Short- and long-term (final height) data in children with normal variant short stature treated with growth hormone

Growth hormone (GH) treatment to final height in children with idiopathic short stature: evidence for a dose effect

OBJECTIVES

To investigate in an open-label randomized study, the effect of two doses of growth hormone (GH) on final height and height velocity during the first 2 years of treatment of children with idiopathic short stature (mean baseline height standard deviation score [SDS] -3.2).

STUDY DESIGN

Patients were treated with GH at 0.24 mg/kg/week, 0.24 mg/kg/week for the first year and at 0.37 mg/kg/week thereafter (0.24-->0.37), or 0.37 mg/kg/week. Final height was evaluated in 50 patients at study completion (mean treatment duration, 6.5 years).

RESULTS

Patients who received 0.37 mg/kg/week (n = 72) experienced a significantly greater increase in height velocity than those who received 0.24 mg/kg/week (n = 70) (treatment difference = 0.8 cm/year; P = .003) or 0.24-->0.37 mg/kg/week (n = 67) (treatment difference = 0.9 cm/year; P = .001). For the 50 patients for whom final height measurements were available, mean height SDS increased by 1.55, 1.52, and 1.85 SDS, respectively, for the three dose groups. For the primary comparison between the 0.37 mg/kg/week and 0.24 mg/kg/week dose groups, the mean treatment difference (adjusted for differences in baseline predicted height SDS) was 0.57 SDS (3.6 cm; P = .025). Mean overall height gains (final height minus baseline predicted height) were 7.2 cm and 5.4 cm for the 0.37 mg/kg/week and 0.24 mg/kg/week dose groups, respectively, without dose effects on safety parameters. Final height measurements were within the normal adult height range for 94% of patients randomized to 0.37 mg/kg/week who continued to final height.

CONCLUSION

GH treatment dose-dependently increases height velocity and final height in children with idiopathic short stature.

Growth Hormone Use in Children with Idiopathic Short Stature

OBJECTIVE:

To review the indication, pharmacology, pharmacokinetics, efficacy, and adverse effects of recombinant human growth hormone in children with idiopathic short stature (ISS).

DATA SOURCES:

A MEDLINE search (1966–December 2003) was performed using the key words human growth hormone, somatropin, Humatrope, normal children, somatrem, and idiopathic short stature. Food and Drug Administration Advisory Committee Meeting minutes were also reviewed.

STUDY SELECTION AND DATA EXTRACTION:

The data presented in this review were obtained from published literature, abstracts presented at scientific meetings, and information on file with the manufacturer. Additional articles from these sources were also identified. Current issues of pediatric and endocrinology journals were reviewed for the most recent articles. Articles only addressing the use of growth hormone in normal, healthy children were used.

DATA SYNTHESIS:

Somatropin is indicated for use in children with ISS. Studies have shown modest benefit to final height achieved and, at the doses used for ISS, there have been no adverse effects associated with somatropin. Many questions still exist, however, concerning the most appropriate age to initiate treatment and duration of treatment. There are also many ethical concerns surrounding patient selection criteria and potential for increased off-label use.

CONCLUSIONS:

Growth hormone has been found to have modest efficacy in improving final height in children with ISS. The specific patient population likely to achieve maximal benefit, optimal dosage regimens, and the long-term adverse effects of extended duration of therapy are unknown.

Growth hormone secretory pattern and response to treatment in children with short stature followed to adult height

OBJECTIVE

To compare the relative utility of GH stimulation tests and assays of spontaneous GH secretion as predictors of change in height standard deviation score at the end of GH treatment in children with short stature.

PATIENTS AND METHODS

We retrospectively studied 116 children (67 boys and 49 girls) with subnormal growth rates and short stature, defined as a height of more than 2SD below the mean for age and sex. The patients were classified according to their pattern of findings on baseline pharmacological GH stimulation tests and a 12-h assay of nocturnal spontaneous GH secretion. Twenty-eight patients (24%) had normal hormone levels by both methods (group I); 14 (12%) had normal levels by stimulation tests but subnormal levels by the physiological assay (group II); 48 (41%) had subnormal levels on pharmacological stimulation, with normal physiologic levels (group III); and 26 (22%) had subnormal levels by both methods (group IV). All children in groups II and IV, and 27 in group III, designated IIIb, were treated with recombinant GH at 0.7 U (0.23 mg/kg) of body weight per week. GH secretory patterns were related to final height SD scores and other growth parameters, after the patients had attained their adult stature 6.7 +/- 2.2 years (SD) after GH evaluation.

RESULTS

The five groups were similar with respect to mean baseline height SD scores for chronological as well as bone age. Whether assessed as absolute or parentally adjusted (relative) values, mean gains in height SD scores were significantly greater in treated patients with physiological hormone deficiency (groups II and IV) than in those with normal hormone levels (group I, untreated controls). Relative height gains were 1.03 +/- 1.45 cm (6.6 +/- 9.28 cm) and 1.85 +/- 1.21 cm (SDS; 11.8 +/- 7.74 cm) in groups II and IV respectively, compared with only 0.11 +/- 0.42 cm (0.7 +/- 2.68 cm) in group I (P < 0.01 and P < 0.001). GH treatment failed to improve either the absolute or parentally adjusted final height of patients with GH deficiency by stimulation tests but normal levels by physiological assay.

CONCLUSION

Long-term administration of GH to short children with normal spontaneous GH secretion is not associated with an appreciable increase in adult height.

Adult height in children with idiopathic short stature treated with growth hormone

Idiopathic short stature (ISS) includes a heterogeneous group of patients with common characteristics to those of familial short stature and constitutional delay. Some authors state that these children can often respond to GH treatment, thus increasing their adult height. The aims of this study were to determine the effect of GH treatment (0.5-0.7 IU/kg/week) and the influence of some initial variables on adult height in patients with ISS. It was a non-randomized, observational study of 30 boys with ISS and a historical control group of 42 patients. The patients were followed until achieving their adult height. The mean height gain of the treated group attributable to GH was 4.5 cm. A stepwise regression model considering predicted adult height and target height as independent variables and final height as dependent variable gave an R2 coefficient of 0.38. We conclude that GH significantly increases final height in boys with ISS.

Is there a place for combined therapy with GnRH agonist plus growth hormone in improving final height in short statured children?

The availability of recombinant human growth hormone (GH) and the optimization of substitutive therapy have improved final growth in children with GH deficiency, but despite this some of them fail to grow to their genetic potential. In particular, this may occur in patients who started the substitutive therapy too late and/or in whom bone age progressed too fast during GH administration. In these patients, with unfavorable auxological characteristics, the administration of a GnRH agonist in combination with GH may slow down bone maturation and prolong prepubertal growth, mimicking, to some extent, the growth pattern of patients with GH + Gn deficiency who grow better than children with isolated GHD. A different condition in which such a combined therapy might be used is the short normal child. As they are short but normally-growing children, the onset of puberty is in general appropriate for their chronological age but precocious for their height age. Thus, slowing down pubertal maturation may increase the time available for growth. GH would sustain growth during both GnRHa administration and after its withdrawal, when puberty starts again. Our preliminary results suggest that the administration of GH + GnRHa in combination may have a positive effect on final height in selected children with isolated GHD and in short normal children.

Lipid profile, glucose tolerance and insulin sensitivity after more than four years of growth hormone therapy in non-growth hormone deficient adolescents

OBJECTIVE

To study the effects of long-term (> 4 years) growth hormone (GH) therapy on insulin sensitivity, glucose tolerance and lipid profile in non-GH deficient adolescents at completion of their growth.

SUBJECTS

Thirty non-GH deficient (15 'idiopathic' short stature, 8 intrauterine growth retardation, 7 partial GH deficiency in childhood but normal on retesting) were recruited, median (range) age 16.9 years (15-20.3) prior to ceasing their GH therapy. Their median (range) duration of GH treatment was 7.9 years (4-11). Insulin sensitivity was also recorded in 10 normal controls with a median (range) age of 20.5 years (18.4-22.3).

METHODS

Insulin sensitivity was assessed by a short insulin tolerance test in 18 patients on GH therapy and controls. It was repeated in 14 patients six months after stopping their GH therapy. A 3-h standard oral glucose tolerance test (OGTT) was performed in 19 patients on GH therapy, and repeated after 6 months off GH in 10 patients. Fasting lipids were also measured.

RESULTS

Insulin sensitivity index was significantly lower in the patients on GH therapy than in the controls, (median (range)) 3.7%/min (1.2-5.3) and 5.3%/min (3.8-6.2), respectively. Six months after termination of GH therapy, insulin sensitivity increased significantly from 3.6%/min (1.2-5) to 4. 8%/min (2.8-5.6). Fasting plasma insulin decreased significantly off GH therapy from 10.1 to 3.6 mU/l. The area under the insulin curve during the OGTT was also significantly higher on GH therapy. Apart from one patient with impaired glucose tolerance on GH treatment, plasma glucose concentrations remained within the normal range. No lipid abnormalities were recorded.

CONCLUSIONS

These data suggest that long-term GH therapy may cause insulin resistance in non GH deficient adolescents, but usually with neither impaired glucose tolerance nor hyperlipidaemia.