IGFs and IGFBPs in GH insensitivity

The Multiple Functions of Insulin Put into Perspective: From Growth to Metabolism, and from Well-Being to Disease

Insulin has pleiotropic effects, and is of importance both as a key regulator of glucose metabolism and as a growth factor [...].

Growth and Puberty in Children with Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD) are gastrointestinal tract pathologies of unknown etiology; they have an alternating trend, with active and silent phases. IBD are classified in two main forms: ulcerative colitis (UC) and Crohn’s disease (CD). Both have chronic and recurrent course, gastrointestinal symptoms, and extraintestinal manifestations. The altered immune response role seems to be important both in UC and CD. In the majority of cases, CD begins with abdominal pain, diarrhea, decrease in appetite, and weight loss; there can be also perianal fistulas, rhagades, and perianal recurrent abscesses. In addition, retarded growth and delayed puberty can precede the development of the disease or can even be predominant at onset. Growth retardation is found in 40% of IBD patients, but the underlying mechanism of this and other extra-intestinal manifestations are partially known: the main hypotheses are represented by malnutrition and inflammatory response during the active phase of the disease. The increased level of pro-inflammatory cytokines can influence growth, but also the onset of puberty and its progression. In addition, it could be essential to clarify the role and the possible effects of all the currently used treatments concerning growth failure and delayed puberty.

Growth and the Growth Hormone-Insulin Like Growth Factor 1 Axis in Children With Chronic Inflammation: Current Evidence, Gaps in Knowledge, and Future Directions

Growth failure is frequently encountered in children with chronic inflammatory conditions like juvenile idiopathic arthritis, inflammatory bowel disease, and cystic fibrosis. Delayed puberty and attenuated pubertal growth spurt are often seen during adolescence. The underlying inflammatory state mediated by proinflammatory cytokines, prolonged use of glucocorticoid, and suboptimal nutrition contribute to growth failure and pubertal abnormalities. These factors can impair growth by their effects on the GH-IGF axis and also directly at the level of the growth plate via alterations in chondrogenesis and local growth factor signaling. Recent studies on the impact of cytokines and glucocorticoid on the growth plate further advanced our understanding of growth failure in chronic disease and provided a biological rationale of growth promotion. Targeting cytokines using biological therapy may lead to improvement of growth in some of these children, but approximately one-third continue to grow slowly. There is increasing evidence that the use of relatively high-dose recombinant human GH may lead to partial catch-up growth in chronic inflammatory conditions, although long-term follow-up data are currently limited. In this review, we comprehensively review the growth abnormalities in children with juvenile idiopathic arthritis, inflammatory bowel disease, and cystic fibrosis, systemic abnormalities of the GH-IGF axis, and growth plate perturbations. We also systematically reviewed all the current published studies of recombinant human GH in these conditions and discussed the role of recombinant human IGF-1.

Growth problems in children with IBD

Crohn's disease in childhood causes linear growth retardation, which has a substantial effect on management of this disease. By contrast, growth is rarely a problem in children presenting with ulcerative colitis. Depending on how growth failure is defined, approximately one-third of children with Crohn's disease have growth retardation at diagnosis. Although corticosteroids can suppress growth, decreased height at diagnosis demonstrates that this finding is a consequence of the disease and not merely an adverse effect of treatment. Both inflammation and undernutrition contribute to decreased height velocity. Increased cytokine production acts both on the hepatic expression of insulin-like growth factor 1 (IGF-1) and at chondrocytes of the growth plates of long bones. Growth hormone insensitivity caused by deranged immune function is a major mechanism in growth retardation. Resolution of inflammation is the cornerstone of treatment, but current studies on growth hormone and IGF-1 might yield therapies for those children whose inflammation is refractory to treatment.

Diagnosis of endocrine disease: limitations of the IGF1 generation test in children with short stature

The IGF1 generation test (IGFGT) is often used during the assessment of suspected GH insensitivity (GHI). We report the results of a survey undertaken in 2010 to determine the use of IGFGT amongst members of the European Society for Paediatric Endocrinology to evaluate suspected GHI. The literature surrounding the usefulness and limitations of IGFGT are reviewed, and recommendations provided for its use. Of 112 paediatric endocrinologists from 30 countries who responded to the survey, 91 (81%) reported that they had used the IGFGT in the previous 2 years; >10 IGFGT protocols were used. The IGFGT impacted treatment decisions for 97% of the respondents and was a prerequisite for recombinant human IGF1 treatment for 45% of respondents. From a literature review, sensitivity of the IGFGT was evaluated as 77-91% in molecularly proven cases of GHI; specificity was ≤97%, depending on the protocol. The positive predictive value of the IGFGT is likely to be low, as the frequency of normality is predictably higher than that of abnormality in GH signalling. Given the limitations of the IGFGT in the most severe cases of GHI syndrome (GHIS), the ability of the IGFGT to detect less severe GHIS is doubtful. In a pragmatic approach, the IGFGT may not be useful for the diagnosis of GHIS.

STAT5b deficiency: lessons from STAT5b gene mutations

Growth hormone (GH) regulates insulin-like growth factor (IGF)-I production primarily through activation of the GH receptor (GHR)-signal transducer and activator of transcription (STAT)-5b signaling cascade. One of four STAT proteins (STAT1, -3, -5a and -5b) activated by the GH-GHR system, the critical importance of STAT5b in IGF-I production became evident with the identification of homozygous, autosomal recessive STAT5b mutations in patients who presented with severe postnatal growth failure, growth hormone insensitivity syndrome (GHIS) and marked IGF-I deficiency. Unlike GHIS due to GHR mutations, patients carrying STAT5b mutations also presented with chronic pulmonary disease and evidence of perturbations of T-cell homeostasis. At present, no single treatment(s) is available to improve both poor statural growth and immune deficiency. Continued clinical evaluations of patients with STAT5b mutations and elucidating the impact of the mutation on STAT5b structure and function, are important to understanding the pathophysiology of this rare, complex, disease (MIM 245590).

The rationale and development of therapeutic insulin-like growth factor axis inhibition for lung and other cancers

The insulin-like growth factor (IGF) axis involves elements of endocrine, paracrine, and autocrine control. It is centrally involved in normal development and growth. Core signaling is driven through the IGF-1 receptor (IGF-1R) in either homo-multimeric complexes or hetero-multimeric complexes with the insulin receptor (IR). Signaling is affected by a large number of upstream and downstream factors, including the differential expression of various intracellular IR substrates, a range of stimulatory ligands (insulin, IGF-1, and IGF-2), the expression of specific clearance receptors (eg, IGF-2R), and different IGF-binding proteins. Considerable evidence exists to implicate aspects of the IGF axis in the development and maintenance of many different nonneoplastic and neoplastic diseases, including both small-cell lung cancer and non-small-cell lung cancer (NSCLC). A large number of different anticancer strategies directed against the IGF axis are being developed. Monoclonal antibodies directed against the IGF-1R are the furthest advanced clinically. Hyperglycemia appears to be a class effect. To date, the major difference among the antibodies used in clinical trials seems to be their plasma half-lives, leading to a number of different administration regimens being taken forward. Early signals of monotherapy activity have been notably reported in patients with Ewing sarcoma and in several other cancers. Encouraging increases in the NSCLC response rate have already been reported after the addition of an anti-IGF-1R antibody to first-line carboplatin and paclitaxel. Explorations of aspects of ligands, binding proteins, receptors, and receptor substrates are all ongoing to identify potential biomarkers predictive of benefit from IGF axis intervention.

Insulin-like growth factor-I in growth and metabolism

Deficiency of insulin-like growth factor-I (IGF-I) results in growth failure. A variety of molecular defects have been found to underlie severe primary IGF-I deficiency (IGFD), in which serum IGF-I concentrations are substantially decreased and fail to respond to GH therapy. Identification of more patients with primary or secondary IGFD is likely with investigative and diagnostic progress, particularly in the assessment of children with idiopathic short stature. Diagnosis of IGFD requires accurate and reliable IGF-I assays, adequate normative data for reference, and knowledge of IGF-I physiology for proper interpretation of data. Recombinant human IGF-I (rhIGF-I) treatment improves stature in patients with severe primary IGFD, and has also been shown to improve glycaemic control and insulin sensitivity in patients with severe insulin resistance. Ongoing studies of patients receiving rhIGF-I will allow further evaluation of the clinical utility of this treatment, with concurrent increase in our understanding of IGF-I and conditions of IGFD.

Profile of mecasermin for the long-term treatment of growth failure in children and adolescents with severe primary IGF-1 deficiency

Growth hormone insensitivity syndrome (GHI) or insulin-like growth factor-1 (IGF-1) deficiency (IGFD) is characterized by deficit of IGF-1 production due to alteration of response of growth hormone (GH) receptor to GH. This syndrome is due to mutation of GH receptor or IGF-1 gene and patients affected showed no response to GH therapy. The only treatment is recombinant IGF-1 (mecasermin), which has been available since 1986, but approved in the United States by the US Food and Drug Administration only in 2005 and in Europe by the European Medicines Agency in 2007. To date, few studies are available on long-term treatment with mecasermin in IGFD patients and some of them have a very small number of subjects. In this review we discuss briefly clinical features of severe primary IGFD, laboratory findings, and indications for treatment. Results of long-term therapy with rhIGF1 (mecasermin) in patients affected by severe primary IGFD and possible side effects are explained.

The IGF system and cytokine interactions and relationships with longitudinal growth in prepubertal patients with cystic fibrosis

OBJECTIVE

Growth delay is a feature of patients with cystic fibrosis (CF). CF is a condition characterized by chronic inflammation that has been shown to modify the IGF system, which is essential for normal growth, and is related to pulmonary function in CF patients. We aimed to verify whether circulating levels of tumour necrosis factor (TNF)-alpha, interleukin (IL)-6, insulin and the IGF system were related and/or had relationships with linear growth in children with CF.

DESIGN AND PATIENTS

Seventeen prepubertal CF patients (nine males and eight females) in a stable clinical condition were enrolled. Auxological parameters, pulmonary function and the Shwachman-Kulczycki (S-K) score were assessed, and serum samples were drawn at baseline and after 12 months.

MEASUREMENTS

TNF-alpha, IL-6, IGF-I, IGF-II, IGFBP-1, IGFBP-2, IGFBP-3 and insulin were assayed using specific commercial kits.

RESULTS

At baseline, TNF-alpha serum concentration was related to serum IGF-I concentration (R = 0.53), IGF-II bioactivity (IGF-II/IGFBP-3 molar ratio, R = +0.52) and insulin concentration (R = +0.63). Changes in serum IL-6 and IGFBP-2 concentrations during the 12-month observation were positively correlated (R = +0.63). Changes in height standard deviation score (Ht SDS) were correlated with IGF-I serum concentrations at baseline (R =+0.67) and after 12 months (R = +0.70), with IGF-I bioavailability and with IGFBP-1 serum concentrations (R = -0.88). Body mass index (BMI) SDS correlated with IGF bioavailability.

CONCLUSIONS

This study showed a relationship between inflammatory status and the IGF system, and an effect of these interactions on longitudinal growth. Moreover, a role for insulin in growth was identified. Better control of inflammation and preservation of insulin secretion could benefit these patients.

[Short stature investigation: clinical, laboratorial and genetic aspects concerning the growth hormone insensitivity (GHI)]

It is reported in this study the clinical, laboratory and genetic aspects of short stature investigation with emphasis to the diagnostic approach of growth hormone insensitivity (GHI). This patient in case presented typical clinical features of GHI and his laboratory findings at prepubertal age were typical of those observed in GHI patients (low IGF-1 and IGFBP-3 levels, with high basal and stimulated GH levels). However, during the puberty, he presented normal IGFBP-3 and IGF-1 levels that hindered the diagnosis. The molecular study disclosed a mutation in exon 7 of growth hormone receptor gene (S226I). The steps that demonstrated the causative effect of this mutation are shown here, and also a review of Brazilian GHI cases is given and new molecular defects in this field are discussed as well.

High insulinlike growth factor binding protein 1 level predicts incident congestive heart failure in the elderly

BACKGROUND

Low levels of insulinlike growth factor 1 (IGF-I) may influence the development of age-related cardiovascular diseases including congestive heart failure (CHF). Insulinlike growth factor binding protein 1 (IGFBP-1), which increases during catabolic states and inhibits anabolic IGF-I effects, is increased in patients with CHF and has been associated prospectively with increased mortality among older adults and survivors of myocardial infarction. We investigated the association between fasting plasma levels of IGF-I, IGFBP-1, IGFBP-3, and insulin and risk of incident CHF in the prospective Cardiovascular Health Study.

METHODS

From among 5,888 adults 65 years old and older in the Cardiovascular Health Study, we studied 566 incident CHF cases and 1,072 comparison subjects after exclusion of underweight individuals (body mass index <18.5 kg/m(2)) and insulin users. Hazard ratios (HRs) with 95% CIs for CHF were estimated after adjustment for age, race, sex, hypertension, systolic blood pressure, lipid levels, left ventricular hypertrophy, coronary disease, C-reactive protein, health status, diabetes, and body mass index.

RESULTS

High baseline IGFBP-1 level was a significant predictor of CHF, independent of established CHF risk factors and inflammation markers. The HR per SD of IGFBP-1 was 1.22 (95% CI 1.07-1.39, P < .01). Relative to the lowest IGFBP-1 tertile, the HR was 1.29 (95% CI 0.96-1.74, P = .09) for the second IGFBP-1 tertile and 1.47 (95% CI 1.06-2.04; P = .02) for the highest IGFBP-1 tertile (tertile cut points 19.5 and 35.8 ng/mL). Total IGF-I, IGFBP-3, or insulin levels had no association with CHF after adjustment for CHF risk factors.

CONCLUSIONS

High circulating IGFBP-1 level may be a CHF risk factor among older adults.

Short stature and decreased insulin-like growth factor I (IGF-I)/growth hormone (GH)-ratio in an adult GH-deficient patient pointing to additional partial GH insensitivity due to a R179C mutation of the growth hormone receptor

OBJECTIVE

Genetic factors play an expanding role in understanding growth hormone (GH) disorders, therefore the German KIMS Pharmacogenetics Study was initiated with the aim of genotyping various GH-/IGF-I-axis-related genes of GH-deficient adult patients to investigate genotype:phenotype relationships and response to GH therapy.

PATIENTS AND METHODS

129 consecutively enrolled GH-deficient adult patients were genotyped for variant 1 (V1) of the alternatively spliced noncoding exons in the 5'-untranslated region and for the nine coding exons of the GH receptor (GHR) gene, which obviously play a striking role in the function of the GH-IGF-I-axis. After detection of a heterozygous, non-synonymous mutation R179C in exon 6 in one single patient with acquired GH-deficiency (GHD) in late adulthood, analysis of her clinical data followed, leading to the diagnosis of mild short stature (-1.5SD). For further endocrine evaluation, five pituitary stimulation tests (arginine) of this patient were statistically compared to stimulation tests (arginine) of ten GH-deficient control patients, retrospectively.

RESULTS

The formerly in patients with Laron syndrome and idiopathic short stature reported mutation R179C leads to an amino acid change from an arginine residue (codon CGC) to a cysteine residue (codon TGC) in position 179 of the extracellular domain of the GHR. Statistical analysis revealed significant decreased IGF-I/GH(0) ratio (p=0.004) and IGF-I/GH(max) ratio (p=0.001) of the index patient compared to the control patients, implying growth hormone resistance of the index patient at the level of the GHR, according to the detected R179C mutation.

CONCLUSIONS

This study reports on the unusual case of a patient with mild short stature, who acquired GHD in late adulthood due to a non-secreting pituitary adenoma and get additionally diagnosed for pre-existing growth hormone insensitivity due to a formerly in two short statured patients described, single, heterozygous, non-synonymous mutation in the GHR. Our findings support the theory that heterozygous mutations in the GHR gene can have mild phenotypical consequences.

Growth hormone receptor gene mutations in two Italian patients with Laron Syndrome

Laron Syndrome (LS) represents a condition characterized by GH insensitivity caused by molecular defects in the GH receptor (GHR) gene or in the post-receptor signalling pathway. We report the molecular characterization of two unrelated Italian girls from Sicily diagnosed with LS. The DNA sequencing of the GHR gene revealed the presence of different nonsense mutations, occurring in the same background haplotype. The molecular defects occurred in the extracellular domain of the GHR leading to a premature termination signal and to a truncated non-functional receptor. In one patient, a homozygous G to T transversion, in exon 6, led to the mutation GAA to TAA at codon 180 (E180X), while in the second patient a homozygous C to T transition in exon 7 was detected, causing the CGA to TAA substitution at codon 217 (R217X). Both probands presented the polymorphisms Gly168Gly and Ile544Leu in a homozygous state in exons 6 and 10, respectively. The E180X represents a novel defect of the GHR gene, while the R217X mutation has been previously reported in several patients from different ethnic backgrounds but all from countries located in the Mediterranean and Middle Eastern region.

Growth hormone insensitivity and severe short stature in siblings: a novel mutation at the exon 13-intron 13 junction of the STAT5b gene

BACKGROUND/AIMS

Growth hormone insensitivity (GHI) is characterized by severe short stature, high serum growth hormone (GH), low serum IGF-I and IGFBP-3 levels and is classically associated with genetic defects of the GH receptor (GHR). Recently, mutations of the STAT5b gene have been identified and shown to be associated with GHI and severe IGF deficiency. We investigated 2 sisters from a consanguineous family from Kuwait, with clinical and biochemical features of GHI, in whom no molecular defects in the GHR were identified.

METHODS

Serum and DNA were analyzed.

RESULTS

In addition to GHI, siblings 2 and 1 presented with, respectively, a diagnosis of juvenile idiopathic arthritis and recurrent pulmonary infections. Molecular analysis of the STAT5b gene revealed a novel homozygous deletion of a G at the junction of exon 13-intron 13. The parents, who are of normal height, were heterozygous for the mutation.

CONCLUSIONS

This is the first STAT5b defect to be identified in siblings, further supporting the autosomal recessive mode of transmission of STAT5b deficiency. The results affirm that defective STAT5b is an etiology for IGF deficiency and the GHI phenotype, and emphasize the importance of considering this diagnosis in patients with IGF deficiency, especially when associated with diverse immunological problems.

Long-term treatment with recombinant insulin-like growth factor (IGF)-I in children with severe IGF-I deficiency due to growth hormone insensitivity

CONTEXT

Children with severe IGF-I deficiency due to congenital or acquired defects in GH action have short stature that cannot be remedied by GH treatment.

OBJECTIVES

The objective of the study was to examine the long-term efficacy and safety of recombinant human IGF-I (rhIGF-I) therapy for short children with severe IGF-I deficiency.

DESIGN

Seventy-six children with IGF-I deficiency due to GH insensitivity were treated with rhIGF-I for up to 12 yr under a predominantly open-label design.

SETTING

The study was conducted at general clinical research centers and with collaborating endocrinologists.

SUBJECTS

Entry criteria included: age older than 2 yr, sd scores for height and circulating IGF-I concentration less than -2 for age and sex, and evidence of resistance to GH.

INTERVENTION

rhIGF-I was administered sc in doses between 60 and 120 microg/kg twice daily.

MAIN OUTCOME MEASURES

Height velocity, skeletal maturation, and adverse events were measured.

RESULTS

Height velocity increased from 2.8 cm/yr on average at baseline to 8.0 cm/yr during the first year of treatment (P < 0.0001) and was dependent on the dose administered. Height velocities were lower during subsequent years but remained above baseline for up to 8 yr. The most common adverse event was hypoglycemia, which was observed both before and during therapy. It was reported by 49% of treated subjects. The next most common adverse events were injection site lipohypertrophy (32%) and tonsillar/adenoidal hypertrophy (22%).

CONCLUSIONS

Treatment with rhIGF-I stimulates linear growth in children with severe IGF-I deficiency due to GH insensitivity. Adverse events are common but are rarely of sufficient severity to interrupt or modify treatment.

Genetic, physiologic and ecogeographic factors contributing to variation in Homo sapiens: Homo floresiensis reconsidered

A new species, Homo floresiensis, was recently named for Pleistocene hominid remains on Flores, Indonesia. Significant controversy has arisen regarding this species. To address controversial issues and refocus investigations, I examine the affinities of these remains with Homo sapiens. Clarification of problematic issues is sought through an integration of genetic and physiological data on brain ontogeny and evolution. Clarification of the taxonomic value of various 'primitive' traits is possible given these data. Based on this evidence and using a H. sapiens morphological template, models are developed to account for the combination of features displayed in the Flores fossils. Given this overview, I find substantial support for the hypothesis that the remains represent a variant of H. sapiens possessing a combined growth hormone-insulin-like growth factor I axis modification and mutation of the MCPH gene family. Further work will be required to determine the extent to which this variant characterized the population.

Adaptive stress response in segmental progeria resembles long-lived dwarfism and calorie restriction in mice

How congenital defects causing genome instability can result in the pleiotropic symptoms reminiscent of aging but in a segmental and accelerated fashion remains largely unknown. Most segmental progerias are associated with accelerated fibroblast senescence, suggesting that cellular senescence is a likely contributing mechanism. Contrary to expectations, neither accelerated senescence nor acute oxidative stress hypersensitivity was detected in primary fibroblast or erythroblast cultures from multiple progeroid mouse models for defects in the nucleotide excision DNA repair pathway, which share premature aging features including postnatal growth retardation, cerebellar ataxia, and death before weaning. Instead, we report a prominent phenotypic overlap with long-lived dwarfism and calorie restriction during postnatal development (2 wk of age), including reduced size, reduced body temperature, hypoglycemia, and perturbation of the growth hormone/insulin-like growth factor 1 neuroendocrine axis. These symptoms were also present at 2 wk of age in a novel progeroid nucleotide excision repair-deficient mouse model (XPD^G602D/R722W/XPA^−/−) that survived weaning with high penetrance. However, despite persistent cachectic dwarfism, blood glucose and serum insulin-like growth factor 1 levels returned to normal by 10 wk, with hypoglycemia reappearing near premature death at 5 mo of age. These data strongly suggest changes in energy metabolism as part of an adaptive response during the stressful period of postnatal growth. Interestingly, a similar perturbation of the postnatal growth axis was not detected in another progeroid mouse model, the double-strand DNA break repair deficient Ku80^−/− mouse. Specific (but not all) types of genome instability may thus engage a conserved response to stress that evolved to cope with environmental pressures such as food shortage.

Oxidative damage to cellular components, including fats, proteins, and DNA, is an inevitable consequence of cellular energy use and may underlie both normal and pathological aging. Calorie restriction delays the aging process and extends lifespan in a number of lower organisms including rodents. Inborn defects in the postnatal growth axis resulting in dwarfism can also extend lifespan. Both may function via overlapping pathways impacting on energy metabolism. Here, we report a novel DNA repair-deficient mouse model with symptoms of the related premature aging disorders Cockayne syndrome and trichothiodystrophy, namely reduced fat deposits, neurological dysfunction, failure to thrive, and reduced lifespan. Surprisingly, we also observed traits usually associated with extended longevity as found in calorie restriction and dwarfism, including reduced blood sugar and reduced insulin-like growth factor-1. These characteristics were present at 2 wk of age, that is, during the period of rapid postnatal development, but returned to normal by sexual maturation at 10 wk. Furthermore, they were absent altogether in another premature aging mouse model with a distinct DNA repair defect. Specific types of unrepaired DNA damage may thus elicit a preservative organismal response affecting energy metabolism that is similar to the one that evolved to cope with the stress of food shortage.

Growth hormone, VEGF and FGF: involvement in rheumatoid arthritis

Adult rheumatoid arthritis (RA), a systemic autoimmune disorder of unknown etiology, is characterized by dysfunctional cellular and humoral immunity, enhanced migration and attachment of peripheral macrophages and pro-inflammatory leukocytes to the synovium and articular cartilage of diarthrodial joints. The progressive destruction of cartilage and bone in RA is a result of elevated pro-inflammatory cytokine gene expression, synovial neovascularization, proteinase-mediated dissolution of articular cartilage matrix and osteoclast-mediated subchondral bone resorption. Juvenile chronic arthritis (JCA) is disease with manifestations similar to adult RA that occurs in childhood. JCA usually causes precocious joint destruction and often also presents with evidence of growth plate anomalies and reduced stature. Three proteins play an integral role in both adult RA and JCA. These are somatotropin (also called pituitary growth hormone (GH)), vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF). GH is responsible for regulating long bone growth and skeletal maturation through its capacity to stimulate insulin-like growth factor-I (IGF-1) synthesis by hepatocytes. Mechanisms responsible for growth plate disturbances and short stature in children with JCA include deficient GH production, GH-insensitivity resulting from defects in the GH receptor, suppressed IGF-1 synthesis or neutralization of IGF-1 action by IGF-1 binding proteins (IGFBPs). In addition, GH has also been implicated in perpetuating inflammation and pain in adult RA. VEGF has been shown to be the critical angiogenesis factor responsible for vascular proliferation and blood vessel invasion of the synovial lining membrane in RA. Acidic FGF (FGF-1) and basic FGF (FGF-2) have also been implicated in aberrant synoviocyte proliferation (i.e. synovial hyperplasia) and apoptosis resistance in adult RA.