Effects of long-term treatment with growth hormone on bone and mineral metabolism in children with growth hormone deficiency

Vitamin D in pituitary driven osteopathies

The evidence that pituitary hormones may bypass peripheral endocrine glands to exert remarkable effects on the skeleton is gaining ground. Both hormonal excess and deficit may determine impairment in bone structure, and they commonly result in bone loss in patients affected by pituitary and neuroendocrine disorders. Vertebral fractures are the most common skeletal alterations and may occur independently of bone mass. Use of vitamin D (VD) supplementation is still debated in this setting. This review will focus on the interactions between different metabolites of VD and pituitary hormones, and the effects of VD supplementation on bone metabolism in patients with pituitary diseases.

Bone Turnover Markers during Growth Hormone Therapy for Short Stature Children Born Small for Gestational Age

Growth hormone therapy (GHT) can improve growth velocity and final height, but can also accelerate the process of bone growth, which is related to structural bone modeling in both formation and resorption. This study evaluated the capacity of bone turnover markers to predict early growth response to one year of GHT in short stature children born small for gestational age (SGA). This study included 25 prepubertal children born SGA. We estimated P1NP (N-terminal procollagen type 1), CTX (C-terminal telopeptide of collagen type 1), P3NP (N-terminal procollagen type 3), NT-pro-CNP (amino-terminal C-type natriuretic peptide) and Ca-P metabolism using standard ECLIA (electrochemiluminescence), RIA (radioimmunoassay), and ELISA (enzyme-linked immunosorbent assay) methods. A statistically significant increase in bone resorption markers (CTX) was found at both 6 and 12 months. P1NP bone markers were increased at 6 months and after 12 months of therapy. The P3NP marker for collagen synthesis also increased after 12 months of therapy. We obtained significant increases in phosphorus levels at 6 and 12 months, and similar ALP (alkaline phosphatase) increases. We found a significant correlation between height (cm) and CTX after 6-12 months, as well as a P1NP/height (SD) correlation after 12 months. Calcium levels significantly correlated with height (SD) after 12 months. We found strong reactions of bone resorption and bone formation markers during growth hormone therapy, which may determine their selection as predictors of GHT outcome in children born SGA. However, the issue requires further research.

The Intricacies of Renal Phosphate Reabsorption-An Overview

To maintain an optimal body content of phosphorus throughout postnatal life, variable phosphate absorption from food must be finely matched with urinary excretion. This amazing feat is accomplished through synchronised phosphate transport by myriads of ciliated cells lining the renal proximal tubules. These respond in real time to changes in phosphate and composition of the renal filtrate and to hormonal instructions. How they do this has stimulated decades of research. New analytical techniques, coupled with incredible advances in computer technology, have opened new avenues for investigation at a sub-cellular level. There has been a surge of research into different aspects of the process. These have verified long-held beliefs and are also dramatically extending our vision of the intense, integrated, intracellular activity which mediates phosphate absorption. Already, some have indicated new approaches for pharmacological intervention to regulate phosphate in common conditions, including chronic renal failure and osteoporosis, as well as rare inherited biochemical disorders. It is a rapidly evolving field. The aim here is to provide an overview of our current knowledge, to show where it is leading, and where there are uncertainties. Hopefully, this will raise questions and stimulate new ideas for further research.

Growth Hormone and IGF1 Actions in Kidney Development and Function

Growth hormone (GH) exerts multiple effects on different organs including the kidneys, either directly or via its main mediator, insulin-like-growth factor-1 (IGF-1). The GH/IGF1 system plays a key role in normal kidney development, glomerular hemodynamic regulation, as well as tubular water, sodium, phosphate, and calcium handling. Transgenic animal models demonstrated that GH excess (and not IGF1) may lead to hyperfiltration, albuminuria, and glomerulosclerosis. GH and IGF-1 play a significant role in the early development of diabetic nephropathy, as well as in compensatory kidney hypertrophy after unilateral nephrectomy. Chronic kidney disease (CKD) and its complications in children are associated with alterations in the GH/IGF1 axis, including growth retardation, related to a GH-resistant state, attributed to impaired kidney postreceptor GH-signaling and chronic inflammation. This may explain the safety of prolonged rhGH-treatment of short stature in CKD.

Prenatal nutrition supplementation and growth biomarkers in preadolescent Bangladeshi children: A birth cohort study

Little is known about the usefulness of biomarkers to study the influence of prenatal nutrition supplementation in improving child growth. Anthropometry is not always straightforward to understand how nutrition might impact growth, especially in settings with high rates of malnutrition and infections. We examined the effects of prenatal supplementation on growth and growth biomarkers and the relationship between anthropometric measures and growth biomarkers of children at 4.5 and 9 years of age. Children were enrolled from a longitudinal cohort, where mothers were randomized into daily supplementation with either early‐food (≤9 gestation week [GW]) or usual‐food (~20 GW) (608 kcal 6 days/week); they were further randomized to receive 30‐mg or 60‐mg iron with 400‐μg folic acid, or multiple micronutrients (MM) in rural Bangladesh. Anthropometric data were collected from mothers at GW8 and children at 4.5 (n = 640) and 9 years (n = 536). Fasting blood was collected from children at each age. Early‐food supplementation showed reduced stunting and underweight at 4.5 and 9 years age respectively compared to usual‐food. Prenatal supplementations did not have any effect on growth biomarkers except for STAT5b expression which was lower in the early‐food compared to the usual‐food group (β = −0.21; 95 CI% = −0.36, −0.07). Plasma concentrations of 25‐hydroxy vitamin D and calcium were both inversely associated with weight‐for‐age and body mass index‐for‐age Z‐scores at 9 years, particularly in early‐food and MM groups. Although there was minimal effect on child growth by prenatal supplementations, the associations of biomarkers with anthropometric indices were predominantly driven by timing of food or MM supplementations.

Renal effects of growth hormone in health and in kidney disease

Growth hormone (GH) and its mediator insulin-like growth factor-1 (IGF-1) have manifold effects on the kidneys. GH and IGF receptors are abundantly expressed in the kidney, including the glomerular and tubular cells. GH can act either directly on the kidneys or via circulating or paracrine-synthesized IGF-1. The GH/IGF-1 system regulates glomerular hemodynamics, renal gluconeogenesis, tubular sodium and water, phosphate, and calcium handling, as well as renal synthesis of 1,25 (OH)2 vitamin D3 and the antiaging hormone Klotho. The latter also acts as a coreceptor of the phosphaturic hormone fibroblast-growth factor 23 in the proximal tubule. Recombinant human GH (rhGH) is widely used in the treatment of short stature in children, including those with chronic kidney disease (CKD). Animal studies and observations in acromegalic patients demonstrate that GH-excess can have deleterious effects on kidney health, including glomerular hyperfiltration, renal hypertrophy, and glomerulosclerosis. In addition, elevated GH in patients with poorly controlled type 1 diabetes mellitus was thought to induce podocyte injury and thereby contribute to the development of diabetic nephropathy. This manuscript gives an overview of the physiological actions of GH/IGF-1 on the kidneys and the multiple alterations of the GH/IGF-1 system and its consequences in patients with acromegaly, CKD, nephrotic syndrome, and type 1 diabetes mellitus. Finally, the impact of short- and long-term treatment with rhGH/rhIGF-1 on kidney function in patients with kidney diseases will be discussed.

Improved General and Height-Specific Quality of Life in Children With Short Stature After 1 Year on Growth Hormone

OBJECTIVE

Short stature in children and adolescents may lead to social and emotional stress, with negative effects on quality of life (QoL). GH treatment may improve QoL through height normalization. Our objective here was to evaluate general and height-specific QoL after 1 year of GH treatment.

DESIGN

Prospective, single-center, observational cohort study.

METHODS

Children ≥ 4 years of age starting GH at our center from 2012 to 2015 to treat short stature were studied. Patients with serious diseases, syndromic short stature, or developmental delay were excluded. At treatment initiation and 1 year later, patients and their parents completed the general PedsQL 4.0 and height-specific Quality of Life in Short Stature Youth (QoLiSSY) questionnaires. Correlations between self-report and parent-report scores and between height gain and QoL improvements were assessed based on Pearson correlation coefficients.

RESULTS

Seventy-four children (42 boys, 32 girls), median age (± SD), 10.2 ± 3.0 years (range, 4.1 to 16.6 years), were included. The self-report PedsQL indicated significant improvements in emotional (P = 0.02) and social (P = 0.03) QoL. As assessed by the QoLiSSY, children reported improvement of social QoL (+0.2 SD; P = 0.04), and parents reported improvement of children's physical (+0.1 SD; P < 0.0001), emotional (+0.3 SD; P < 0.0001), and social (+0.3 SD; P < 0.0001) QoL. Height SD score (SDS) gains showed moderate positive correlations with QoLISSY self-report score gains (R = 0.53, R2 = 0.28; P < 0.001) and QoLISSY parent-report gains (R = 0.60, R2 = 0.41; P < 0.00001).

CONCLUSIONS

After 1 year of GH treatment, children had significant gains in emotional and social QoL, as assessed by a general self-report questionnaire and height-specific parent-report questionnaire.

Vitamin D and growth hormone in children: a review of the current scientific knowledge

Background

Human growth is a complex mechanism that depends on genetic, environmental, nutritional and hormonal factors. The main hormone involved in growth at each stage of development is growth hormone (GH) and its mediator, insulin-like growth factor 1 (IGF-1). In contrast, vitamin D is involved in the processes of bone growth and mineralization through the regulation of calcium and phosphorus metabolism. Nevertheless, no scientific study has yet elucidated how they interact with one another, especially as a dysfunction in which one influences the other, even if numerous biochemical and clinical studies confirm the presence of a close relationship.

Main body

We reviewed and analyzed the clinical studies that have considered the relationship between vitamin D and the GH/IGF-1 axis in pediatric populations. We found two main areas of interest: the vitamin D deficiency status in patients affected by GH deficit (GHD) and the relationship between serum vitamin D metabolites and IGF-1. Although limited by some bias, from the analysis of the studies presented in the scientific literature, it is possible to hypothesize a greater frequency of hypovitaminosis D in the subjects affected by GHD, a reduced possibility of its correction with only substitution treatment with recombinant growth hormone (rGH) and an improvement of IGF-1 levels after supplementation treatment with vitamin D.

Conclusions

These results could be followed by preventive interventions aimed at reducing the vitamin D deficit in pediatric age. In addition, further research is needed to fully understand how vitamin D and growth are intertwined.

Pituitary Diseases and Bone

Neuroendocrinology of bone is a new area of research based on the evidence that pituitary hormones may directly modulate bone remodeling and metabolism. Skeletal fragility associated with high risk of fractures is a common complication of several pituitary diseases such as hypopituitarism, Cushing disease, acromegaly, and hyperprolactinemia. As in other forms of secondary osteoporosis, pituitary diseases generally affect bone quality more than bone quantity, and fractures may occur even in the presence of normal or low-normal bone mineral density as measured by dual-energy X-ray absorptiometry, making difficult the prediction of fractures in these clinical settings. Treatment of pituitary hormone excess and deficiency generally improves skeletal health, although some patients remain at high risk of fractures, and treatment with bone-active drugs may become mandatory. The aim of this review is to discuss the physiological, pathophysiological, and clinical insights of bone involvement in pituitary diseases.

The Growth Hormone Receptor: Mechanism of Receptor Activation, Cell Signaling, and Physiological Aspects

The growth hormone receptor (GHR), although most well known for regulating growth, has many other important biological functions including regulating metabolism and controlling physiological processes related to the hepatobiliary, cardiovascular, renal, gastrointestinal, and reproductive systems. In addition, growth hormone signaling is an important regulator of aging and plays a significant role in cancer development. Growth hormone activates the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway, and recent studies have provided a new understanding of the mechanism of JAK2 activation by growth hormone binding to its receptor. JAK2 activation is required for growth hormone-mediated activation of STAT1, STAT3, and STAT5, and the negative regulation of JAK-STAT signaling comprises an important step in the control of this signaling pathway. The GHR also activates the Src family kinase signaling pathway independent of JAK2. This review covers the molecular mechanisms of GHR activation and signal transduction as well as the physiological consequences of growth hormone signaling.

Vitamin D in children with growth hormone deficiency due to pituitary stalk interruption syndrome

Background

Recent studies have shown a relationship between vitamin D status and growth hormone (GH) and insulin-like growth factor 1 (IGF1). The objective of this study was to assess vitamin D status in children with GH deficiency due to pituitary stalk interruption syndrome (PSIS) and to investigate the relationship between 25-hydroxyvitamin D (25OHD) and 1,25-dihydroxyvitamin D (1,25 (OH) ₂D) serum levels and patient characteristics.

Methods

A retrospective single-center study of 25OHD and 1,25(OH)₂D serum concentrations in 50 children with PSIS at the initial evaluation before treatment.

Results

Mean concentrations of 33.2 ± 18.0 ng/mL for 25OHD and 74.5 ± 40.7 ng/L for 1,25(OH)₂D were measured. Additionally, 25OHD concentrations were significantly higher in boys than in girls (p = 0.04) and lower in the cold season than in the sunny season (p = 0.03). Significant positive correlations were observed between the GH peak and serum 1,25 (OH) ₂D concentrations (Rho = 0.35; p = 0.015) and the 1,25(OH)₂D/25OHD ratio (Rho = 0.29; p < 0.05). No correlation was found for other characteristics, including IGF1.

Conclusions

Vitamin D status in children with hypothalamic-pituitary deficiency due to PSIS was similar to that reported in national and European studies in healthy children. The positive significant correlations between the GH peak and the 1,25 (OH)₂D concentration as well as with the 1,25 (OH)₂D/25OHD ratio suggest that even in these patients who had severely impaired GH secretion and low IGF1 levels, an interplay between the GH/IGF1 axis and the vitamin D system still exists.

Vitamin D across growth hormone (GH) disorders: From GH deficiency to GH excess

The interplay between vitamin D and the growth hormone (GH)/insulin-like growth factor (IGF)-I system is very complex and to date it is not fully understood. GH directly regulates renal 1 alpha-hydroxylase activity, although the action of GH in modulating vitamin D metabolism may also be IGF-I mediated. On the other hand, vitamin D increases circulating IGF-I and the vitamin D deficiency should be normalized before measurement of IGF-I concentrations to obtain reliable and unbiased IGF-I values. Indeed, linear growth after treatment of nutritional vitamin D deficiency seems to be mediated through activation of the GH/IGF-I axis and it suggests an important role of vitamin D as a link between the proliferating cartilage cells of the growth plate and GH/IGF-I secretion. Vitamin D levels are commonly lower in patients with GH deficiency (GHD) than in controls, with a variable prevalence of insufficiency or deficiency, and this condition may worsen the already known cardiovascular and metabolic risk of GHD, although this finding is not common to all studies. In addition, data on the impact of GH treatment on vitamin D levels in GHD patients are quite conflicting. Conversely, in active acromegaly, a condition characterized by a chronic GH excess, both increased and decreased vitamin D levels have been highlighted, and the interplay between vitamin D and the GH/IGF-I axis becomes even more complicated when we consider the acromegaly treatment, both medical and surgical. The current review summarizes the available data on vitamin D in the main disorders of the GH/IGF-I axis, providing an overview of the current state of the art.

Muscle and skeletal health in children and adolescents with GH deficiency

In addition to promoting linear growth, GH plays a key role in the regulation of bone and muscle development and metabolism. Although GH deficiency is frequently listed among the causes of secondary osteoporosis in children, its impact on bone and muscle health and on fracture risk is still not completely established. Current data suggest that childhood-onset GH deficiency can affect bone and muscle mass and strength, with GH replacement therapy exerting beneficial effects. Moreover, GH withdrawal at final height can result in reduced peak bone and muscle mass, potentially leading to increased fracture risk in adulthood. Thus, the muscle-bone unit in GH deficient subjects should be monitored during childhood and adolescence in order to prevent osteoporosis and increased fracture risk and GH replacement should be tailored to ensure an optimal bone and muscle health.

Modifiable Factors Associated With Aging Phenotypes Among Adult Survivors of Childhood Acute Lymphoblastic Leukemia

PURPOSE

Survivors of childhood acute lymphoblastic leukemia (ALL) are at risk for low bone mineral density (BMD) and frail health, outcomes potentially modifiable by altering health behaviors and/or treating endocrine abnormalities. We evaluated associations between lifestyle and hormonal deficits with risk of low BMD and frailty among survivors of ALL.

PATIENTS AND METHODS

Participants included 862 survivors of ALL (median age, 31.3 years [range, 18.4 to 59.7 years]) enrolled in the St Jude Lifetime Cohort study. Bone density was measured using quantitative computed tomography of L1 through L2 vertebrae; low BMD was defined as an age- and sex-standardized z score < -1. The presence of frailty or prefrailty was defined as having at least two of the following: low muscle mass, self-reported exhaustion, low energy expenditure, slow walking speed, and weakness. Hormonal deficiencies were determined according to medical history, medications, and laboratory findings (insulin-like growth factor 1, follicle-stimulating hormone, luteinizing hormone, and testosterone levels). Logistic regression was used to examine associations between lifestyle (smoking, alcohol consumption, and activity levels) and deficiencies in growth hormone (GHD) and/or sex steroids with low BMD and frailty.

RESULTS

Thirty percent of survivors met criteria for low BMD, and 18.6% for frailty/prefrailty. After adjusting for body mass index, low BMD was associated with GHD (odds ratio [OR], 1.59; 95% CI, 1.02 to 2.13) and current smoking (OR, 1.71; 95% CI, 1.02 to 2.85) among men; and GHD (OR, 2.18; 95% CI, 1.26 to 3.78) and moderate alcohol consumption (OR, 2.09; 95% CI, 1.14 to 3.83) among women. After adjusting for current age, the odds of frailty/prefrailty were increased among men with GHD (OR, 2.97; 95% CI, 1.56 to 5.67) and those who smoked (OR, 3.26; 95% CI, 1.65 to 6.43); there were no significant associations among women.

CONCLUSION

The findings suggest that survivors of ALL should receive counseling regarding lifestyle and undergo screening for hormonal deficits to minimize the risk of low BMD and frailty.

The effect of GH treatment on serum FGF23 and Klotho in GH-deficient children

BACKGROUND

Normal phosphate homeostasis is essential for normal linear growth. The phosphaturic fibroblast growth factor 23 (FGF23)/Klotho axis is a major regulator of phosphate homeostasis; therefore, an intact FGF23/Klotho axis is important for normal linear growth. On the other hand, GH/IGF1 axis has opposing effects on phosphate homeostasis, but the underline mechanisms remain unclear.

AIM

The main objective of this study was to investigate the possible interactions of FGF23 and its co-receptor Klotho, with growth hormone (GH)/IGF1 axis in the regulation of phosphate metabolism in GH-deficient children under GH treatment.

METHODS

We studied 23 GH-deficient children, before and 3 months after the onset of GH treatment. Anthropometry and assessment of biochemical parameters were performed, as well as measurement of FGF23 (intact FGF23/iFGF23 and C-terminal FGF23/cFGF23) and soluble α-Klotho (sKlotho) levels.

RESULTS

After 3 months on GH treatment, the elevation of serum phosphate and TmPO4/GFR (P<0.0001 and P<0.01 respectively) was accompanied by a significant increase in cFGF23 (P<0.01), iFGF23 (P<0.0001), sKlotho (P<0.0001) and IGF1 (P<0.0001). Serum phosphate and TmPO4/GFR were positively associated with iFGF23 (P<0.01 and P<0.05) and IGF1 (P<0.05 and P<0.05). iFGF23 levels were positively correlated with sKlotho (P<0.001), IGF1 (P<0.0001) and height SDS (P<0.0001), whereas sKlotho was positively associated with IGF1 (P<0.0001) and height SDS (P<0.001).

CONCLUSION

The increase in serum phosphate, which we found in GH-deficient children under GH treatment, is not associated with suppression but rather than with upregulation of the phosphaturic FGF23/Klotho axis.

Proportionate Dwarfism in Mice Lacking Heterochromatin Protein 1 Binding Protein 3 (HP1BP3) Is Associated With Alterations in the Endocrine IGF-1 Pathway

Heterochromatin protein 1 binding protein 3 (HP1BP3) is a recently described histone H1-related protein with roles in chromatin structure and transcriptional regulation. To explore the potential physiological role of HP1BP3, we have previously described an Hp1bp3(-/-) mouse model with reduced postnatal viability and growth. We now find that these mice are proportionate dwarfs, with reduction in body weight, body length, and organ weight. In addition to their small size, microcomputed tomography analysis showed that Hp1bp3(-/-) mice present a dramatic impairment of their bone development and structure. By 3 weeks of age, mice of both sexes have severely impaired cortical and trabecular bone, and these defects persist into adulthood and beyond. Primary cultures of both osteoblasts and osteoclasts from Hp1bp3(-/-) bone marrow and splenocytes, respectively, showed normal differentiation and function, strongly suggesting that the impaired bone accrual is due to noncell autonomous systemic cues in vivo. One major endocrine pathway regulating both body growth and bone acquisition is the IGF regulatory system, composed of IGF-1, the IGF receptors, and the IGF-binding proteins (IGFBPs). At 3 weeks of age, Hp1bp3(-/-) mice exhibited a 60% reduction in circulating IGF-1 and a 4-fold increase in the levels of IGFBP-1 and IGFBP-2. These alterations were reflected in similar changes in the hepatic transcripts of the Igf1, Igfbp1, and Igfbp2 genes. Collectively, these results suggest that HP1BP3 plays a key role in normal growth and bone development by regulating transcription of endocrine IGF-1 components.

Seasonal variations in vitamin D in relation to growth in short prepubertal children before and during first year growth hormone treatment

PURPOSE

This study investigated the relationship between seasonal variations in 25-hydroxyvitamin D (25(OH)D) levels and growth in prepubertal children during both the pretreatment year and the first year of GH treatment.

METHODS

The study included 249 short prepubertal children with a broad range of GH secretion, GH(max) during a 24 h profile median 23; range 1-127 mU/L, 191 boys (mean age ± SD, 8.6 ± 2.6 years), 58 girls (7.5 ± 1.9 years) receiving GH treatment (mean 43 µg/kg/day; range 17-99 µg/kg/day). Serum 25(OH)D was measured using an automated IDS-iSYS immunoassay.

RESULTS

25(OH)D levels showed seasonal variation, and decreased significantly during GH treatment. 25(OH)D levels at start and first year reduction in 25(OH)D, correlated (-) with the first year growth response during treatment. The degree of GH secretion capacity within our study population of mainly non-GH deficient children and 25(OH)D sufficient (67 ± 29 nmol/L) had no influence on 25(OH)D levels. Growth during GH treatment were independent of seasonal variations in 25(OH)D. Multiple regression analysis showed that 25(OH)D levels at treatment start, together with auxological data and IGF-binding protein-(3)SDS, explained 61 % of the variation in first year gain in heightSDS.

CONCLUSION

25(OH)D levels were associated with first year growth response to GH and may be a useful contribution to future growth prediction models.

Role of growth hormone in enchondroplasia and chondral osteogenesis: evaluation by X-ray of the hand

BACKGROUND

The process of growth and maturation of long (radius and ulna) and short (metacarpals and phalanges) bones of the hand (enchondroplasia) differs from that of the carpal cuboid bones (chondral osteogenesis). This study aimed to assess the impact of growth hormone (GH) on these two processes of bone maturation.

METHODS

Subjects of the study were 95 prepubertal children: 30 children with GH deficiency and 65 children with idiopathic short stature, aged 7.4 ± 1.9 y (mean ± SD) (trial registration number 98-0198-033). Bone maturation was assessed by the Greulich and Pyle method from X-rays obtained at the start and at 1 and 2 y of GH treatment, separately for carpals, long bones, and short bones, and was expressed as years of delay relative to chronological age.

RESULTS

At GH start, the delay in bone maturation in the GH-deficient group was significantly greater for carpals (3.6 ± 1.3 y) than for long (3.0 ± 1.3 y) and short (1.7 ± 1.1 y) bones. The delay was nonsignificantly greater for carpal bones in GH-deficient subjects than in subjects with idiopathic short stature (3.6 ± 1.3 vs. 3.1 ± 1.1 y, respectively) and was normalized after 2 y of GH treatment.

CONCLUSION

The dominant effect of GH was on chondral osteogenesis, with milder effect on enchondroplasia. A distinct delay in carpal and long-bone maturation, which normalizes during 2 y of GH treatment, was typical in GH-deficient children. Therefore, separate carpal bone assessment in bone age reading is needed.

High prevalence of hypovitaminosis D in Sicilian children affected by growth hormone deficiency and its improvement after 12 months of replacement treatment

PURPOSE

Although the correlation between vitamin D and growth hormone (GH)-insulin-like growth factor 1 (IGF1) axis is documented, as of date, few and conflicting studies have prospectively analyzed vitamin D before and after GH treatment. Our aim was to evaluate as to how the condition of GH deficiency (GHD) or GH treatment influences vitamin D in children.

METHODS

Eighty Sicilian GHD children (M/F 58/22; mean age 10.3 years), grouped according to the season of evaluation in group A (June-September; 41 children) and group B (November-February; 39 children), were evaluated at baseline and after 12 months of GH treatment.

RESULTS

Twenty-eight children (35 %) were vitamin D insufficient and 32 (40 %) deficient at baseline, and lower vitamin D levels were found in group B than in A (17.3 ± 5.3 vs. 31.1 ± 11.1 ng/ml; p < 0.001). A positive correlation between vitamin D and baseline GH levels (p < 0.001) was found. After 12 months, increased vitamin D was found both in all children (34.4 ± 16.4 vs. 24.5 ± 11.1 ng/ml; p = 0.002) and in group A (38.5 ± 14 vs. 31.1 ± 11.1 ng/ml; p < 0.001) and B (30 ± 17.7 vs. 17.3 ± 5.3 ng/ml; p < 0.001). Overall, only 25 (31 %) children remained insufficient and 15 (19 %) deficient, with an increase in prevalence of children with normal levels (p = 0.001).

CONCLUSIONS

Our data demonstrated a very high prevalence of hypovitaminosis D in Sicilian GHD children, with an improvement after 12 months of GH treatment. Vitamin D assessment should therefore be considered routinely in GHD children both at diagnosis and during the follow-up.

Growth hormone, insulin-like growth factor-1, and the kidney: pathophysiological and clinical implications

Besides their growth-promoting properties, GH and IGF-1 regulate a broad spectrum of biological functions in several organs, including the kidney. This review focuses on the renal actions of GH and IGF-1, taking into account major advances in renal physiology and hormone biology made over the last 20 years, allowing us to move our understanding of GH/IGF-1 regulation of renal functions from a cellular to a molecular level. The main purpose of this review was to analyze how GH and IGF-1 regulate renal development, glomerular functions, and tubular handling of sodium, calcium, phosphate, and glucose. Whenever possible, the relative contributions, the nephronic topology, and the underlying molecular mechanisms of GH and IGF-1 actions were addressed. Beyond the physiological aspects of GH/IGF-1 action on the kidney, the review describes the impact of GH excess and deficiency on renal architecture and functions. It reports in particular new insights into the pathophysiological mechanism of body fluid retention and of changes in phospho-calcium metabolism in acromegaly as well as of the reciprocal changes in sodium, calcium, and phosphate homeostasis observed in GH deficiency. The second aim of this review was to analyze how the GH/IGF-1 axis contributes to major renal diseases such as diabetic nephropathy, renal failure, renal carcinoma, and polycystic renal disease. It summarizes the consequences of chronic renal failure and glucocorticoid therapy after renal transplantation on GH secretion and action and questions the interest of GH therapy in these conditions.

Interactions between vitamin D and IGF-I: from physiology to clinical practice

The interplay between vitamin D and IGF-I is complex and occurs at both endocrine and paracrine/autocrine levels. Vitamin D has been shown to increase circulating IGF-I and IGFBP-3, with the consistent finding of a positive correlation between vitamin D and IGF-I serum values in population-based cohorts of healthy subjects. The modulation of IGF-I and IGFBP-3 concentrations by vitamin D may impact recombinant human (rh) GH dosing for the treatment of GHD. It might also underlie some of the extra-skeletal beneficial effects ascribed to vitamin D. On the other hand, IGF-I stimulates renal production of 1,25-dihydroxyvitamin D, which increases calcium and phosphate availability in the body and suppresses PTH secretion. This effect is responsible for an altered calcium-phosphate balance in uncontrolled acromegaly and might also account for the improvement in bone metabolism associated with rhGH treatment in patients with GHD. Data on the paracrine/autocrine vitamin D-IGF-I interactions are abundant, but mostly not linked to one another. As a result, it is not possible to draw a comprehensive picture of the physiological and/or pathological interrelations between vitamin D, IGF-I and IGF-binding proteins (IGFBP) in different tissues. A potential role of vitamin D action is related to its association with carcinogenesis, a paradigm being breast cancer. Current evidence indicates that, in breast tumours, vitamin D modulates the IGF-I/IGFBP ratio to decrease proliferation and increase apoptosis.

Enhanced effect of zinc and calcium supplementation on bone status in growth hormone-deficient children treated with growth hormone: a pilot randomized controlled trial

Reduced bone mineral content in growth hormone-deficient children (GHD) has been reported. Calcium, zinc, and vitamin D play an important role in bone formation. Hence, the aim of this pilot randomized controlled study was to evaluate the effect of calcium, vitamin D, and zinc supplementation in prepubertal GHD children treated with GH on bone health parameters. After 1 year of treatment with GH (20 mg/m(2)/week), 31 GHD (mean age 8.7 ± 2.8 years, 18 boys) prepubertal children were randomised to receive calcium (500 mg/day) and vitamin D (60,000 IU/3 months) [Group A] or a similar supplement of calcium, vitamin D, and zinc (as per Indian Recommended Allowance) [Group B] along with GH therapy for the next 12 months. The two groups were similar in anthropometric and body composition parameters at baseline (p > 0.1). After 1 year of GH therapy, height-adjusted % gain was similar in both groups, 48 % in bone mineral content (BMC) and 45 % in bone area (BA). Height-adjusted % increase in BMC was significantly (p < 0.05) higher in the second year than in the first in both the groups. This % increase in BMC and BA was greater in Group B (51 and 36 % respectively) than in Group A (49 and 34 %), although marginally (p < 0.05). Supplementation of calcium and vitamin D along with GH therapy in GHD Indian children has the potential for enhancing bone mass accrual; this effect was further enhanced through the addition of zinc supplement.

The effect of growth hormone deficiency on size-corrected bone mineral measures in pre-pubertal children

Growth hormone deficiency (GHD) in children has been frequently perceived to be a cause of low bone mass accrual. The confounding effects of poor growth limit the interpretation of prior studies of bone health in GHD. We studied size-corrected bone mineral measures in 30 pre-pubertal GHD children and 75 healthy controls. Our study shows that size-corrected whole-body bone mineral content of GHD children were comparable with controls.

INTRODUCTION

The purpose of this study is to evaluate the effects of GHD on size-corrected bone measures at the lumbar spine (LS) and the whole body (WB).

METHODS

LS bone area (BA), LS bone mineral content (BMC), WB BA, WB BMC, and lean body mass (LBM) were measured in 30 pre-pubertal GHD children and 75 controls by dual-energy X-ray absorptiometry. Multiple linear regressions were used to calculate size-corrected (Sc) LS BA(Sc), LS BMC(Sc), WB BA(Sc), and WB BMC(Sc) from control subjects using height and age as independent variables. Furthermore, the relationship between muscle and bone was studied by first assessing LBM for height (LBM(Ht)) and then determining WB BMC for LBM (WB BMC(LBM)). All values were converted to Z-scores and compared with the control.

RESULTS

At diagnosis, WB BMC(Sc) Z-score of GHD children was not significantly different from controls. However, mean Z-scores of LS BA(Sc) (-0.89 ± 0.84, p < 0.0001), LS BMC(Sc) (-0.70 ± 1.1, p < 0.001), WB BA(Sc) (-0.65 ± 1.0, p < 0.006), and LBM(Ht) (-0.66 ± 1.7, p < 0.01) were significantly reduced, and WB BMC(Lbm) (0.78 ± 1.5, p < 0.003) was significantly higher in GHD children than controls.

CONCLUSION

Size-corrected WB BMC of GHD children were comparable with controls, and bones were normally adapted for muscle mass. Determinants of bone strength which may primarily be affected by GHD are muscle mass, bone size, and geometry rather than bone mass.

Risk factors for osteoporosis in long-term survivors of intracranial germ cell tumors

SUMMARY

We measured bone mineral densities in 28 intracranial germ cell tumor long-term survivors. There was the high prevalence of osteoporosis and osteopenia, 25.0% and 42.9%, respectively, and three additional risk factors, male sex, a low lean mass, and adult growth hormone replacement, were identified.

INTRODUCTION

Intracranial germ cell tumor long-term survivors (iGCTLS) have many risk factors for osteoporosis, including irradiation from cancer therapy and multiple hormone deficiencies. However, no study of bone mineral density (BMD) has been conducted in iGCTLS because these tumors are rare. The aims of this study were to evaluate the prevalence of osteoporosis and to identify risk factors associated with reduced bone mass in iGCTLS.

METHODS

We evaluated BMD and body composition of 28 iGCTLS (10.9 ± 5.2 years after cancer treatment; 13 males) using dual-energy X-ray absorptiometry. To determine risk factors, we analyzed the medical history, including the nature of the tumor, treatment modality, endocrine status, hormone replacement therapy, lifestyle, and biochemical parameters.

RESULTS

Twenty-five percent of iGCTLS were diagnosed with osteoporosis and 42.9% with osteopenia. Most males (92.3%) had low BMD. Lean mass (LM) was positively correlated with BMD in all regions of interest, and the starting age of adult growth hormone (GH) replacement was negatively correlated with the BMD Z-score at the femur neck. In logistic regression analysis, male sex and low LM were related to low BMD.

CONCLUSIONS

The iGCTLS had a high prevalence of low BMD. We found that male sex, low LM, and delayed start of adult GH replacement were risk factors for osteoporosis. Therefore, the BMD of all iGCTLS should be evaluated, and if it is low, proper management should be started early.

The insulin-like growth factor system in bone: basic and clinical implications

The insulin-like growth factor (IGF) regulatory system is critical for skeletal growth and maintenance. Initially there was great hope that the recombinant IGFs might be used clinically for disorders ranging from short stature to fracture repair and osteoporosis. Although this potential was not realized, basic and translational studies have continued, providing significant insights into the role of this family of growth factors in skeletal homeostasis and the pathophysiology of several bone disorders. This article reviews the importance of the IGF regulatory system in skeletal growth and maintenance.

Changes in plasma FGF23 in growth hormone deficient children during rhGH therapy

BACKGROUND

Children with growth hormone deficiency (GHD) have increased renal phosphorus reabsorption during rhGH therapy, Fibroblast growth factor 23 (FGF23) is a known regulator of serum phosphorus and may be responsible for this effect.

METHODS

Prospective study in GHD children investigating changes in plasma C-terminal FGF23 (C-FGF23), markers of mineral metabolism, and insulin-like growth factor (IGF-1) in the first year of rhGH therapy. Normal stature children served as baseline controls.

RESULTS

The two groups at baseline were similar, except GHD patients had lower baseline TmP/GFR vs. controls (p < 0.05). C-FGF23 in GHD patients trended upward at follow-up 1 (p = 0.058) and significantly increased at follow-up 2 (p = 0.0005) compared to baseline. TmP/GFR also rose at follow-up 1 (p = 0.002) and follow-up 2 (p = 0.027). The C-FGF23 rise persisted after adjusting for age, gender, sex, total calcium, and phosphorus (p < 0.01) but attenuated after adjusting for TmP/GFR or IGF-1.

CONCLUSIONS

C-FGF23 rises during rhGH therapy in spite of increased Tmp/GFR, an unanticipated observation given the role of FGF23 as a phosphaturic factor. The C-FGF23 rise may be a secondary response during rhGH therapy.

Growth hormone: health considerations beyond height gain

The therapeutic benefit of growth hormone (GH) therapy in improving height in short children is widely recognized; however, GH therapy is associated with other metabolic actions that may be of benefit in these children. Beneficial effects of GH on body composition have been documented in several different patient populations as well as improvements in lipid profile. Marked augmentation of bone mineral density also seems evident in many pediatric populations. Some of these benefits may require continued therapy past the acquisition of adult height. With long-term therapy of any kind, the adverse consequences of treatment should also be considered. Fortunately, long-term GH treatment seems to be safe and well-tolerated. This review describes the long-term metabolic effects of GH treatment in the pediatric population and considers how these may benefit children who are treated with GH.

Insulin-like growth factor-I and bone: lessons from mice and men

Studies of humans and animals have illustrated a strong association between insulin-like growth factor (IGF)-I and skeletal acquisition. However, the precise molecular and cellular mechanisms underlying this effect still largely remain unknown. Recent advances in molecular and genetic techniques for in vivo studies provide excellent tools for us to explore how circulating and skeletal insulin-like growth factor-I (IGF-I) may affect not only peak bone mass but also bone loss. This review highlights recent findings that shed new light on the interaction of the IGF-I signaling pathway with other skeletal networks, and the role of IGF-I in the bone marrow milieu.

Growth hormone, insulin-like growth factors, and the skeleton

GH and IGF-I are important regulators of bone homeostasis and are central to the achievement of normal longitudinal bone growth and bone mass. Although GH may act directly on skeletal cells, most of its effects are mediated by IGF-I, which is present in the systemic circulation and is synthesized by peripheral tissues. The availability of IGF-I is regulated by IGF binding proteins. IGF-I enhances the differentiated function of the osteoblast and bone formation. Adult GH deficiency causes low bone turnover osteoporosis with high risk of vertebral and nonvertebral fractures, and the low bone mass can be partially reversed by GH replacement. Acromegaly is characterized by high bone turnover, which can lead to bone loss and vertebral fractures, particularly in patients with coexistent hypogonadism. GH and IGF-I secretion are decreased in aging individuals, and abnormalities in the GH/IGF-I axis play a role in the pathogenesis of the osteoporosis of anorexia nervosa and after glucocorticoid exposure.

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.

Long-term effects of growth hormone (GH) on bone mineral status and bone turnover markers in patients with isolated GH deficiency and multiple pituitary hormone deficiency

OBJECTIVE

This study was designed to assess the long-term effects of growth hormone (GH) replacement therapy on bone mass and bone turnover markers in children with isolated GH deficiency (IGHD) and multiple pituitary hormone deficiency (MPHD).

MATERIALS AND METHODS

Fifty children (35 IGHD, 15 MPHD) receiving GH replacement therapy were enrolled in the study. The patients were followed for 38.6 +/- 15.7 months (1-5 years). Bone mineral density (BMD) of the lumbar region and bone turnover markers [PTH, osteocalcin, bone-specific alkaline phosphatase (boneALP), and the carboxyterminal propeptide of type-1 collagen (CPP-I)] were assessed annually.

RESULTS

The height standard deviation score (SDS) of patients with IGHD and MPHD at diagnosis was statistically significant (P = 0.012), and the change in height SDS during 3 years (Deltaheight SDS(3 years)) was statistically similar between these two groups (P = 0.651). The BMD z-scores of the two groups were comparable at the start of GH therapy (P = 0.083), and then increased in both groups similarly during 5 years of GH replacement therapy (F = 0.349, P = 0.567). When the BMD z-scores during 5 years of GH therapy were analysed in the IGHD and MPHD groups separately, it was found that the BMD z-score increased significantly in IGHD (P < 0.001) but the increase was not significant in MPHD (P = 0.140). Multiple regression analysis showed that the change in BMD z-score during 3 years of GH therapy (DeltaBMD z-score(3 years)) was predicted by the BMD z-score and height SDS at the start of GH therapy and by Deltaheight SDS(3 years) in the IGHD group (t = -2.582, P = 0.02; t = 2.322, P = 0.034 and t = 2.908, P = 0.01, respectively). Age and BMD z-score and height SDS at diagnosis were found to have predictive values for the DeltaBMD z-score(3 years) (t = -3.652, P = 0.022; t = -4.073, P = 0.015 and t = 3.389, P = 0.028, respectively) in the MPHD group. The changes in boneALP, osteocalcin, CPP-1 and PTH levels during the therapy were statistically similar between the IGHD and MPHD groups.

CONCLUSION

BMD increased during GH therapy in the IGHD and MPHD groups. GH had a positive effect on bone mass in the short as well as the long term. Early diagnosis and treatment could improve peak bone mass in patients with MPHD. The time and dose of sex steroids for pubertal induction and progression, which mimics physiological secretion, might also contribute to bone accretion in patients with MPHD.

Calcium Supplementation Increases Bone Mass in GH-Deficient Prepubertal Children during GH Replacement

BACKGROUND/AIMS

Since GH plays an important role in bone mineralization, and several studies demonstrated the positive influence of a higher calcium intake on bone mass, we studied the effect of calcium supplementation in GHD children during GH therapy.

METHODS

28 prepubertal GHD children, 5.0-9.9 years old, were assigned to two groups: group A (n = 14; 7 females) treated with GH, and group B (n = 14; 7 females) treated with GH + calcium gluconolactate and carbonate (1 g calcium/day per os). Auxological parameters, total bone mineral content (TBMC) and density (TBMD), leg BMC and BMD, lumbar BMD, fat mass (FM) and lean tissue mass (LTM), blood 25-hydroxyvitamin D (25-OHD), parathyroid hormone (PTH), osteocalcin (OC) and urinary N-terminal telopeptide of type I collagen (NTx) were determined at the start of therapy and after 1 and 2 years of treatment.

RESULTS

During the 2 years of the study, TBMC, TBMD, leg BMC and BMD (but not lumbar BMD) increased in both groups of patients, however after 2 years of treatment they were significantly higher in the calcium-supplemented group B than in group A (p < 0.05, for all parameters). At the start of therapy, in both groups of patients percentage FM was higher and total and leg LTM lower than in controls (p < 0.05 for each parameter). Thereafter, FM decreased and LTM increased and after 2 years they were both different from baseline (p < 0.05). After 2 years of treatment, leg BMC and BMD were more positively correlated with regional leg LTM in patients of group B (r = 0.834 and r = 0.827, respectively; p < 0.001) than in patients of group A (r = 0.617 and r = 0.637, respectively; p < 0.05). 25-OHD and PTH levels were in the normal range in all patients at the start and during treatment. OC levels were lower and urinary NTx levels higher in patients than in controls (p < 0.05 for both parameters), either at the start and after 1 year of treatment. After 2 years of treatment, OC levels were significantly higher than at the start of the study (p < 0.05) in both groups of patients, but they were higher in group B than in group A (p < 0.05); on the contrary, urinary Ntx levels were lower in group B than in group A (p < 0.05).

CONCLUSION

In GHD children, treated with GH, calcium supplementation improved bone mass; it may aid in reaching better peak bone mass and in protecting weight-bearing bones, usually completed in childhood to maximum levels, from risk of osteoporosis and fractures later in life.

Pediatric reference intervals for bone markers

Bone markers are specific bone-derived molecules that reflect bone remodeling activity and can be classified into two categories: bone formation and bone resorption markers. Children have significantly elevated bone marker levels due to high skeletal growth velocity and rapid bone turnover during childhood growth. Many physiological and pathological processes may influence bone metabolism and bone marker concentrations during childhood growth. Measurements of bone markers may be useful in investigating skeletal diseases in children and monitoring the response to treatment. This review documents recent advances in analytical methods, preanalytical considerations related to each marker and particularly highlights the most valuable bone formation markers, bone alkaline phosphatase and osteocalcin, and bone resorption markers, pyridinium cross-links and cross-linked telopeptides. Age- and sex-specific pediatric reference intervals and their limitations in clinical application are also discussed.

Effect of growth hormone therapy and puberty on bone and body composition in children with idiopathic short stature and growth hormone deficiency

The state of bone health and the effect of growth hormone (GH) therapy on bone and body composition in children with idiopathic short stature (ISS) are largely unknown. A direct role of GH deficiency (GHD) on bone density is controversial. Using dual-energy X-ray absorptiometry, this study measured total body bone mineral content (TB BMC), body composition, and volumetric bone mineral density (vBMD) at the lumbar spine (LS) and femoral neck (FN) in 77 children (aged 3-17 years) with ISS (n = 57) and GHD (n = 20). Fifty-five children (GHD = 13) receiving GH were followed over 24 months including measurement of bone turnover. At diagnosis, size-corrected TB BMC SDS was greater (P <or= 0.002) and LSvBMD SDS lower (P < 0.03) than zero in both prepubertal ISS and GHD subjects, but FNvBMD SDS was reduced only in the GHD group (P < 0.05). The muscle-bone relation, as assessed by the BMC/lean mass (LTM) ratio SDS was not different between groups. During GH therapy, prepubertal GHD children gained more height (1.58 [0.9] SDS) and LTM (0.87 [0.63] SDS) compared to prepubertal ISS children (0.75 [0.27] and 0.17 [0.25] SDS, respectively). Percent body fat decreased in GHD (-5.94% [4.29]) but not in ISS children. Total body BMC accrual was less than predicted in all groups accompanied by an increase in bone turnover. Puberty led to the greatest absolute, but not relative, increments in weight, LTM, BMI, bone mass, and LSvBMD. Our results show that children with ISS and GHD differ in their response to GH therapy in anthropometry, body composition, and bone measures. Despite low vBMD values at diagnosis in both prepubertal groups, size-corrected regional or TB bone data were generally within the normal range and did not increase during GH therapy in GHD or ISS children. Growth hormone had great effects on the growth plate and body composition with subsequent gains in height, LTM, bone turnover, and bone mass accrual, but no benefit for volumetric bone density over 2 years.

Estudio de la masa ósea en el déficit de hormona de crecimiento

OBJECTIVES

To evaluate bone mineral density by radiogrametric study of metacarpal bone diameter and cortical thickness in patients with growth hormone deficiency (GHD) before and during treatment with growth hormone (GH).

PATIENTS AND METHODS

We studied 92 children with GHD (60 boys and 32 girls) divided into two groups: group I: 66 previously untreated patients (42 boys and 24 girls) aged between 3 and 14 years old; group II: 66 patients (42 girls and 24 boys) treated with GH and with a mean age of 10.2 +/- 3.1 years at treatment onset. Bone mass was studied indirectly by radiogrametry; the bone diameter and cortical thickness of the 2nd-3rd and 4th metacarpal bones were measured with a magnifying glass. As reference standards we used the Spanish longitudinal growth and development study (Andrea Prader Center, Zaragoza) in children aged between 0.5 and 9 years and the Swiss longitudinal standards in children aged 10 years of age and older. Statistical significance was set at p < 0.05.

RESULTS

Group I (spontaneous evolution): cortical thickness values were below the mean with statistically significant differences al 11, 12 and 13 years of age in girls and at 12, 13 and 14 years in boys. Bone diameter was diminished compared with controls in all the study periods and was significantly reduced at 8, 9, 10 and 11 years of age in girls and at 8, 10, 11, 12, 13 and 14 years in boys. Group II: (effect of GH treatment): cortical regression analysis showed a sharp increase in the first year of treatment with a subsequent moderate increase, which was statistically significant. Bone diameter showed a similar pattern with a significant increase which was more pronounced in the first period.

CONCLUSIONS

Children with GHD have decreased bone mass before initiation of treatment and therefore show deficient acquisition of peak bone mass, which in normal conditions occurs during in the first 4-5 years of life and during adolescence. GH replacement therapy leads to recovery of bone mass, which is more pronounced in the first year of treatment and prevents the progressive reduction that appears in untreated patients. Therefore, GH treatment plays an important role in peak bone mass acquisition in children with GHD.

Hypovitaminosis D in acutely injured pediatric burn patients

PROBLEM

The prevalence of vitamin D insufficiency, its etiology, and associated sequelae among acutely injured burn patients is unknown.

OBJECTIVE

This study assessed vitamin D and endocrine status, as well as the effect of anabolic agents, in pediatric patients who had sustained burns in excess of 25% total body surface area (TBSA).

SUBJECTS

Sixty-nine patients with a mean TBSA burn of 50.6+/-2.2% (range 27% to 94%) and full thickness injury of 41.3+/-3.0% (range 0% to 94%) were studied. Subjects ranged in age from 0.6 to 18 years (mean, 5.8+/-0.6 years). Main outcome measures Blood samples were obtained for serum 25-hydroxyvitamin D (D25), 1,25-dihydroxyvitamin D (D1,25), albumin, cortisol, triiodothyronine (T3), tetraiodothyronine (T(4)), thyroid stimulating hormone (TSH), and parathormone (PTH).

RESULTS

Two hundred eighty morning blood samples of D25 and D1,25 demonstrated that 45% and 26.2% were low and 8.9% and 11% were very low, respectively. At least one low D25 or D1,25 level occurred in 62.3% of all subjects. Very low levels were noted in 23.2% of all patients. There was an increased incidence of hyperparathyroidism in patients with very low serum D25. Vitamin D25 and D1,25 levels were lower in subjects with larger burns or inhalation injury, as well as those treated with thyroxine or oxandrolone. Serum albumin, cortisol, T(4), and TSH were not correlated with concentration of vitamin D.

CONCLUSIONS

Demonstration of a high incidence of low serum vitamin D indicates vitamin D status may be significantly compromised in burned children. It is unclear why vitamin D deficiency exists in this population. The most effective way to improve vitamin D status remains elusive at this time.

Indications and strategies for continuing GH treatment during transition from late adolescence to early adulthood in patients with GH deficiency: the impact on bone mass

GH plays an important role in longitudinal bone growth and maturation during childhood and adolescence. However, GH has important metabolic functions other than bone growth, which become more apparent during young adulthood, when growth has been completed. Indeed, GH deficiency (GHD) in adult life is a recognized clinical syndrome which includes symptoms such as increased central adiposity, decreased lean body mass, reduced bone mineral density (BMD), increased atherogenic risk, cerebrovascular and cardiac morbidity and mortality, and reduced quality of life. As approximately one quarter of the children with GHD should continue GH administration in adulthood, it is important to reconfirm GHD at the end of growth in order to select patients with severe GHD who need to resume GH therapy with an appropriate age-related dosage. Some evidence indicates that most peak bone mass (PBM) is achieved by the end of adolescence but small increases in BMD continue during the period of transition from late adolescence to young adulthood. Some young adults with GHD show a persistent increase of lumbar BMD after the completion of growth even after discontinuation of treatment suggesting a spontaneous progression towards lumbar PBM or a continuing effect of the treatment. The data indicates that adolescents with GHD who do not reach lumbar PBM at the time of discontinuation of GH treatment can achieve a BMD lower than their genetic potential if they are not treated during the transition to young adulthood.

Parathyroid responsiveness to hypocalcemic and hypercalcemic stimuli in adult growth hormone deficiency after growth hormone replacement

Adult growth hormone deficiency (AGHD) is associated with osteoporosis. Previous reports have suggested that alterations in parathyroid gland responsiveness to changes in calcium concentration may play a role in the genesis of osteoporosis in untreated AGHD patients. We investigated the endogenous parathyroid hormone [PTH-(1-84)] response to hypocalcemic and hypercalcemic stimuli induced by sodium EDTA and calcium gluconate infusion, respectively, and to PTH-(1-34) infusion in AGHD patients before and during GH replacement (GHR). We have demonstrated that the maximum PTH-(1-84) stimulation and suppression occurred at significantly higher calcium concentrations and in response to smaller changes in calcium concentrations after GHR. The calcemic response to the effects of PTH-(1-34) infusion significantly increased after GHR. The calcium set point (the calcium concentration at which the rate of PTH secretion is one-half of its maximal value) significantly increased in all groups after 3 mo on GHR, and it increased further at 12 mo. Our results suggest increased parathyroid gland sensitivity to smaller changes in serum calcium and increased end-organ sensitivity to the effects of PTH in AGHD patients after GHR. These findings may help us to understand the mechanisms underlying the genesis of osteoporosis in AGHD patients.

Gender variation in PTH sensitivity and rhythmicity following growth hormone replacement in adult growth hormone-deficient patients

BACKGROUND

Adult GH deficiency (AGHD) is associated with osteoporosis and reduced bone turnover; factors improved by GH replacement (GHR), with men gaining greater benefit than women. Reduction in sensitivity of bone and kidney to the effects of PTH may underlie AGHD changes in bone turnover. We determined the gender difference in PTH target-organ sensitivity following GHR in AGHD patients.

DESIGN, PATIENTS AND MEASUREMENTS

Twenty AGHD patients (10 men) were admitted to hospital before and after GHR initiation. Half-hourly blood samples were collected for PTH, calcium, nephrogenous cyclic AMP (NcAMP, marker of PTH activity), type-I collagen C-telopeptide (CTX, bone resorption marker) and procollagen type-I amino-terminal propeptide (PINP, bone formation marker).

RESULTS

The 24-h mean PTH concentration decreased in both genders (P < 0.001), with maximal changes seen 6 and 12 months following GHR in men and women, respectively. Increases in 24-h mean NcAMP (P < 0.05), calcium (P < 0.001) and bone turnover markers (P < 0.001) occurred in both genders following GHR, with maximal changes at 1 month in men, but at 3 months for NcAMP, calcium and CTX and 12 months for PINP in women. Maximal NcAMP increase was higher in men (P = 0.009).

CONCLUSIONS

Following GHR, PTH target-organ sensitivity increased in both genders, demonstrated by simultaneous reduction in PTH concentration and increase in NcAMP, calcium and bone turnover. In women, improvement in renal PTH sensitivity was delayed and reduced, and changes in bone turnover were delayed, with increase in bone resorption preceding bone formation. Both factors may contribute to the reduced bone mineral density (BMD) response to GHR observed in women.

Four-Year Review of Burns as an Etiologic Factor in the Development of Long Bone Fractures in Pediatric Patients

Reduced bone density has been documented in children after burns. This loss of bone may place children at heightened risk for fractures. The medical records of all acutely injured patients with burns in excess of 40% TBSA burn admitted to our institution between January 1, 1997, through December 31, 2000, were reviewed for fracture incidence. Patients with fractures sustained during the course of initial trauma were not included in the review. One hundred four records were reviewed. These patients had a mean age of 6.7 +/- 0.51 years, (range, 0.2 to 18.0) and a mean %TBSA burn of 59.9 +/- 1.60 (range, 40 to 98) with a mean full-thickness %burn of 51.7 +/- 2.16 (range, 0 to 95). Fifteen long bone fractures were documented in six patients during the review time frame. All fractures were initially suspected by physical therapy personnel upon regularly scheduled therapy sessions and subsequently verified by x-ray. All fractures identified by this review occurred in children less than 3 years of age. Most fractures were noted during the rehabilitation phase of injury (range, 73 to 283 days after burn) once wounds were more than 95% healed, except for one child, who sustained multiple fractures during the acute recovery phase at a referring hospital. A 5.8% incidence of fractures was noted in patients with burns in excess of 40% (6 of 104 admissions). The etiology of the fractures is unknown, although the hormonal milieu postburn, depressed vitamin D status, inadequate protein intake, and decreased weight-bearing activity are potential contributory factors. In addition, infants and toddlers tend to provide more resistance to therapy because of an inherent lack of cognition. This may account for the increased breaks in this population.

Effects of growth hormone replacement on parathyroid hormone sensitivity and bone mineral metabolism

Adult GH deficiency (AGHD) is associated with reduced bone mineral density, and decreased end-organ sensitivity to the effects of PTH has been suggested as a possible underlying mechanism. We investigated the effects of GH replacement (GHR) on PTH circulating activity and its association with phosphocalcium metabolism and bone turnover in 16 (8 men and 8 women) AGHD patients. Half-hourly blood and 3 hourly urine sampling was performed on each patient over a 24-h period before GHR and then after 1, 3, 6, and 12 months of GHR. GH was commenced at a dose of 0.5 IU/d and was titrated to achieve and maintain an IGF-I SD score within 2 SD of the age-related reference range. The target IGF-I SD score was achieved within 3 months and was maintained at 12 months after GHR in all patients. Our results demonstrated a significant decrease in serum PTH at all visits after GHR compared with baseline values (P < 0.001), with a concomitant increase in nephrogenous cAMP excretion at 1 (P < 0.001) and 3 (P < 0.05) months and increases in serum calcium (P < 0.001), serum phosphate (P < 0.001), 1,25-dihydroxyvitamin D(3) (P < 0.001), type I collagen C-telopeptide (a bone resorption marker; P < 0.001), and procollagen type I amino-terminal propeptide (a bone formation marker; P < 0.001). Simultaneously, we observed a significant decrease in urinary calcium excretion (P < 0.001) and an increase in maximum tubular phosphate reabsorption (P < 0.001). Together these results suggest increased end-organ responsiveness to the effects of circulating PTH resulting in increased bone turnover and reduced calcium excretion. Significant circadian rhythms were observed for serum PTH, phosphate, type I collagen C-telopeptide, and procollagen type I amino-terminal propeptide before and after GHR. However, sustained PTH secretion was observed between 1400-2200 h, with a reduced nocturnal rise in untreated AGHD patients, whereas PTH secretion decreased significantly between 1400-2200 h (P < 0.001), with a significant increase in nocturnal PTH secretion (P < 0.001) after 12 months of GHR. Our results demonstrate that GH may have a regulatory role in bone mineral metabolism, and our data provide a possible underlying mechanism for the development of osteoporosis in AGHD patients. The changes observed after GHR may further explain the beneficial effects of GHR on bone mineral density that have consistently been reported.

Positive linear growth and bone responses to growth hormone treatment in children with types III and IV osteogenesis imperfecta: high predictive value of the carboxyterminal propeptide of type I procollagen

Extreme short stature is a cardinal feature of severe osteogenesis imperfecta (OI), types III and IV. We conducted a treatment trial of growth hormone in children with OI and followed linear growth velocity, bone metabolism markers, histomorphometrics, and vertebral bone density. Twenty-six children with types III and IV OI, ages 4.5-12 years, were treated with recombinant growth hormone (rGH), 0.1-0.2 IU/kg per day for 6 days/week, for at least 1 year. Length, insulin-like growth factor (IGF-I), insulin-like growth factor binding protein (IGFBP-3), bone metabolic markers, and vertebral bone density by DXA were evaluated at 6-month intervals. An iliac crest biopsy was obtained at baseline and 12 months. Approximately one-half of the treated OI children sustained a 50% or more increase in linear growth over their baseline growth rate. Most responders (10 of 14) had moderate type IV OI. All participants had positive IGF-I, IGFBP-3, osteocalcin, and bone-specific alkaline phosphatase responses. Only the linear growth responders had a significant increase in vertebral DXA z-score and a significant decrease in long bone fractures. After 1 year of treatment, responders' iliac crest biopsy showed significant increases in cancellous bone volume, trabecular number, and bone formation rate. Responders were distinguished from nonresponders by higher baseline carboxyterminal propeptide (PICP) values (p < 0.05), suggesting they have an intrinsically higher capacity for collagen production. The results show that growth hormone can cause a sustained increase in the linear growth rate of children with OI, despite the abnormal collagen in their bone matrix. In the first year of treatment, growth responders achieve increased bone formation rate and density, and decreased fracture rates. The baseline plasma concentration of PICP was an excellent predictor of positive response.