The Efficacy of Anastrozole and Growth Hormone Therapy on Adult Height in Six Adolescent Males with Growth Hormone Deficiency or Idiopathic Short Stature

Background. Data on adult height outcomes of the use of Anastrozole and Growth Hormone (GH) in pubertal males with Growth hormone deficiency (GHD) and Idiopathic short stature (ISS) are limited. Objective. We examined the effect of Anastrozole and GH therapy on near adult height (NAH) with pubertal males with GHD or ISS.Methods. Retrospective review of 419 charts from 2008 to 2015.The primary outcomes are NAH compared to mid-parental target height (MPTH) and predicted adult height (PAH). Results. We identified 23 patients (5 SGA/IUGR, 1 Noonan syndrome, 6 GHD, and 11 ISS). Six patients (4 GHD; 2 ISS) achieved NAH. Prior to Anastrozole treatment, the mean chronological age was 13.9 ± 0.2 years (range 13.7–14.4), bone age was 13.6 ± 0.6 years (range 12.5–14), mean height SDS was −1.5 ± 0.5 (range −0.8 to −2.3), and mean PAH was 162.6 ± 5.9 cm (range 153.5–168.6). MPTH was 173.6 cm ± 7 (range 161.8–181.6). Patients received Anastrozole for an average of 30.5 months (range 19–36 months). At NAH, the mean chronological age was 16.7 ± 0.8 years (range 15.9–18.1 years) and height was 170 ± 1.8 cm (range 168.5–173.4 cm). The mean height SDS improved to +0.81 ± 0.6 (range +0.08 to +1.92, p = 0.002). Net height gain was 7.3 cm compared to pretreatment PAH (p < 0.01) and overall the mean adult height remained 3.5 cm below MPTH. Conclusion. Anastrozole and GH therapy can be effective in augmenting adult height without significant side effects. However, the long-term safety and efficacy of aromatase inhibitor use in pediatrics remain limited.


Background
Approximately 17% of adult male height and 12% of adult female height result from the pubertal growth spurt [1].Maximizing the pubertal growth spurt in children with growth hormone deficiency (GHD) or idiopathic short stature (ISS) is challenging due to limited time available for linear growth.Different modalities to increase the adult height in pubertal adolescents with GHD and ISS include high dose GH therapy, gonadotropin releasing hormone analogs, and more recently aromatase inhibitors (AI) [2].
AI block the aromatase enzyme, which prevents conversion of testosterone to estrogen, delays closure of the epiphyses, and may prolong the time period for pubertal growth.The identification of one male with a point mutation in the estrogen receptor gene [3] and another male with a point mutation in the aromatase enzyme gene [4,5] confirmed that estrogen is the principal hormone causing epiphyseal closure.Studies involving AI in male patients with constitutional delay of growth and puberty [6,7], ISS [8,9], and GHD [10] suggest that AI can delay bone age acceleration and increase predicted adult height (PAH).However, data regarding adult height outcomes are limited [6][7][8][9][10][11][12].
In the current study, we reviewed growth and height outcomes for six male adolescents with GHD or ISS treated with GH therapy to determine whether Anastrozole improves the adult height above the pretreatment PAH.

Methods
This is a retrospective chart review of male patients between 12 and 18 years of age who were seen at the pediatric endocrinology clinic at Rhode Island Hospital from January 2008 to July 2015.We identified patients between 12  We identified 419 patients with those diagnoses.We reviewed the charts of these patients to identify those treated with Anastrozole in addition to GH therapy.We identified 23 patients with a diagnosis of short stature, GHD, or ISS and treatment with GH and Anastrozole.The following inclusion criteria were applied to these patients: (a) GHD was defined as either (i) short stature characterized by a height less than 2 standard deviations below the mean height for chronological age and sex [13] or (ii) poor growth (growth velocity ≤ 25 percentile) [ [10].NAH was defined as growth velocity less than 2.5 cm per year or bone age ≥ 15 years in a fully pubertal male.Anthropometric measures were obtained using digital scales and Harpenden stadiometer.Bone age X-ray was assessed based on the method of Greulich and Pyle [15].One pediatric endocrinologist read all bone age studies.Pubertal stage was assessed by physical examination according to Tanner's criteria [16].Tanner staging was performed by one pediatric endocrinologist.Outcome measures were pretreatment PAH, height, and height SDS, and posttreatment height SDS and NAH.PAH was calculated using the method of Bayley and Pinneau [17].Rhode Island Hospital Institutional Research Board approved the study.

Assays.
Serum concentrations of testosterone, LH, FSH, and estradiol were measured at baseline and annually at Esoterix Laboratory Services, Calabasas Hills, California.Serum LH and FSH were measured by chemiluminescent assay.Serum testosterone was measured by liquid chromatography with isotope dilution mass spectrometry detection after supported liquid extraction.Analysis was performed using high-pressure liquid chromatography separation with tandem mass spectrometric detection (LC-MS/MS).Testosterone stable labelled isotope was added as internal standard to all sample and standard aliquots.The samples were extracted, evaporated, reconstituted, and then injected onto an LC-MS/MS system.A triple quadrupole mass spectrometer was used for detection.The amount of testosterone in each sample was calculated from a linear plot generated by purified testosterone standards ranging from 2.5 to 5000 ng/dL.Serum estradiol was measured using twodimensional liquid chromatography (HPLC) with tandem mass spectrometry detection after liquid-liquid extraction.Carbon-13 labelled DL-estradiol was added to serum aliquots to evaluate and correct for recovery of the estradiol from each sample.Extract supernatants from samples and standards were separated, dried, and reconstituted.A triple quadrupole mass spectrometer was used for detection.The amount of estradiol in each sample was calculated from a linear plot generated by purified estradiol standards ranging from 1.0 to 500 pg/mL.

Statistical Analysis.
The primary endpoint of this study was NAH compared to pretreatment PAH and mid-parental target height (MPTH).Continuous variables were reported as mean with standard deviation and median with ranges.Treatment group differences were evaluated with two-sampled test with equal variance.A  value of less than 0.05 was considered statistically significant.

Discussion
Our study showed that the use of Anastrozole in addition to GH therapy resulted in a statistically significant increase in NAH compared to pretreatment PAH in boys with ISS or GHD.The delay in the tempo of bone age acceleration caused by aromatase inhibition and decreased estrogen resulted in a significant net gain in height.Overall our cohort achieved a mean net height gain of 7.3 cm compared to pretreatment PAH.However the mean NAH remained 3.5 cm below the mean MPTH.Initial use of AI was studied in children with constitutional delay of puberty.Wickman et al. demonstrated a 5.1 cm mean height gain compared to the pretreatment PAH in children with constitutional delay of puberty who were treated with AI for twelve months, in combination with low dose testosterone therapy for 6 months [6].The same subjects were followed until near final height [7] and the boys treated with AI attained a mean NAH 6.7 cm higher compared to the control group.
Subsequent studies were done in patients with ISS and GHD [8,10,11].Hero et al. [8] in a prospective doubleblinded, randomized, placebo controlled study showed that subjects with ISS treated with Letrozole have an increased PAH by 5.9 cm and height SD score for bone age increased by 0.7 SD score.Mauras et al. in a double-blinded [10], randomized, placebo controlled clinical trial observed a net increase in PAH of 4.5 ± 1.2 cm after 2 years and 6.7 ± 1.4 cm after 3 years of treatment with Anastrozole.In this study, safety data including glucose and lipid profile were similar between groups.The investigators observed that the patients who received Anastrozole in addition to GH therapy had significant delay in bone age advancement, which resulted in statistically significant net gain in PAH.
Also Rothenbuhler et al. [11] conducted a prospective randomized study to compare GH alone and GH and Anastrozole in 24 adolescent boys with ISS who achieved NAH.Height gain compared to the pretreatment PAH was +4.6 cm greater and height SDS at NAH was +0.7 SD score greater in the subjects treated with GH and Anastrozole compared to the GH alone group.More recently, Mauras et al. [9] in a randomized trial of 3-arm comparator study using AI, GH, and combination of AI and GH demonstrated that combination treatment increased linear growth significantly from baseline when used for 2-3 years.At near adult height the absolute change in height SDS from baseline was +0.8 in AI, +1.0 in GH, and +1.3 in GH/AI.The height SDS at near adult height was −1.4 ± 0.1 in AI group, −1.4 ± 0.2 in GH group, and −1.0 ± 0.1 in AI/GH group.The subjects tolerated the AI well without significant side effects.Despite the limited number of subjects and lack of control group, the study showed positive results using AI/GH in augmenting the final height.The mean height SDS at baseline in our study was similar to Mauras's study; however the PAH in our study was more compromised compared to their MPTH.Despite small number of patients in our study, our findings provide additional evidence of potential benefit of AI in augmenting adult height.
Limitations of our study include a small sample size, lack of control group, heterogeneous nature of the patients, and retrospective study design.However, the results of our study are consistent with the previous studies of the efficacy of Anastrozole in augmenting adult height.Larger prospective, randomized, controlled clinical trials are needed to evaluate the efficacy and safety of AI in children with ISS and GH deficiency in augmenting adult height.
In summary, Anastrozole in addition to GH increased adult height significantly compared to pretreatment PAH in this small cohort of boys with ISS or GHD.This suggests that Anastrozole therapy is effective in augmenting adult height without significant side effects during therapy.However, the long-term safety and efficacy of aromatase inhibitors in boys with GH deficiency and ISS remains limited and further investigation is needed.

6 Figure 2 :
Figure 2: Patients with near adult height comparing to predicted adult height prior to Anastrozole treatment and mid-parental height.

Figure 3 :
Figure 3: Comparison of height SDS before and after Anastrozole treatment.

Table 1 :
Baseline clinical characteristics of study patients before initiation of GH therapy.
3.2.Clinical Characteristics before Initiation of Anastrozole.Mean chronological age was 13.9 ± 0.27 years (range 13.7 to 14.4) and bone age was 13.6 ± 0.6 years (range 12.5 to 14).Mean height SDS was −1.5 ± 0.5 (range −0.8 to −2.3).Mean PAH was 162.6 ± 5.9 cm (range 153.5 to 168.6) compared to mean MPTH of 173.6 ± 7 cm (range 161.8 to 181.6).Mean annualized growth velocity was 9.3 ± 3.1 cm per year (range 5 to 12.7).Patients had a mean testicular volume 13.6 mL (range 10-20 mL).Median duration of GH therapy before initiation of Anastrozole was 14.5 months.The GH dose for all patients ranged from 0.22 to 0.36 mg/kg/week.Table2compares the baseline characteristics of each patient before and after Anastrozole treatment.3.3.Near Adult Height.At NAH, the mean chronological age was 16.7 ± 0.8 years (range 15.9 to 18.1) and mean bone age was 15.5 ± 1.6 years (range 14 to 17).The mean NAH was 170 ± 1.8 cm (range 168.5 to 173.4) compared to mean MPTH of 173.6 ± 7 cm (range 161.8 to 181.6).Five out of 3.4.Safety Issues.All patients tolerated Anastrozole well and no patients report any side effects of Anastrozole including nausea, vomiting, abdominal pain, back pain, mood changes, or hot flashes.Endocrine evaluation including serum testosterone, LH, and FSH were followed periodically and were within normal limits.Table3summarizes the most recent available laboratory evaluation.

Table 2 :
Comparison of clinical characteristics of patients before and after Anastrozole treatment.

Table 3 :
Available laboratory data at NAH.
Laboratory data at NAH was not available for Patient 5.