Decreased trabecular bone mineral density in children with idiopathic short stature: normalization of bone density and increased bone turnover after 1 year of growth hormone treatment

Effects of growth hormone on bone modeling and remodeling in hypophysectomized young female rats: a bone histomorphometric study

Growth hormone (GH) deficiency causes decreased bone mineral density and osteoporosis, predisposing to fractures. We investigated the mechanism of action of GH on bone modeling and remodeling in hypophysectomized (HX) female rats. Thirty female Sprague-Dawley rats at age 2 months were divided into three groups with 10 rats each: control (CON) group, HX group, and HX + GH (3 mg/kg daily s.c.) group, for a 4-week study. Hypophysectomy resulted in cessation of bone growth and decrease in cancellous bone mass. Periosteal bone formation decreased and bone turnover rate of endocortical and trabecular surfaces increased as compared to the CON group. GH administration for 4 weeks restored weight gain and bone growth and mitigated decrease in bone density after hypophysectomy. However, trabecular bone mass in the proximal tibial metaphysis remained lower in group HX + GH than in group CON. Dynamic histomorphometric analysis showed that bone modeling of periosteal bone formation and growth plate elongation was significantly higher in group HX + GH than in group HX. New bone formed beneath the growth plate was predominately woven bone in group CON and group HX + GH. Bone remodeling and modeling-remodeling mixed modes in the endocortical and PTM sites were enhanced by GH administration; both bone formation and resorption activities were significantly higher than in group HX. In conclusion, GH administration to HX rats reactivated modeling activities in modeling predominant sites and increased new bone formation. GH administration also increases remodeling activities in remodeling predominant sites, giving limited net gain in the bone mass.

Influence of birth size and body composition on bone mineral density in early adulthood: the PROGRAM study

BACKGROUND/OBJECTIVES

Low bone mineral density (BMD) may lead to osteoporosis and is associated with increased fracture risk. Associations between BMD and various factors have been reported. Our objective was to investigate whether birth size, lean body mass (LBM) and fat mass (FM) are determinants of BMD of the total body (BMD(TB)) and the lumbar spine (BMD(LS)).

METHODS

In the PROgramming factors for GRowth And Metabolism (PROGRAM) study of a cohort of 312 young adults aged 18-24 years, BMD(TB) and BMD(LS) were determined by dual-energy X-ray absorptiometry (DXA). Subsequently, differences in BMD(TB) and BMD(LS) were analysed in four subgroups: young adults born small for gestational age with short stature (SGA-S) or with catch-up growth (SGA-CU), or born appropriate for gestational age (AGA) with idiopathic short stature (ISS) or with normal stature (controls).

RESULTS

Adult weight, LBM, FM and weight gain during childhood were the main positive determinants for BMD(TB) in early adulthood, whereas birth size had no influence (adjusted R(2) = 0.50). Gender, adult weight, LBM, FM and weight gain were the significant determinants of BMD(LS). In the subgroups, after correction for age, gender and adult body size, the ISS group had a significantly lower BMD(TB) than controls but there was no difference in BMD(LS) between the subgroups.

CONCLUSIONS

Prenatal growth has no significant influence on BMD(TB) and BMD(LS) in early adulthood. Gender and postnatal growth, particularly weight gain, are the main positive determinants. To achieve a normal BMD in adulthood, healthcare workers should aim for a normal weight gain in children.

Idiopathic short stature: management and growth hormone treatment

In the management of ISS auxological, biochemical, psychosocial and ethical elements have to be considered. In boys with constitutional delay of growth and puberty androgens are effective in increasing height and sexual characteristics, but adult height is unchanged. GH therapy is efficacious in increasing height velocity and adult height, but the inter-individual variation is considerable. The effect on psychosocial status is uncertain. Factors affecting final height gain include GH dose, height deficit in comparison to midparental height, age and first year height velocity. In case of a low predicted adult height at the onset of puberty, addition of a GnRH analogue can be considered. Although GH therapy appears safe, long-term monitoring is recommended.

Serum procollagen type 1 amino-terminal propeptide (P1NP) as an early predictor of the growth response to growth hormone treatment: Comparison of intrauterine growth retardation and idiopathic short stature

There is no way to predict early the growth response to growth hormone (GH) treatment in short children with intrauterine growth retardation (IUGR) or idiopathic short stature (ISS).

OBJECTIVE

To evaluate the capacity of the procollagen type 1 amino-terminal propeptide (P1NP), a new marker of bone formation, to help in this prediction.

PATIENTS AND METHODS

Longitudinal study of 30 patients treated at 7.7 (range: 2.2-12.5) years for IUGR (n=16) or ISS (n=14) with GH (0.47 and 0.33 or 0.4mg/kg/week respectively). P1NP and insulin-like growth factor I (IGF I) were measured before and after 3-6 months of GH treatment.

RESULTS

Before treatment, IUGR patients were younger and shorter than ISS patients, but their other characteristics were similar. IGF I Z-score (ZS) and P1NP concentrations were positively correlated in the whole population (Rho=0.48; P=0.01). After 3-6 months of treatment, both concentrations increased in IUGR and ISS (P<0.01). They remained correlated only in ISS (Rho=0.54; P<0.05). P1NP before treatment was negatively correlated (Rho=-0.67, P=0.015) with the growth rate (SD) during the first year of treatment in ISS but not in IUGR; IGF I ZS was not. The changes in P1NP for the whole population over 3-6 months, but not the changes in IGF I ZS, were positively correlated with the growth rate (Rho=0.41, P=0.03).

CONCLUSIONS

Lower basal plasma P1NP concentrations predict better growth response to GH treatment during the first year in ISS children. Greater increases in its concentrations after 3-6 months of GH treatment may also predict a better growth response in both ISS and IUGR.

A review of the effects of therapy on growth and bone mineralization in children with congenital adrenal hyperplasia

The medical management of children with congenital adrenal hyperplasia (CAH) can be challenging with regard to optimizing final height. Insufficient glucocorticoid suppression of adrenal hormone production will result in acceleration of bone maturation and premature epiphyseal fusion, while appropriate or excessive glucocorticoid therapy can be accompanied by suppression of the growth axis. The extent of the growth suppression appears to be affected by the type and dose of glucocorticoid. Some studies suggest that such growth suppression can be ameliorated through concomitant use of growth hormone (GH) therapy. Available data published over the last 10 years on height outcomes in CAH patients treated with glucocorticoids will be reviewed.

Long-term outcome of growth hormone therapy in children and adolescents

Growth hormone (GH) has been available for more than 4 decades for the treatment of GH deficiency. Initially, GH was extracted from the pituitary glands of human cadavers, but its use was discontinued following the transmission of the Creutzfeldt-Jakob virus. After the development of recombinant GH (somatropin) in 1985, an 'unlimited' commercial source of GH has been available, allowing for the treatment of a large number of short GH-deficient and -sufficient children. Refinements in both the dosage and the frequency of administration of GH have allowed GH-deficient children to reach nearly normal final heights, although mostly they are still below their target heights. Decreased bone mineral densities and increased concentrations of fasting and postprandial lipids, coagulation factors, and several independent cardiovascular risk factors have been reported in GH-deficient children and adolescents and appear to improve with GH administration. The short-term administration of GH to mostly non-GH-deficient short children with Turner syndrome, chronic renal insufficiency (CRI), intrauterine growth retardation (IUGR), and idiopathic short stature (ISS) has resulted in increased growth velocities. In addition, the final height of patients with Turner syndrome and CRI appears to improve with the long-term administration of GH. Final height data are still lacking in adolescents with IUGR, but height standard deviation score and final height predictions appear to improve with therapy. Based on the incomplete and inconclusive available data, one must conclude that GH treatment of children with ISS cannot be advised. The use of GH at replacement doses in children with GH deficiency has resulted in rare and generally reversible adverse effects. The long-term administration of pharmacologic GH doses to short, mostly non-GH-deficient children must, however, still be viewed with caution, as long-term complications cannot as yet be fully evaluated. GH therapy must be individualized and should be limited only to children with severe short stature or a significantly decreased growth velocity, to children under considerable stress due to their short stature, and to patients in whom low GH or low insulin-like growth factor-1 secretion might be the rate-limiting factors for growth. The cost of the medication and the inconvenience of daily GH injections to otherwise mostly healthy short children must also be taken into account.

The effect of short- and long-term growth hormone treatment on bone mineral density and bone metabolism of prepubertal children with idiopathic short stature: a 3-year study

OBJECTIVE

We recently reported that children with idiopathic short stature (ISS) have decreased lumbar spine bone mineral density (BMD) that increases after 1 year of GH therapy. The aim of this study was to confirm these short-term results and to evaluate the effect of long-term GH therapy on the BMD of children with ISS.

PATIENTS AND DESIGN

We treated a group of 16 short, slow-growing but otherwise healthy non-GH-deficient prepubertal children (8 girls and 8 boys) with a chronological age of 9.5 +/- 0.9 years, a bone age of 8.1 +/- 1.2 years and a height of 124.3 +/- 6.3 cm (height-SDS of -2.1 +/- 0.6) with GH at a dose of 0.1 IU/kg/day for 3 consecutive years.

MEASUREMENTS

Height was determined at 3-month intervals and annual growth velocities were calculated. Bone ages and BMD were measured every 12 months by dual-energy X-ray absorptiometry, as were serum concentrations of the carboxy-terminal propeptide of type 1 collagen (PICP) and the carboxy-terminal cross-linked telopeptide of type 1 collagen (ICPT).

RESULTS

Growth velocity increased from 4.0 +/- 0.8 cm/year to 8.7 +/- 1.5 and 8.0 +/- 1.7 cm/year at 12 and 36 months of GH therapy, respectively, while height-SDS improved from -2.1 +/- 0.6 to -1.6 +/- 0.4 after 36 months of GH (P < 0.0001). Baseline lumbar spine BMD was decreased when compared to that of a control group of healthy children paired for gender, bone age and height (0.640 +/- 0.08 g/cm2vs. 0.730 +/- 0.08 g/cm2; P < 0.003). Lumbar spine BMD increased after 1 year of GH from 0.640 +/- 0.08 to 0.749 +/- 0.08 g/cm2 (P < 0.05), reaching levels similar to that of controls followed for 1 year without therapy (0.749 +/- 0.04 g/cm2vs. 0.760 +/- 0.08 g/cm2). During this period lumbar spine BMD increased 14.5% in the ISS subjects and 3.9% in the controls. Over the following 2 years of GH therapy the lumbar spine BMD of our ISS patients increased at a rate similar to that of the control population, so that after 3 years of consecutive GH therapy the lumbar spine BMD of ISS children was comparable to that of the controls (0.784 +/- 0.12 g/cm2vs. 0.785 +/- 0.09 g/cm2). Femoral neck BMD of our patients was similar to that of the controls at baseline and at 36 months. Following 1 year of GH treatment serum concentrations of PICP increased from 229.6 +/- 63.5 to 358.6 +/- 87.9 micro g/l, while levels of ICTP increased from 9.6 +/- 5.9 to 13.7 +/- 2.1 micro g/l. After 36 months of GH therapy, PICP and ICTP values had decreased to 303.3 +/- 67.2 micro g/l and 11.3 +/- 3.3 micro g/l, respectively, and were no longer significantly different from baseline.

CONCLUSIONS

Children with ISS have decreased lumbar spine BMD, which normalized after 1 year of GH. Over the next 2 years of therapy lumbar spine BMD increased at a normal rate, so that after 3 consecutive years of GH the lumbar spine BMD of children with ISS was similar to that of controls. Bone turnover increased with treatment as indicated by a rise in bone formation and bone resorption markers.

Growth hormone therapy

Since 1958 growth hormone (GH) has been used as substitution treatment for children with GH deficiency. At present, it is clear that a dose of 0.23 mg/kg/week can lead to a final height close to target height, but in view of the wide inter-individual variation, alternative regimens based on invidualizing the dosage with the help of prediction models are being investigated. The best strategy during puberty (increase the dosage, delay puberty) is still uncertain. The value of GH in idiopathic short stature is still heavily debated, although the average final height gain on 0.33 mg/kg/week is 5-7 cm. GH is efficacious in short stature due to chronic renal failure and Prader-Willi syndrome. In other conditions insufficient data are available. There are few side-effects.

Urinary excretion of pyridinium crosslinks in short children treated with growth hormone

The aim of this study was to evaluate the effect of growth hormone (GH) treatment on bone resorption in children with GH deficiency and those with idiopathic short stature. The study population included seven children with subnormal spontaneous GH secretion and 13 children with idiopathic short stature, all of them pre-pubertal. Anthropometric measurements, free, protein-bound and total urinary pyridinoline (Pyd) and deoxypyridinoline (Dpd), serum GH, and serum immunoreactive PTH were measured at baseline and months 1, 3, 6 and 12 of GH treatment. The urinary excretion of total Pyd and Dpd, standardized by the cube of height (m3) in overnight, 24-hour urine collections was not different from age-matched healthy controls at baseline in either group of patients. During treatment with human recombinant GH, both pyridinium crosslinks increased above normal values, reaching a peak after one month in children with GH deficiency and later (after 3-6 months) in children with short stature. Free and total crosslink forms were correlated, and GH treatment did not affect the proportion of free to bound crosslinks. Serum concentrations of iPTH showed a moderate but not statistically significant increase. This study provides no evidence of reduced bone resorption in untreated GH deficiency or in idiopathic short stature. GH treatment induced a marked, but temporary, increase of bone resorption in both groups of patients.

Bone mineral density and body composition in Noonan's syndrome: effects of growth hormone treatment

We assessed bone mineral density (BMD) and body composition in children with Noonan's syndrome (NS) before and during growth hormone (GH) treatment. Sixteen children (12 boys, 4 girls) with NS aged 5.8-14.2 (mean 10.0) years were studied for 2 years. Anthropometry, BMD measurements by radiographic absorptiometry and bioimpedance measurements (Akern-BIA 101/S) were performed at baseline and after 3, 6, 12 and 24 months. Daily GH dosage was 0.05 mg/kg. Trabecular volumetric BMD was normal; cortical BMD was in the lower normal range at baseline and slightly increased over the 2 years. Fat free mass and total body water were below normal at the start and increased significantly over the first 3 months, with a slight increment thereafter. Percentage fat mass decreased over the first 6 months and increased thereafter. These findings are comparable to the data on body composition in short normal children and girls with Turner's syndrome treated with GH.

Preservation of bone mass in pediatric dialysis and transplant patients

Renal osteodystrophy continues to be a major challenge to the physician treating the child with end-stage renal disease (ESRD). The gold standard for the assessment of bone status is bone histomorphometry, which divides bone pathology into 3 main types; high-turnover, low-turnover, and mixed disease. The high-turnover disease, related to hyperparathyroidism, has been the one most extensively investigated; however, optimal therapy, especially in the growing child, is yet unclear. Overzealous treatment might result in adynamic bone disease (an extreme example of low-turnover disease), and further interference with statural growth. Pre-existent bone disease after kidney transplantation seems to worsen immediately, probably because of the high dose of corticosteroids used. In children who attain normal kidney function in the allograft, bone status seems to improve over time. Little is known about bone in transplanted patients with reduced glomerular filtration rate (GFR). The correlation between bone histology and its main surrogates, bone remodeling markers and bone mineral density, is yet unclear, but it might serve to follow the progress of an individual patient. New therapeutic modalities aimed at suppressing hyperparathyroidism, and consequently bone resorption, as well as agents directly attenuating bone resorption, should be further investigated for their effect on bone in patients with ESRD or after transplantation. Similarly, agents stimulating bone formation, particularly growth hormone, require further attention for their potential to improve bone status. Bone health and the child's somatic growth at ESRD or after kidney transplantation are closely related, and therapy should be aimed at achieving optimal results for both.

Evaluation of radial bone mineral content in prepubertal children with constitutional delay of growth

We have previously reported that children with constitutionally delayed growth (CDG) have significantly lower spinal bone mineralization than children with familial short stature (FSS). The aim of the present study was to evaluate whether the decreased bone mineralization in children with CDG also affects the radius, which has a lower bone turnover than the spine. To avoid the possibility of size-related artifacts in the assessment of bone mineral data, data were corrected for bone and body size. Radial bone mineral content (RBMC) and radial bone mineral density (RBMD) were measured by dual energy X-ray absorptiometry (Hologic QDR 1000/w) in 56 short prepubertal children aged 5-11 years. All children had height below the 10th percentile for chronological age (CA), and bone age (BA) less than 10 years, 29 of them with clinical diagnosis of CDG and 27 of them with FSS. The mean (+/- SD) RBMD was significantly lower in the children with CDG than in the FSS group (0.361 +/- 0.035 vs 0.385 +/- 0.033 g/cm2, p<0.05). RBMC was significantly lower in CDG than in FSS, when multiple regression analysis was performed by using radial scanned bone area (RSBA), body weight and height, sex and BA as independent variables (p = 0.03). These data indicate that the decreased bone mineralization in children with CDG also affects peripheral bone, and that this finding is not due to bone or body size artifacts.