Use and abuse of human growth hormone

Growth hormone, enhancement and the pharmaceuticalisation of short stature

This paper takes the biological drug human Growth Hormone (hGH) as a case study to investigate processes of pharmaceuticalisation and medicalisation in configuring childhood short stature as a site for pharmaceutical intervention. Human growth hormone is considered to have legitimate applications in treating childhood growth hormone deficiency and short stature associated with other recognised conditions. It is also regarded by bioethicists and others as a form of human biomedical enhancement when applied to children with idiopathic or 'normal' short stature. The purpose of this study is not to evaluate whether treatment of idiopathic short stature is enhancement or not, but to evaluate how some applications of hGH in treating short stature have come to be accepted and stabilised as legitimate 'therapies' while others remain contested as 'enhancements'. A comparative, historical approach is employed, drawing on approaches from medical sociology and Science and Technology Studies (STS) to set out a socio-technical history of hGH in the US and UK. Through this history the relative influence and interplay of drivers of pharmaceuticalisation, including industry marketing and networks of drug distribution, and processes of medicalisation will be employed to address this question and simultaneously query the value of enhancement as a sociological concept.

A longitudinal study of craniofacial growth in idiopathic short stature and growth hormone-deficient boys treated with growth hormone

The aim of this prospective, longitudinal, controlled study is to describe the long-term safety and efficacy of growth hormone (GH) administration on craniofacial morphology in boys with short stature. Forty-six boys, who started GH treatment at the Department of Paediatrics Göteborg Paediatric Growth Research Centre, were consecutively included in the study. Twenty-five boys were classified as growth hormone-deficient (GHD) and 21 as idiopathic short stature (ISS). The patients were injected with 33 (n=31) or 67 (n=15) microg GH/kg body weight/day. The mean age at the start of treatment was 11.8 years [standard deviation (SD) 1.7]. To assess craniofacial growth, standard lateral cephalometric radiographs were obtained at the start of GH treatment, annually during 4 years, and at the end of GH treatment or when growth was less than 1 cm/year. The mean follow-up period was 6.4 years (SD 1.4). Growth changes were compared with boys from a semi-longitudinal reference group of 130 healthy subjects, 7-21 years of age. t-tests for independent and paired samples and multiple regression analysis were applied. Age- and gender-specific standard deviation scores for the cephalometric variables were calculated. Repeated measures analysis of variance was used to identify significant covariates over time, such as low/high GH dose and GHD/ISS and orthodontic treatment. During the study period, eight (out of 40) boys were treated with fixed orthodontic appliances, three with functional appliances (activators), and three with other appliances (plates and lingual arches). During GH treatment period, an overall enhancement in growth of the facial skeleton was observed in boys with short stature. The changes induced by GH yielded a more prognathic growth pattern, a more anterior position of the jaws in relation to the cranial base, and increased anterior rotation of the mandible. The mandibular corpus length and anterior face height of the GH-treated boys were greater at the end of the study compared with the boys in the reference group. No differences in growth response were noted either between the GHD and ISS boys or between those treated with either 33 (low dose) or 67 (high dose) microg GH/kg body weight/day. The only change that remained significantly correlated with orthodontic treatment was the alteration in mandibular ramus height, showing a larger change in the boys who had not undergone orthodontic therapy. The findings of this study demonstrate that GH treatment has a favourable influence on the craniofacial growth pattern of boys with short stature without acromegalic features.

Turner syndrome: an update and review for the primary pediatrician

Turner syndrome (TS) is among the most common of the sex chromosomal aneuploidies. It results from the absence of one sex chromosome (or part of an X chromosome) in a female, leaving only one X chromosome present in the cell. Primary care physicians should be able to recognize the presenting signs and symptoms of TS, and once the diagnosis is confirmed by a chromosome analysis, they should be able to serve as a valuable source of support for the patient and her family and understand the most current treatments available.

The exercise-induced growth hormone response in athletes

Human growth hormone (hGH) is secreted in a pulsatile fashion, generally following a circadian rhythm. A number of physiological stimuli can initiate hGH secretion, the most powerful, non-pharmacological of which are sleep and exercise. hGH has many varied roles throughout life, from growth itself, including the turnover of muscle, bone and collagen, to the regulation of selective aspects of metabolic function including increased fat metabolism and the maintenance of a healthier body composition in later life. The exercise-induced growth hormone response (EIGR) is well recognised and although the exact mechanisms remain elusive, a number of candidates have been implicated. These include neural input, direct stimulation by catecholamines, lactate and or nitric oxide, and changes in acid-base balance. Of these, the best candidates appear to be afferent stimulation, nitric oxide and lactate. Resistance training results in a significant EIGR. Evidence suggests that load and frequency are determining factors in the regulation of hGH secretion. Despite the significant EIGR induced by resistance training, much of the stimulus for protein synthesis has been attributed to insulin-like growth factor-1 with modest contributions from the hGH-GH receptor interaction on the cell membrane. The EIGR to endurance exercise is associated with the intensity, duration, frequency and mode of endurance exercise. A number of studies have suggested an intensity 'threshold' exists for EIGR. An exercise intensity above lactate threshold and for a minimum of 10 minutes appears to elicit the greatest stimulus to the secretion of hGH. Exercise training above the lactate threshold may amplify the pulsatile release of hGH at rest, increasing 24-hour hGH secretion. The impact of chronic exercise training on the EIGR remains equivocal. Recent evidence suggests that endurance training results in decreased resting hGH and a blunted EIGR, which may be linked to an increased tissue sensitivity to hGH. While the potential ergogenic effects of exogenous GH administration are attractive to some athletes, the abuse of GH has been associated with a number of pathologies. Identification of a training programme that will optimise the EIGR may present a viable alternative. Ageing is often associated with a progressive decrease in the volume and, especially, the intensity of exercise. A growing body of evidence suggests that higher intensity exercise is effective in eliciting beneficial health, well-being and training outcomes. In a great many cases, the impact of some of the deleterious effects of ageing could be reduced if exercise focused on promoting the EIGR. This review examines the current knowledge and proposed mechanisms for the EIGR, the physiological consequences of endurance, strength and power training on the EIGR and its potential effects in elderly populations, including the aged athlete.

The psychosocial consequences of short stature: a review of the evidence

The advent of biosynthetic growth hormone (GH) has been accompanied by a transformation in the clinical management of youths with short stature. An important--if not always explicitly stated--goal of endocrine therapies is an improvement in the psychological adaptation of individuals with short stature. Negative stereotypes regarding short stature constitute a potential source of psychosocial stress for the affected child and, in turn, the entire family. Nevertheless, studies have demonstrated that the psychological adaptation of individuals who are shorter than average is largely indistinguishable from others, whether in childhood, adolescence or adulthood. "Short stature" as an isolated physical characteristic appears to hold little value as a predictor of the individual's psychological adaptation or quality of life. In order to avoid the unwarranted medicalizing of healthy short stature, clinicians would be well advised to incorporate factors beyond auxology in the decision-making algorithm when selecting and preparing patients for possible growth-promoting therapies.

The development of delivery agents that facilitate the oral absorption of macromolecular drugs

Macromolecules comprise a growing group of new drugs with great clinical promise. To date, the therapeutic application of these drugs has been limited, because they are effective only when administered parenterally. Unfortunately, macromolecular drugs are not absorbed following nonparenteral dosing, because the mechanisms of the human body are designed to degrade and/or exclude them. To overcome the numerous obstacles to the noninvasive delivery of these drugs, various approaches are under investigation including the use of delivery agents to promote drug absorption. This review provides a summary of the novel approaches currently in progress in the areas of transdermal, transmucosal, and oral delivery of macromolecular drugs facilitated by delivery agents. We review our own novel work in this area in some detail, including the methods developed for the synthesis of the delivery agents, in vitro screening techniques developed to select compounds for in vivo testing, and the results of in vivo screening in both rats and primates, including preliminary safety and efficacy studies. Finally, the results of Phase I clinical studies showing the oral delivery of heparin are presented.

Transport of human growth hormone across Caco-2 cells with novel delivery agents: evidence for P-glycoprotein involvement

Emisphere Technologies, Inc. has synthesized a series of small molecules which have been shown to improve protein absorption through mucosal tissue. This enhancement is specific between protein and a particular delivery agent. Despite the specificity of interaction, the mechanism of enhanced tissue penetration is still unclear. The purpose of this work is to understand the enhancement mechanism(s) of these delivery agents by using Caco-2 cells as a model membrane. It was found that the bidirectional transepithelial fluxes of human growth hormone (hGH) in the presence of these delivery agents across human intestinal epithelial Caco-2 cell line showed marked asymmetry. Average permeability coefficient values obtained in the apical (AP) to basolateral (BL) direction were lower than those of the reverse (BL to AP) direction. On the other hand, the fluxes for human growth hormone alone were symmetric. When P-glycoprotein inhibitors were included in the transport medium, the permeability coefficient values of BL to AP direction were significantly decreased while the transport was increased in the reverse direction in the presence of delivery agents. P-glycoprotein inhibitors had no effect on the transport of human growth hormone alone. This study shows that human growth hormone alone can be transported across Caco-2 cells in very limited quantities by passive diffusion, but in the presence of delivery agents, human growth hormone can be effluxed in a P-glycoprotein-mediated fashion. This also indirectly shows that the human growth hormone has become more lipophilic in the presence of delivery agents.

Randomised trial of growth hormone in short normal girls

BACKGROUND

There are few data on the long-term outcome of growth-hormone treatment in short normal children. We assessed the impact of growth-hormone treatment on pubertal development and near-final height in girls.

METHODS

In a randomised controlled trial, we studied ten girls, with a mean age of 8.07 years and height 2 SDs or more below the mean for their age, and eight short untreated controls matched for age, and 20 short untreated girls who did not give consent for randomisation. The girls received either 30 IU/m2 somatropin per week as daily subcutaneous injections or no treatment. We assessed pubertal staging and height gain every 6 months.

FINDINGS

Eight treated girls completed a mean of 6.2 years' therapy. By a mean age of 16.4 years, their mean height SD score had changed significantly from -2.42 to -1.14 (p=0.008) and they were, on average, 7.5 cm taller than the girls in the control group (height SD scores did not change significantly from -2.55) and 6.0 cm taller than the non-consent group. The timing of each pubertal stage, and the age and amplitude of peak height velocity were similar for all groups.

INTERPRETATION

Growth-hormone therapy effectively increased height SD score among short normal girls started on treatment in early to mid childhood, with no untoward effect on pubertal progression.

Moral assessment of growth hormone therapy for children with idiopathic short stature

The prescription of growth hormone therapy for children who are not growth hormone deficient is one of the controversies in contemporary paediatric endocrinology. Is it morally appropriate to enhance the growth, by means of medical treatment, of a child wish idiopathic short stature? The medical, moral, and philosophical questions in this area are many. Data on the effects of human growth hormone (hGH) treatment will not on their own provide us with answers, as these effects have to be evaluated from a normative perspective. In this article we consider hGH treatment for children of idiopathic short stature from three normative perspectives: the goals of medicine, the good of the patient, and the public good. We argue that the prevention of psychological and social problems due to short stature (and not merely the enhancement of growth) should be the ultimate goal of medical treatment and research.

Effects of exogenous growth hormone on skeletal muscle of young female rats

We examined the effects of exogenous growth hormone (GH) treatment on the soleus and rectus femoris muscles of young female rats. Rat GH (1.8 IU/mg) was administered for 3 weeks by subcutaneous injection, twice a day, at doses of 0.5, 0.6, and 0.8 mg/day during the 1st, 2nd and 3rd week, respectively. Final body weight, as well as wet and dry weight, of the soleus and rectus femoris muscles were significantly greater in the GH-treated group, compared to controls. Muscle weight to body weight ratios did not differ between the two groups. The fiber type composition of the soleus muscle was determined by histochemical staining for myosin ATPase activity. No statistically significant difference was found between the GH-treated and the control groups in the percentages of fiber types. However, GH treatment significantly increased the cross-sectional area of type II fibers of the soleus muscle. These results suggest that, in young female rats, acceleration of body weight gain by homologous GH administration is accompanied by a proportional hypertrophy of skeletal muscle mass. Increased muscle mass is due to hypertrophy of muscle fibers. Type II muscle fibers appear to be more sensitive to GH stimulation.

Exogenously administered growth hormone and insulin-like growth factor-I alter intracellular Ca2+ handling and enhance cardiac performance. In vitro evaluation in the isolated isovolumic buffer-perfused rat heart

It has been proposed that chronic treatment with growth hormone (GH) or insulin-like growth factor-I (IGF-I) in the rat may enhance cardiac function in vivo. To confirm these findings and elucidate the mechanisms by which cardiac function is modulated, we studied isolated buffer-perfused rat hearts after 4 weeks of treatment with high doses of GH and IGF-I alone or in combination. Mechanical parameters were measured at 50% of the intracardiac balloon volume at which maximal developed pressure (DevP) occurred. EC50 of the force-Ca2+ relationship and maximal Ca(2+)-activated systolic wall stress (max sigma s) were assessed by increasing Ca2+ in the perfusate in a stepwise fashion and plotting systolic wall stress (sigma s) versus intracellular peak systolic Ca2+, measured by the aequorin bioluminescence method. We found a marked increase of systolic pressure (Ps), DevP, and (+dP/dt)/DevP in the treated groups compared with the control group. The combination group showed a blunted effect. sigma s was increased in all treated groups for a perfusate Ca2+ concentration of > 1.5 mmol/L. The enhanced systolic performance can be explained by an increase of the overall Ca2+ responsiveness due to an increased maximal response to Ca2+ even though the EC50 of the Ca(2+)-dose response was also slightly increased. Ps was further enhanced by an increase of the relative wall thickness induced by the treatment. Diastolic pressure, diastolic Ca2+, and the amplitude and time course of the Ca2+ transient were not influenced by any treatment protocol. All treatments caused increases of body and heart weight. These data support the hypothesis that both IGF-I and GH directly affect cardiac performance by altering cardiac geometry as well as by enhancing max sigma s.

4-[4-[(2-Hydroxybenzoyl)amino]phenyl]butyric acid as a novel oral delivery agent for recombinant human growth hormone

A series of N-acetylated, non-alpha, aromatic amino acids was prepared and shown to promote the absorption of recombinant human growth hormone (rhGH) from the gastrointestinal tract. Seventy compounds in this family were tested in vivo in rats. Of the compounds tested, 4-[4-[(2-hydroxybenzoyl)amino]phenyl]butyric acid was identified as a preclinical candidate and was used to demonstrate the oral delivery of rhGH in primates. A significant positive correlation was found between the relative log k' of the delivery agents, as determined by HPLC on an immobilized artificial membrane (IAM) column, and serum rhGH concentrations following oral or colonic dosing in rats. Structure-activity relationships have also been developed on the basis of electronic effects and hydrogen-bonding characteristics of the aromatic amide substituents.

Endocrine regulation of craniofacial growth

This paper presents an updated review of the role of endocrine factors in craniofacial and dental development. Some unpublished results of the author's own studies are presented. Longitudinal growth studies have shown the similarity of facial and somatic growth rates, whereas dental development has been found to be independent. The increased therapeutic use of the growth hormone (GH) has focused attention on the dental and craniofacial effects of GH. Whereas delayed and advanced cranial base and facial growth is obvious in conditions with either lack or excess of GH, the effect of GH on the dentition is less clear. Thyroid hormones seem to be necessary for the eruptive movement of teeth. Sex steroids clearly have an effect on facial and cranial base growth and are also odontogenic, but the effects have not been much studied. The growth-inhibiting effect of corticosteroids is explained partly by the reduced response of cartilage cells to insulin-like growth factor-1. Experimentally, the effect is also seen in the condylar cartilage, but clinical studies have not been published. In tooth eruption an accelerating effect has been noted in experimental animals. The role of androgenic hormones in mandibular growth stimulation is discussed.