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The Journal of Clinical Endocrinology & Metabolism 91(5):1862–1867 Copyright © 2006 by The Endocrine Society doi: 10.1210/jc.2005-1500
Sequential Comparisons of One-Month and Three-Month Depot Leuprolide Regimens in Central Precocious Puberty Angela Badaru, Darrell M. Wilson, Laura K. Bachrach, Patricia Fechner, Laura M. Gandrud, Eileen Durham, Kupper Wintergerst, Carolyn Chi, Karen O. Klein, and E. Kirk Neely Division of Pediatric Endocrinology and Diabetes (A.B., D.M.W., L.K.B., P.F., L.M.G., E.D., K.W., C.C., E.K.N.), Stanford University, Stanford, California 94305; and Department of Pediatrics (K.O.K.), University of California, San Diego, California 92123 Background: Dosing of monthly depot leuprolide (DL) in central precocious puberty (CPP) varies considerably. U.S. practitioners use 7.5–15 mg, in contrast with the international standard of 3.75 mg. Pubertal suppression using the newer 3-month DL also has been reported from Europe. To date there have been no direct comparisons of these different DL doses. Objectives: In an open 12-month protocol, we tested the efficacy of three DL doses (7.5 mg- and 3.75 mg-1 month and 11.25 mg-3 month) given sequentially to subjects treated for CPP. Primary outcome measures were stimulated gonadotropin (Gn) levels at 12-wk intervals. The null hypothesis was no difference among doses. Methods: Both existing and new patients with CPP received our standard therapy (DL 7.5 mg every 4 wk) for a minimum of 24 wk. In subjects with DL-stimulated LH 2 IU/liter or less, the dose was changed to 3.75 mg every 4 wk and evaluated 12 wk later. Subjects who met LH criteria (⬍4.5 IU/liter) on 3.75 mg then received a single dose of 11.25 mg-3 month and were reevaluated 12 wk later. Serum LH/FSH and sex steroids were obtained 40 min after DL injection.
D
EPOT GNRH ANALOGS (GnRHa) have become the mainstay of therapy for central, or gonadotropin (Gn)dependent, precocious puberty (CPP). Through continuous stimulation, GnRHa desensitize the pituitary gonadotrope and suppress Gn release. Adequate Gn suppression halts pubertal progression and decelerates the growth and skeletal maturation induced by premature exposure to sex steroids. With short-acting, inadequate, or intermittent GnRHa dosing, suppression waxes and wanes, potentially stimulating Gn release instead. In contrast, excessive dosing is unnecessarily expensive and theoretically could result in side effects such as growth deceleration or reduced bone density accrual. Depot leuprolide (depot Lupron, DL) is by far the most commonly used GnRHa in the United States and has become the drug of choice in the treatment of CPP. Its depot formulation offers the advantage of consistent pituitary suppresFirst Published Online January 31, 2006 Abbreviations: AL, Aqueous leuprolide; CPP, central precocious puberty; DL, depot leuprolide; E2, estradiol; Gn, gonadotropins; GnRHa, GnRH analog. JCEM is published monthly by The Endocrine Society (http://www. endo-society.org), the foremost professional society serving the endocrine community.
Results: Thirty subjects were enrolled (20 naive; 24 girls, 6 boys), and 21 were evaluated on all three DL doses. DL-stimulated LH levels (mean ⫾ SD) were 1.30 ⫾ 0.74, 1.73 ⫾ 0.99, and 2.13 ⫾ 1.41 on 7.5 mg, 3.75 mg, and 11.25 mg-3 month, respectively (7.5 vs. 3.75 mg, P ⫽ 0.019; 7.5 mg vs. 11.25 mg-3 month, P ⫽ 0.004, Wilcoxon ranked sign test). Mean FSH levels were 2.86 ⫾ 1.91, 3.91 ⫾ 1.98, and 3.96 ⫾ 1.34, respectively (7.5 vs. 3.75 mg, P ⫽ 0.017; 7.5 mg vs. 11.25 mg-3 month, P ⫽ 0.020). No differences were detected in mean sex steroid levels. Conclusions: Stimulated LH and FSH levels were significantly higher during therapy with both the 3.75 mg and 11.25 mg-3 month depot leuprolide doses, compared with 7.5 mg, contradicting the null hypothesis of no difference. These data suggest that low-dose 1- and 3-month DL preparations are associated with persistently greater gonadal stimulation in most CPP patients, but the LH/FSH results were not corroborated by differences in sex steroid levels. Whether various DL doses lead to long-term therapeutic differences remains to be determined. (J Clin Endocrinol Metab 91: 1862–1867, 2006)
sion and the convenience of monthly administration. However, dosing practices for monthly DL in CPP vary widely, ranging from 3.75 to 15 mg, usually at 4-wk intervals but sometimes more frequently. The recommended starting dose in the United States is 0.3 mg/kg, with a minimum to maximum range of 7.5–15 mg. In contrast, the European and Asian standard was established at 3.75 mg. In Japan, Tanaka et al. (1) reported pubertal suppression using 3.75 mg every 4 wk and calculated a minimum suppressive dose of 0.03 mg/kg, one tenth the U.S. recommendation. In France, Carel et al. (2) achieved long-term pubertal suppression on 3.75 mg every 4 wk in 49 children with CPP. This significant discrepancy between the U.S dose of 7.5–15 mg and the international dose of 3.75 mg has never been fully evaluated. The same group of French investigators (3) has reported adequate suppression of GnRH-stimulated Gn levels and appropriate clinical responsiveness using the newer 11.25 mg depot preparation given every 3 months, equivalent in total dose to 3.75 mg monthly but delivered in a different slowrelease polymer. Many pediatric endocrinologists in the United States have also begun using the 3-month preparation, on the basis of the reported long-term efficacy and the attractiveness of a reduced burden of clinic visits for both family and clinic.
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To date, direct comparisons of these different DL dose preparations have not been made. Results from the original dose-finding studies, as well as any informal dose comparisons bridging separate clinical trials, have been undermined by variable and insensitive Gn assays along with subjective or blunt outcome measures, such as bone age advance and pubertal staging. The striking 4-fold dosing variation in the monthly doses inadvertently predisposes a large number of children to either inadequate suppression or exposure to unnecessarily high doses. On the other hand, if the long duration preparations are equally effective, the convenience of administration would compel their broader use. We therefore established a protocol to test the hypothesis that three different DL dose preparations are at least equivalent in short-term efficacy, assessed by suppression of Gn and sex steroids. Subjects and Methods Subjects Children already established on DL therapy (TAP Pharmaceuticals, Deerfield, IL) for CPP who were likely to continue for more than 1 yr, as well as all newly diagnosed patients with CPP who were commencing DL therapy, were invited to participate. Established patients had received our standard DL (7.5 mg every 4 wk) for at least 24 wk before dose change. CPP was defined clinically in girls less than 8 yr as stage 2 breasts or greater and in boys less than 9 yr as stage 2 genitalia with testicular volume 4 cc or more. The laboratory criterion was GnRH- or GnRHastimulated LH greater than 6 IU/liter or spontaneous LH greater than 0.3 IU/liter (4). Written informed consent was obtained from the parents of all participants before enrollment. A written assent was obtained from children older than 7 yr. The protocol was approved by the Stanford University Administrative Panel on Human Subjects in Medical Research.
Evaluation and laboratory testing History and physical exam, including pubertal stage and three heights, were obtained every 12 wk for a year of study. Bone ages were not performed due to their inaccuracy in a limited duration study (5). A venous blood sample at each 12-wk visit was drawn 40 min after DL injection (6). LH and FSH were performed by immunochemiluminometric assay (Esoterix, Calabasas Hills, CA), with thresholds of sensitivity of 0.02 IU/liter (4). Interassay coefficients of variation for the LH assay are 5.2 and 4.2% at 1.4 and 5.7 IU/liter, respectively, the approximate range of levels observed in the study. Interassay coefficient of variation for the FSH assay is 7.8% at 4.2 IU/liter. Estradiol and testosterone were performed by RIA (Esoterix). Estradiol by ultrasensitive recombinant cell bioassay was performed using previously published methods (7). Intra- and interassay coefficients of variation at 1.8 pg/ml (7 pmol/liter) are 15%. Samples for this assay were run in two batches, with a threshold of sensitivity of 0.27 pg/ml in the first and 0.049 pg/ml in the second. For data analysis, undetectable levels from both batches were set at 0.27 pg/ml. The normal female prepubertal range is 1.72 pg/ml or less (ⱕ6.3 pmol/liter) (7).
Dose modification protocol To ensure adequate pubertal suppression, we initially followed our customary clinical approach to CPP therapy in all participants. Established and naive subjects all received our standard therapeutic DL dose of 7.5 mg every 4 wk for a minimum of 24 wk (note: 4 wk and 1 month or monthly are used interchangeably throughout but specifically refer to the former). From prior experience, this duration allows sufficient time for cessation of pubertal progression and stabilization of hormone levels before the additional confounding factor of dose adjustment. The dose modification protocol described below (Fig. 1) was designed to test the effects of dose reduction and providing for a dose increase if Gn
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FIG. 1. Schematic of the DL dosing protocol in naive subjects. Established subjects entered the study at visit wk 12 regardless of prior duration of therapy. testing suggested insufficient clinical or biochemical suppression according to standard clinical practice. After the minimum 24 wk, the DL dose was reduced from 7.5 to 3.75 mg in subjects whose DL-stimulated LH was suppressed at the prior visit to a level established a priori as clearly representing complete suppression (LH ⱕ 2 IU/liter). This threshold was selected to exclude incompletely suppressed children from being subjected to a potential rise in gonadal stimulation from a lowering of the DL dose. Children with DL-stimulated LH above the 2 IU/liter threshold at 12 wk but 2 IU/liter or less at the follow-up visit at 24 wk were allowed to enter the dose-reduction phase of the study at the 28-wk visit. If DL-stimulated LH levels were marginally suppressed (2– 4.5 IU/liter) at both the 12and 24-wk visits, subjects were maintained on DL 7.5 mg throughout follow-up. If LH levels were above 4.5 IU/liter at any visit, the dosemodification algorithm called for an increase in DL dose to 11.25 mg every 4 wk and if persistently elevated, to every 3 wk. At the fourth injection of 3.75 mg DL (generally wk 36 in naive subjects), subjects were tested for LH suppression on the new dose. Those who continued to show adequate pubertal suppression (DLstimulated LH ⬍ 4.5 IU/liter) after dose reductions were converted to the 11.25 mg-3 month depot formulation at the next monthly visit (40 wk). The higher LH threshold for advance from 3.75 mg monthly to the 11.25 mg-3 month DL was selected to avoid a situation in which subjects might be required to remain on the lower monthly dose rather than advancing to the longer duration medication, which was clearly the inducement for most families to enroll in the study. Children who began the 11.25 mg-3 month DL preparation at wk 40 were reevaluated at the next injection (wk 52). Accordingly, a large cohort of subjects was evaluated on the three different DL doses at three successive visits (generally 24, 36, and 52 wk), therefore acting as their own controls. If there was evidence of treatment failure at any time, such as persistent local reaction, clearly pubertal levels of LH (ⱖ4.5 IU/liter), or clinical progression, investigators had the option of immediate termination of drug or increase in dose, based on clinical assessment.
Statistics Differences in LH, FSH, and estradiol levels among dose groups were evaluated by Wilcoxon ranked sign test. Comparisons of doses for stimulating Gn and changes in growth velocity during each 3-month interval were evaluated by paired t test. FSH concentrations in males, which are lower than in females with CPP, were separately analyzed.
Results
Characteristics of the 30 enrolled subjects are shown in Table 1. Mean age at the start of DL therapy was 8.18 ⫾ 1.42 yr. Mean GnRH-stimulated LH at diagnosis was 10.8 ⫾ 9.6 IU/liter, and mean stimulated FSH was 8.6 ⫾ 2.9 IU/liter. Mean age at the transition to the lower DL dose was 9.38 ⫾ 1.36 yr in females and 9.55 ⫾ 1.24 yr in males. Six of the 30 subjects had DL-stimulated LH levels in excess of 2 IU/liter at both the 12- and 24-wk evaluation and according to the protocol were not eligible for dose reduction. This total included three of 20 naive subjects and three of 10 established patients. At the final 7.5-mg injection before possible dose transition (24 wk in naive subjects), the DL-
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TABLE 1. Patient summary (n ⫽ 30) No. of subjects (%)
Gender Male Female Etiology of early puberty Organic Idiopathic Treatment for short stature Duration of DL before dose reduction ⬎6 months 6 months Lowest post-DL LH on 7.5 mg Greater than 2 IU/liter 2 IU/liter or less (proceed to lower dose) Study progress Dropout Completed three doses
6 (20) 24 (80) 14 (47) 14 (47) 2 (6) 10 (33) 20 (67) 6 (20) 24 (80) 3 (12) 21 (88)
stimulated LH mean in all 30 patients was 1.71 ⫾ 1.5 IU/liter (range 0.07–3.8). Of the remaining 24 subjects after exclusion, three did not transition from 3.75 mg to 11.25 mg-3 month. One was lost to follow-up, another discontinued therapy for age-related reasons, and the third exceeded the treatment failure criterion for high LH level (4.9 IU/liter) on 3.75 mg at wk 36, reverting per protocol to 7.5 mg, with subsequent suppression. A summary of Gn testing in the 21 subjects tested sequentially while receiving all three DL dose preparations is shown in Table 2. In this cohort, DL-stimulated LH (Fig. 2) and FSH (Fig. 3) concentrations were significantly higher during therapy on both low dose 3.75 mg DL and the 3-month DL preparation when compared with the standard 7.5-mg dose. Mean age at dose transition from 7.5 to 3.75 mg was 9.48 ⫾ 1.28 yr. Mean weight at DL dose reduction to 3.75 mg was 35 ⫾ 7.28 kg in naive patients and 40.12 ⫾ 10.33 kg in established patients. There was no correlation of body weight, age, or duration of therapy with Gn levels achieved during therapeutic monitoring. Of note, subjects were tested while receiving 7.5 mg at both visits preceding dose transition, demonstrating that LH and FSH concentrations were stable before the dose change. These data argue against random or temporal drift or regression to the mean as explanations for the rise in Gn levels on the lower doses. To test the possible confounding factor that the three DL doses might have functionally different concentrations of free leuprolide available to stimulate Gn release following injection, we took advantage of subjects receiving the first injection of each new DL dose (Table 3 and Fig. 1). The stimulation tests at wk 12 and 24 used 7.5 mg and 3.75 mg, respectively, but both tests reflected therapy on 7.5 mg be-
FIG. 2. DL-stimulated serum LH concentrations in 21 subjects (males and females) on the three different DL doses administered at sequential 12-wk visits, with repeat testing on the initial 7.5 mg-1 month dose. Means designated by bars.
cause wk 20 had been a 7.5-mg injection. Similarly, stimulation tests at wk 36 and 40 used 3.75 mg and the 11.25 mg 3-month, respectively, both reflecting therapy on 3.75 mg. There were no differences among the three DL doses when tested as stimulating agents for Gn secretion (Table 3), discounting that as a factor in the differences in LH and FSH
TABLE 2. Mean DL-stimulated LH (IU/liter) and FSH (IU/liter) levels while receiving the three DL doses
LH FSH
n
7.5 mg-1 month
3.75 mg-1 month
11.25 mg-3 months
21 16
1.30 ⫾ 0.74 2.86 ⫾ 1.91
1.73 ⫾ 0.99 3.91 ⫾ 1.98
2.13 ⫾ 1.41 3.96 ⫾ 1.34
7.5 vs. 3.75 mg: P ⫽ 0.019 (LH), 0.017 (FSH); 7.5 vs. 11.25 mg-3 months: P ⫽ 0.004 (LH), 0.020 (FSH); 3.75 vs. 11.25 mg-3 months: P ⫽ 0.08 (LH), 0.82 (FSH).
FIG. 3. DL-stimulated serum FSH concentrations in 16 subjects (females only) on the three different DL doses administered at sequential 12-wk visits, with repeat testing on the initial 7.5 mg-1 month dose. Means designated by bars.
Badaru et al. • Comparisons of Depot Leuprolide Doses
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TABLE 3. Validity of using different DL doses to stimulate Gn pulses in monitoring therapy n
Prior DL dose
24
7.5 mg
11
3.75 mg
Stimulating DL
Peak LH
7.5 mg 3.75 mg 3.75 mg 11.25 mg-3 mo
1.23 ⫾ 0.59 1.27 ⫾ 0.69 1.74 ⫾ 1.17 1.69 ⫾ 1.33
P
0.71 0.741
levels among doses. Furthermore, the stimulating DL used to assess Gn secretion at 24 and 36 wk was 3.75 mg at both visits. Thus, any difference in Gn levels could not be attributable to the stimulation test itself. The differences in Gn levels after dose reduction were not accompanied by detectable changes in sex steroid concentrations. Mean serum testosterone levels in males did not change with dose transition. In four of five boys, the testosterone concentration at all treatment visits was less than 10 ng/dl, the standard threshold differentiating prepubertal from pubertal status. In the other boy, testosterone levels ranged marginally in the pubertal range both before and after dose transition. Mean serum testosterone levels on the three sequential DL doses were unchanged at 6.2 ⫾ 3.2, 5.2 ⫾ 3.2, and 7.0 ⫾ 4.3 ng/dl, respectively. It is notable that three of the six children with DL-stimulated LH rising above 3 IU/ liter on the lower doses were boys, but none exhibited a rising testosterone level. In girls, most serum estradiol levels were below the levels of detectability of both assays, regardless of dose, with only 28 of 94 estradiol (E2) measurements during DL therapy detectable by ultrasensitive assay. Mean (⫾ sd) E2 levels by ultrasensitive assay on the three sequential DL doses were 0.41 ⫾ 0.46 (range 0.27–1.8), 0.56 ⫾ 0.46 (range 0.27–1.4), and 0.73 ⫾ 0.76 (range 0.27–2.1) pg/ml, in contrast with a pretreatment mean E2 of 47 ⫾ 92 pg/ml (range 0.27–254). There were no differences among any of the three doses, by either assay, in either the mean E2 level or the number of patients with detectable E2. Furthermore, no correlation between E2 and either LH or FSH concentration was observed. Mean DL-stimulated LH level in subjects with detectable E2 was identical to that found in subjects with undetectable E2. Physical correlates of puberty such as pubertal staging and testicular volume were not detectably different during the successive intervals on each dose. Given the study’s shortterm duration and the subjectivity of assessment, we did not expect to see such changes. Mean annualized growth rates in 16 subjects with sequential quarterly heights were 5.8, 5.3, and 3.6 cm/yr on 7.5 mg, 3.75 mg, and 11.25 mg 3-month, respectively. Growth rates were significantly lower during the 12-wk period on 11.25 mg 3-month, compared with 3.75 mg. This finding is presumably attributable to a trend evident in the naive patients but not the established patients, reflecting the gradual decline in height velocity in the first year of DL therapy in CPP. There was certainly no increase in height velocity observed at transition to the lower DL doses. We thus found no rise in sex steroid concentration or progression in secondary sexual characteristics to match the increase in Gn release seen with the 3.75 mg and 11.25 mg-3 month doses.
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Discussion
The significant discrepancy between U.S. and international practices regarding the initial dose of monthly depot leuprolide in treatment of CPP has largely been ignored. Pediatric endocrinologists in the United States historically have used notably higher monthly doses (7.5–15 mg or ⬃300 g/kg) than their counterparts in Europe and Asia (3.75 mg, ⬃100 g/kg for the typical naive patient). In an early DL dosing trial in CPP, Parker et al. (8) calculated a mean suppressive dose of approximately 330 g/kg, about 7.5 mg monthly. A smaller study by Cook et al. (9), using urinary Gn as primary outcome, showed incomplete suppression in some subjects on 7.5 mg. In contrast, Tanaka et al. (1) compared 10, 30, and 90 g/kg (the last being roughly equal to 3.75 mg-1 month) in a larger study of 36 children and concluded that the minimum suppressive dose was 30 g/kg, which is 10-fold less than the recommended dose in the United States and much lower than 3.75 mg monthly. In France, Carel et al. (2) achieved long-term pubertal suppression on 3.75 mg every 4 wk in 49 children with CPP. The same group (3) also reported adequate Gn suppression and sustained clinical benefits with the newer 11.25 mg-3 month depot. To clarify the question of appropriate dose, we directly compared two different monthly DL doses and the 3-month DL by sequentially administering them to subjects with CPP. A randomization design might have been preferable, but the sequential design was chosen to ensure initial clinical suppression. Given the limited usefulness of other measures of efficacy within the study’s short-term design, stimulated Gn levels were used as the objective primary end point, using highly sensitive Gn assays. The null hypothesis was to find no difference in Gn suppression among the three dosing regimens. The results demonstrated instead that therapy with either the 3.75-mg DL dose or its longer duration dose equivalent, 11.25 mg-3 month, leads to higher levels of LH and FSH when compared with the standard dose of 7.5 mg monthly. A few patients exhibited clinically worrisome increases in Gn levels, necessitating reversion to standard dosing, and the majority of subjects had slightly higher LH and FSH levels on the lower DL doses. The rise in Gn levels on transition from 7.5 to 3.75 mg monthly is directly attributable to the reduction in dose. One question from the results is whether the poorer Gn suppression with 11.25 mg-3 month is due to the lower total dose or is further affected by the different frequency of delivery, because the two doses deliver the same functional monthly dose at different release rates through the use of distinct polymers. We saw a trend, but not a significant difference, in LH suppression between DL delivered as 3.75 mg monthly vs. 11.25 mg every 3 months, and there was clearly no difference in FSH levels. The LH results imply that the problem of higher Gn levels with 11.25 mg-3 month is largely attributable to inadequate total dose but may be influenced by mode of delivery. If the issue were solely cumulative dose, then the available 22.5 mg-3 month DL injection might achieve Gn suppression equal to that of 7.5 mg monthly. This speculation remains to be tested. One caveat in interpreting our dose data is the exclusion
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of DL-treated subjects with stimulated LH concentrations persistently greater than 2 IU/liter from initiating the dosereduction protocol, totaling 20% of patients on the standard 7.5-mg dose. We thus introduced a recruitment bias toward subjects with more stringent initial LH suppression. Although we did not anticipate quite so many exclusions, the purpose was to protect any marginally suppressed patients from further deterioration in clinical status on reduction in dose. In retrospect, it is somewhat regrettable that these exclusions prevented us from observing the consequences of dose reduction in subjects who were more marginally suppressed on standard dosing. On the other hand, it was clinically prudent, given that LH did rise with dose reduction, and such patients might have been exposed to more exaggerated rises in Gn. If anything, preemptive exclusion of subjects with borderline Gn suppression may have resulted in an underestimate of the Gn escape that can occur on reduction to 3.75 mg, delivered in either 1-month or 3-month form. The rise in Gn levels is also not due to an artifactual regression to the mean because we controlled for this by measuring unchanged Gn responses at two separate visits before dose modification. Furthermore, the tendency is for LH to gradually decline during the first and subsequent years of DL therapy (Neely, E. K., unpublished data). An additional concern regarding the upward trend in Gn with lower DL dose is our use of dissimilar DL doses as Gn-stimulating agents. The gold standard for monitoring GnRHa therapy has been the iv GnRH stimulation test. We previously demonstrated that a single sample drawn after sc GnRH stimulation provides a reliable alternative (10). However, the unavailability of GnRH in recent years has eliminated its use by either mode of administration. We also demonstrated that 7.5 mg DL contains free leuprolide sufficient to stimulate an immediate LH surge to levels equal to or greater than those seen following GnRH testing, thus allowing a simple and convenient way to monitor therapy (6). Our presumption in this study was that the 3.75 mg 1-month and 11.25 mg 3-month doses also contain supraphysiologic amounts of GnRHa sufficient to stimulate an equivalent LH surge. Relevant data come from pharmacokinetic studies in men with prostate cancer, showing that peak plasma leuprolide levels 1–3 h after DL injection are clearly dose dependent (11–14). Furthermore, the distinct biodegradable microspheres in the 1- and 3-month formulations (15) theoretically could influence the magnitude of postinjection LH rise. In light of these considerations, we evaluated whether the lower DL doses might be less effective in stimulating LH and thus confound our interpretation of the dose-change effects. We took advantage of subjects receiving the first dose of each new DL to assess for potential differences in stimulating Gn release. Because the LH and FSH levels achieved were clearly identical, we concluded that all three DL doses contain a functionally equivalent amount of free leuprolide and therefore did not adversely affect the reliability of testing. The unavailability of GnRH for stimulation testing has led to widespread acceptance of both DL and shorter-acting aqueous leuprolide (AL) for therapeutic monitoring. However, suitable LH thresholds following leuprolide stimulation are not as well established as those for GnRH stimulation
Badaru et al. • Comparisons of Depot Leuprolide Doses
in either diagnosis or monitoring of CPP. Garibaldi et al. (16) found a peak LH of 2.3 IU/liter after AL stimulation in prepubertal females, whereas Ibanez et al. (17) reported a mean AL-stimulated LH of approximately 1.4 IU/liter in their prepubertal controls. Interestingly, they also demonstrated that AL-stimulated LH levels are higher than GnRHstimulated LH levels in pubertal children but not in prepubertal children. During DL therapy, we previously found LH levels to be comparable 40 min after either GnRH or DL injection, with means of 0.6 and 0.8 IU/liter, respectively (6). In contrast, Brito et al. (18) recently reported during treatment of CPP that DL-stimulated LH (2 h after 3.75 mg) is significantly higher than GnRH-stimulated LH (2.7 ⫾ 1.9 vs. 1.4 ⫾ 0.6 IU/liter, using the DELFIA immunofluorometric assay; Wallac, Turku, Finland). It is thus unclear how much higher LH levels might rise following leuprolide vs. GnRH injection. This question is germane to the conclusion by Brito et al. (18) that DL-stimulated LH up to 6.6 IU/liter is acceptable during therapy; we consider that threshold too high for optimal outcome. The initial 30 subjects in the current study exhibited a mean postinjection LH of 1.7 ⫾ 1.5 IU/liter after 6 or more months on 7.5 mg DL, and all achieved an LH less than 4 IU/liter, which we use empirically as the threshold for treatment adequacy. The fundamental unanswered question regarding GnRHa use in CPP, other than the controversial age cutoff for initiation of therapy, is whether maximal therapeutic suppression of Gn secretion results in any important additional longterm clinical benefit. It is clear that even the low range of DL doses cause a marked diminution in Gn secretion and reduction in sex steroids. Numerous studies of long-term efficacy of various GnRHa have demonstrated the desired outcomes, such as slowing of growth and bone maturation, cessation of advance in secondary sexual characteristics, and gain in final height over pretreatment predicted height. Yet none of these studies has paid particularly close attention to accurate measurement of Gn at the low range achieved. The French and Japanese studies of long-term 3.75 mg DL clearly show the benefits of GnRHa therapy, but the LH assays used were not sensitive in the low pediatric range. Arguably, further suppression of Gn and sex steroids might lead to greater gains in final height, and inadequate suppression might otherwise negate the potential benefits of therapy. On the other hand, it is plausible that complete suppression of the normal low prepubertal secretion of Gn and sex steroids could harm growth (19, 20). Long-term randomized studies to final height across the DL dose range, and ultimately comparisons of DL with the newer GnRHa implants, are required to answer these questions. We were in fact unable to link the higher Gn levels seen with low-dose or 3-month with comparable increases in sex steroid levels. Changes in serum estrogen concentrations could not be completely assessed, in the sense that levels were generally below the thresholds of sensitivity in either estrogen assay on all three DL doses. Interpretation of this finding depends on whether undetectable levels of estrogen are clinically significant. Estrogen assays historically have been problematic and insensitive in early puberty, including the commercial Esoterix assay used here. However, the ultrasensitive assay is capable of reliably measuring levels in the range typically observed in prepubertal children (7).
Badaru et al. • Comparisons of Depot Leuprolide Doses
Thus, the fact that most levels were below the threshold of detectability in all DL dose groups could be taken to mean that all DL doses are clinically efficacious. We also did not see a trend to pubertal progression by any standard physical measure. Pubertal stage did not vary in subjects on low-dose or 3-month DL, but these manifestations are subjectively interpreted and not particularly useful in monitoring except in fairly obvious treatment failure. Changes in growth velocity, questionably accurate during such brief intervals, and bone age, which we did not obtain for the same reason, typically lag behind biochemical indicators in the establishment of pubertal suppression. Thus, it was not surprising that growth rate continued to decline during successive 3-month intervals of initial DL therapy, rather than reflecting any difference due to dose change. In summary, we do not know the implications of the variable degrees of Gn suppression achieved through different DL dosing regimens. Although cost and convenience of administration are legitimate considerations in DL therapy, the most important concern is delivering the most effective suppression of puberty for optimal long-term growth. Our results are cautionary regarding the use of lower DL doses in CPP. Given the higher Gn levels, we do not believe that 3.75 mg monthly DL offers any real clinical advantage over the standard U.S. dose of 7.5 mg or higher, which will continue to be our initial dose. On the other hand, given the sex steroid results, we have not produced a compelling enough argument to recommend to our international colleagues the elimination of 3.75 mg as their standard dose. Potential solutions to this practice dilemma include starting at a lower dose of DL and titrating upward for insufficient Gn suppression, or conversely, beginning at a higher DL dose and titrating downward as long as a certain Gn threshold is maintained. As for the 3-month DL, its clinical use is gradually increasing among pediatric endocrinologists in the United States. Whether the considerable convenience of the 3-month DL warrants the potential risk of higher Gn levels during therapy is a matter of clinical judgment, for the moment untested by long-term clinical trials. Acknowledgments We are grateful to Bonita Baker for technical support. Received July 7, 2005. Accepted January 19, 2006. Address all correspondence to: E. Kirk Neely, M.D., Room S302, Stanford University Medical Center, Stanford, California 94305. E-mail:
[email protected]. This work was supported by The Endocrine Society. Research was not National Institutes of Health supported. A.B. was supported by a fellowship grant from the Glaser Pediatric Research Network. Funding was also provided by the Innovations in Patient Care Fund at the Lucile Packard Children’s Hospital at Stanford University. The authors have nothing to declare.
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