The biggest problem faced by pubertal short stature boys is limited growth potential. The treatment goal is to exploit their residual growth ability and make the children obtain satisfactory height (close to THt). At present, there is little literatures on GH combined with letrozole in the treatment of adolescent short boys followed up to FAH. In pubertal boys with severe idiopathic short stature, GH(0.13U/kg·d), or combination treatment (aromatase inhibitor/GH) for the next 24 months. Subjects were then randomized to treatment with GH and one kind of aromatase inhibitor (n=25, anastrozole or letrozole—balanced 1:1) . The mean height gain at 24 months was 18.9±0.8cm, and the absolute change in height from baseline at near FAH was 22.5±1.4cm [6]. In our study, 20 cases reached FAH. Although 25 cases in the above study were all near FAH, none of FAH. In our study, GH dosage (0.15-0.2U/kg.d) was slightly higher than that of the above study considering the maximum residual growth capacity. But the dose of GH in our study was within the recommended guidelines of GH usage [12]. The treatment duration was 1.94±0.67yr, and mean height gain was 17.34±5.53cm. If calculated by 24 months, the net height gain was 17.9 cm, which was close to the 24 months height gain (18.9 cm) of the above study. In our study, the net height gain was 24.47±6.70cm at FAH, which was close to that of near FAH (22.5±1.4 cm) in above study. However, unlike the above reports, the end point of our study was FAH. In our study, the effect of GH combined with letrozole alone on FAH was observed, and we aimed to avoid the interference of mixed factors of letrozole and anastrozole. And they have different inhibitory rates on estrogen (letrozole >99.1%, anastrozole 97.3%) [2]. In terms of the number of GH combined with letrozole, there were 20 cases in our study, while there was only 12-13 cases in the above study .
In 2017, a study reported that 96 adolescent boys were divided into 4 groups. The height SDS of anastrozole, GH combined with anastrozole, letrozole, GH combined with letrozole were 0.8±0.7, 0.7±0.7, 0.3±0.5 and 1.2±0.8, respectively. There were 22 cases of near FAH and no cases of FAH. And there was significant differences among these groups and no side effects were found. GH combined with letrozole can maximize near FAH [13]. Compared with 9 cases of NFAH achieved by GH combined with letrozole in the literature [13], there were no differences for indexes before treatment such as between bone age [(13.28±1.09)y & (13.00±0.93)y], height [(152.17±6.99)cm & (148.20±6.87)cm] between that of our study and the above study (13), [(Z=-1.182, p=0.237)&(t=1.432, p=0.163)]. But the PFAH1 (161.02±4.12cm) before therapy in our study was lower than that of the above study (170.27±2.35cm) (t=6.251, p<0.000). And the THt (167.67±3.56cm) before therapy in our study was lower than that of the above study (172.89±4.53cm) (t=3.357, p=0.002). But there was no significant difference of NFAH in above study and FAH in our study (174.58±7.01cm&172.67±2.72cm), (t=0.793, p=0.448). So it indicated that there was the same efficacy between our study and the above study [13].
Compared with 5 cases of NFAH achieved by letrozole in the literature [13], there were no differences for indexes before treatment such as between bone age [(13.60±0.78)y & (13.00±0.93)y], height [(157.30±5.82)cm & (148.20±6.87)cm] between that of our study and the above study [13], [(t=-1.336, p=0.195)&(t=-1.336, p=0.195)]. But the PFAH1 (161.02±4.12cm) before therapy in our study was lower than that of the above study (174.16±1.11cm) (t=-6.965, p<0.000). And the THt (167.67±3.56cm) before therapy in our study was lower than that of the above study (176.20±1.92cm) (t=-5.113, p<0.000). But there was the same efficacy between our study and the above study [13], and there was no difference for NFAH in above study and FAH in our study [171.06±2.33cm&172.67±2.72cm], (t=-1.207, p=0.240), so it indicated that the GH combined with letrozole was superior than that of letrozole alone.
Compared with 3 cases of near FAH achieved by GH combined with anastrozole in the literature [13], there were no differences for bone age before treatment between [(13.33±0.29)y & (13.00±0.93)y] between that of our study and the above study, (Z=-1.189, p=0.234). And the height (148.20±6.87cm) before therapy in our study was lower than that (152.83±7.08cm) of the above study (t=-1.087, p=0.289), as well as the PFAH1 (161.02±4.12cm) in our study and that (172.00±6.03cm) of the above study(t=-4.088, p=0.001), and the THt (167.67±3.56cm) in our study and that (174.50±2.60cm) of the above study(Z=2.332, p=0.020). However, there was the same efficacy between our study and the above study [13], and there was no difference for NFAH in above study and FAH in our study [168.83±5.86cm&172.67±2.72cm], (t=-1.115, p=0.375), so it indicated that the GH combined with letrozole was superior than that of letrozole alone, while the number of cases was limited and further study need be researched.
Compared with 5 cases of near FAH achieved by anastrozole in the literature [13], there were no differences for indexes before treatment such as between bone age [(12.60±0.65)y &(13.00±0.93)y], height [(149.00±5.76)cm & (148.20±6.87)cm] between that of our study and the above study (13), [(t=0.474, p=0.640)&(t=-0.163, p=0.872)]. But the PFAH1 (161.02±4.12cm) before therapy in our study was lower than that of the above study (173.84±6.55cm) (t=-2.622, p=0.015). And the THt (167.67±3.56cm) before therapy in our study was lower than that of the above study (171.75±2.96cm) (Z=-1.360, p=0.174). But there was the same efficacy between our study and the above study (13), and there was no difference for near FAH in above study and FAH in our study [172.80±5.12cm&172.67±2.72cm], (t=0.083, p=0.935), so it indicated that the GH combined with letrozole was superior than that of anastrozole alone.
Letrozole can significantly inhibit bone age progress and improve FAH in adolescent short boys. In a prospective, double-blind, randomized, placebo-controlled clinical study, thirty-one boys, aged 9.0-14.5 yr, with idiopathic short stature were studied.The boys were treated with the aromatase inhibitor letrozole (2.5 mg/d) for 2 yr. The main outcome measure was the change in PAH after 24 months of treatment. The level of serum testosterone in letrozole group was significantly higher than that in control group. After 2 years of treatment, the range of serum testosterone entering puberty was 17.3-1385 ng/dl, while the level of serum estradiol was similar to that before treatment [14]. In this study, testosterone [(6.807+2.339) ng/ml, ranging from 2.13 to 11.28ng/ml] after treatment was higher than thatof before treatment [(2.167+1.692) ng/ml, ranging from 0.19 to 5.33ng/ml]. Serum estradiol (13.000+12.472) pg/ml was significantly lower than before treatment (21.731+16.870) pg/ml. The bone age minus chronological age changed from 0.88±0.83 to 0.35±1.34. It indicated that letrozole prevented the conversion of testosterone to estradiol, and promoted the slow growth of bone age, and gradually shortened thebone age minus chronological age, and it provided the opportunity for FAH, and serum testosterone were in normal range.
It indicated that GH combined with GnRHa did not yet improve FAH in adolescent short boys. Thirty-two adolescents with Tanner stage 2-3, age and bone age (BA) less than 12 yr for girls or less than 13 yr for boys, height SDS less than -2.0 SDS or between -1.0 and -2.0 SDS plus a PAH less than -2.0 SDS were randomly allocated to receive GH plus GnRHa (n=17) or no treatment (n=15) for 3 yr. FAH was assessed at the age of 18 yr or older in girls or 19 yr or older in boys.FAH was no difference between treatment and control groups. Mean lumbar spine bone mineral density and bone mineral apparent density tended to be lower in treated boys. GH plus GnRHa can not be considered routine treatment for children with idiopathic short stature [15].
Among the common side effects of GH, scoliosis progression during GH therapy appears due to rapid growth rather than as a direct side effect of GH. Scoliosis is observed in ∼ 0.2% of children with idiopathic short stature or idiopathic growth hormone deficiency treated with GH [16 -17]. In our study, there was a case of scoliosis with a growth rate of 10.9 cm/year. It was considered that the growth rate of scoliosis was related to its rapid growth. However, it was regrettable that the child had not received anteroposterior and lateral spine radiographs before treatment, so it was necessary to do anteroposterior and lateral spine radiographs before GH.
In addition to the common side effects of GH, many scholars have paid attention to the side effects of letrozole in short-stature boys, but there is some controversy. In a survey in 2015, in order to assess the effects of aromatase inhibitors in male children and adolescents with short stature, the author searched the Cochrane Library (2014, Issue 7), MEDLINE, EMBASE, and the World Health Organization ICTRP trial register from their inception until August 2014. Four RCTs involving 207 participants (84 on interventions) were in the review. Trials included males with constitutional delay of growth and puberty, idiopathic short stature, and GH deficiency. A significant proportion (45%) of prepubertal boys with idiopathic short stature treated with letrozole developed mild morphological abnormalities of their vertebrae, compared with none in the placebo group [18]. The incidence of vertebral deformation in children with idiopathic short stature increased after letrozole was used, but there was the similar incidence between letrozole group and control group, so it may be other reasons for the vertebral deformation [19]. Vertebral deformities do not occur in boys with delayed puberty treated with letrozole for one year [20]. No case with abnormal vertebral morphology was found in our study. Therefore, the effect of letrozole on skeletal system needs further study.