological examination. Eleven women (27%) had spontaneous menses, with menarche at the age of 14 to as late as 31 years. The hymen was intact in all except one. Poor hygiene was observed in eight women, three women with vulvovaginitis, and five with irritated vulva related to poor hygiene. Gynecological ultrasound was performed in 27 women. In 22, endometrial thickness was less than 5 mm. The median antral follicular count (AFC) was 6 (<10th percentile for age). No correlation between AFC and menstruation or BMI was found. Mean FSH level was 5.7 ± 3.6 IU, LH was 2.29 ± 2.23, and estradiol was 128 ± 76 pmol/L. Data on DEXA measurements were available in 25 women aged 16-39. Median spine T score was -1.3 (range between 0.5 and -3.7), and hip T score was -1.2 (range between 0.8 and -3.3). A negative correlation was found between endometrial thickness and the presence of osteopenia or osteoporosis (r = -0.5, p = 0.013). Despite our recommendations, only eight of 14 women agreed to hormonal treatment or contraception. One woman who received treatment had a thromboembolic event. Routine health care for women with PWS should include gynecological examinations. The gynecological evaluation should include external genital examination, assessment of hygiene, obtaining a blood sample for hormone levels, and documenting a history of sexual experience or sexual abuse. Hormonal treatment or contraception should be offered when appropriate.

Growth hormone treatment for adults with Prader-Willi syndrome: another point of view.

Growth hormone treatment for children with Prader Willi syndrome (PWS) has shown proven benefits not only in increasing final height but also with positive effects on body composition and motor development. In a recent letter to the editor, Hoybye and colleagues recommend growth hormone treatment for adults with PWS based exclusively on the genetic diagnosis and without regard for growth hormone secretory status. We question whether the benefits of growth hormone treatment in PWS adults, mainly improvement in body composition, are significant enough to justify the as yet unkown consequences of long-term treatment in an adult population. Morbidity and mortality in PWS are mainly due to complications of obesity, and growth hormone treatment does not result in a decrease in BMI or waist circumference. Increases in insulin-like factor-1 as a result of growth hormone treatment over the course of several decades in PWS adults raises concern over possible increase risk of cancer. Compliance with daily injections is likely to be poor. We suggest that efforts to provide appropriate dietary and exercise regimens may be more beneficial and cost-effective than advocating for growth hormone treatment for adults with PWS.

Syndrome-Related Risk Factors for Sexual Abuse: The Example of Prader-Willi Syndrome.

Many genetic disorders associated with intellectual disability are characterized by unique behavioral phenotypes which may have serious psychological consequences such as increasing the risk for sexual abuse (SA). Prader-Willi Syndrome (PWS), a severe neurogenetic syndrome with uncontrollable hyperphagia and high threshold for pain, is an excellent example of this issue. The absence of reports on SA in PWS highlights the lack of awareness to the topic. Our aim was to report on SA in individuals with PWS, describe its unique characteristics, and offer recommendations for its prevention. Caregivers of all individuals with genetically confirmed PWS living in the only two residential facilities designated for PWS in Israel were interviewed for a history of sexual behavior and abuse, and medical data were collected from their files. SA was reported in a quarter of the sample. In most of the cases (78%), food reward was used by the perpetrators to attract their victims. Age at SA ranged from 11 to 29 years. Most of the individuals did not disclose the event and some continued to initiate inappropriate sexual activity to obtain food. Characteristics unique to PWS, such as food-seeking behaviors and high threshold for pain, likely contribute to the risk for SA. These findings suggest that syndrome-specific programs for SA prevention should be considered for individuals with any genetic syndrome with behavioral problems that may increase SA risk.

Early puberty in end stage renal failure and renal transplant recipients.

Background Delayed puberty and hypogonadism are common in children with chronic kidney disease and in renal transplant recipients, but precocious puberty has rarely been reported in these populations. We describe six girls with precocious and/or early-onset, rapidly progressive puberty before and following renal transplantation. Methods Of 112 children under the age of 18 years (67 boys, 45 girls) who received renal transplants between 2010 and 2018, six girls presented with precocious or rapidly progressive early puberty at ages 6-7/12, 7-2/12, 7-4/12, 8, 8-8/12 and 8-11/12 years. Clinical evaluation included measurements of height, weight, body mass index (BMI), Tanner staging and bone age assessment. Gonadotropin responses to intravenous gonadotropin releasing hormone (GnRH) or intramuscular triptorelin acetate were determined. Results Tanner breast stage 3 was noted at 2-6 years following renal transplantation in five girls, four with preserved kidney function. One girl began puberty before renal transplantation. Peak luteinizing hormone (LH) and follicular stimulating hormone (FSH) levels were 6.5, 20.2, 7.83, 19.1, 9 and 2.2 mIU/mL and 13, 8.3, 8.01, 7.5, 8.1 and 7.7 mIU/mL, respectively. Treatment with an intramuscular slow-release formulation of triptorelin acetate every 4 weeks slowed progression of breast development. Conclusions Although delayed puberty is more common in children with renal disease, precocious puberty can also be seen. Evaluation of growth and puberty by a pediatric endocrinologist should be part of the routine care for all children following kidney transplantation.

Incomplete methylation of a germ cell tumor (Seminoma) in a Prader-Willi male.

BACKGROUND: Prader-Willi syndrome (PWS) is a multisystem genetic disorder characterized by lack of satiety leading to morbid obesity, variable degrees of mental retardation, behavior disorders, short stature, and hypogonadism. The underlying genetic cause for PWS is an imprinting defect resulting from a lack of expression of several paternally inherited genes embedded within the 15q11.2-q13 region. Although the clinical expression of hypogonadism in PWS is variable, there are no known cases of fertility in PWS men. In this paper, we described a pure, nearly diploid seminoma in an apparently 32 year-old infertile man with PWS due to maternal uniparental disomy (UPD) on chromosome 15. The development of a germ cell tumor in this subject was an unanticipated result. The aim of this study was to explore the origin of the germ cell tumor in this PWS male patient. METHODS: To explain the origin of the germ cell tumor (seminoma) in our PWS patient we have characterized the tumor for cell morphology and tumor type by pathological examination (H&E and immuno-stainings), evaluated its karyotype by chromosomal microarray analysis and confirmed its UPD origin by haplotype analysis. In addition, DNA methylation status of the PWS- and H19- imprinting centers in wild-type and affected fibroblasts, patient derived induced pluripotent stem cells (iPSCs), and PWS seminoma were determined by bisulfite DNA colony sequencing. RESULTS: To explain the apparent contradiction between the existence of a germ cell tumor and hypogonadism we first confirmed the germ cell origin of the tumor. Next, we determined the tumor chromosomal composition, and validated the presence of a maternal UPD in all examined cell types from this patient. Finally, we characterized the maternal imprints in the PWS and H19 imprinting centers in the tumor and compared them with patient's fibroblasts and iPSCs derived from them. Unpredictably, methylation was reduced to 50% in the tumor, while preserved in the other cell types. CONCLUSION: We infer from this assay that the loss of methylation in the PWS-IC specifically in the tumor of our patient is most likely a locus-specific event resulting from imprint relaxation rather than from general resetting of the imprints throughout the genome during germ line specification.

Physical activity and maximal oxygen uptake in adults with Prader-Willi syndrome.

BACKGROUND: Prader-Willi Syndrome (PWS) is the most common genetic syndrome causing life-threatening obesity. Strict adherence to a low-calorie diet and regular physical activity are needed to prevent weight gain. Direct measurement of maximal oxygen uptake (VO2 max), the "gold standard" for assessing aerobic exercise capacity, has not been previously described in PWS. OBJECTIVES: Assess aerobic capacity by direct measurement of VO2 max in adults with PWS, and in age and BMI-matched controls (OC), and compare the results with values obtained by indirect prediction methods. METHODS AND PATIENTS: Seventeen individuals (12 males) age: 19-35 (28.6 ± 4.9) years, BMI: 19.4-38.1 (27.8 ± 5) kg/m2 with genetically confirmed PWS who exercise daily, and 32 matched OC (22 males) age: 19-36 (29.3 ± 5.2) years, BMI: 21.1-48.1 (26.3 ± 4.9) kg/m2. All completed a medical questionnaire and performed strength and flexibility tests. VO2 max was determined by measuring oxygen consumption during a graded exercise test on a treadmill. RESULTS: VO2 max (24.6 ± 3.4 vs 46.5 ± 12.2 ml/kg/min, p < 0.001) and ventilatory threshold (20 ± 2 and 36.2 ± 10.5 ml/kg/min, p < 0.001), maximal strength of both hands (36 ± 4 vs 91.4 ± 21.2 kg, p < 0.001), and flexibility (15.2 ± 9.5 vs 26 ± 11.1 cm, p = 0.001) were all significantly lower for PWS compared to OC. Predicted estimates and direct measurements of VO2 max were almost identical for the OC group (p = 0.995), for the PWS group, both methods for estimating VO2 max gave values which were significantly greater (p < 0.001) than results obtained by direct measurements. CONCLUSIONS: Aerobic capacity, assessed by direct measurement of VO2 max, is significantly lower in PWS adults, even in those who exercise daily, compared to OCs. Indirect estimates of VO2 max are accurate for OC, but unreliable in PWS. Direct measurement of VO2 should be used for designing personal training programs and in clinical studies of exercise in PWS.

Targeting the endocannabinoid/CB1 receptor system for treating obesity in Prader-Willi syndrome.

OBJECTIVE: Extreme obesity is a core phenotypic feature of Prader-Willi syndrome (PWS). Among numerous metabolic regulators, the endocannabinoid (eCB) system is critically involved in controlling feeding, body weight, and energy metabolism, and a globally acting cannabinoid-1 receptor (CB1R) blockade reverses obesity both in animals and humans. The first-in-class CB1R antagonist rimonabant proved effective in inducing weight loss in adults with PWS. However, it is no longer available for clinical use because of its centrally mediated, neuropsychiatric, adverse effects. METHODS: We studied eCB 'tone' in individuals with PWS and in the Magel2-null mouse model that recapitulates the major metabolic phenotypes of PWS and determined the efficacy of a peripherally restricted CB1R antagonist, JD5037 in treating obesity in these mice. RESULTS: Individuals with PWS had elevated circulating levels of 2-arachidonoylglycerol and its endogenous precursor and breakdown ligand, arachidonic acid. Increased hypothalamic eCB 'tone', manifested by increased eCBs and upregulated CB1R, was associated with increased fat mass, reduced energy expenditure, and decreased voluntary activity in Magel2-null mice. Daily chronic treatment of obese Magel2-null mice and their littermate wild-type controls with JD5037 (3 mg/kg/d for 28 days) reduced body weight, reversed hyperphagia, and improved metabolic parameters related to their obese phenotype. CONCLUSIONS: Dysregulation of the eCB/CB1R system may contribute to hyperphagia and obesity in Magel2-null mice and in individuals with PWS. Our results demonstrate that treatment with peripherally restricted CB1R antagonists may be an effective strategy for the management of severe obesity in PWS.

A disease specific questionnaire for assessing behavior in individuals with Prader-Willi syndrome.

OBJECTIVE: Prader-Willi syndrome (PWS) is a genetic multisystem disorder with various medical, cognitive, behavioral and psychiatric problems. PWS is caused by the lack of expression of paternal genes on chromosome 15q2-q13 due to a deletion (70-75%), uniparental disomy (25-30%) or imprinting center defect (<5%). The common PWS behavioral and psychiatric characteristics are very typical in all ethnicities and were reported worldwide. Still, each individual has a specific profile of these common traits and the severity of his or her symptoms varies over time. Behavioral problems are the most important factor affecting the quality of life of both the individuals and their families. There is a need for a standardized tool to assess the specific behavioral profile of each individual and its present severity, in order to enable physicians to tailor the specific treatment needed and assist in a more accurate clinical follow up. To the best of our knowledge no such a tool has been standardized and published. We developed, based on the literature (mainly Forster and Gourash's paradigm) and our clinical experience, a 37 item disease specific questionnaire, the "PWS Behavioral Questionnaire" (PWSBQ) for assessing behavior in PWS patients. The purpose of the present study was to validate this tool in the entire adolescent and adult PWS population in Israel. METHODS: The PWSBQ focuses on five major domains-abnormal emotional regulation, food-seeking related behavior, lack of flexibility, oppositional behavior and interpersonal problems and lastly body related behaviors. Caregivers of all Hebrew speaking individuals with PWS over the age of 12 years attending the Israeli national multidisciplinary PWS clinic were recruited. Of the 54 eligible individuals, 53 participated. They were interviewed with the PWSBQ and in addition filled the "Hyperphagia Questionnaire" and the "Child Behavioral Checklist" (CBCL). After verifying the questionnaire's content validity, all items on the PWSBQ were analyzed for internal reliability by calculating Cronbach's α. Criterion validity was evaluated by correlation testing with regard to the Hyperphagia Questionnaire and CBCL. In order to assess the questionnaire's interpretability, the correlation between the PWSBQ and the "Clinical Global Impression" (CGI) scores was evaluated. RESULTS: The PWSBQ total score was positively correlated with both the CBCL total score and the CGI score (0.662 and 0.549, p<0.001 respectively). Of the five domains, four had acceptable internal reliability (excluding the body related behaviors domain, which was thus removed from the total score). Criterion validity was established for the four domains remaining in the statistical analysis (abnormal emotional regulation, food seeking related behavior, lack of flexibility and oppositional behavior and interpersonal problems). CONCLUSIONS: Our findings suggest that the PWSBQ is a valid and reliable tool for the assessment of current behavioral problems among individuals with PWS. Although further research is needed in order to verify PWSBQ's ability to identify changes in the behavioral status of a given individual, it can now be used both in research and in a clinical setting, enabling the physician to plan the most suitable treatment based on the current behavioral status.

Time to menarche and final height after histrelin implant treatment for central precocious puberty.

OBJECTIVE: To compare final height, change in body mass index (BMI), and time from end of treatment until menarche in girls with central precocious puberty treated with the histrelin implant versus depot gonadotropin releasing hormone agonist injections. STUDY DESIGN: Chart review, interview, and final height measurements of 2 groups of girls with central precocious puberty; triptorelin depot (TD) group: 23 girls were treated from age 8.4 ± 0.3 with monthly injections of TD, for 26.7 ± 2.5 months; histrelin implant group: 11 girls were treated from age 8.7 ± 0.3 years for 28.4 ± 3.7 months, of whom 9 initially received monthly TD injections for 1.5-39 months. Final height, BMI (pretreatment vs recent), and time between either implant removal or last injection to menarche were compared. RESULTS: Time between removal of implant or last injection and menarche was 9.3 ± 1.5 (histrelin implant group) versus 16.1 ± 1.7 (TD group) months (P = .02). Predicted height at implant insertion was 156.8 ± 2.6 cm, and final height was 161.1 ± 2.0 cm (not significant [NS]). Predicted height for TD was 155.2 ± 1.9 cm and final height was 157.9 ± 1.7 cm (NS). Change from onset of treatment to final BMI-SDS for histrelin implant was -0.41 ± 0.3, and for TD was -0.03 ± 0.2 (NS). CONCLUSIONS: Menarche occurred sooner after implant removal. There was no difference in final height or BMI outcomes between the 2 treatment modalities.

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.

Hypogonadism in females with Prader-Willi syndrome from infancy to adulthood: variable combinations of a primary gonadal defect and hypothalamic dysfunction.

OBJECTIVE: The variable hypogonadism in Prader-Willi syndrome (PWS) has generally been attributed to hypothalamic dysfunction. Recent studies have documented primary testicular dysfunction in PWS males. Our aims were to characterize sexual development and reproductive hormones in PWS females and to investigate the etiology of hypogonadism. DESIGN: A cross-sectional study. METHODS: Physical examination was performed on 45 PWS females (aged 6 weeks to 32 years) and blood samples were obtained for hormonal analyses. RESULTS: Age of onset and progression of puberty varied; most adults had incomplete sexual development. Spontaneous menarche was reported in four (aged 15-30 years) but all had subsequently developed secondary amenorrhea or oligomennorrhea. Anti-Mullerian hormone levels were within the normal range in all age groups. Inhibin B was consistently low or undetectable; only five women had levels in the low-normal range (20-54 pg/ml). LH was normal in most children, but low (<1.0 IU/l) in 9 of 15 adults. FSH was within the normal range for age in most children, but low (<0.5 IU/l) in 10 and high in four adults. Estradiol levels were normal-low and androgen levels were normal in the majority. CONCLUSIONS: Pubertal development in PWS females, as in males, is characterized by normal adrenarche, pubertal arrest, and hypogonadism due to variable combinations of a unique primary gonadal defect and hypothalamic dysfunction.

Primary testicular dysfunction is a major contributor to abnormal pubertal development in males with Prader-Willi syndrome.

BACKGROUND: Recent studies challenge the assumption that hypogonadism in Prader-Willi syndrome (PWS) is due only to hypothalamic dysfunction. OBJECTIVES: The aims of the study were to characterize sexual development and reproductive hormones in PWS males and investigate the etiology of hypogonadism. METHODS: Physical examination and blood sampling were performed on 37 PWS males, ages 4 months to 32 yr. RESULTS: All had a history of undescended testes; age at orchiopexy ranged from 2 months to 6 yr. Pubertal signs were variable, but none achieved full genital development. Anti-Mullerian hormone (AMH) levels in PWS boys were near the lower limits of normal, decreasing from 44.4 +/- 17.8 ng/ml (mean +/- sd) in young children to 5.9 +/- 4.7 ng/ml in adolescents, similar to normal males. In contrast, inhibin B was consistently low (27.1 +/- 36.1 pg/ml) or undetectable in all age groups. In adult males, FSH levels were high (20.3 +/- 18.3 IU/liter), LH levels were normal (4.2 +/- 4.3 IU/liter), and testosterone levels were low (1.87 +/- 1.17 ng/ml). Only two adults had severe hypogonadotropic hypogonadism with undetectable levels of LH and FSH and high AMH levels (34.9 and 36.7 ng/ml), unlike the other nine adults with AMH levels 2.6 +/- 2.1 ng/ml. Androstenedione (1.06 +/- 0.30 ng/ml) and DHEAS (281.1 +/- 143.6 microg/dl) in adult PWS were normal. CONCLUSIONS: Pubertal development in PWS is characterized by normal adrenarche, variable hypothalamic dysfunction, and hypogonadism due to a unique testicular defect. Primary testicular dysfunction is a major component of hypogonadism in PWS.

Prolonged remission of severe Cushing syndrome without adrenalectomy in an infant with McCune-Albright syndrome.

A 4 month-old girl presented with severe Cushing syndrome caused by McCune-Albright syndrome. After undergoing 19 months of pharmacologic suppression of cortisol production, she has been in clinical remission for more than 6 years. Adrenalectomy may be avoidable even in severe cases of Cushing syndrome associated with McCune-Albright syndrome.

Role of a founder c.201_202delCT mutation and new phenotypic features of congenital lipoid adrenal hyperplasia in Palestinians.

CONTEXT: Congenital lipoid adrenal hyperplasia (CLAH), caused by mutations in steroidogenic acute regulatory protein (StAR), is most frequent in Japanese and Palestinians. We report eight Palestinians from four unrelated families with CLAH. OBJECTIVE: The objective of the study was to identify the mutation(s) in StAR, correlate genotype with phenotype, and determine whether the common mutation represents a founder mutation. PATIENTS AND SETTING: Clinical, histopathological, and molecular genetic characterization was performed in these eight patients. RESULTS: All affected individuals (three XY, five XX) presented neonatally with undetectable adrenocortical hormones and are responding to replacement therapy. Only two sisters had neurodevelopmental deficits. Histopathological findings of excised XY gonads included accumulation of fat in Leydig cells. Significantly, already at 1 yr of age, positive placental alkaline phosphatase and octamer binding transcription factor staining indicated neoplastic potential. Sequence analysis of StAR revealed homozygosity for c.201_202delCT mutation in all eight cases, causing premature termination of the StAR protein. This mutation was confirmed to be a founder mutation using both an intragenic microsatellite and several single nucleotide polymorphism markers. Screening of 100 normal Jerusalem Palestinians detected no carriers of this mutation. CONCLUSION: CLAH is rare in the general Palestinian population. In most Palestinian cases, a founder c.201_202delCT mutation in StAR is the cause. The observed early neonatal presentation may reflect the major StAR protein truncation caused by this mutation. A crucial role for StAR in the central nervous system was not supported with normal neurological examinations in six of eight cases. Finally, we advocate early gonadectomy in XY CLAH cases, given the early onset of neoplastic changes observed histologically.

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.