Role of the Growth Hormone/Insulin-like Growth Factor-1 Paracrine Axis in Rheumatic Diseases

Growth hormone-receptor disruption in mice reduces osteoarthritis and chondrocyte hypertrophy

Excessive growth hormone (GH) has been shown to promote joint degeneration in both preclinical and clinical studies. Little is known about the effect of disrupted GH or GH receptor (GHR) on joint health. The goal of this study is to investigate joint pathology in mice with either germline (GHR-/-) or adult inducible (iGHR-/-) GHR deficiency. Knee joints from male and female GHR-/- and WT mice at 24 months of age were processed for histological analysis. Also, knee joints from male and female iGHR-/- and WT mice at 22 months of age were scanned by micro-CT (μCT) for subchondral bone changes and characterized via histology for cartilage degeneration. Joint sections were also stained for the chondrocyte hypertrophy marker, COLX, and the cartilage degeneration marker, ADAMTS-5, using immunohistochemistry. Compared to WT mice, GHR-/- mice had remarkably smooth articular joint surfaces and an even distribution of proteoglycan with no signs of degeneration. Quantitatively, GHR-/- mice had lower OARSI and Mankin scores compared to WT controls. By contrast, iGHR-/- mice were only moderately protected from developing aging-associated OA. iGHR-/- mice had a significantly lower Mankin score compared to WT. However, Mankin scores were not significantly different between iGHR-/- and WT when males and females were analyzed separately. OARSI scores did not differ significantly between WT and iGHR-/- in either individual or combined sex analyses. Both GHR-/- and iGHR-/- mice had fewer COLX+ hypertrophic chondrocytes compared to WT, while no significant difference was observed in ADAMTS-5 staining. Compared to WT, a significantly lower trabecular thickness in the subchondral bone was observed in the iGHR-/- male mice but not in the female mice. However, there were no significant differences between WT and iGHR-/- mice in the bone volume to total tissue volume (BV/TV), bone mineral density (BMD), and trabecular number in either sex. This study identified that both germline and adult-induced GHR deficiency protected mice from developing aging-associated OA with more effective protection in GHR-/- mice.

Circular RNAs: Potential biomarkers and therapeutic targets for autoimmune diseases

The outcomes and prognosis of autoimmune diseases depend on early diagnosis and effective treatments. However, symptoms of early autoimmune diseases are often remarkably similar to many inflammatory diseases, leading to difficulty in precise diagnosis. Circular RNAs (circRNAs) belong to a novel class of endogenous RNAs, functioning as microRNA (miRNA) sponges or participating in protein coding. It has been shown in many studies that patients with autoimmune diseases have aberrant circRNA expression in liquid biopsy samples (such as plasma, saliva, and urine). Thus, circRNAs are potential biomarkers for the diagnosis and prognosis of autoimmune diseases. Moreover, overexpression and depletion of target circRNAs can be utilized as possible therapeutic approaches for treating autoimmune diseases. In this review, we summarized recent progress in the roles of circRNAs in the pathogenesis of autoimmune diseases, including rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, and type 1 diabetes. We also discussed their potential as biomarkers and therapeutic targets.

Insulin-like Growth Factor-1 (IGF-1) Related Drugs in Pain Management

Objective. The aim of this review is to explore the role of IGF-1 and IGF-1R inhibitors in pain-related conditions and assess the effectiveness of IGF-1-related drugs in pain management. Specifically, this paper investigates the potential involvement of IGF-1 in nociception, nerve regeneration, and the development of neuropathic pain. Methods. We conducted a search of the PUBMED/MEDLINE database, Scopus, and the Cochrane Library for all reports published in English on IGF-1 in pain management from origination through November 2022. The resulting 545 articles were screened, and 18 articles were found to be relevant after reading abstracts. After further examination of the full text of these articles, ten were included in the analysis and discussion. The levels of clinical evidence and implications for recommendations of all the included human studies were graded. Results. The search yielded 545 articles, of which 316 articles were deemed irrelevant by reading the titles. There were 18 articles deemed relevant after reading abstracts, of which 8 of the reports were excluded due to lack of IGF-1-related drug treatment after reviewing the full text of the articles. All ten articles were retrieved for analysis and discussion. We found that IGF-1 may have several positive effects on pain management, including promoting the resolution of hyperalgesia, preventing chemotherapy-induced neuropathy, reversing neuronal hyperactivity, and elevating the nociceptive threshold. On the other hand, IGF-1R inhibitors may alleviate pain in mice with injury of the sciatic nerve, bone cancer pain, and endometriosis-induced hyperalgesia. While one study showed marked improvement in thyroid-associated ophthalmopathy in humans treated with IGF-1R inhibitor, two other studies did not find any benefits from IGF-1 treatment. Conclusions. This review highlights the potential of IGF-1 and IGF-1R inhibitors in pain management, but further research is needed to fully understand their efficacy and potential side effects.

Can an Aerobic Exercise Programme Improve the Response of the Growth Hormone in Fibromyalgia Patients? A Randomised Controlled Trial

Downgrade alterations in the growth hormone (GH) might be involved in the development of some of the fibromyalgia syndrome (FMS) symptoms. Our aim was to assess the effects of an aerobic exercise programme on the GH levels in patients with FMS. A randomised controlled trial was developed. Sixty-four Spanish women with FMS were randomly assigned to the experimental arm (n = 33) and treated with a 16-week group physical exercise programme based on low impact aerobic dance (three weekly sessions, one-hour each), or to the treatment-as-usual (TAU) control arm (n = 31). The primary outcome was the GH response to acute exercise. Secondary outcomes were GH basal, sensitivity to pain, body composition, aerobic capacity, and quality of life. The ANCOVA results showed a moderate effect of treatment improving the GH response to acute exercise. Other effects were substantial for aerobic capacity, quality of life, and body composition. Pre-intervention GH response to acute exercise was related to improvements in aerobic capacity and quality of life. An aerobic exercise programme may improve the response of the GH, aerobic capacity, body composition, and quality of life in women with FMS. The normalization of neuro-hormonal patterns involving the GH might be key for improving some FMS symptoms.

Mechanisms of bone pain: Progress in research from bench to bedside

The field of research on pain originating from various bone diseases is expanding rapidly, with new mechanisms and targets asserting both peripheral and central sites of action. The scope of research is broadening from bone biology to neuroscience, neuroendocrinology, and immunology. In particular, the roles of primary sensory neurons and non-neuronal cells in the peripheral tissues as important targets for bone pain treatment are under extensive investigation in both pre-clinical and clinical settings. An understanding of the peripheral mechanisms underlying pain conditions associated with various bone diseases will aid in the appropriate application and development of optimal strategies for not only managing bone pain symptoms but also improving bone repairing and remodeling, which potentially cures the underlying etiology for long-term functional recovery. In this review, we focus on advances in important preclinical studies of significant bone pain conditions in the past 5 years that indicated new peripheral neuronal and non-neuronal mechanisms, novel targets for potential clinical interventions, and future directions of research.

Musculoskeletal Effects of Altered GH Action

Growth hormone (GH) is a peptide hormone that can signal directly through its receptor or indirectly through insulin-like growth factor 1 (IGF-1) stimulation. GH draws its name from its anabolic effects on muscle and bone but also has distinct metabolic effects in multiple tissues. In addition to its metabolic and musculoskeletal effects, GH is closely associated with aging, with levels declining as individuals age but GH action negatively correlating with lifespan. GH’s effects have been studied in human conditions of GH alteration, such as acromegaly and Laron syndrome, and GH therapies have been suggested to combat aging-related musculoskeletal diseases, in part, because of the decline in GH levels with advanced age. While clinical data are inconclusive, animal models have been indispensable in understanding the underlying molecular mechanisms of GH action. This review will provide a brief overview of the musculoskeletal effects of GH, focusing on clinical and animal models.

Serum IGF-1 in patients with rheumatoid arthritis: correlation with disease activity

Objective

Insulin-like growth factor (IGF)-1 participates in modulating immunity and inflammation. Its bioactivity is controlled by six IGF-binding proteins (IGFBP-1 to IGFBP-6). In particular, the IGFBP-3 level is reportedly linked to the disease activity of rheumatoid arthritis (RA), consistent with our previous study. Therefore, the present study aimed to reproduce the previous results.

Results

The serum IGFBP-3 level was not significantly different among the three groups according to disease activity based on the DAS28-ESR/CRP (p > 0.05) but was significantly different between the low- and high-disease-activity groups based on the DAS28-CRP (p = 0.036). Meanwhile, the interleukin-6 (IL-6) level moderately correlated with DAS28-CRP (Spearman’s rho = 0.583, p < 0.001).

Macrophages are activated in the rat anterior pituitary under chronic inflammatory conditions

In the anterior lobe of the pituitary gland (AP), non-endocrine cells regulate hormone secretion by endocrine cells. However, the functions of non-endocrine cells in the AP during chronic pain are largely unclear. Here, we show that macrophages, but not folliculostellate (FS) cells, were selectively increased in the AP in the complete Freund's adjuvant (CFA)-induced chronic inflammatory pain model in rats. In addition, IL-1β expression was increased in the AP, and the IL-1β-immunopositive cells were identified as macrophages. On the other hand, increased macrophage density and IL-1β expression were not detected in a neuropathic pain model induced by partial sciatic nerve ligation (PSL). Furthermore, we found c-Fos expression specifically in the somatotrophs under the chronic inflammatory pain condition. Because IL-1β promotes growth hormone (GH) synthesis and release, our results suggest that AP macrophage contributes to GH release through IL-1βduring chronic inflammatory pain.　.

Local Injection of Growth Hormone for Temporomandibular Joint Osteoarthritis

PURPOSE

Osteoarthritis (OA) of the temporomandibular joint (TMJ) elicits cartilage and subchondral bone defects. Growth hormone (GH) promotes chondrocyte growth. The aim of this study was to evaluate the efficacy of intra-articular injections of GH to treat TMJ-OA.

MATERIALS AND METHODS

Monosodium iodoacetate (MIA) was used to induce OA in the TMJs of rats. After confirming the induction of OA, recombinant human GH was injected into the articular cavities of rats. Concentrations of GH and IGF-1 were measured in the blood and synovial fluid, and OA grades of cartilage and subchondral bone degradation were recorded by histological examination and micro-computed tomography.

RESULTS

MIA-induced OA in the rat TMJ upregulated insulin-like growth factor-1 (IGF-1) rather than GH levels. GH and IGF-1 concentrations were increased after local injection of GH, compared with controls. Locally injected GH lowered osteoarthritic scores in the cartilage and subchondral bone of the TMJ.

CONCLUSION

Intra-articular injection of GH improved OA scores in rat TMJs in both cartilage and subchondral bone of the condyles without affecting condylar bone growth. These results suggest that intra-articular injection of human GH could be a suitable treatment option for TMJ-OA patients in the future.

Circulating Insulin-like Growth Factor-1 Levels in Patients with Rheumatoid Arthritis: A Meta-analysis

BACKGROUND AND OBJECTIVES

Insulin-like growth factor-1 (IGF-1) levels have been investigated in rheumatoid arthritis (RA), however, produced inconsistent results. The purpose of this meta-analysis was to derive a more precise conclusion about serum/plasma IGF-1 levels in RA patients.

METHODS

PubMed, Embase and the Cochrane Library databases were searched up to December 2018 in English, and the studies comparing serum/plasma IGF-1 levels between RA group and healthy control group were what we are interested in. The Newcastle-Ottawa Scale (NOS) was used to assess the methodological quality of the included studies. The heterogeneity test was performed by the Cochrane Q statistic and I2 -statistic. The publication bias was evaluated by the funnel plot and Egger's test. The standard mean difference (SMD) with 95% confidence interval (CI) was calculated by the fixed-effects or random-effects model.

RESULTS

A total of eleven articles with 334 cases and 261 controls were finally included. Compared with the healthy group, the RA group had lower circulating IGF-1 levels (pooled SMD= -0.936, 95% CI= -1.382 to -0.489, p<0.001). The subgroup analysis showed that RA patients from Asia (SMD= -0.645, 95% CI= -1.063 to -0.228, p= 0.002) and Europe (SMD= -1.131, 95% CI= -1.767 to -0.495, p<0.001) had lower circulating IGF-1 levels, no significant difference in plasma/serum IGF-1 levels was observed in RA patients from America. Sensitivity analysis indicated the stability and credibility of the overall effect sizes.

CONCLUSION

Patients with RA have lower circulating IGF-1 level than healthy controls, particularly for patients from Asia and Europe. Further studies are necessary to elucidate the role of IGF-1 in the pathological process of RA.

A Systematic Review of Growth Hormone in Pain Medicine: From Rodents to Humans

Objective

Growth hormone (GH) and GH-related signaling molecules play an important role in nociception and development of chronic pain. This review aims to examine the potential molecular mechanisms through which GH-related signaling modulates sensory hypersensitivity in rodents, the clinical pharmacology of GH, and the clinical evidence of GH treatment for several common pain syndromes.

Methods

A search was conducted using the PUBMED/MEDLINE database, Scopus, and the Cochrane library for all reports published in English on GH in pain management from inception through May 2018. A critical review was performed on the mechanisms of GH-related signaling and the pharmacology of GH. The levels of clinical evidence and implications for recommendations of all of the included studies were graded.

Results

The search yielded 379 articles, of which 201 articles were deemed irrelevant by reading the titles. There were 53 reports deemed relevant after reading abstracts. All of these 53 articles were retrieved for the analysis and discussion.

Conclusions

Dysfunction of the GH/insulin-like growth factor 1 (IGF-1)/ghrelin axis was linked to hyperalgesia and several common clinical pain syndromes. Low levels of GH and IGF-1 were linked to pain hypersensitivity, whereas ghrelin appeared to provide analgesic effects. Pretreatment of GH reversed mechanical and thermal hypersensitivity in an animal model of inflammatory pain. Clinical trials support GH treatment in a subgroup of patients with fibromyalgia syndrome (level of evidence: 1B+) or chronic lower back pain syndrome (level of evidence: 2C+).

Inflammation in the hippocampus affects IGF1 receptor signaling and contributes to neurological sequelae in rheumatoid arthritis

Aberrant insulin-like growth factor 1 receptor (IGF1R)/insulin receptor signaling in brain has recently been linked to neurodegeneration in diabetes mellitus and in Alzheimer’s disease. In this study, we demonstrate that functional disability and pain in patients with rheumatoid arthritis (RA) and in experimental RA are associated with hippocampal inflammation and inhibition of IGF1R/insulin receptor substrate 1 (IRS1) signal, reproducing an IGF1/insulin-resistant state. This restricts formation of new neurons in the hippocampus, reduces hippocampal volume, and predisposes RA patients to develop neurological symptoms. Improving IRS1 function through down-regulation of IGF1R disinhibits neurogenesis and can potentially ameliorate neurological symptoms. This opens perspectives for drugs that revert IGF1/insulin resistance as an essential complement to the antirheumatic and antiinflammatory arsenal.

Rheumatoid arthritis (RA) is an inflammatory joint disease with a neurological component including depression, cognitive deficits, and pain, which substantially affect patients’ quality of daily life. Insulin-like growth factor 1 receptor (IGF1R) signaling is one of the factors in RA pathogenesis as well as a known regulator of adult neurogenesis. The purpose of this study was to investigate the association between IGF1R signaling and the neurological symptoms in RA. In experimental RA, we demonstrated that arthritis induced enrichment of IBA1⁺ microglia in the hippocampus. This coincided with inhibitory phosphorylation of insulin receptor substrate 1 (IRS1) and up-regulation of IGF1R in the pyramidal cell layer of the cornus ammoni and in the dentate gyrus, reproducing the molecular features of the IGF1/insulin resistance. The aberrant IGF1R signaling was associated with reduced hippocampal neurogenesis, smaller hippocampus, and increased immobility of RA mice. Inhibition of IGF1R in experimental RA led to a reduction of IRS1 inhibition and partial improvement of neurogenesis. Evaluation of physical functioning and brain imaging in RA patients revealed that enhanced functional disability is linked with smaller hippocampus volume and aberrant IGF1R/IRS1 signaling. These results point to abnormal IGF1R signaling in the brain as a mediator of neurological sequelae in RA and provide support for the potentially reversible nature of hippocampal changes.

Inhibitory Role of Growth Hormone in the Induction and Progression Phases of Collagen-Induced Arthritis

Evidence indicates an intimate connection between the neuroendocrine and the immune systems. A number of in vitro and in vivo studies have demonstrated growth hormone (GH) involvement in immune regulation. The GH receptor is expressed by several leukocyte subpopulations, and GH modulates immune cell proliferation and activity. Here, we found that sustained GH expression protected against collagen-induced arthritis (CIA); in GH-transgenic C57BL/6 (GHTg) mice, disease onset was delayed, and its overall severity was decreased. The anti-collagen response was impaired in these mice, as were inflammatory cytokine levels. Compared to control arthritic littermates, immunized GHTg mice showed significantly lower RORγt (retinoic acid receptor-related orphan receptor gamma 2), IL-17, GM-CSF, IL-22, and IFNγ mRNA expression in draining lymph nodes, whereas there were no differences in IL-21, IL-6, or IL-2 mRNA levels. Data thus suggest that Th17/Th1 cell plasticity toward a pathological phenotype is reduced in these mice. Exogenous GH administration in arthritic DBA/1J mice reduced the severity of established CIA as well as the inflammatory environment, which also shows a GH effect on arthritis progression. These results indicate that GH prevents inflammatory joint destruction in CIA. Our findings demonstrate a modulatory GH role in immune system function that contributes to alleviating CIA symptoms and underlines the importance of endocrine regulation of the immune response.

Chronic Pain in Inflammatory Arthritis: Mechanisms, Metrology, and Emerging Targets-A Focus on the JAK-STAT Pathway

Chronic pain is nowadays considered not only the mainstay symptom of rheumatic diseases but also "a disease itself." Pain is a multidimensional phenomenon, and in inflammatory arthritis, it derives from multiple mechanisms, involving both synovitis (release of a great number of cytokines) and peripheral and central pain-processing mechanisms (sensitization). In the last years, the JAK-STAT pathway has been recognized as a pivotal component both in the inflammatory process and in pain amplification in the central nervous system. This paper provides a summary on pain in inflammatory arthritis, from pathogenesis to clinimetric instruments and treatment, with a focus on the JAK-STAT pathway.

IGF-1R signalling contributes to IL-6 production and T cell dependent inflammation in rheumatoid arthritis

BACKGROUND

Signalling through insulin-like growth factor 1 receptor (IGF-1R) is essential for cell survival, but may turn pathogenic in uncontrolled tissue growth in tumours. In rheumatoid arthritis (RA), the IGF-1R signalling is activated and supports expansion of the inflamed synovia.

AIM

In the present study, we assess if disruption of IGF-1R signalling resolves arthritis.

MATERIAL AND METHODS

Clinical associations of IGF-1R expression in leukocytes of the peripheral blood were studied in 84 RA patients. Consequences of the IGF-1R signalling inhibition for arthritis were studied in mBSA immunised Balb/c mice treated with NT157 compound promoting degradation of insulin receptor substrates.

RESULTS

In RA patients, high expression of IGF-1R in leukocytes was associated with systemic inflammation as verified by higher expression of NF-kB, serum levels of IL6 and erythrocyte sedimentation rate, and higher pain perception. Additionally, phosphorylated IGF-1R and STAT3 enriched T cells infiltrate in RA synovia. Treatment with NT157 inhibited the phosphorylation of IGF-1R and STAT3 in synovia, and alleviated arthritis and joint damage in mice. It also reduced expression of IGF-1R and despaired ERK and Akt signalling in spleen T cells. This limited IL-6 production, changed RoRgt/FoxP3 balance and IL17 levels.

CONCLUSION

IGF-1R signalling contributes to T cell dependent inflammation in arthritis. Inhibition of IGF-1R on the level of insulin receptor substrates alleviates arthritis by restricting IL6-dependent formation of Th17 cells and may open for new treatment strategies in RA.

Rheumatoid Arthritis, Immunosenescence and the Hallmarks of Aging

Age is the most important risk factor for the development of infectious diseases, cancer and chronic inflammatory diseases including rheumatoid arthritis (RA). The very act of living causes damage to cells. A network of molecular, cellular and physiological maintenance and repair systems creates a buffering capacity against these damages. Aging leads to progressive shrinkage of the buffering capacity and increases vulnerability. In order to better understand the complex mammalian aging processes, nine hallmarks of aging and their interrelatedness were recently put forward.

RA is a chronic autoimmune disease affecting the joints. Although RA may develop at a young age, the incidence of RA increases with age. It has been suggested that RA may develop as a consequence of premature aging (immunosenescence) of the immune system. Alternatively, premature aging may be the consequence of the inflammatory state in RA. In an effort to answer this chicken and egg conundrum, we here outline and discuss the nine hallmarks of aging, their contribution to the pre-aged phenotype and the effects of treatment on the reversibility of immunosenescence in RA.

Age-independent effects of hyaluronan amide derivative and growth hormone on human osteoarthritic chondrocytes

AIM

Increased age is the most prominent risk factor for the initiation and progression of osteoarthritis (OA). The effects of human growth hormone (hGH) combined or not with hyaluronan amide derivative (HAD) were evaluated on human OA chondrocytes, to define their biological action and potentiality in OA treatment.

MATERIAL AND METHODS

Cell viability, metabolic activity, gene expression and factors released were tested at different time points on chondrocytes treated with different concentrations of hGH (0.01-10 μg/ml) alone or in combination with HAD (1 mg/ml).

RESULTS

We found that OA chondrocytes express GH receptor and that the different doses of hGH tested did not affect cell viability, metabolic activity or the expression of collagen type 2, 1, or 10 nor did it induce the release of IGF-1 or FGF-2. Conversely, hGH treatment increased the expression of hyaluronan receptor CD44. HAD combined with hGH reduced metabolic activity, IL6 release and gene expression, but not the suppressor of cytokine signaling 2 (SOCS2), which was significantly induced and translocated into the nucleus. The parameters analyzed, independently of the treatments used proportionally decreased with increasing age of the patients.

CONCLUSIONS

hGH only induced CD44 receptor on OA chondrocytes but did not affect other parameters, such as chondrocytic gene markers or IGF-1 or FGF-2 release. HAD reduced all the effects induced by hGH partially through a significant induction of SOCS2. These data show that GH or HAD treatment does not influence the response of the OA chondrocytes, thus the modulation of cellular response is age-independent.

Insulin-like Growth Factor 1 and Adiponectin and Associations with Muscle Deficits, Disease Characteristics, and Treatments in Rheumatoid Arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is associated with low muscle mass and density. The objective of our study was to evaluate associations between 2 serum biomarkers [insulin-like growth factor 1 (IGF-1) and adiponectin] and skeletal muscle in RA.

METHODS

Whole-body dual energy X-ray absorptiometry measures of the appendicular lean mass index (ALMI; kg/m(2)) and total fat mass index (kg/m(2)), as well as the peripheral quantitative computed tomography measures of the lower leg muscle and fat cross-sectional area (CSA; cm(2)) and muscle density (an index of fat infiltration) were obtained from 50 participants with RA, ages 18-70 years. Multivariable linear regression analyses evaluated associations between body composition and levels of adiponectin and IGF-1, adjusted for age, sex, and adiposity.

RESULTS

Greater age was associated with higher adiponectin (p = 0.06) and lower IGF-1 (p = 0.004). Eight subjects had IGF-1 levels below the reference range for their age and sex. These subjects had significantly lower ALMI and muscle CSA in multivariable models. Lower IGF-1 levels were associated with greater clinical disease activity and severity, as well as low ALMI, muscle CSA, and muscle density (defined as 1 SD below normative mean). After adjusting for age and sex, greater adiponectin levels were associated with lower BMI (p = 0.02) as well as lower ALMI, and lower muscle CSA, independent of adiposity (p < 0.05). Only greater Health Assessment Questionnaire scores were significantly associated with lower adiponectin levels.

CONCLUSION

Low IGF-1 and greater adiponectin levels are associated with lower muscle mass in RA. Lower IGF-1 levels were seen in subjects with greater disease activity and severity.

Autocrine/paracrine roles of extrapituitary growth hormone and prolactin in health and disease: An overview

Growth hormone (GH) and prolactin (PRL) are both endocrines that are synthesized and released from the pituitary gland into systemic circulation. Both are therefore hormones and both have numerous physiological roles mediated through a myriad of target sites and both have pathophysiological consequences when present in excess or deficiency. GH or PRL gene expression is not, however, confined to the anterior pituitary gland and it occurs widely in many of their central and peripheral sites of action. This may reflect "leaky gene" phenomena and the fact that all cells have the potential to express every gene that is present in their genome. However, the presence of GH or PRL receptors in these extrapituitary sites of GH and PRL production suggests that they are autocrine or paracrine sites of GH and PRL action. These local actions often occur prior to the ontogeny of pituitary somatotrophs and lactotrophs and they may complement or differ from the roles of their pituitary counterparts. Many of these local actions are also of physiological significance, since they are impaired by a blockade of local GH or PRL production or by an antagonism of local GH or PRL action. These local actions may also be of pathophysiological significance, since autocrine or paracrine actions of GH and PRL are thought to be causally involved in a number of disease states, particularly in cancer. Autocrine GH for instance, is thought to be more oncogenic than pituitary GH and selective targeting of the autocrine moiety may provide a therapeutic approach to prevent tumor progression. In summary, GH and PRL are not just endocrine hormones, as they have autocrine and/or paracrine roles in health and disease.

Mechanisms, impact and management of pain in rheumatoid arthritis

People with rheumatoid arthritis (RA) identify pain as their most important symptom, one that often persists despite optimal control of inflammatory disease. RA pain arises from multiple mechanisms, involving inflammation, peripheral and central pain processing and, with disease progression, structural change within the joint. Consequently, RA pain has a wide range of characteristics-constant or intermittent, localized or widespread-and is often associated with psychological distress and fatigue. Dominant pain mechanisms in an individual are identified by critical evaluation of clinical symptoms and signs, and by laboratory and imaging tests. Understanding these mechanisms is essential for effective management, although evidence from preclinical models should be interpreted with caution. A range of pharmacological analgesic and immunomodulatory agents, psychological interventions and surgery may help manage RA pain. Pain contributes importantly to the clinical assessment of inflammatory disease activity, and noninflammatory components of RA pain should be considered when gauging eligibility for or response to biologic agents. Further randomized controlled trials are required to determine the optimal usage of analgesics in RA, and novel agents with greater efficacy and lower propensity for adverse events are urgently needed. Meanwhile, targeted use of existing treatments could reduce pain in people with RA.

The Association between a History of Parental Addictions and Arthritis in Adulthood: Findings from a Representative Community Survey

Aims. To examine the relationship between a history of parental addictions and the cumulative lifetime incidence of arthritis while controlling for age, sex, race, and four clusters of risk factors: (1) other adverse childhood experiences, (2) adult health behaviors (i.e., smoking, obesity, inactivity, and alcohol consumption), (3) adult socioeconomic status and (4) mental health. Materials and Methods. Secondary analysis of 13,036 Manitoba and Saskatchewan respondents of the population-based 2005 Canadian Community Health Survey. Sequential logistic regression analyses were conducted. Findings. After controlling for demographic characteristics, including age, gender, and race, respondents who reported a history of parental addictions had significantly higher odds of arthritis in comparison to individuals without (OR=1.58; 95% CI 1.38–1.80). Adjustment for socioeconomic status, adult health behaviors, and mental health conditions had little impact on the parental addictions and arthritis relationship. The association between parental addictions and arthritis was substantially reduced when adverse childhood experiences (OR=1.33; 95% CI 1.15–1.53) and all four groups of risk factors collectively (OR=1.30; 95% CI = 1.12–1.51) were included in the analyses; however, the relationship remained statistically significant. Conclusions. A robust association was found between parental addictions and cumulative lifetime incidence of arthritis. This link remained even when controlling for four groups of potential risk factors.

Interaction of the endocrine system with inflammation: a function of energy and volume regulation

During acute systemic infectious disease, precisely regulated release of energy-rich substrates (glucose, free fatty acids, and amino acids) and auxiliary elements such as calcium/phosphorus from storage sites (fat tissue, muscle, liver, and bone) are highly important because these factors are needed by an energy-consuming immune system in a situation with little or no food/water intake (sickness behavior). This positively selected program for short-lived infectious diseases is similarly applied during chronic inflammatory diseases. This review presents the interaction of hormones and inflammation by focusing on energy storage/expenditure and volume regulation. Energy storage hormones are represented by insulin (glucose/lipid storage and growth-related processes), insulin-like growth factor-1 (IGF-1) (muscle and bone growth), androgens (muscle and bone growth), vitamin D (bone growth), and osteocalcin (bone growth, support of insulin, and testosterone). Energy expenditure hormones are represented by cortisol (breakdown of liver glycogen/adipose tissue triglycerides/muscle protein, and gluconeogenesis; water retention), noradrenaline/adrenaline (breakdown of liver glycogen/adipose tissue triglycerides, and gluconeogenesis; water retention), growth hormone (glucogenic, lipolytic; has also growth-related aspects; water retention), thyroid gland hormones (increase metabolic effects of adrenaline/noradrenaline), and angiotensin II (induce insulin resistance and retain water). In chronic inflammatory diseases, a preponderance of energy expenditure pathways is switched on, leading to typical hormonal changes such as insulin/IGF-1 resistance, hypoandrogenemia, hypovitaminosis D, mild hypercortisolemia, and increased activity of the sympathetic nervous system and the renin-angiotensin-aldosterone system. Though necessary during acute inflammation in the context of systemic infection or trauma, these long-standing changes contribute to increased mortality in chronic inflammatory diseases.

Identification of the pathogenic pathways in osteoarthritic hip cartilage: commonality and discord between hip and knee OA

OBJECTIVE

To define for the first time the transcriptomes of normal and end-stage osteoarthritis (OA) hip cartilage.

MATERIALS AND METHODS

RNA was isolated from cartilage within 2h of joint replacement surgery. Gene expression was analyzed using Agilent GeneSpring GX 11 following hybridization to Illumina Human HT-12 V3 microarrays. Real-time reverse-transcription polymerase chain reaction (RT-PCR) was used to validate the expression of six genes identified by microarray as differentially expressed. Gene Set Enrichment Analysis (GSEA) and Ingenuity Pathway Analysis (IPA) were used to investigate enriched functions or canonical pathways amongst differentially expressed genes respectively.

RESULTS

In total we identified 998 differentially expressed genes (fold change ≥ ±1.5, P-value ≤ 0.01) between neck of femur fracture (NOF) (n = 10) and OA hip (n = 9) patient cartilage. These differentially expressed genes were enriched within 71 canonical pathways. A comparison between a comparable knee dataset(20) only identified 229 genes similarly differentially expressed although remarkably 34 canonical pathways overlapped between experiments.

CONCLUSIONS

This study is the first to report a comprehensive gene expression analysis of human hip OA cartilage compared to control (NOF) cartilage at the whole-genome level. Our differential gene expression dataset shows excellent correlation with similar defined studies using comparable tissue but reveals discord between hip and knee OA at the individual gene status but with commonality with regards the molecular pathways involved.

Insulin-like growth factor-1 gene polymorphism in rheumatoid arthritis patients

OBJECTIVES

Insulin-like growth factor-1 (IGF-1) regulates several biological functions, and low plasma levels of IGF-1 are known to contribute towards the pathogenesis of rheumatoid arthritis (RA). In view of the biological significance of IGF-1, we investigated the association of RA with the polymorphism of a 192-bp allele which is cytosine-adenosine repeat located 1 kb upstream from the IGF-1 gene transcription site and is known to regulate serum IGF-1 levels.

METHODS

Blood samples were collected from 52 healthy controls (HC) and 68 RA patients to measure the levels of IGF-1 and to isolate genomic DNA. Polymorphism of the IGF-1 gene was examined using polymerase chain reaction (PCR). Disease severity, duration, and activity were recorded for all RA patients.

RESULTS

We observed that 97% of all the subjects who participated in this study showed the presence of a 192-bp allele of the IGF-1 gene. All healthy controls exhibited the presence of 192-bp wild-type allele. All non-carriers of the 192-bp allele were Arabs and had RA. Gender correlated significantly with allele frequencies as 14% of the male and only 2% of the female RA patients were non-carriers of 192-bp allele. Plasma IGF-1 levels were significantly lower (p < 0.01) in RA patients compared to HC, and all RA patients who were non-carriers of the 192-bp allele had a significantly high disease activity score. No correlation was found between the duration of RA and the presence or absence of this allele.

CONCLUSIONS

This study suggests a possible association of the IGF-1 gene polymorphism with developing RA, particularly in males as non-carriers of the 192-bp allele.

Octreotide for the treatment of systemic lupus erythematosus: clinical effects and an in vitro study on its therapeutic mechanism

Increased serum growth hormone (GH), together with high expression of growth hormone receptor on peripheral blood mononuclear cells (PBMCs), correlates with systemic lupus erythematosus (SLE) activity, suggesting that modulation of GH signaling may affect SLE activity. We explored the effects of octreotide (OCT), an analog of somatostatin that suppresses the release of GH, in SLE. The objectives of the study were to investigate effects of OCT on the proliferative capacity and cytokine expression of PBMCs from patients with SLE and to investigate therapeutic effects of OCT in patients with SLE. PBMCs from 13 active/inactive SLE patients and 11 controls were pretreated with or without GH and cultured with OCT. The proliferation of PBMCs was assessed by MTT assay and cytokines were quantified by ELISA. We compared the clinical response of 12 patients with SLE treated with OCT (100 µg twice daily) with 12 patients treated with prednisone over three months. OCT inhibited PBMC proliferation in a dose-dependent manner and decreased the secretion of interleukin-6 (IL-6), interleukin-10 (IL-10), and interferon-gamma (IFN-γ). Patients treated with OCT demonstrated improvements in SLEDAI, dsDNA titer, complement levels, and erythrocyte sedimentation rate (ESR). OCT inhibited PBMC proliferation and PBMC secretion of IL-6, IL-10 and IFN-γ stimulated by GH. Treatment of patients with OCT resulted in clinical improvement in SLE.

Analysis of osteoarthritis in a mouse model of the progeroid human DNA repair syndrome trichothiodystrophy

The increasing average age in developed societies is paralleled by an increase in the prevalence of many age-related diseases such as osteoarthritis (OA), which is characterized by deformation of the joint due to cartilage damage and increased turnover of subchondral bone. Consequently, deficiency in DNA repair, often associated with premature aging, may lead to increased pathology of these two tissues. To examine this possibility, we analyzed the bone and cartilage phenotype of male and female knee joints derived from 52- to 104-week-old WT C57Bl/6 and trichothiodystrophy (TTD) mice, who carry a defect in the nucleotide excision repair pathway and display many features of premature aging. Using micro-CT, we found bone loss in all groups of 104-week-old compared to 52-week-old mice. Cartilage damage was mild to moderate in all mice. Surprisingly, female TTD mice had less cartilage damage, proteoglycan depletion, and osteophytosis compared to WT controls. OA severity in males did not significantly differ between genotypes, although TTD males had less osteophytosis. These results indicate that in premature aging TTD mice age-related changes in cartilage were not more severe compared to WT mice, in striking contrast with bone and many other tissues. This segmental aging character may be explained by a difference in vasculature and thereby oxygen load in cartilage and bone. Alternatively, a difference in impact of an anti-aging response, previously found to be triggered by accumulation of DNA damage, might help explain why female mice were protected from cartilage damage. These findings underline the exceptional segmental nature of progeroid conditions and provide an explanation for pro- and anti-aging features occurring in the same individual.

Association of circulating insulin-like growth factor 1 with hepatocellular carcinoma: one cross-sectional correlation study

Deregulation of insulin-like growth factor-1 (IGF-1) has been implicated in the pathogenesis of several malignancies. This study aimed to investigate the association of changes in circulating IGF-1 with hepatocellular carcinoma (HCC). The radioimmunoassay was used to analyze serum IGF-1 levels of 65 HCC patients and 165 healthy subjects. Serum IGF-1 levels were significantly decreased in the HCC patients as compared with the healthy subjects (158.46+/-105.07 vs. 247.63+/-149.96 ng/mL, P<0.001). Furthermore, insulin resistance was significantly higher in the HCC patients than the healthy subjects (P=0.027). In addition, the significant correlations of serum IGF-1 levels with age and insulin resistance in the healthy subjects were not noted in the HCC patients. Intriguingly, individuals with hepatitis C virus (HCV), not hepatitis B virus, had remarkably decreased IGF-1 levels in both groups of the HCC patients and healthy subjects. Moreover, in the HCV subgroup, serum IGF-1 levels were significantly reduced in the HCC patients than the healthy subjects (113.14+/-71.28 vs. 172.42+/-74.02 ng/mL, P=0.003). In conclusion, decreased serum IGF-1 levels were associated with HCC and the decrease was remarkably noted in those patients concomitant with chronic hepatitis C.

Extrapituitary growth hormone

Pituitary somatotrophs secrete growth hormone (GH) into the bloodstream, to act as a hormone at receptor sites in most, if not all, tissues. These endocrine actions of circulating GH are abolished after pituitary ablation or hypophysectomy, indicating its pituitary source. GH gene expression is, however, not confined to the pituitary gland, as it occurs in neural, immune, reproductive, alimentary, and respiratory tissues and in the integumentary, muscular, skeletal, and cardiovascular systems, in which GH may act locally rather than as an endocrine. These actions are likely to be involved in the proliferation and differentiation of cells and tissues prior to the ontogeny of the pituitary gland. They are also likely to complement the endocrine actions of GH and are likely to maintain them after pituitary senescence and the somatopause. Autocrine or paracrine actions of GH are, however, sometimes mediated through different signaling mechanisms to those mediating its endocrine actions and these may promote oncogenesis. Extrapituitary GH may thus be of physiological and pathophysiological significance.

The robust association between childhood physical abuse and osteoarthritis in adulthood: findings from a representative community sample

OBJECTIVE

Research suggests a role of early-life trauma in the development of arthritis. This study investigated the relationship between childhood physical abuse and osteoarthritis (OA) while controlling for age, sex, race, and socioeconomic status (SES), in addition to the following types of risk factors for OA: 1) concurrent childhood stressors, 2) adult health behaviors, and 3) depression.

METHODS

Data from the provinces of Manitoba and Saskatchewan were selected from the 2005 Canadian Community Health Survey (n = 13,093). Respondents with missing arthritis data or with arthritis types other than OA were excluded (n = 1,985). Of the 11,108 remaining respondents, 6.9% (n = 854) reported childhood physical abuse by someone close to them, and 10.1% (n = 1,452) reported that they had been diagnosed with OA by a health professional. The regional-level response rate was 84%.

RESULTS

When adjusting for all 3 types of risk factors, a significant association between childhood physical abuse and OA was found (odds ratio [OR] 1.56, 95% confidence interval [95% CI] 1.21-2.00). In contrast, when adjusting for age, sex, race, and SES only, the OR was 1.99 (95% CI 1.57-2.52).

CONCLUSION

The association between childhood physical abuse and OA remained significant, even after controlling for many risk factors that may mediate the relationship. Further research is needed to investigate potential pathways through which arthritis develops as a consequence of childhood physical abuse.

Relationship between Investigative Biomarkers and Radiographic Grading in Patients with Knee Osteoarthritis

Objective. To examine new investigative biomarkers and their relevance for radiographic severity in knee osteoarthritis. Methods. The group comprised 63 patients with 73 knees examined. Patients were divided according to radiographic severity to allow for comparison of biomarker levels. Hyaluronic acid (HA), matrix metalloproteases (MMP-1, MMP-3 and MMP-13), tissue inhibitors of metalloproteases (TIMP-1 and TIMP-2), platelet-derived growth factor (PDGF-AB), transformed growth factor (TGF-beta), vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF) and insulin-like growth factor (IGF-I) were measured on synovial fluid and in plasma releasate at a single time point. Principal component analysis (PCA) followed by analysis of covariance were applied to evaluate data. Results. Four different groups of biomarker were identified in plasma releasates. The first (platelet number, PDGF-AB and TGF-beta) and second groups (HA and IGF-I) were related to radiographic severity, P = .005 and P = .022, respectively. The third (MMP-1 and TIMP-2) and fourth groups (MMP-3 and TIMP-1) represented the catabolic balance, but were not associated to radiographic grading. Three different clusters of biomarkers were found in synovial fluid but did not show any significant association to radiographic grading. Conclusions. New imaging approaches to assess structural deterioration and correlation with biomarker levels are warranted to advance in OA research.

Effect of growth hormone on Cyclooxygenase-2 expression in the hippocampus of rats chronically exposed to ozone

The aim of this study was to determine GH-effects on Cyclooxygenase-2 (COX-2) expression on hippocampus alterations caused by ozone exposure. Seventy male rats were divided into: (1) control; (2) exposed to ozone for 7, 15, and 30 days; (3) exposed to ozone and treated with GH, for 7, 15, and 30 days. Results showed that lipoperoxidation levels and number of COX-2-positive cells increased in all groups exposed to ozone compared to control. In the groups treated with GH, COX-2 immunoreactive cell number decreased with respect to the ozone group. Therefore, GH could provide protection against damage induced by oxidative stress.

Diurnal secretion of growth hormone, cortisol, and dehydroepiandrosterone in pre- and perimenopausal women with active rheumatoid arthritis: a pilot case-control study

Rheumatoid arthritis (RA) is associated with neuroendocrine and immunologic dysfunction leading to rheumatoid cachexia. Although excess proinflammatory cytokines can decrease somatotropic axis activity, little is known about the effects of RA on growth hormone/insulin-like growth factor-1 (GH/IGF-I) axis function. We tested the hypothesis that patients with active RA exhibit decreased GH/IGF-I axis activity. To do so, we conducted a pilot case-control study at a clinical research center in 7 pre- and perimenopausal women with active RA and 10 age- and body mass index-matched healthy women. Participants underwent blood sampling every 20 minutes for 24 hours (8 a.m. to 8 a.m.), and sera were assayed for GH, cortisol, and dehydroepiandrosterone (DHEA). Sera obtained after overnight fasting were assayed for IGF-I, IGF-binding protein (IGFBP)-1, IGFBP-3, C-reactive protein (CRP), interleukin-6 (IL-6), glucose, insulin, and lipids. Body composition and bone mineral density were evaluated by DEXA (dual emission x-ray absorptiometry) scans. In patients with RA, mean disease duration was 7.6 ± 6.8 years, and erythrocyte sedimentation rate, CRP, and IL-6 were elevated. GH half-life was shorter than in control subjects (p = 0.0037), with no other significant group differences in GH deconvolution parameters or approximate entropy scores. IGF-I (p = 0.05) and IGFBP-3 (p = 0.058) were lower, whereas IGFBP-1 tended to be higher (p = 0.066), in patients with RA, with nonsignificantly increased 24-hour total GH production rates. There were no significant group differences in cortisol or DHEA secretion. Lean body mass was lower in patients with RA (p = 0.019), particularly in the legs (p = 0.01). Women with active RA exhibit a trend toward GH insensitivity and relatively diminished diurnal cortisol and DHEA secretion for their state of inflammation. Whether these changes contribute to rheumatoid cachexia remains to be determined.

NCT00034060.

Concentrations of the acute phase reactants high-sensitive C-reactive protein and YKL-40 and of interleukin-6 before and after treatment in patients with acromegaly and growth hormone deficiency

BACKGROUND

Acromegaly is accompanied by increased cardiovascular mortality and a cluster of proatherogenic risk factors. In the general population, ischaemic heart disease (IHD) is associated with elevated levels of inflammatory markers. The acute phase reactant (APR) C-reactive protein (CRP) has been reported to be reduced in acromegaly and increase after treatment, suggesting that excess of GH/IGF-I could have anti-inflammatory effects. This is in accordance with results obtained in patients with growth hormone deficiency (GHD), where increased levels of CRP have been reported.

OBJECTIVE

To investigate the hypothesis that the GH/IGF-I system is a suppressive regulator of inflammatory processes.

SUBJECTS AND METHODS

Twenty-one acromegalic patients and 19 GH-deficient patients were studied. The two APRs CRP and YKL-40 and the proinflammatory cytokine interleukin-6 (IL-6) were measured before and after treatment and in healthy matched controls.

RESULTS

In acromegalic patients, serum concentrations of high-sensitive CRP (hsCRP) and YKL-40 were reduced compared to controls (P < 0.001) and increased (P < 0.001) after treatment, together with IL-6 (P = 0.021), to levels comparable with controls. Pretreatment serum YKL-40 and IL-6 showed a significant inverse correlation with IGF-I and GH. In GH-deficient patients, hsCRP and YKL-40 were elevated compared to controls (P = 0.001 and P = 0.048). During treatment, levels of both APRs showed a trend towards a decrease (P = 0.087 and P = 0.060), and after treatment, levels of YKL-40 no longer differed from that of controls. Serum IL-6 was not different from controls and did not change during GH treatment.

CONCLUSION

The results point to the possibility of a relationship between GH disturbances and inflammatory processes.

Growth Hormone Perturbations in Fibromyalgia: A Review

OBJECTIVE

Fibromyalgia (FM) is a syndrome characterized by chronic widespread pain, fatigue, disrupted sleep, depression, and physical deconditioning. In this article, we review the literature on the normal activity of the hypothalamic-pituitary-growth hormone-insulin-like growth factor-1 (HP-GH-IGF-1) axis and its perturbations in FM subjects.

METHODS

Studies included in this review were accessed through an English language search of Cochrane Collaboration Reviews. Keyword MeSH terms included "fibromyalgia," "growth hormone" (GH), or "insulin-like growth factor-1" (IGF-1).

RESULTS

Twenty-six studies enrolling 2006 subjects were reviewed. Overall, low levels of IGF-1 were found in a subgroup of subjects. Growth hormone stimulation tests often revealed a suboptimal response, which did not always correlate with IGF-1 levels. No consistent defects in pituitary function were found. Of the 3 randomized placebo controlled studies, only 9 months of daily injectable recombinant GH reduced FM symptoms and normalized IGF-1.

CONCLUSIONS

These studies suggest that pituitary function is normal in FM and that reported changes in the HP-GH-IGF-1 axis are most likely hypothalamic in origin. The therapeutic efficacy of supplemental GH therapy in FM requires further study before any solid recommendations can be made.

Hormones and growth factors in the pathogenesis of spinal ligament ossification

Ossification of the spinal ligaments (OSL) is a pathologic condition that causes ectopic bone formation and subsequently results in various degrees of neurological deficit, but the etiology of OSL remains almost unknown. Some systemic hormones, such as 1,25-dihydroxyvitamin D, parathyroid hormone (PTH), insulin and leptin, and local growth factors, such as transforming growth factor-beta (TGF-beta), and bone morphogenetic protein (BMP), have been studied and are thought to be involved in the initiation and development of OSL. This review article summarizes these studies, delineates the possible mechanisms, and puts forward doubts and new questions. The related findings from studies of genes and target cells in the ligament of OSL are also discussed. Although these findings may be helpful in understanding the pathogenesis of OSL, much more research needs to be conducted in order to investigate the nature of OSL.

Update on the biology of the chondrocyte and new approaches to treating cartilage diseases

Osteoarthritis (OA) is a joint disease that involves degeneration of articular cartilage, limited intraarticular inflammation manifested by synovitis and changes in the subchondral bone. The aetiology of OA is largely unknown, but since it may involve multiple factors, including mechanical, biochemical and genetic factors, it has been difficult to identify unique targets for therapy. Chondrocytes, which are the unique cellular component of adult articular cartilage, are capable of responding to structural changes in the surrounding cartilage matrix. Since the initial stages of OA involve increased cell proliferation and synthesis of matrix proteins, proteinases and cytokines in the cartilage, laboratory investigations have focused on the chondrocyte as a target for therapeutic intervention. The capacity of the adult articular chondrocyte to regenerate the normal cartilage matrix architecture is limited, however, and the damage becomes irreversible unless the destructive process is interrupted. Current pharmacological interventions that address chronic pain are insufficient and no proven disease-modifying therapy is available. Identification of methods for early diagnosis is of key importance, since therapeutic interventions aimed at blocking or reversing structural damage will be more effective when there is the possibility of preserving normal homeostasis. At later stages, cartilage tissue engineering with or without gene therapy with anabolic factors will also require therapy to inhibit inflammation and block damage to newly repaired cartilage. This review will focus on experimental approaches currently under study that may lead to elucidation of effective strategies for therapy in OA, with emphasis on mediators that affect the function of chondrocytes and interactions with surrounding tissues.

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.