The efficacy of growth hormone in different types of growth failure. An analysis of 101 cases

Human Growth and Growth Hormone: From Antiquity to the Recominant Age to the Future

Since antiquity Man has been fascinated by the variations in human (and animal) growth. Stories and art abound about giants and little people. Modern genetics have solved some of etiologies at both extremes of growth. Serious study began with the pathophysiology of acromegaly followed by early attempts at treatment culminating in modern endoscopic surgery and multiple pharmacologic agents. Virtually at the same time experiments with the removal of the pituitary from laboratory animals noted the slowing or stopping of linear growth and then over a few decades the extraction and purification of a protein within the anterior pituitary that restored, partially or in full, the animal's growth. Human growth hormone was purified decades after those from large animals and it was noted that it was species specific, that is, only primate growth hormone was metabolically active in primates. That was quite unlike the beef and pork insulins which revolutionized the care of children with diabetes mellitus. A number of studies included mild enzymatic digestion of beef growth hormone to determine if those "cores" had biologic activity in primates and man. Tantalizing data showed minimal but variable metabolic efficacy leading to the "active core" hypothesis, for these smaller peptides would be amenable to peptide synthesis in the time before recombinant DNA. Recombinant DNA changed the landscape remarkably promising nearly unlimited quantities of metabolically active hormone. Eight indications for therapeutic use have been approved by the Food and Drug Administration and a large number of clinical trials have been undertaken in multiple other conditions for which short stature in childhood is a sign. The future predicts other clinical indications for growth hormone therapy (and perhaps other components of the GH?IGF-1 axis), longer-acting analogues and perhaps a more physiologic method of administration as virtually all methods at present are far from physiologic.

An analysis of the clinical and cost effectiveness of growth hormone replacement therapy before and during puberty: should we increase the dose?

AIM

To investigate the influence of growth hormone (GH) on linear growth before and during puberty in children with GH deficiency.

METHODS

We analysed the relationship between pubertal growth and GH dose in a large dataset of children (n = 236) with GH deficiency using multiple linear regression and multilevel modelling with repeated measures analysis. Additionally, we examined the cost benefit of increasing doses of GH during puberty.

RESULTS

Multilevel modelling revealed a highly significant role for GH dose in the pre-pubertal period (p < 0.001), but a non-significant effect on height gain after pubertal onset (p = 0.32). Important predictors of height gain after puberty onset included gender, age at puberty and number of injections of GH/week. Cost analysis showed that in an average child use of high dose GH, at an extra EUR 5,925 (GBP 4,753/USD 7,538)/year, would produce a height gain of 0.80 cm/year (above baseline growth) pre-pubertally, compared to only 0.20 cm/year post-puberty onset.

CONCLUSIONS

The influence of GH dose on height gain after puberty onset is at best a modest one. Cost analysis shows use of high doses of GH post-puberty onset has significant cost implications without providing a worthwhile gain in adult height for children with GH deficiency.

Growth hormone treatment for short stature in children born small for gestational age

Children born small for gestational age (SGA) who do not show catch-up in the first 2 years generally remain short for life. Although the majority of children born SGA are not growth hormone (GH) deficient, GH treatment is known to improve average growth in these children.Early studies using GH in children born SGA demonstrated increased height velocity, but these effects tended to be short-term with effects decreasing when GH treatment stopped. With refined GH regimens, significant effects on height have been shown, with gains of approximately 1 standard deviation score after 2 years. Studies have also shown that long-term continuous GH therapy can significantly increase final height to within the normal range. GH treatment of children born SGA does not appear to unduly affect bone age or pubertal development. Growth prediction models have been used to identify various factors involved in the response to GH therapy with age at start, treatment duration, and GH dose showing strong effects. Genetic factors such as the exon 3 deletion of the GH receptor may contribute to short stature of children born SGA and may also be involved in the responsiveness to GH treatment, but there remain other unknown genetic and/or environmental factors. No unexpected safety concerns have arisen in GH therapy trials. In particular, no long-term adverse effects have been seen for glucose metabolism, and positive effects have been shown for lipid profiles and blood pressure.GH treatment in short children born SGA has shown a beneficial, growth-promoting effect in both the short-and long-term, and has become a recognized indication in both the US and Europe. Further studies on individualized treatment regimens and long-term safety are ongoing.

Growth hormone treatment in children: review of safety and efficacy

Since the advent of growth hormone (GH), the pediatric applications of GH therapy have expanded. Children with a wide variety of growth disorders have received GH treatment. The therapeutic effects and safety profile of GH in a number of pediatric conditions are reviewed, including GH deficiency (GHD), Turner syndrome, chronic renal failure, children born small for gestational age, Prader-Willi syndrome, juvenile chronic arthritis, and cystic fibrosis. GH therapy has been clearly shown to improve height velocity during childhood in a variety of pediatric conditions in which growth is compromised. There is now data that confirms GH treatment also improves final height in a number of diagnostic subgroups. Early initiation and individualization of GH treatment has the potential to normalize childhood growth in children with idiopathic GHD and enable them to achieve their genetic target height in a cost-effective manner. In children in whom GHD is not the main factor compromising growth, supra-physiological doses of GH have been shown to increase height velocity during childhood and final height. The development of predictive models for these conditions may allow further improvements in height outcome while maintaining an acceptable safety profile. Survivors of childhood malignancy, particularly those who have had craniospinal irradiation, represent a particularly challenging group. They appear to be less responsive to GH than children with idiopathic GHD and have a tendency to enter puberty at an earlier age. Both of these factors have a negative impact on their final height. Strategies that combine GH treatment with suppression of puberty using a gonadotropin releasing hormone analog may result in improved height outcomes. When children with GHD are treated with standard doses of GH there is a strong safety record. Adverse events during GH therapy are uncommon and often not drug related. Continued surveillance into adult life is crucial however, particularly in children receiving supra-physiological doses of GH or whose underlying condition increases their risk of adverse effects.

Growth and adult height in GH-treated children with nonacquired GH deficiency and idiopathic short stature: the influence of pituitary magnetic resonance imaging findings

We analyzed the final height of 146 short children with either nonacquired GH deficiency or idiopathic short stature. Our purpose was 1) to assess growth according to the pituitary magnetic resonance imaging findings in the 63 GH-treated children with GH deficiency and 2) to compare the growth of the GH-deficient patients with normal magnetic resonance imaging (n = 48) to that of 32 treated and 51 untreated children with idiopathic short stature (GH peak to provocative tests >10 microg/liter). The mean GH dose was 0.44 IU/kg.wk (0.15 mg/kg.wk), given for a mean duration of 4.6 yr. Among the GH-deficient children, 15 had hypothalamic-pituitary abnormalities (stalk agenesis), all with total GH deficiency (GH peak <5 microg/liter). They were significantly shorter and younger at the time of diagnosis than those with normal magnetic resonance imaging, had better catch-up growth (+2.7 +/- 0.9 vs. +1.3 +/- 0.8 SD score; P < 0.01), and reached greater final height (-1.1 +/- 1.0 vs. -1.7 +/- 1.0 SD score; P < 0.05). Among patients with normal magnetic resonance imaging, there was no difference in catch-up growth and final height between partial and total GH deficiencies. GH-deficient subjects with normal magnetic resonance imaging and treated and untreated patients with idiopathic short stature had comparable auxological characteristics, age at evaluation, and target height. Although they had different catch-up growth (+1.3 +/- 0.8, +0.9 +/- 0.6, and +0.7 +/- 0.9 SD score, respectively; P < 0.01, by ANOVA), these patients reached a similar final height (-1.7 +/- 1.0, -2.1 +/- 0.8, and -2.1 +/- 1.0 SD score, respectively; P = 0.13). Pituitary magnetic resonance imaging findings show the heterogeneity within the group of nonacquired GH deficiency and help to predict the response to GH treatment in these patients. The similarities in growth between the GH-deficient children with normal magnetic resonance imaging and those with idiopathic short stature suggest that the short stature in the former subjects is at least partly due to factors other than GH deficiency.

Prediction of height velocity of prepubertal children with growth hormone deficiency in the first year of treatment with recombinant human growth hormone

AIM

Several methods have been developed to predict the outcome of growth hormone (GH) therapy in children with growth hormone deficiency (GHD).

METHODS

Over 50 factors for each of 92 prepubertal patients with GHD (26 patients with total and 45 patients with partial GHD, 21 patients with neurosecretory dysfunction) were collected and included in multiple regression analyses and other nonlinear models to predict height velocity (HV) (cm/yr) in the first year of treatment. Afterwards the model was validated by two other cohorts of patients from other universities, which followed the same treatment regime as our clinic.

RESULTS

Twelve parameters had a significant correlation to HV (p<0.05) and a coefficient of determination >20%. Two parameters (In BA, In GHmax) showed a coefficient of determination >60% for children with GHD in multiple regression analysis. The validation of the mathematical model against another data set showed different results. GH was measured by the same method, but BA was scored at the first clinic as in our clinic by only one doctor and in the other university by several radiologists. The accuracy of prediction in the first clinic was significantly higher than in the other university.

CONCLUSION

This model demonstrates that exact scoring of BA and precise measurement of GHmax in the stimulation test is necessary, and if carried out carefully leads to useful prediction values for determining height velocity.

Testosterone stimulates insulin-like growth factor-I and insulin-like growth factor-I-receptor gene expression in the mandibular condyle--a model of endochondral ossification

Puberty is associated with an increase in the plasma concentration of sex steroids, GH, and insulin-like growth factor-I (IGF-I). Gonadal steroid hormones are important for the normal pubertal growth spurt and skeletal growth. The mechanism by which gonadal steroids induce skeletal growth is still not fully understood. To better understand the direct effect sex steroids have on bone growth, we studied an isolated organ culture system of the mandibular condyle, derived from 3.5-5.5-week-old male and female mice. We found that testosterone 10(-6) M, but not estradiol, stimulated thymidine incorporation into the DNA of male-derived condyle. Three days of testosterone treatment doubled the condyle size and increased the chondroprogenitor zone, while maintaining the normal gradient of the developing chondrocytes. Immunohistochemistry and in situ hybridization techniques showed that testosterone stimulated IGF-I and IGF-I-R and their messenger RNAs (mRNAs) mainly in the mature chondrocyte layer. Immunoneutralization of IGF-I in the testosterone-treated condyle caused the disappearance of the chondroblast and young chondrocyte layers, though the progenitor cell layer remained almost unaffected. Overtreatment with testosterone (dose or duration) accelerated condylar ossification. In the presence of testosterone 10(-5) M (high dose), calcification "climbs" up to the chondroprogenitor zone, and most of the condylar chondrocytes are replaced by bone tissue. Similar changes occurred after 7 days of testosterone treatment (long duration) with 10(-6) M. In conclusion, testosterone stimulates growth and local production of IGF-I and IGF-I-R in chondrocyte cell layers of an isolated organ culture of mice mandibular condyle. Part of the effect testosterone has on condylar growth is mediated by IGF-I.

Childhood onset of GH deficiency: reassessment of GH status and effects of substitution

The final height of 77 patients with growth hormone (GH) insufficiency of childhood onset was analysed. Patients were treated between 1968 and 1996 for 1-15 years. The mean final height in patients with severe GH deficiency was 163.9 cm (males) or 151.1 cm (female patients). In patients with partial GH insufficiency, the mean final heights were 166.2 and 157.7 cm, respectively, and in patients with GH deficiency caused by intracerebral tumours, 175.9 or 160.2 cm, respectively. Late established diagnosis, lack of (pituitary) GH during the time prior to 1980 or low frequency of injections per week were related to the fact that final height was often below the target height range. In four of 51 retested patients with childhood onset GH deficiency, a normal response of the pituitary gland to pharmacological testing was found, whereas all other patients still suffered from GH insufficiency. An increased amount of fat and a decreased amount of lean body mass as well as low bone mineral density (12 out of 15 patients) could be demonstrated at re-evaluation.

Spontaneous growth and response to growth hormone treatment in children with growth hormone deficiency and idiopathic short stature

Isolated idiopathic growth hormone deficiency (GHD) and idiopathic short stature (ISS) can be difficult to distinguish, but the therapeutical consequences are different. In this report the data on final height of untreated and treated children with GHD and ISS are reviewed. Untreated GH-deficient individuals who underwent spontaneous puberty (22 male, 14 female patients) reached a mean final height of 4.7 SD (range 3.9 to 6.0) below the population's mean. If puberty was induced (19 male patients), mean final height SD score (SDS) was -3.1. Traditional regimens of GH administration (2-4 injections/wk) in 236 children (184 boys, 52 girls) with GHD and spontaneous puberty resulted in a final height SDS of -2.8 (range -1.5 to -4.7). In 190 children in whom puberty was induced (139 boys, 51 girls) mean final height was -1.6 (range - -1.1 to -2.4). The mean gain in final height SDS is therefore estimated at 1.5-2.0 in average cases, and 3.5 in extreme cases. Preliminary data suggest that on present regimens mean final height may approach target height. In untreated boys with ISS the mean final height was 2-5 cm lower than that predicted before puberty, whereas in girls it was almost equal to the prediction. After GH treatment the mean final height was 0.4-3.0 cm higher than the predicted adult height, which results in an average net gain in final height SDS of approximately 0.5-0.8 (3-5 cm).

Mulibrey nanism: three additional patients and a review of 39 patients

We report on 3 patients with Mulibrey nanism (MN), or Perheentupa syndrome: the first 2 sibs from Argentina and a new patient from Spain. All 3 patients had growth failure, short stature, abnormal pigmentary retinal changes, and a J-shaped sella turcica. These findings are considered major criteria of MN. Two had pericardial constriction, which is a frequent and life-threatening abnormality in this syndrome. MN is a rare autosomal recessive condition. Reviewing the 39 patients described so far, we have classified the anomalies into the very frequent (present in more than 66%), frequent (in at least 25%), and not frequent. Identifying the anomalies specific to MN should help its early diagnosis and treatment.

Growth hormone treatment of idiopathic short stature: analysis of the database from KIGS, the Kabi Pharmacia International Growth Study

Within the Kabi Pharmacia International Growth Study (KIGS) database, there is information on 1017 (700 male/317 female) patients with idiopathic short stature (ISS). These patients were started on recombinant human growth hormone (GH) at a median age of 10.8 years, a bone age of -1.8 SDS, a height of -2.6 SDS and a predicted adult height (PAH) (Bailey-Pinneau method) of -2.5 SDS. The median dose of GH was 0.6 IU/kg body weight/week and the frequency of injections was six/week. According to the relationship with target height the patients were classified into 'familial short stature (FSS)' (height SDS > target height SDS -1.28) and into 'non-FSS' (height SDS < target height SDS -1.28). During the first year of GH treatment there was an overall increment in the median height velocity from 4.4 to 7.4 cm/year. Over 3 years of GH treatment, cross-sectional analysis demonstrated an overall increment in median PAH of 1.2 SDS. There was a positive correlation between gain in PAH and the GH dose (n = 202, r = 0.18, p < 0.01) during the first year. Longitudinal analysis in 84 patients showed an overall increment of PAH of 0.7 SDS over 2 years of treatment. When applying the KIGS first-year prediction model for patients with idiopathic GH deficiency on cohorts of prepubertal children with FSS and non-FSS, a lower responsiveness to GH in the non-FSS group was observed. It is concluded that higher than substitutive doses of GH are required for the long-term improvement of growth in ISS.

Prediction of the growth response in children with various growth disorders treated with growth hormone: analyses of data from the Kabi Pharmacia International Growth Study. International Board of the Kabi Pharmacia International Growth Study

Analyses to predict the growth response to recombinant human growth hormone (GH) in prepubertal children during the first year of treatment were performed on data from 472 patients with idiopathic GH deficiency (IGHD), 202 children with Turner's syndrome, 327 children with idiopathic short stature (ISS) and 135 children with intrauterine growth retardation (IUGR). In IGHD, 56% of the variability of the response could be predicted from a model based on six variables. These variables could be ranked in order of importance as follows: target height SDS minus height SDS, chronological age, frequency of GH injections, dose of GH, weight-for-height index, and birth weight SDS. When the model for IGHD was applied to Turner's syndrome, ISS and IUGR, there was a high degree of similarity between the predicted and achieved growth response in ISS and IUGR. However, an uneven distribution within the plot of Studentized residuals in ISS and IUGR suggested heterogeneity within these populations. Prediction of growth in Turner's syndrome was greatly exaggerated by the model for IGHD, suggesting a different pathogenesis as the basis of the growth disorder. Specific prediction models were therefore developed for Turner's syndrome, ISS and IUGR. In all three disorders, the dose of GH was found to be the most important predictor, suggesting that, in contrast to IGHD, first-year growth is governed less by the difference between height and the presumed genetically determined target height. Again, in contrast to IGHD, this suggests that catch-up phenomena are not involved.(ABSTRACT TRUNCATED AT 250 WORDS)

Short stature: new challenges in growth hormone therapy

Until recently, the limited supplies of pituitary derived growth hormone (GH) enabled us to treat only those patients who were classical GH deficient. With the unlimited supplies of recombinant GH available, there is no limitation to the number of patients we can treat. It becomes necessary, however, to select those patients who will most benefit from GH therapy. Our preliminary results demonstrate that the short-term growth response to growth hormone is not an all-or-none phenomenon. The lower the growth velocity and the growth hormone reserve, the better the growth response to therapy. On the other hand we do not recommend institution of GH therapy for children with a normal growth rate and a normal GH spontaneous secretion. In children with classical GH deficiency (GHD) and in children with a subnormal spontaneous secretion of GH (NSD) adult height prediction decreases when GH therapy is started at an age older than 12. We have found that GHD and NSD boys differ in their growth pattern. Pubertal maturation and bone age maturation progress more rapidly in NSD patients. Therefore special caution is needed in NSD patients older than 12 years. The older the patient and the longer the treatment period, the faster the pubertal process can advance. Further studies are needed before recommendations for therapy in non-classical GHD patients can be made. Until patients involved in clinical trials reach final height, recommendations for new indications cannot be made.

Antibody deficiency and isolated growth hormone deficiency in a girl with Mulibrey nanism

A combination of humoral immunodeficiency and isolated growth hormone deficiency was observed in a girl with Mulibrey nanism. The humoral immunodeficiency consisted of subnormal concentration of serum IgG, in particular IgG2 and IgG4, and low concentration of serum IgM. Serum IgA and IgD were elevated, IgE was absent. Antibody response in vivo was very low or absent and opsonization in vitro was defective. Total B-cell number was low. In addition, the serum kappa/lambda light chain ratios within the immunoglobulin classes G, A, and M were abnormal. The defective antibody response may be linked to the abnormal kappa/lambda light chain ratios. Endocrine functions were normal except for isolated growth hormone deficiency. Therapy with human growth hormone resulted in increased growth velocity but did not improve humoral immune functions.

Conventional and nonconventional uses of growth hormone

Although GH has been available as a therapeutic agent for the GH-deficient child for more than 30 years, the conditions of its use have yet to be optimized. The availability of biosynthetic material has provided researchers with the opportunity to develop the protocols necessary to begin to finally answer the most fundamental questions pertaining to dose, frequency, and duration of treatment. It has also permitted the initiation of prospective trials in a large number of conditions that result in childhood short stature, with the expectation that some or many of them will be treated effectively and safely. Finally, it has opened the door to an entire spectrum of potentially new uses of GH and other growth factors for so-called nonconventional indications. That these have implications that range from the short-term rapid healing of a burn graft site, to the more efficient induction of ovulation, to the long-term preservation of lean body mass has excited the interest of investigators in many fields of medicine and physiology. Thus, the recent progress reported in this paper is really the beginning of the new research that will take place with GH and growth factors.

Evaluation of growth hormone secretion and treatment

The secretion of growth hormone (GH) is regulated by a complex system that includes both neurotransmitters and feedback by hormonal and metabolic substrates. Over the last few years it has been recognized that GH release varies over a wide spectrum from deficient to excessive secretion. The diagnosis of GH deficiency is based on a combination of anthropometric and clinical signs on the one hand and an inadequate stimulated and/or spontaneous GH secretion on the other. There is no distinct boundary between deficient and sufficient GH secretion. The cut-off limit for normal GH release is accordingly relative and has increased over the past decade from 5 to 10 micrograms/l. The effect of GH therapy on growth can be evaluated only after treatment for at least 6 months. There is, therefore, an indisputable need for methods that would reflect growth response soon after the start of treatment. There are several promising biochemical candidates, e.g. the aminoterminal propeptide of type III procollagen, the carboxyterminal propeptide of procollagen I and the bone Gla-protein, which may turn out to be useful early indicators of the growth response to long-term GH therapy.

Predictors of growth response to growth hormone in otherwise normal short children

Sixty prepubertal short children (39 boys) with heights less than 2 SD for age and gender were treated daily for 1 year with recombinant human growth hormone (GH), either 0.1 IU/kg (group 0.1, n = 32) or 0.05 IU/kg (group 0.05, n = 28). Reserve of GH was determined by at least one GH provocative stimulus and 24-hour continuous blood withdrawal to determine the integrated concentration of GH (IC-GH). All participants had a GH response to provocative tests greater than 10 micrograms/L. The height velocity (mean +/- SD) of the group as a whole increased from 4.46 +/- 1.02 to 7.59 +/- 1.65 cm/yr (p less than 0.001). The growth velocity of group 0.1 was significantly greater than that of group 0.05 (8.1 +/- 1.5 vs 7.0 +/- 1.65 cm/yr; p less than 0.01). Bone age did not advance more than 1 year during the treatment period. Growth velocity after 1 year of GH therapy was inversely correlated with the IC-GH in both groups, as was the pretreatment height velocity. We found no correlation of growth velocity during GH therapy with other measures such as parental heights, bone age/chronologic age ratio, maximal GH response to provocative tests, chronologic age, or pretreatment insulin-like growth factor I levels. We conclude that the best predictors for the 1-year growth outcome of short children with a normal GH response to provocative tests are the pretreatment growth velocity and the IC-GH. The short-term benefit from GH therapy in children with a normal growth velocity and a normal IC-GH is poor, whereas marked growth acceleration is noted in children with a low growth velocity and a low 24-hour IC-GH.

Growth of males with idiopathic hypopituitarism without growth hormone treatment

We report auxologic data on 23 males with idiopathic hypopituitarism who grew up at a time when human growth hormone (GH) was not yet available, while receiving other appropriate hormonal substitution. We had reported previously that their adult heights were not significantly less than those of similar patients who had received GH. In the absence of GH the pubertal growth period was remarkably protracted, averaging 8.7 years for 19 patients during androgen substitution. Pubertal increment in height averaged 20.4 cm during induced puberty, a figure which compares favourably with those reported for GH-treated patients. This implies that GH does not increase the height gained during pubertal growth; the increase in the rate of growth appears to be off-set by a rise in the rate of skeletal maturation. During pubertal growth acceleration of growth of the skeleton seems unavoidably associated with acceleration of its maturation. Adult heights were significantly correlated with the heights at the time of onset of pubertal growth. This is evidence in favour of attempts to stimulate prepubertal growth much more than hitherto by earlier, higher, and more frequent doses of GH. It remains to be proved, however, that before puberty the processes of growth and maturation of the skeleton can be dissociated.

Turner syndrome: effect of hormone therapies on height velocity and adult height

76 patients with Turner syndrome received estrogen alone, androgen and estrogen started simultaneously or, after preceding androgen therapy, estrogen with or without androgen. Six patients had spontaneous pubertal development and received no estrogen. Two patients received human growth hormone with androgen during greater than 2.0 years. Height velocity increased during all therapies to mean SD scores of 7.6 during androgen-estrogen started simultaneously, 4.6 during androgen alone, 4.2 during androgen-estrogen after preceding androgen, 2.7 during estrogen alone, and 0.6 during estrogen after preceding androgen. Adult height was measured in all cases, it was 145.5 +/- 5.7 (mean +/- SD) for the whole series without significant differences between the groups. It correlated strongly with midparent height, and was greater for patients with the 45,X karyotype than for the others combined.

Growth hormone deficiency

Growth hormone deficiency is relative, not absolute. Conventional stimulation tests of hGH release do not recognise some children who will benefit from hGH treatment and it is probably justified, at this point, undertaking a six month trial of hGH in all short children who are growing slowly (less than 4 cm/yr). Accurate anthropomorphic measurements are therefore obligatory. Most hGH deficient children (both idiopathic and secondary to cranial irradiation) have hypothalmic dysfunction as the cause of the deficiency. Treatment with hGH is most efficacious if given in frequent divided doses and GH-RH can also be used to treat some patients. Patients with Turner's syndrome and possibly other conditions associated with short stature may benefit from hGH treatment.

Early initiation of growth hormone treatment: influence on final height

Retrospective growth data for 34 hGH deficient patients who had been treated for at least 3 years with hGH were analysed in a Belgian multicentre study. Final height was related to target height and was usually below it, but it was not determined by chronological or bone ages, bone age delay, height velocity before or during therapy, nor by duration of treatment. Total height gain during long-term substitution with hGH is inversely related to chronological and bone ages at the start of therapy, and is positively related to the duration of therapy. Early diagnosis of hGH deficiency is thus important, as it allows catch-up growth to optimal height before puberty, which in turn results in a good pubertal growth spurt.

Dose-response relationship in the treatment of hypopituitary children with human growth hormone: a retrospective survey

During the past 15 years, dose-response studies of hGH have been limited to prepubertal patients with complete somatotrophic deficiency, who have usually been treated with hGH three times/week within a dose range of 10-40 IU/kg/year. In such studies a weak positive correlation has been found (r = 0.429, p less than 0.001) with marked important individual variations. Very few or no data have been published regarding the dose-response relationship after the first year of hGH treatment, or when the dose is increased because the growth rate is waning, or during puberty. The present paper reports some data on these issues. A group of 32 young hGH deficient children, whose bone age was 0-4 years, was followed up for at least 3 years with hGH given intramuscularly three times weekly at doses of 12-48 IU/kg/year (mean, 25 +/- 9 IU/kg/year - i.e. approximately 0.15 IU/kg/injection). A dose-response relationship existed during the first year but not during the following 2 years nor for the height gain obtained at the end of the third year of treatment. The results of an increase of the dose of hGH by 33-66% in 13 prepubertal hGH deficient children whose growth rate had decreased after 2-5 years of treatment were fair in 6, limited in 4 and absent in 3, and did not relate to the extent of dose increase. However, this series is too small to allow definite conclusions. The growth rate of 67 adolescents with complete hGH deficiency and normal spontaneous puberty was close to the normal mean in the 45 males but much less in the 22 females. Although the least favourable results came from cases with post-radiotherapy hypopituitarism, the mean total pubertal growth spurt in patients with idiopathic hGH deficiency was also below the average, mainly in the girls, and with a large range of individual variation. An important fact was that bone age increased more than height age or chronological age in these hypopituitary pubertal patients. No dose-response relationship was found in this group, within a limited range of doses (40 patients receiving 16-20 IU/kg/year injected three times weekly, 19 receiving less than 16 IU/kg/year and 8 receiving more than 20 IU/kg/year). It may be concluded that in prepubertal hypopituitary children, hGH at a dose of approximately 20 IU/kg/year at the onset of treatment is probably appropriate. The lack of a dose-response relationship after the first year of treatment suggests that higher initial doses should be avoided.(ABSTRACT TRUNCATED AT 400 WORDS)

Growth hormone treatment in girls with Turner's syndrome. A review of the literature

Most girls with Turner's syndrome seemed to increase their growth rate during the first year of growth hormone treatment. The gain is rarely more than 3 cm/year. In 3 studies the combination of growth hormone and an anabolic steroid resulted in higher growth rates compared to those with each individual compound. The results of long-term treatment (more than one year) also appear to be positive. The impact of growth hormone therapy on final height has not yet been established, however.

Growth response to human growth hormone treatment in children with partial and total growth hormone deficiency

The growth response during the first and second years of human growth hormone (hGH) treatment was studied in 14 prepubertal children with so-called "partial" GH deficiency (peak GH between 8 and 15 mU/l) and compared to 28 prepubertal children with "total" GH deficiency (peak GH less than 8 mU/l). There was no difference in growth acceleration between children with partial and total GH deficiency, when initial covariables were taken into account. In a stepwise multiple regression analysis initial stature, pre-treatment growth velocity and skinfold thickness were shown to be most related to growth response, but after exclusion of 3 children with a genetic form of total GH deficiency and partial TSH deficiency this relationship was lost. GH levels during provocation tests and auxological criteria have a poor predictive value for growth response to hGH therapy.

Treatment of growth hormone deficiency

According to the results reported in the literature and from our own experience, the following recommendations for the treatment of children with GHD can be given: In order to start GH replacement therapy in early childhood the diagnosis of GHD should be made as early as possible. The growth hormone dose during prepubertal age should not fall short of 12 IU/m2 per week. During spontaneous or induced puberty, the dose needs to be increased, possibly by a factor of two. Daily subcutaneous injections appear most suitable. Treatment with growth hormone releasing factors in cases with hypothalamic GHD, although a promising alternative to the treatment with hGH (Thorner et al, 1985), must be considered experimental at this point. Thyroxine replacement at a daily dose of 75-100 micrograms/m2 should be given in cases of secondary hypothyroidism. Glucocorticoid replacement, if required, should be given at low doses (e.g. hydrocortisone 10 (to 15) mg/m2 per day in divided doses). In cases with additional gonadotropin deficiency, sex steroids (or anabolic steroids) should be given with frequent monitoring of bone maturity not before the age of 13 in girls or 15 years in boys. In boys depot testosterone starting at low doses (e.g. 50-100 mg/month i.m.) will induce a puberty-like increment in height velocity. Since the effect of oestrogens--even in low doses--on growth is uncertain, their administration before achievement of near-normal adult height should be avoided. With the advancement of diagnostic techniques and with the experience in treatment accumulated over the past 25 years, patients with GHD need no longer become dwarfs.

Growth hormone neurosecretory dysfunction

The basis for understanding clinical disorders in the neuroregulation of GH secretion is derived from the complexity of the CNS-hypothalamic-pituitary axis. Studies in animals and humans demonstrate an anatomic, physiological and pharmacological evidence for neurosecretory control over GH secretion including neurohormones (GRH, somatostatin), neurotransmitters (dopaminergic, adrenergic, cholinergic, serotonergic, histaminergic, GABAergic), and neuropeptides (gut hormones, opioids, CRH, TRH, etc). The observation of a defect in the neuroregulatory control of GH secretion in CNS-irradiated humans and animals led to the hypothesis of a disorder in neurosecretion, GHND, as a cause for short stature. We speculate that in this heterogeneous group of children a disruption in the neurotransmitter-neurohormonal functional pathway could modify secretion ultimately expressed as poor growth velocity and short stature.

Growth hormone therapy of short stature

Considerable progress has been made in the diagnosis and treatment of growth hormone-related short stature. Knowledge about growth hormone releasing factor (GRF) and somatomedin C has provided the possibility of distinguishing between hypothalamic and pituitary growth hormone deficiency and growth hormone resistance. It has been shown that treatment with GRF may stimulate growth in certain cases of growth hormone deficiency. Recombinant DNA techniques may, in the near future, provide sufficient amounts of GRF, growth hormone and possibly somatomedin C for clinical use. At present, many countries have prohibited the use of human pituitary growth hormone due to a possible risk of transmission of Creutzfeldt-Jakob disease. It has become increasingly clear that several short children without classical growth hormone deficiency, may increase their growth velocity during growth hormone treatment. There are many medical, psychological, ethical and economical implications involved in the extended treatment of children with short stature. It is necessary to maintain a restricted approach towards the treatment of children with short stature, and such treatment should be prescribed and controlled by a limited number of well-trained paediatric endocrinologists. This article reviews some of the present knowledge in this rapid developing field of paediatric endocrinology.

Which children should have growth hormone therapy?

Existing criteria for the diagnosis of growth hormone (GH) deficiency do not identify all children who can be made to grow faster with GH. There is a spectrum of GH secretion in short slowly growing normal children and in some cases the secretion may be inadequate to promote optimum growth in height. A diagnostic/therapeutic trial of GH therapy, with auxological monitoring, may be the only means of identifying some patients who will benefit. Assessment of the place for GH therapy in the treatment of short stature requires special knowledge of childhood diseases, growth, and endocrinology.

When are we diagnosing growth hormone deficiency?

The height and age at presentation of 458 children beginning treatment with growth hormone between January 1980 and June 1984 were retrospectively analysed. Three hundred and nine children with isolated growth hormone deficiency had a mean (SD) age of 10 (4.1) years on beginning treatment and a mean (SD) height standard deviation score (SDS) of -3.73 (0.93). One hundred and nine patients with hypothalamopituitary tumours began treatment with growth hormone on average 3.3 years after diagnosis of the tumour and at a mean (SD) height SDS of -2.42 (1.49). In both of these categories the height SDS showed a considerable improvement compared with previous reports. Forty two patients with growth hormone deficiency secondary to cranial irradiation started treatment with growth hormone on average 6.1 years after treatment for their tumours and had a height SDS of -2.45 (1.02) compared with that of -2.45 (0.98) seen in nine similar patients from the United Kingdom starting treatment with growth hormone between 1975 and 1978. Although closer surveillance of short children in the community is leading to earlier diagnosis of growth hormone deficiency, this could possibly be diagnosed earlier if routine screening of height was to be carried out at school entry. In addition, patients who have received cranial irradiation should be regularly measured and investigated when their height velocity becomes subnormal.

Growth hormone treatment for short stature

Fifteen short but otherwise normal children, 4.3 to 15.5 years old, with heights greater than 3 S.D. below the mean value for age, growth rates less than or equal to 5.0 cm per year, and normal serum levels of immunoreactive growth hormone in response to provocative stimuli (peak greater than or equal to 10 ng per milliliter) were treated with intramuscular injections of pituitary growth hormone (0.1 U per kilogram) three times weekly for six months, as were 14 children with documented growth hormone deficiency. In all the latter children growth rate increased by more tan 2.0 cm per year during treatment. In 6 of the 14 short normal children who remained prepubertal, growth rate also increased, by 2.2 to 4.2 cm per year during treatment; four of these children had normal base-line serum somatomedin C concentrations. In both short normal children and children with growth hormone deficiency, the increment in serum somatomedin C concentrations after 4 or 10 daily injections of growth hormone correlated with bone age but not with later growth or growth hormone levels. Among the short normal children, those who responded to growth hormone were younger and had a greater delay in bone age and a slower pretreatment growth rate than the nonresponders. These observations suggest that a dose of growth hormone comparable to that used for the treatment of hypopituitarism increases growth rate in some short normal children.