GH safety workshop position paper: a critical appraisal of recombinant human GH therapy in children and adults

Recombinant human GH (rhGH) has been in use for 30 years, and over that time its safety and efficacy in children and adults has been subject to considerable scrutiny. In 2001, a statement from the GH Research Society (GRS) concluded that 'for approved indications, GH is safe'; however, the statement highlighted a number of areas for on-going surveillance of long-term safety, including cancer risk, impact on glucose homeostasis, and use of high dose pharmacological rhGH treatment. Over the intervening years, there have been a number of publications addressing the safety of rhGH with regard to mortality, cancer and cardiovascular risk, and the need for long-term surveillance of the increasing number of adults who were treated with rhGH in childhood. Against this backdrop of interest in safety, the European Society of Paediatric Endocrinology (ESPE), the GRS, and the Pediatric Endocrine Society (PES) convened a meeting to reappraise the safety of rhGH. The ouput of the meeting is a concise position statement.

Disruption of the association of integrin-associated protein (IAP) with tyrosine phosphatase non-receptor type substrate-1 (SHPS)-1 inhibits pathophysiological changes in retinal endothelial function in a rat model of diabetes

AIMS/HYPOTHESIS

We have previously shown that the association of integrin-associated protein (IAP) with tyrosine phosphatase non-receptor type substrate-1 (SHPS-1) regulates the response of cells, including osteoclasts, osteoblasts, smooth muscle and retinal endothelial cells, to IGF-I. Here we sought to: (1) determine whether the regulation of IGF-I responsiveness by the association of IAP with SHPS-1 is a generalised response of endothelial cells; (2) identify the mechanism by which this association contributes to changes in endothelial cell responses to IGF-I; and (3) determine whether inhibition of this association alters pathophysiological changes occurring in vivo.

METHODS

Endothelial cells were maintained in 5 mmol/l glucose and at hyperglycaemic levels, and exposed to an anti-IAP antibody that disrupts the association between IAP and SHPS-1. A rodent model of diabetes with endothelial cell dysfunction was used to investigate the role of the association of IAP with SHPS-1 in endothelial cell function in vivo.

RESULTS

Endothelial cells maintained in 5 mmol/l glucose showed constitutive cleavage of the extracellular domain of IAP (which contains the SHPS-1 binding site), with no association between IAP and SHPS-1 being detected. In contrast, hyperglycaemia inhibited IAP cleavage, allowing IAP to associate with SHPS-1 and IGF-I to stimulate SHPS-1 tyrosine phosphorylation. Exposure to the anti-IAP antibody inhibited IGF-I-stimulated tube formation and increased permeability. In the rodent model, basal IAP-SHPS-1 association was not detected in retinal extracts from normal rats, but was fully restored in rats with diabetes. The anti-IAP antibody inhibited the association of IAP with SHPS-1, and reduced retinal vascular permeability and leucocyte adherence to levels similar to those in non-diabetic rats. The antibody also significantly inhibited the aberrant neovascularisation induced by hypoxia.

CONCLUSIONS/INTERPRETATION

Our results demonstrate that the increased association of IAP with SHPS-1 contributes to the pathophysiological changes in the endothelium that are induced by hyperglycaemia and hypoxia.

Guidelines for acromegaly management: an update

OBJECTIVE

The Acromegaly Consensus Group reconvened in November 2007 to update guidelines for acromegaly management.

PARTICIPANTS

The meeting participants comprised 68 pituitary specialists, including neurosurgeons and endocrinologists with extensive experience treating patients with acromegaly. EVIDENCE/CONSENSUS PROCESS: Goals of treatment and the appropriate imaging and biochemical and clinical monitoring of patients with acromegaly were enunciated, based on the available published evidence.

CONCLUSIONS

The group developed a consensus on the approach to managing acromegaly including appropriate roles for neurosurgery, medical therapy, and radiation therapy in the management of these patients.

Diagnosis and treatment of acromegaly complications

The Pituitary Society in conjunction with the European Neuroendocrine Association held a consensus workshop to develop guidelines for diagnosis and treatment of the co-morbid complications of acromegaly. Fifty nine pituitary specialists (endocrinologists, neurosurgeons and cardiologists) assessed the current published literature on acromegaly complications in light of recent advances in maintaining tight therapeutic control of GH hypersecretion. The impact of elevated GH levels on cardiovascular disease, hypertension, diabetes, sleep apnea, colon polyps, bone disease, reproductive disorders, and neuropsychologic complications were considered. Guidelines are proposed for effective management of these complications in the context of overall acromegaly control. When appropriate, requirements for prospective evidence-based studies and surveillance database development are enunciated. Effective management of co-morbid acromegaly complications will lead to improved morbidity and mortality in acromegaly.

Assessment of growth parameters and life span of GHR/BP gene-disrupted mice

GH has many biological roles, including promotion of growth. Most, if not all, of its roles are achieved through interaction with its receptor. We chose to study the effects of loss of GH signaling on growth and aging in a mouse model for Laron Syndrome (LS) in which the GHR/BP gene has been disrupted. We observed that mice homozygous for the disruption (-/-) were significantly smaller than normal wild-type (+/+) mice as well as mice heterozygous for the disruption, even at 1.5 yr of age. IGF-I levels were also significantly lower in the -/- mice and remained low as the mice aged. IGFBP-3 levels were severely reduced in the -/- mice, whereas IGFBP-1, -2, and -4 levels remained unchanged. Finally, the -/- mice lived significantly longer than +/+ and +/- mice. The latter result contradicts the anti-aging GH data and suggests the need for further analysis of GH and aging.

Unequal impact of age, percentage body fat, and serum testosterone concentrations on the somatotrophic, IGF-I, and IGF-binding protein responses to a three-day intravenous growth hormone-releasing hormone pulsatile infusion in men

We here investigate the potential rescue of the relative hyposomatotropism of aging and obesity by 3-day pulsatile GHRH infusions (i.v. bolus 0.33 microg/kg every 90 min) in 19 healthy men of varying ages (18 to 66 years) and body compositions (12 to 37% total body fat). Baseline (control) and GHRH-driven pulsatile GH secretion (in randomly ordered sessions) were quantitated by deconvolution analysis of 24-h (10-min sampling) serum GH concentration profiles measured in an ultrasensitive (threshold 0.005 microg/l) chemiluminescence assay. GHRH infusion significantly increased the mean (24-h) serum GH concentration (0.3 +/- 0.1 basal vs 2.4 +/- 0.4 microg/l treatment; P = 0.0001), total daily pulsatile GH production rate (21 +/- 9.5 vs 97 +/- 17 microg/l/day; P = 0.01), GH secretory burst frequency (11 +/- 0.5 vs 17 +/- 0.3 events/day; P = <0.01), and mass of GH released per burst (1.1 +/- 0.4 vs 5.9 1 microg/l; P < 0.01), as well as serum IGF-I (261 +/- 33 vs 436 +/- 37 microg/l; P = 0.005), insulin (45 +/- 13 vs 79 +/- 17 mU/l; P = 0.0002), and IGF binding protein (IGFBP)-3 (3320 +/- 107 vs 4320 +/- 114 microg/l; P = 0.001) concentrations, while decreasing IGFBP-1 levels (16 +/- 1.2 vs 14 +/- 0.09 microg/l; P = 0.02). Serum total testosterone and estradiol concentrations did not change. GHRH treatment also reduced the half-duration of GH secretory bursts, and increased the GH half-life. GHRH-stimulated 24-h serum GH concentrations and the mass of GH secreted per burst were correlated negatively with age (R[value]:P[value] = -0.67:0.002 and -0.58:0.009 respectively), and percentage body fat (R:P = -0.80:0.0001 and -0.65:0.0005 respectively), but positively with serum testosterone concentrations (R:P = +0.55:0.016 and +0.53:0.019 respectively). GHRH-stimulated plasma IGF-I increments correlated negatively with age and body mass index, and positively with serum testosterone, but not with percentage body fat. Cosinor analysis disclosed persistent nyctohemeral rhythmicity of GH secretory burst mass (with significantly increased 24-h amplitude and mesor values) but unchanged acrophase during fixed pulsatile GHRH infusions, which suggests that both GHRH- and non-GHRH-dependent mechanisms can modulate the magnitude (but only non-GHRH mechanisms can modulate the timing) of somatotrope secretory activity differentially over a 24-h period. In summary, diminished GHRH action and/or non-GHRH-dependent mechanisms (e.g. somatostatin excess, putative endogenous growth hormone-releasing peptide deficiency etc.) probably underlie the hyposomatotropism of aging, (relative) obesity, and/or hypoandrogenemia. Preserved or increased tissue IGF-I responses to GHRH-stimulated GH secretion (albeit absolutely reduced, suggesting GHRH insensitivity in obesity) may distinguish the pathophysiology of adiposity-associated hyposomatotropism from that of healthy aging.

Serum insulin-like growth factor-binding protein-3 levels in the diagnosis of acromegaly

Insulin-like growth factor-binding protein-3 (IGFBP-3) is a GH-dependent protein that binds insulin-like growth factor-I (IGF-I) in the circulation and modulates its action at the tissue level. Because IGFBP-3 is a stable and specific marker of somatotroph function, we hypothesized that it would be a useful biochemical marker in the diagnosis of patients with acromegaly and the assessment of surgical cure. We, therefore, investigated the sensitivity of serum IGFBP-3 levels to detect GH excess in 44 patients with clinical acromegaly and pathologically confirmed somatotroph adenomas, including a cohort of 18 patients with untreated disease evaluated before transsphenoidal surgery and medical therapy. IGFBP-3 levels were compared to IGF-I and random GH levels before and after transsphenoidal surgery. Concordance among IGFBP-3, IGF-I, and GH suppressibility by glucose was also determined. In addition, the response of IGFBP-3 to glucose suppression was investigated. All 18 patients with untreated acromegaly had elevated serum IGFBP-3 levels, ranging from 4,186-10,026 micrograms/L (mean +/- SD, 6566 [plusm] 1800 micrograms/L). There was no overlap with the age-adjusted normative ranges (P = 0.0001 in patients 18-55 yr old and P = 0.0176 in patients > 55 yr old) or with the levels obtained in age-comparable controls (P = 0.0001). In 11% of untreated patients with clinical findings of acromegaly and a pathologically confirmed adenoma, IG-FBP-3 levels were elevated, although GH was suppressed to less than 2 micrograms/L with glucose. In these patients, IGF-I levels were either normal or minimally elevated and considered nondiagnostic. IGFBP-3 and IGF-I levels were correlated in patients with untreated acromegaly (r = 0.650; P = 0.0162) and after transsphenoidal surgery (r = 0.644; P = 0.0001). Neither IGF-I nor IGFBP-3 correlated with random GH levels before surgery. However, both IGF-I (r = 0.471; P = 0.0001) and IGFBP-3 (r = 0.259; P = 0.041) correlated with random GH levels in patients studied more than 1 month after transsphenoidal surgery. IGFBP-3 and IGF-I levels were concordant with GH suppressibility by glucose (P = 0.0039) and IGFBP-3 decreased with glucose suppression in 7 of 10 patients. These data indicate that IGFBP-3 is a sensitive physiological marker of somatotroph function and is concordant with glucose suppression and IGF-I levels before and after transsphenoidal surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

NIH conference. Insulin-like growth factors in health and disease

The insulin-like growth factor (IGF) family of peptides, binding proteins, and receptors are ubiquitous and important for normal human growth and development. Modern techniques including specific radioimmunoassays, radioreceptor assays and recombinant DNA technology have improved our understanding of the role of IGFs in growth and development. In addition to enhancing our understanding of normal physiology, these techniques assess changes in these hormones, binding proteins, and receptors in pathologic conditions including growth retardation, acromegaly, malnutrition, diabetes, and malignancy. Further, these studies have led to improvement in the assessment of responses to certain therapies used in the treatment of these diseases and may lead to improvements in these therapies.

Platelet-derived growth factor-induced alterations in vinculin distribution in porcine vascular smooth muscle cells

Exposure of porcine vascular smooth muscle cells to platelet-derived growth factor (PDGF; 18-180 ng/ml) but not epidermal growth factor (EGF; 30 ng/ml), somatomedin C (SmC; 30 ng/ml), or insulin (10 microM), results in a rapid, reversible, time- and concentration-dependent disappearance of vinculin staining in adhesion plaques; actin-containing stress fibers also become disrupted following exposure of cells to PDGF. Disappearance of vinculin staining from adhesion plaques is also caused by 12-O-tetradecanoyl-phorbol-13-acetate (TPA; 200-400 nM), though the time course of the disappearance of vinculin staining under these conditions takes longer than in cells exposed to PDGF. The PDGF-induced removal of vinculin from adhesion plaques was inhibited in a concentration-dependent fashion by 8-(N,N-diethylamino) octyl-3,4,5-trimethoxybenzoate (TMB-8; 0.25-4 microM) and leupepetin (2-300 microM), and by n-alpha-tosyl-L-lysine chloromethylketone (TLCK; 100 microM) and trifluoperazine (TFP; 2.5 microM). Addition of PDGF to vascular smooth muscle cells caused a rapid, transient increase in cytosolic free calcium, from a basal resting level of 146 +/- 6.9 nM (SEM, n = 62) to 414 +/- 34 nM (SEM, n = 22) as determined using the calcium-sensitive indicator Fura-2 and Digitized Video Microscopy. This increase in cellular calcium preceded the disappearance of vinculin from adhesion plaques and was partially blocked by pretreatment of cells with TMB-8 but not leupeptin. This rise in cytosolic free calcium was found to occur in approximately 80% of the sample population and displayed both spatial and temporal subcellular heterogeneity. Exposure of cells to TPA (100 nM) did not result in a change in cytosolic free calcium. Both PDGF (20 ng/ml) and TPA (100 nM) caused cytosolic alkalinization which occurred after PDGF-induced disruption of vinculin from adhesion plaques, as determined using the pH-sensitive indicator BCECF and Digitized Video Microscopy. PDGF stimulated DNA synthesis and vinculin disruption in a similar dose-dependent fashion. Both could be inhibited by leupeptin or TMB-8. These results suggest that 1) exposure of vascular smooth muscle cells to PDGF is associated with the disruption of vinculin from adhesion plaques, 2) PDGF-induced vinculin disruption is regulated by an increase in cytosolic calcium (but not cytosolic alkalinization), and involves proteolysis; 3) activation of protein kinase C also causes vinculin removal from adhesion plaques but by a calcium-independent mechanism, and 4) the cellular response to PDGF-stimulated increases in cytosolic free calcium is heterogeneous.(ABSTRACT TRUNCATED AT 400 WORDS)

Program evaluation in epilepsy rehabilitation

The Vocational Services Program of the University of Washington Regional Epilepsy Center is described, and data relating to the first 106 clients who entered the program are examined. A major emphasis of the study was characteristic differences between those clients later competitively employed and program dropouts. Other study purposes related to examining client satisfaction ratings of different aspects of services and establishing whether a relationship existed between seizure occurrences and job loss. Stepwise discriminant function analysis indicated that "months employed in the last 24" appeared to be the stable discriminator between the employed and dropout groups. The group later employed averaged 12 of the prior 24 months in employment, whereas dropouts approximated 7. Associated psychiatric/addictions treatment was initially a key outcome discriminator, but it did not hold up on cross-validation. Subjects were more satisfied with individualized client services (e.g., counseling sessions) than with group activities (e.g., Job Club). As opposed to seizures, emotional/attitudinal difficulties with this rehabilitation population appeared to be the primary reason for job loss. A work adjustment or job station program can be critical for these individuals and others with neurological impairments. The importance of counselor follow-up after the initial job placement is also underscored. This program, with about half of its clients entering unsubsidized jobs, basically replicated the results of other community-oriented epilepsy rehabilitation programs.

Relationship of General Aptitude Test Battery scores to successful employment for epileptics in a rehabilitation setting

The US Employment Service's (USES) General Aptitude Test Battery (GATB), when used with USES-developed cut-off scores, has been found to be an accurate predictor of successful job performance. In the present study, results of the GATB scores obtained by vocational rehabilitation clients (n = 15) who were successfully placed into permanent employment were evaluated with reference to published GATB norms and cut-off scores. The major finding of this study was that the scores were not accurate predictors of successful employment for this population. Subjects' subtest scores averaged between 1/2 and 2 SD below the published means, with scores on subtests measuring motor speed and dexterity producing the lowest values. Subtests measuring verbal and visual--spatial ability produced relatively higher values. In only 3 instances was successful employment predicted by the cut-off scores. For the entire sample, GATB scores were frequently low enough to indicate poor job performance in nearly all occupations covered by published cut-off scores. Based on the results from the present study, and considering the wide-spread use of the GATB in the United States, a more comprehensive research project is being implemented to adapt GATB material for use with the targeted population.

Pure alpha-secreting pituitary adenomas

Isolated hypersecretion of the alpha subunit of the glycoprotein hormones occurred in two men with previously diagnosed "nonfunctioning chromophobe adenomas." The alpha hypersecretion was unresponsive to hypothalamic releasing hormone, thyroid hormone, and sex-steroid hormones. After trans-sphenoidal surgery and conventional pituitary irradiation, alpha secretion was decreased. Increased quantities of immunologically active and biologically inactive luteinizing hormone (LH) material were detected in serum and in tumor homogenate. Immunologic and gel-chromatographic studies determined that only the alpha subunit was present and that it was cross-reacting in the LH immunoassay. These studies suggest that the alpha subunit may be a useful marker of pituitary tumors, particularly in patients without clinical evidence of hormonal hypersecretion.