Nitric oxide may mediate the hemodynamic effects of recombinant growth hormone in patients with acquired growth hormone deficiency. A double-blind, placebo-controlled study

Special features on insulin resistance, metabolic syndrome and vascular complications in hypopituitary patients

Pituitary hormone deficiency, hypopituitarism, is a dysfunction resulting from numerous etiologies, which can be complete or partial, and is therefore heterogeneous. This heterogeneity makes it difficult to interpret the results of scientific studies with these patients.Adequate treatment of etiologies and up-to-date hormone replacement have improved morbidity and mortality rates in patients with hypopituitarism. As GH replacement is not performed in a reasonable proportion of patients, especially in some countries, it is essential to understand the known consequences of GH replacement in each subgroup of patients with this heterogeneous dysfunction.In this review on hypopituitarism, we will address some particularities regarding insulin resistance, which is no longer common in these patients with hormone replacement therapy based on current guidelines, metabolic syndrome and its relationship with changes in BMI and body composition, and to vascular complications that need to be prevented taking into account the individual characteristics of each case to reduce mortality rates in these patients.

Atherosclerotic burden and cerebral small vessel disease: exploring the link through microvascular aging and cerebral microhemorrhages

Cerebral microhemorrhages (CMHs, also known as cerebral microbleeds) are a critical but frequently underestimated aspect of cerebral small vessel disease (CSVD), bearing substantial clinical consequences. Detectable through sensitive neuroimaging techniques, CMHs reveal an extensive pathological landscape. They are prevalent in the aging population, with multiple CMHs often being observed in a given individual. CMHs are closely associated with accelerated cognitive decline and are increasingly recognized as key contributors to the pathogenesis of vascular cognitive impairment and dementia (VCID) and Alzheimer's disease (AD). This review paper delves into the hypothesis that atherosclerosis, a prevalent age-related large vessel disease, extends its pathological influence into the cerebral microcirculation, thereby contributing to the development and progression of CSVD, with a specific focus on CMHs. We explore the concept of vascular aging as a continuum, bridging macrovascular pathologies like atherosclerosis with microvascular abnormalities characteristic of CSVD. We posit that the same risk factors precipitating accelerated aging in large vessels (i.e., atherogenesis), primarily through oxidative stress and inflammatory pathways, similarly instigate accelerated microvascular aging. Accelerated microvascular aging leads to increased microvascular fragility, which in turn predisposes to the formation of CMHs. The presence of hypertension and amyloid pathology further intensifies this process. We comprehensively overview the current body of evidence supporting this interconnected vascular hypothesis. Our review includes an examination of epidemiological data, which provides insights into the prevalence and impact of CMHs in the context of atherosclerosis and CSVD. Furthermore, we explore the shared mechanisms between large vessel aging, atherogenesis, microvascular aging, and CSVD, particularly focusing on how these intertwined processes contribute to the genesis of CMHs. By highlighting the role of vascular aging in the pathophysiology of CMHs, this review seeks to enhance the understanding of CSVD and its links to systemic vascular disorders. Our aim is to provide insights that could inform future therapeutic approaches and research directions in the realm of neurovascular health.

Growth hormone in pediatric chronic kidney disease: more than just height

Recombinant human growth hormone therapy, which was introduced in the 1980s, is now routine for children with advanced chronic kidney disease (CKD) who are exhibiting growth impairment. Growth hormone usage remains variable across different centers, with some showing low uptake. Much of the focus on growth hormone supplementation has been on increasing height because of social and psychological effects of short stature. There are, however, numerous other changes that occur in CKD that have not received as much attention but are biologically important for pediatric growth and development. This article reviews the current knowledge about the multisystem effects of growth hormone therapy in pediatric patients with CKD and highlights areas where additional clinical research is needed. We also included clinical data on children and adults who had received growth hormone for other indications apart from CKD. Ultimately, having robust clinical studies which examine these effects will allow children and their families to make more informed decisions about this therapy.

Dyslipidaemia and growth hormone deficiency - A comprehensive review

Growth hormone deficiency (GHD) is a common complication of several pituitary and hypothalamic disorders and dependent on the onset of disease. It may have severe clinical implications ranging from growth retardation in childhood-onset, to impaired lipid metabolism and increased cardiovascular risk and mortality in adults. GH effectively modulates lipid metabolism at multiple levels and GHD has been associated with an atherogenic lipid profile, that can be reversed by GH replacement therapy. Despite increasing knowledge on the effects of GH on several key enzymes regulating lipid metabolism and recent breakthroughs in the development and wider availability of recombinant GH preparations, several questions remain regarding the replacement therapy in adults with GHD. This review aims to comprehensively summarize the current knowledge on (i) lipid profile abnormalities in individuals with GHD, (ii) proposed mechanisms of action of GH on lipid and lipoprotein metabolism, and (iii) clinical implications of GH replacement therapy in individuals diagnosed with GHD.

Effects of Growth Hormone on Adult Human Gonads: Action on Reproduction and Sexual Function

Growth hormone (GH), which is commonly considered to be a promoter of growth and development, has direct and indirect effects on adult gonads that influence reproduction and sexual function of humans and nonhumans. GH receptors are expressed in adult gonads in some species including humans. For males, GH can improve the sensitivity of gonadotropins, contribute to testicular steroidogenesis, influence spermatogenesis possibly, and regulate erectile function. For females, GH can modulate ovarian steroidogenesis and ovarian angiogenesis, promote the development of ovarian cells, enhance the metabolism and proliferation of endometrial cells, and ameliorate female sexual function. Insulin-like growth factor-1 (IGF-1) is the main mediator of GH. In vivo, a number of the physiological effects of GH are mediated by GH-induced hepatic IGF-1 and local IGF-1. In this review, we highlight the roles of GH and IGF-1 in adult human gonads, clarify potential mechanisms, and explore the efficacy and the risk of GH supplementation in associated deficiency and assisted reproductive technologies. Besides, the effects of excess GH on adult human gonads are discussed as well.

Covert actions of growth hormone: fibrosis, cardiovascular diseases and cancer

Since its discovery nearly a century ago, over 100,000 studies of growth hormone (GH) have investigated its structure, how it interacts with the GH receptor and its multiple actions. These include effects on growth, substrate metabolism, body composition, bone mineral density, the cardiovascular system and brain function, among many others. Recombinant human GH is approved for use to promote growth in children with GH deficiency (GHD), along with several additional clinical indications. Studies of humans and animals with altered levels of GH, from complete or partial GHD to GH excess, have revealed several covert or hidden actions of GH, such as effects on fibrosis, cardiovascular function and cancer. In this Review, we do not concentrate on the classic and controversial indications for GH therapy, nor do we cover all covert actions of GH. Instead, we stress the importance of the relationship between GH and fibrosis, and how fibrosis (or lack thereof) might be an emerging factor in both cardiovascular and cancer pathologies. We highlight clinical data from patients with acromegaly or GHD, alongside data from cellular and animal studies, to reveal novel phenotypes and molecular pathways responsible for these actions of GH in fibrosis, cardiovascular function and cancer.

COVID-19 and hypopituitarism

Besides the pulmonary manifestations caused by severe acute respiratory syndrome (SARS) coronavirus 2 (SARS-CoV-2), an emerging endocrine phenotype, which can heavily impact on the severity of the syndrome, has been recently associated with coronavirus disease 2019 (COVID-19). Patients with pituitary diseases or the pituitary gland itself may also be involved in COVID-19 clinical presentation and/or severity, causing pituitary apoplexy.Moreover, hypopituitarism is frequently burdened by several metabolic complications, including arterial hypertension, hyperglycemia, obesity and vertebral fractures, which have all been associated with poor outcomes and increased mortality in patients infected by SARS-CoV-2.This review will discuss hypopituitarism as a condition that might have a bidirectional relationship with COVID-19 due to the frequent presence of metabolic comorbidities, to the direct or indirect pituitary damage or being per se a potential risk factor for COVID-19. Finally, we will address the current recommendations for the clinical management of vaccines in patients with hypopituitarism and adrenal insufficiency.

Growth hormone deficiency in adults with hypopituitarism-What are the risks and can they be eliminated by therapy?

Growth hormone (GH) deficiency develops early in patients with hypothalamic-pituitary disorders and is therefore common among these patients. GH deficiency in adults is associated with increased morbidity, increased body fat mass, abdominal obesity, dyslipidaemia, reduced exercise capacity, impaired cardiac function as well as reduced self-reported well-being and impaired quality of life. Since recombinant human GH became available as replacement therapy more than 25 years ago, randomised controlled trials and long-term studies, together with meta-analyses, have shown improved outcomes in adult patients with hypopituitarism receiving GH. Many of the features associated with GH deficiency in adults improve, or even normalize, and the safety profile is reassuring. The increased interest in GH deficiency in adults with hypothalamic-pituitary disorders has also contributed to the identification of other factors of importance for an outcome such as the replacement of other pituitary hormone deficiencies, and the management of the underlying hypothalamic-pituitary disease, most commonly a pituitary tumour. In this narrative review, we summarize the burden of GH deficiency in adults with hypopituitarism, the impact of GH replacement on the outcome, as well as safety. Based on currently available data, GH replacement should be considered routine management of adults with hypopituitarism.

Hypothalamic-Pituitary Diseases and Erectile Dysfunction

Several hormones contribute to ensure penile erection, a neurovascular phenomenon in which nitric oxide plays a major role. Erectile dysfunction (ED), which is defined as the persistent inability to obtain or maintain penile erection sufficient for a satisfactory sexual performance, may be due to arteriogenic, neurogenic, iatrogenic, but also endocrinological causes. The hypothalamus–pituitary axis plays a central role in the endocrine system and represents a fundamental link between the brain and peripheral glands, including gonads. Therefore, the hormonal production of the hypothalamic–pituitary axis can control various aspects of sexual function and its dysregulation can compromise erectile function. In addition, excess and deficiency of pituitary hormones or metabolic alterations that are associated with some pituitary diseases (e.g., Cushing’s disease and acromegaly, hypopituitarism) can determine the development of ED with different mechanisms. Thus, the present review aimed to explore the relationship between hypothalamic and pituitary diseases based on the most recent clinical and experimental evidence.

Factors Affecting the Re-Endothelialization of Endothelial Progenitor Cell

The vascular endothelium, which plays an essential role in maintaining the normal shape and function of blood vessels, is a natural barrier between the circulating blood and the vascular wall tissue. The endothelial damage can cause vascular lesions, such as atherosclerosis and restenosis. After the vascular intima injury, the body starts the endothelial repair (re-endothelialization) to inhibit the neointimal hyperplasia. Endothelial progenitor cell is the precursor of endothelial cells and plays an important role in the vascular re-endothelialization. However, re-endothelialization is inevitably affected in vivo and in vitro by factors, which can be divided into two types, namely, promotion and inhibition, and act on different links of the vascular re-endothelialization. This article reviews these factors and related mechanisms.

Urine Nitric Oxide Is Lower in Parents of Autistic Children

Parents raising children with autism spectrum disorder (ASD) usually carry on their daily life under tremendous stress, but limited empirical research has been devoted to this population. It is known that parents' health status directly impacts therapeutic outcome of ASD children. As an important regulator in cardiovascular, nervous and immune systems, nitric oxide (NO) levels haven't been reported in parents of ASD children yet. In this study, we measured urine nitrite and nitrate from 43 ASD parents (ASD-P), and 43 healthy adults in the same range of age (Control) who didn't have any ASD descendants. Comparison between the ASD-P and Control groups showed that NO 2 - , NO 3 - , and NO 2 - / NO 3 - were all significantly lower in the ASD-P group. Analysis on the interaction effect of sex and group indicated that urine NO 3 - of mothers in ASD-P was lower than that in females of the Control group, but no significant difference was observed between males in both groups. It is for the first time that urine nitric oxide metabolites (nitrite, nitrate) levels were precisely reported to differentiate parents of autistic children from other adults without ASD descendants. This phenomenon suggests that parents (especially mothers) of autistic children might have experienced more mental and physical stressors, which led to decreased NO levels during metabolism. Further investigations are necessary to uncover the etiology of low urine NO among parents of autistic children.

Growth hormone therapy in adults with growth hormone deficiency: a critical assessment of the literature

PURPOSE

Growth hormone (GH) therapy has been studied as treatment for clinical manifestations of adult-onset growth hormone deficiency (AO-GHD), including cardiovascular risk, bone health, and quality of life. Patients with AO-GHD typically also have significant history of pituitary pathology and hypopituitarism, which raises the question of what proportion of their clinical presentation can be attributed to GHD alone. Currently, much of the existing data for GH therapy in AO-GHD come from uncontrolled retrospective studies and observational protocols. These considerations require careful reassessment of the role of GH as a therapeutic agent in adult patients with hypopituitarism.

METHODS

We contrast results from placebo-controlled trials with those from uncontrolled and retrospective studies for GH replacement in patients with hypopituitarism. We also examine the evidence for the manifestations of AO-GHD being attributed to GHD alone, as well as the data on adults with congenital, life-long untreated isolated GHD.

RESULTS

The evidence for increased morbidity and mortality in hypopituitary patients with GHD, and for the benefits of GH therapy, are conflicting. There remains the possibility that the described clinical manifestations of AO-GHD may not be due to GHD alone, but may also be related to underlying pituitary pathology, treatment history and suboptimal hormone replacement.

CONCLUSIONS

In the setting of inconsistent data on the benefits of GH therapy, treatment of AO-GHD remains an individualized decision. There is a need for more randomized, placebo-controlled studies to evaluate the long-term outcomes of GH therapy in adults with hypopituitarism.

Why Should Growth Hormone (GH) Be Considered a Promising Therapeutic Agent for Arteriogenesis? Insights from the GHAS Trial

Despite the important role that the growth hormone (GH)/IGF-I axis plays in vascular homeostasis, these kind of growth factors barely appear in articles addressing the neovascularization process. Currently, the vascular endothelium is considered as an authentic gland of internal secretion due to the wide variety of released factors and functions with local effects, including the paracrine/autocrine production of GH or IGF-I, for which the endothelium has specific receptors. In this comprehensive review, the evidence involving these proangiogenic hormones in arteriogenesis dealing with the arterial occlusion and making of them a potential therapy is described. All the elements that trigger the local and systemic production of GH/IGF-I, as well as their possible roles both in physiological and pathological conditions are analyzed. All of the evidence is combined with important data from the GHAS trial, in which GH or a placebo were administrated to patients suffering from critical limb ischemia with no option for revascularization. We postulate that GH, alone or in combination, should be considered as a promising therapeutic agent for helping in the approach of ischemic disease.

The heart in growth hormone (GH) deficiency and the cardiovascular effects of GH

Besides its effects on longitudinal growth in childhood and its metabolic effects with consequences on body composition and lipid levels, growth hormone (GH) has important roles on maintaining the structure and function of the normal adult heart. GH/insulin like growth factor-I (IGF-I) also interacts with the vascular system and plays a role in the regulation of vascular tone. GH deficiency (GHD) in adulthood is associated with increased fat mass (particularly visceral) and abnormal lipid profile, which may contribute to the excess cardiovascular mortality observed in patients with panhypopituitarism. Treatment with GH improved body composition (by increasing lean mass and decreasing fat mass) and improved lipid profile. It also has beneficial effects on vascular walls. The improvement in cardiovascular morbidity and mortality induced by GH is less clear as data are scarce and obtained on small populations. The importance of alteration in cardiac morphology and function observed in GHD is debated, particularly when cardiac magnetic resonance is used rather than echocardiography. The effects of treatment with GH on heart function and morphology are modest when studied by echocardiography.

Titrating Growth Hormone Dose to High-Normal IGF-1 Levels Has Beneficial Effects on Body Fat Distribution and Microcirculatory Function Despite Causing Insulin Resistance

To clarify the mechanism underlying the described U-shaped relation of both low and high levels of IGF-1 with cardiovascular disease this study explores the effect of decreasing and increasing growth hormone dose in GH deficient adults on (micro)vascular function, body composition and insulin resistance. In this randomized clinical trial, thirty-two subjects receiving GH therapy with an IGF-1 concentration between -1 and 1 SD score (SDS) for at least one year were randomized to receive either a decrease (IGF-1 target level of -2 to -1 SDS) or an increase of their daily GH dose (IGF-1 target level of 1 to 2 SDS) for a period of 24 weeks. Microvascular endothelium (in)dependent vasodilatation and vasomotion, vascular stiffness by pulse wave analysis, and HOMA-IR were measured. At the end of the study 30 subjects (65.6% men, mean age 46.6 (SD 9.9) years) were analyzed. There was a favorable effect of increasing the IGF-1 level on waist circumference compared to decreasing the IGF-1 level (p=0.05), but a detrimental effect on insulin resistance (p=0.03). Decreasing IGF-1 level significantly lowered the endothelial domain of vasomotion (p=0.03), whereas increasing IGF-1 level increased the contribution of the neurogenic domain (p=0.05). This change was related to the favorable change in waist circumference. In conclusion, increasing IGF-1 levels was beneficial for body composition but detrimental with respect to insulin resistance. The contribution of the neurogenic vasomotion domain increased in parallel, and could be explained by the favorable change in waist circumference.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, identifier NCT01877512.

Glomerular filtration rate, blood pressure and microalbuminuria in adults born SGA: A 5-year longitudinal study after cessation of GH treatment

BACKGROUND

Growth hormone treatment increases glomerular filtration rate (GFR), as serum IGF-I stimulates the renin-angiotensin system. Infants born with a low birth weight have a smaller number of nephrons, which cause a lower GFR, a higher blood pressure and a higher albumin-to-creatinine ratio in early adulthood.

METHOD

A total of 261 young adults born SGA, previously treated with growth hormone (SGA-GH), were longitudinally followed. Glomerular filtration rate, based on serum creatinine levels, was determined at cessation of GH treatment and at 6 months, 2 years and 5 years thereafter. Glomerular filtration rate, blood pressure and urinary albumin-to-creatinine ratio at 5 years after cessation of GH were compared with untreated age-matched controls (56 untreated short subjects born SGA [SGA-S], 118 subjects born SGA with spontaneous catch-up growth [SGA-CU], 135 subjects born appropriate for gestational age [AGA]).

RESULTS

Glomerular filtration rate decreased significantly only during the first 6 months after cessation of GH treatment, while remaining well within the normal range (124.6 vs 120.2 mL/min/1.73 m² , P < .001). SGA-GH adults had a similar GFR, blood pressure and urinary albumin-to-creatinine ratio as the healthy controls born SGA and AGA.

CONCLUSION

In conclusion, our 5 years longitudinal follow-up study shows a decrease in GFR during 6 months after GH cessation, but thereafter GFR remained stable and within the normal range. Glomerular filtration rate, blood pressure and urinary albumin-to-creatinine ratio at 21 years of age were similar in GH-treated young adults born SGA and untreated controls born SGA or AGA. We conclude that long-term GH treatment in children born SGA has no unfavourable effects on kidney function in early adulthood. PRÉCIS: We present a longitudinal study on kidney function in the follow-up of growth hormone-treated young adults who were born small for gestational age.

GHRH-mediated GH release is associated with sympathoactivation and baroreflex resetting: a microneurographic study in healthy humans

Previous research suggested substantial interactions of growth hormone (GH) and sympathetic nervous activity. This cross talk can be presumed both during physiological (e.g., slow-wave sleep) and pathological conditions of GH release. However, microneurographic studies of muscle sympathetic nerve activity (MSNA) and assessment of baroreflex function during acute GH-releasing hormone (GHRH)-mediated GH release were not conducted so far. In a balanced, double-blind crossover design, GHRH or placebo (normal saline) were intravenously administered to 11 healthy male volunteers. MSNA was assessed microneurographically and correlated with blood pressure (BP) and heart rate (HR) at rest before (pre-) and 30-45 (post-I) and 105-120 min (post-II) after respective injections. Additionally, baroreflex function was assessed via graded infusion of vasoactive drugs. GHRH increased GH serum levels as intended. Resting MSNA showed significant net increases of both burst rate and total activity from pre- to post-I and post-II following GHRH injections compared with placebo (ANOVA for treatment and time, burst rate: P = 0.028; total activity: P = 0.045), whereas BP and HR were not altered. ANCOVA revealed that the dependent variable MSNA was not affected by the independent variables mean arterial BP (MAP) or HR (MAP: P = 0.006; HR: P = 0.003). Baroreflex sensitivity at baroreflex challenge was not altered. GHRH-mediated GH release is associated with a significant sympathoactivation at central nervous sites superordinate to the simple baroreflex feedback loop because GH induced a baroreflex resetting without altering baroreflex sensitivity.

Dipeptidyl Peptidase-4 Inhibition Potentiates Stimulated Growth Hormone Secretion and Vasodilation in Women

BACKGROUND

Diminished growth hormone (GH) is associated with impaired endothelial function and fibrinolysis. GH-releasing hormone is the primary stimulus for GH secretion and a substrate of dipeptidyl peptidase-4. We tested the hypothesis that dipeptidyl peptidase-4 inhibition with sitagliptin increases stimulated GH secretion, vasodilation, and tissue plasminogen activator (tPA) activity.

METHODS AND RESULTS

Healthy adults participated in a 2-part double-blind, randomized, placebo-controlled, crossover study. First, 39 patients (29 women) received sitagliptin or placebo on each of 2 days separated by a washout. One hour after study drug, blood was sampled and then arginine (30 g IV) was given to stimulate GH. Vasodilation was assessed by plethysmography and blood sampled for 150 minutes. Following a washout, 19 of the original 29 women received sitagliptin alone versus sitagliptin plus antagonist to delineate GH receptor (GHR)- (n=5), nitric oxide- (n=7), or glucagon-like peptide-1 receptor- (n=7) dependent effects. Sitagliptin enhanced stimulated GH secretion (P<0.01 versus placebo, for 30 minutes) and free insulin-like growth factor-1 (P<0.001 versus placebo, after adjustment for baseline) in women. Vasodilation and tPA increased in all patients, but sitagliptin enhanced vasodilation (P=0.01 versus placebo) and increased tPA (P<0.001) in women only. GHR blockade decreased free insulin-like growth factor-1 (P=0.04 versus sitagliptin alone) and increased stimulated GH (P<0.01), but decreased vascular resistance (P=0.01) such that nadir vascular resistance correlated inversely with GH (rs=-0.90, P<0.001). GHR blockade suppressed tPA. Neither nitric oxide nor glucagon-like peptide-1 receptor blockade affected vasodilation or tPA.

CONCLUSIONS

Sitagliptin enhances stimulated GH, vasodilation, and fibrinolysis in women. During sitagliptin, increases in free insulin-like growth factor-1 and tPA occur via the GHR, whereas vasodilation correlates with GH but occurs through a GHR-independent mechanism.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01701973.

Effect of growth hormone replacement therapy on plasma diacron-reactive oxygen metabolites and endothelial function in Japanese patients: The GREAT clinical study

Patients with growth hormone deficiency (GHD) have an increased risk of atherosclerosis and vascular mortality. Evidence suggests that endothelial dysfunction is involved in all stages of atherogenesis. This study examined the effect of growth hormone (GH) replacement therapy on diacron-reactive oxygen metabolites (d-ROMs) and endothelial function in Japanese patients with GHD, using peripheral arterial tonometry. This was an open-label, prospective, case-control study. Nine patients with GHD who had not previously received any GH replacement therapy were enrolled. The following parameters were evaluated at baseline (before treatment), and after 24 weeks of GH replacement therapy: endothelial function using the reactive hyperemia index (RHI; EndoPAT^® system), d-ROMs, blood pressure, and fasting lipid levels. Plasma GH and insulin-like growth factor-1 (IGF-1) levels were measured at baseline and after 24 weeks of GH replacement therapy. We also enrolled eight controls with pituitary disease but no GH deficiency. Over 24 weeks of GH replacement therapy, the serum IGF-1 levels normalized with significant improvement in the RHI (from 1.65 ± 0.33 to 1.92 ± 0.26, p < 0.05) and decreased d-ROM levels (from 356.8 ± 64.1 to 303.1 ± 43.3 U.CARR, p < 0.05). There were no significant improvements in the RHI or d-ROM levels in controls. GH replacement therapy in Japanese patients with GHD may be mediated by the reduced oxidative stress and the d-ROMs associated with the treatment.

Blood asymmetric dimethylarginine and nitrite/nitrate concentrations in short-stature children born small for gestational age with and without growth hormone therapy

Objective

To investigate the basal amino acid metabolism and impact of growth hormone (GH) therapy in short-stature children born small for gestational age (short SGA children).

Methods

In this age-matched case-control study, the basal blood levels of amino acids, asymmetric dimethylarginine (ADMA), and nitrite/nitrate (NOx) were compared between 24 short SGA children and 25 age-matched normal children. Changes in these parameters were assessed for 12 months in 12 short SGA children initiating GH therapy (Group A) and 12 age-matched short SGA children without GH therapy (Group B).

Results

The arginine levels were significantly lower in the short SGA than in normal children. The ADMA levels were significantly higher and NOx levels were significantly lower in the short SGA than normal children. In Group A, the ADMA level was significantly lower and NOx level was significantly higher at 6 months than at baseline. At 12 months, the ADMA level in Group A began to increase, but the NOx level remained the same. Group B showed no significant changes.

Conclusions

This study is the first to show that ADMA is promoted and nitric oxide is suppressed in short SGA children and that GH therapy affects the production of ADMA and nitric oxide.

Novel Actions of Growth Hormone in Podocytes: Implications for Diabetic Nephropathy

The kidney regulates water, electrolyte, and acid-base balance and thus maintains body homeostasis. The kidney’s potential to ensure ultrafiltered and almost protein-free urine is compromised in various metabolic and hormonal disorders such as diabetes mellitus (DM). Diabetic nephropathy (DN) accounts for ~20–40% of mortality in DM. Proteinuria, a hallmark of renal glomerular diseases, indicates injury to the glomerular filtration barrier (GFB). The GFB is composed of glomerular endothelium, basement membrane, and podocytes. Podocytes are terminally differentiated epithelial cells with limited ability to replicate. Podocyte shape and number are both critical for the integrity and function of the GFB. Podocytes are vulnerable to various noxious stimuli prevalent in a diabetic milieu that could provoke podocytes to undergo changes to their unique architecture and function. Effacement of podocyte foot process is a typical morphological alteration associated with proteinuria. The dedifferentiation of podocytes from epithelial-to-mesenchymal phenotype and consequential loss results in proteinuria. Poorly controlled type 1 DM is associated with elevated levels of circulating growth hormone (GH), which is implicated in the pathophysiology of various diabetic complications including DN. Recent studies demonstrate that functional GH receptors are expressed in podocytes and that GH may exert detrimental effects on the podocyte. In this review, we summarize recent advances that shed light on actions of GH on the podocyte that could play a role in the pathogenesis of DN.

Cardiovascular alterations in adult GH deficiency

There is a growing body of evidence indicating that patients with adult GH deficiency (GHD) are characterized by a cluster of traditional and emerging cardiovascular risk factors and markers, which can significantly increase their cardiovascular morbidity and mortality possibly linked to aberrations in GH status. Patients with adult GHD present multiple different cardiovascular abnormalities. In addition, cardiovascular risk in adult GHD is increased due to altered body composition, abnormal lipid profile, insulin resistance and impaired glucose metabolism. Cardiovascular risk factors can be reversed, at least partially, after GH replacement. However, evidence on the effects of GH replacement on cardiovascular events and mortality is too limited in adult GHD patients. Aim of this review is to provide an at-a-glance overview of the role of the GH/IGF-I on the cardiovascular system and the state of art of the effects of GH replacement on cardiovascular system.

Mature coconut water exhibits antidiabetic and antithrombotic potential via L-arginine-nitric oxide pathway in alloxan induced diabetic rats

BACKGROUND

The aims of the present study were to assess whether the antidiabetic activity of mature coconut water (MCW) is mediated through L-arginine-nitric oxide pathway in diabetic rats, and to study the effects of MCW on blood coagulation.

METHODS

Diabetes was induced in male Sprague-Dawley rats by injecting them with alloxan (150 mg/kg body weight). MCW (4 mL/100 g body weight) and L-arginine (7.5 mg/100 g body weight) was given orally for 45 days. L-NAME was given at a dose of 0.5 mg/kg body weight. Concentrations of blood glucose, plasma insulin, glycosylated hemoglobin (HbA1c), L-arginine, urine volume and urinary creatinine levels, activity of nitric oxide synthase (NOS), and arginase as well as the abnormalities in hemostasis and thrombosis were measured in all the experimental groups.

RESULTS

Treatment with MCW and L-arginine reduced the concentration of blood glucose and HbA1c in diabetic rats. MCW and L-arginine treatment exhibited significant antithrombotic activity in diabetic rats, which was evident from the reduced levels of WBC, platelets, fibrin, and fibrinogen. MCW and L-arginine treatment prolonged the prothrombin time in diabetic rats and reduced the activity of Factor V. In addition to this, the activity of nitric oxide synthase, liver and plasma arginine content, and urinary nitrite were higher in MCW-treated diabetic rats whereas L-NAME treatment inhibited the beneficial effects induced by MCW and arginine.

CONCLUSIONS

The results clearly indicate that L-arginine is a major factor responsible for the antidiabetic and antithrombotic potential of coconut water, and is mediated through the L-arginine-nitric oxide pathway.

The prolactin family hormones regulate vascular tone through NO and prostacyclin production in isolated rat aortic rings

AIM

Prolactin family hormones include growth hormone, placental lactogen and prolactin, which are able to regulate angiogenesis via NO and prostaglandins. However, their effects on vascular tone are not fully understood. The aim of this study was to evaluate the effects of prolactin family hormones on rat vascular tone in vitro.

METHODS

Aortic rings were prepared from adult male rats and precontracted with phenylephrine, then treated with the hormones and drugs. The tension was measured with isometric force displacement transducer connected to a polygraph. NO production and prostacyclin release in physiological solution was determined. Cultured rat aortic endothelial cells (RAECs) were treated with the hormones and drugs, and the phosphorylation of eNOS at serine 1177 was assessed using Western bolt analysis.

RESULTS

Administration of growth hormone or placental lactogen (0.01-100 nmol/L) induced endothelium-dependent vasodilation. Both the hormones significantly increased the phosphorylation of eNOS in RAECs and NO level in physiological solution. Preincubation with L-NAME blocked growth hormone- or placental lactogen-induced vasodilation and NO production. Preincubation with an antibody against growth hormone receptors blocked growth hormone- and placental lactogen-induced vasodilation. Addition of a single dose of prolactin (0.01 nmol/L) induced sustained vessel relaxation, whereas multiple doses of prolactin induced a biphasic contraction-relaxation effect. The vascular effects of prolactin depended on endothelium. Prolactin significantly increased the level of prostacyclin I2 in physiological solution. Preincubation with indomethacin or an antibody against prolactin receptors blocked prolactin-induced vasodilation.

CONCLUSION

The prolactin family hormones regulate rat vascular tone, selectively promoting either relaxation or contraction of vascular smooth muscle via activation of either growth hormone receptors or prolactin receptors within the endothelium.

GH and the cardiovascular system: an update on a topic at heart

In this review, the importance of growth hormone (GH) for the maintenance of normal cardiac function in adult life is discussed. Physiological effects of GH and underlying mechanisms for interactions between GH and insulin-like growth factor I (IGF-I) and the cardiovascular system are covered as well as the cardiac dysfunction caused both by GH excess (acromegaly) and by GH deficiency in adult hypopituitary patients. In both acromegaly and adult GH deficiency, there is also increased cardiovascular morbidity and mortality possibly linked to aberrations in GH status. Finally, the status of the GH/IGF-I system in relation to heart failure and the potential of GH as a therapeutic tool in the treatment of heart failure are reviewed in this article.

Impact of adult growth hormone deficiency on metabolic profile and cardiovascular risk [Review]

Adult growth hormone deficiency (GHD) is a well defined clinical condition, which is characterized by abnormal body composition, impaired physical activity and decreased quality of life. In addition, in recent years, growing interest has been shown towards cardiovascular risks in adult patients affected by GHD. In this regard, GHD is widely known to be associated with increased mortality, likely due to the increase of risk factors, such as central obesity, impaired lipid and glucose profiles and other less-known risk factors, such as inflammatory cytokines, endothelial dysfunction and oxidative stress. However, very few papers have recently discussed this topic. In this review, the aim is to clarify this issue by discussing evidence regarding the effects of adult GHD on metabolic and cardiovascular profiles.

Both low and high serum IGF-1 levels associate with increased risk of cardiovascular events in elderly men

CONTEXT

Most previous prospective studies suggest that low serum IGF-1 associates with increased risk of cardiovascular disease (CVD) events whereas other studies suggest that high serum IGF-1 associates with increased risk of CVD events.

OBJECTIVE

We tested the hypothesis that not only low, but also high serum IGF-1 levels associate with increased risk of CVD events in elderly men.

SETTING AND DESIGN

Serum IGF-1 levels were measured in 2901 elderly men (age 69-81 years) included in the Swedish cohort of the prospective, population-based Osteoporotic Fractures in Men Study (MrOS), Sweden cohort. Data for CVD events were obtained from national Swedish registers with no loss of followup.

RESULTS

During followup (median, 5.1 y) 589 participants experienced a CVD event. The association between serum IGF-1 and risk of CVD events was nonlinear, and restricted cubic spline Cox regression analysis revealed a U-shaped association between serum IGF-1 levels and CVD events (P < .01 for nonlinearity). Low as well as high serum IGF-1 (quintile 1 or 5 vs quintiles 2-4) significantly associated with increased risk for CVD events (hazard ratio [HR] = 1.25, 95% confidence interval, [CI], 1.02-1.54; and HR = 1.35, 95% CI 1.10-1.66, respectively). These associations remained after adjustment for prevalent CVD and multiple risk factors. High serum IGF-1 associated with increased risk of coronary heart disease (CHD) events but not with risk of cerebrovascular events.

CONCLUSIONS

Both low and high serum IGF-1 levels are risk markers for CVD events in elderly men. The association between high serum IGF-1 and CVD events is mainly driven by CHD events.

Extracellular water and blood pressure in adults with growth hormone (GH) deficiency: a genotype-phenotype association study

Objectives

Growth hormone deficiency (GHD) in adults is associated with decreased extracellular water volume (ECW). In response to GH replacement therapy (GHRT), ECW increases and blood pressure (BP) reduces or remains unchanged. Our primary aim was to study the association between polymorphisms in genes related to renal tubular function with ECW and BP before and 1 year after GHRT. The ECW measures using bioimpedance analysis (BIA) and bioimpedance spectroscopy (BIS) were validated against a reference method, the sodium bromide dilution method (Br⁻).

Design and Methods

Using a candidate gene approach, fifteen single-nucleotide polymorphisms (SNPs) in nine genes with known impact on renal tubular function (AGT, SCNN1A, SCNN1G, SLC12A1, SLC12A3, KCNJ1, STK39, WNK1 and CASR) were genotyped and analyzed for associations with ECW and BP at baseline and with their changes after 1 year of GHRT in 311 adult GHD patients. ECW was measured with the Br⁻, BIA, and BIS.

Results

Both BIA and BIS measurements demonstrated similar ECW results as the reference method. At baseline, after adjustment for sex and BMI, SNP rs2291340 in the SLC12A1 gene was associated with ECW volume in GHD patients (p = 0.039). None of the SNPs influenced the ECW response to GHRT. One SNP in the SLC12A3 gene (rs11643718; p = 0.024) and three SNPs in the SCNN1G gene [rs5723 (p = 0.02), rs5729 (p = 0.016) and rs13331086 (p = 0.035)] were associated with the inter-individual differences in BP levels at baseline. A polymorphism in the calcium-sensing receptor (CASR) gene (rs1965357) was associated with changes in systolic BP after GHRT (p = 0.036). None of these associations remained statistically significant when corrected for multiple testing.

Conclusion

The BIA and BIS are as accurate as Br⁻ to measure ECW in GHD adults before and during GHRT. Our study provides the first evidence that individual polymorphisms may have clinically relevant effects on ECW and BP in GHD adults.

Growth hormone replacement normalizes impaired fibrinolysis: new insights into endothelial dysfunction in patients with hypopituitarism and growth hormone deficiency

BACKGROUND

Cardiovascular morbidity in adult patients with growth hormone deficiency (GHD) and hypopituitarism is increased. Clustering of cardiovascular risk factors leading to endothelial dysfunction and impaired fibrinolysis has also been reported and may account for progression to overt vascular changes in these patients. However, effect of long lasting GH replacement therapy on fibrinolytic capacity in GH deficient patients has not been investigated so far.

OBJECTIVE

To investigate fibrinolysis before and after challenge with venous occlusion in GHD patients with hypopituitarism before and during one year of growth hormone replacement.

DESIGN

Hospital based, interventional, prospective study.

INVESTIGATED SUBJECTS

Twenty one patient with GHD and fourteen healthy control subjects matched for age, sex and body mass index (BMI).

METHODS

Anthropometric, metabolic and fibrinolytic parameters were measured at the start and after three, six and twelve months of treatment with human recombinant GH.

RESULTS

At baseline GHD patients had significantly impaired fibrinolysis compared to healthy persons. During treatment with GH, significant changes were observed in insulin like growth factor 1(IGF-1) [from baseline 6.9(2.4-13.5) to 22.0(9.0-33.0) nmol/l after one month of treatment; p<0.01] and fibrinolysis. Improvement in fibrinolysis was mostly attributed to improvement of stimulated endothelial tissue plasminogen activator (t-PA) release in response to venous occlusion [from baseline 1.1(0.4-2.6) to 1.9(0.5-8.8) after one year of treatment; p<0.01].

CONCLUSION

Growth hormone replacement therapy has favorable effects on t-PA release from endothelium and net fibrinolytic capacity in GHD adults, which may contribute to decrease their risk of vascular complications.

Growth hormone and Klotho

Acromegaly is characterized by excessively high GH and IGF1 levels. Recent data suggest that soluble Klotho (sKlotho) is also elevated in patients with active acromegaly. sKlotho decreases towards normal following removal of the GH-producing pituitary adenoma. The Klotho gene was identified in mice following its accidental disruption by ectopic DNA. It is an ageing suppressor gene of restricted expression (mainly in kidneys, brain, and parathyroid and pituitary glands) encoding a transmembrane protein, mKlotho. mKlotho serves as a co-receptor in fibroblast growth factor 23 (FGF23) signalling. FGF23 promotes urinary phosphate excretion and inhibits the synthesis of calcitriol. The ectodomain of mKlotho is enzymatically released to result in a humoral factor, sKlotho, which exerts systemic effects (on ion channels and signalling pathways), possibly by working as an enzyme that modifies glycans of cell surface glycoproteins. GH enhances renal phosphate reabsorption and calcitriol production, i.e. exerts effects in the proximal tubule opposing those attributed to mKlotho, and attenuates calciuria in the distal tubule similar to sKlotho. sKlotho can be measured in extracellular fluids (serum, urine and cerebrospinal fluid (CSF)) by an ELISA. In line with predominant expression of Klotho in kidneys and choroid plexus, concentrations of sKlotho are particularly high in urine and CSF. Determination of sKlotho in serum and urine (both presumably reflecting GH action on the kidneys) could be used as a supplementary tool in the diagnosis and follow-up of patients with acromegaly. The question arises whether GH exerts selected actions via modifying activities of Klotho.

Pituitary disease mortality: is it fiction?

During the last 20 years a tremendous improvement in the care of patients with pituitary tumors and of hypopituitarism has been achieved. If we resolve most of the possible causes of the increased cardiovascular disease and stroke mortality a normal survival is expected in these patients. Recently, a large population based study showed a decline in the risk of non-fatal stroke and of non-fatal cardiac events in GH deficient patients. This improvement was achieved by complete hormone replacement, including long term GH replacement, together with prescription of cardio protective drugs. If we follow the latest achievements in pituitary imaging, surgery techniques, hormone substitutions, cardio protective medications, we would expect a normal longevity in these patients. This review will focus on; (1) pituitary insufficiencies and hormone substitutions, (2) modes of cranial radiotherapy, and (3) new techniques in the surgery of a pituitary adenoma.

The GH/IGF-1 axis in obesity: pathophysiology and therapeutic considerations

Obesity has become one of the most common medical problems in developed countries, and this disorder is associated with high incidences of hypertension, dyslipidaemia, cardiovascular disease, type 2 diabetes mellitus and specific cancers. Growth hormone (GH) stimulates the production of insulin-like growth factor 1 in most tissues, and together GH and insulin-like growth factor 1 exert powerful collective actions on fat, protein and glucose metabolism. Clinical trials assessing the effects of GH treatment in patients with obesity have shown consistent reductions in total adipose tissue mass, in particular abdominal and visceral adipose tissue depots. Moreover, studies in patients with abdominal obesity demonstrate a marked effect of GH therapy on body composition and on lipid and glucose homeostasis. Therefore, administration of recombinant human GH or activation of endogenous GH production has great potential to influence the onset and metabolic consequences of obesity. However, the clinical use of GH is not without controversy, given conflicting results regarding its effects on glucose metabolism. This Review provides an introduction to the role of GH in obesity and summarizes clinical and preclinical data that describe how GH can influence the obese state.

Pre-weaning growth hormone treatment reverses hypertension and endothelial dysfunction in adult male offspring of mothers undernourished during pregnancy

Maternal undernutrition results in elevated blood pressure (BP) and endothelial dysfunction in adult offspring. However, few studies have investigated interventions during early life to ameliorate the programming of hypertension and vascular disorders. We have utilised a model of maternal undernutrition to examine the effects of pre-weaning growth hormone (GH) treatment on BP and vascular function in adulthood. Female Sprague-Dawley rats were fed either a standard control diet (CON) or 50% of CON intake throughout pregnancy (UN). From neonatal day 3 until weaning (day 21), CON and UN pups received either saline (CON-S, UN-S) or GH (2.5 ug/g/day)(CON-GH, UN-GH). All dams were fed ad libitum throughout lactation. Male offspring were fed a standard diet until the end of the study. Systolic blood pressure (SBP) was measured at day 150 by tail cuff plethysmography. At day 160, intact mesenteric vessels mounted on a pressure myograph. Responses to pressure, agonist-induced constriction and endothelium-dependent vasodilators were investigated to determine vascular function. SBP was increased in UN-S groups and normalised in UN-GH groups (CON-S 121±2 mmHg, CON-GH 115±3, UN-S 146±3, UN-GH 127±2). Pressure mediated dilation was reduced in UN-S offspring and normalised in UN-GH groups. Vessels from UN-S offspring demonstrated a reduced constrictor response to phenylephrine and reduced vasodilator response to acetylcholine (ACh). Furthermore, UN-S offspring vessels displayed a reduced vasodilator response in the presence of L-NG-Nitroarginine Methyl Ester (L-NAME), carbenoxolone (CBX), L-NAME and CBX, Tram-34 and Apamin. UN-GH vessels showed little difference in responses when compared to CON and significantly increased vasodilator responses when compared to UN-S offspring. Pre-weaning GH treatment reverses the negative effects of maternal UN on SBP and vasomotor function in adult offspring. These data suggest that developmental cardiovascular programming is potentially reversible by early life GH treatment and that GH can reverse the vascular adaptations resulting from maternal undernutrition.

Reduced arterial stiffness in patients with acromegaly: non-invasive assessment by the cardio-ankle vascular index (CAVI)

In patients with acromegaly, cardiovascular diseases are the most common cause of death. Arterial stiffness is increasingly recognized as a valuable surrogate marker for predicting cardiovascular events. To evaluate the vascular status of acromegalic patients, we used the cardio-ankle vascular index (CAVI) to reflect the arterial stiffness from the heart to the ankles. We analyzed 21 acromegalic patients, comprising five patients with untreated active acromegaly, one patient treated with medication and 15 patients who underwent transsphenoidal surgery. Among the 15 patients with surgery, 10 received additional therapies with dopamine agonists and/or somatostatin analogs. All patients with acromegaly unexpectedly showed significant reductions in the CAVI, indicating reduced arterial stiffness, compared with age- and sex-matched controls, regardless of whether they underwent surgery. There was a significant negative correlation between the CAVI and the serum insulin-like growth factor (IGF)-I level in these patients. Active acromegalic patients were associated with lower CAVI than controlled patients. Sequential measurements of the CAVI and serum IGF-I before and after treatment with octreotide and transsphenoidal surgery revealed that a reduced IGF-I level after treatment was accompanied by CAVI elevation. The present findings indicate that the CAVI is negatively correlated with the serum IGF-I level in acromegaly. These findings are consistent with previous reports indicating that the GH/IGF-I axis reduces peripheral vascular resistance. This non-invasive assessment can reflect the present vascular status and would be a useful marker for evaluation of therapeutic effects in patients with acromegaly.

The cardiovascular system in growth hormone excess and growth hormone deficiency

The clinical conditions associated with GH excess and GH deficiency (GHD) are known to be associated with an increased risk for the cardiovascular morbidity and mortality, suggesting that either an excess or a deficiency in GH and/or IGF-I is deleterious for cardiovascular system. In patients with acromegaly, chronic GH and IGF-I excess commonly causes a specific cardiomyopathy characterized by a concentric cardiac hypertrophy associated with diastolic dysfunction and, in later stages, with systolic dysfunction ending in heart failure if GH/IGF-I excess is not controlled. Abnormalities of cardiac rhythm and anomalies of cardiac valves can also occur. Moreover, the increased prevalence of cardiovascular risk factors, such as hypertension, diabetes mellitus, and insulin resistance, as well as dyslipidemia, confer an increased risk for vascular atherosclerosis. Successful control of the disease is accompanied by a decrease of the cardiac mass and improvement of cardiac function and an improvement in cardiovascular risk factors. In patients with hypopituitarism, GHD has been considered the under- lying factor of the increased mortality when appropriate standard replacement of the pituitary hormones deficiencies is given. Either childhood-onset or adulthood-onset GHD are characterized by a cluster of abnormalities associated with an increased cardiovascular risk, including altered body composition, unfavorable lipid profile, insulin resistance, endothelial dysfunction and vascular atherosclerosis, a decrease in cardiac mass together with an impairment of systolic function mainly after exercise. Treatment with recombinant GH in patients with GHD is followed by an improvement of the cardiovascular risk factors and an increase in cardiac mass together with an improvement in cardiac performance. In conclusion, acromegaly and GHD are associated with an increased risk for cardiovascular morbidity and mortality, but the control of GH/IGF-I secretion reverses cardiovascular abnormalities and restores the normal life expectancy.

Growth hormone, prolactin, and sexuality

GH and PRL, although not considered as 'classi cal' sexual hormones, could play a role in the endocrine control of sexual function both in men and women. Physiologically, PRL seems to be involved in the central control of sexual behavior and activity, by modulating mainly the effects of dopaminergic and serotoninergic systems on sexual function. Indeed, circulating PRL levels increase after orgasm and may potentially play a role in the acute regulation of further sexual arousal following orgasm both in men and women. On the other hand, either short-term or long-term PRL in crease can modulate central nervous system areas involved in the control of sexual function and, peripherally, can directly influence mechanisms of penile erection in men, and presently only as an hypothesis, mechanisms related to the sexual response of genitalia in women. Furthermore, chronic hyperprolactinemia is classically associated with hypogonadotropic hypogonadism and sexual dysfunction in both sexes. Successful treatment of chronic hyperprolactinemia generally restores normal sexual function both in men and women although this effect is not only related to relapse of gonadal function. Hypoprolactinemia is recently recognised as a possible risk factor of arteriogenic erectile dysfunction while a possible role on female sexual function is not known. The physiological role of GH on sexual function is not fully elucidated. GH is an important regulator of hypothalamus-pituitary-gonadal axis and seems to participate in the regulation of the sexual response of genitalia in men, and potentially also in women. Sexual function in men and women with GH deficiency (GHD) and GH excess, particularly in acromegaly, is scantily studied and GH- or IGF-I-dependent effects are difficult to quantify. Nevertheless, a decrease of desire and arousability both in men and women, together with an impairment of erectile function in men, have been described both in patients with GHD and acromegaly, although it is not clear whether they are dependent directly on the hormone defect or excess or they are consequence of the hypogonadism or the different clinical complications or the physical disfigurement and psychological imbalance, which are associated with the diseases, and are potentially affecting sexual function. Data on beneficial effects of GH replacement therapy and specific surgical or pharmacological approach for acromegaly are far to be fully elucidated although restoring normal GH/IGF-I levels have been associated to improvement of sexual function.

Hormone replacement therapy and physical function in healthy older men. Time to talk hormones?

Improving physical function and mobility in a continuously expanding elderly population emerges as a high priority of medicine today. Muscle mass, strength/power, and maximal exercise capacity are major determinants of physical function, and all decline with aging. This contributes to the incidence of frailty and disability observed in older men. Furthermore, it facilitates the accumulation of body fat and development of insulin resistance. Muscle adaptation to exercise is strongly influenced by anabolic endocrine hormones and local load-sensitive autocrine/paracrine growth factors. GH, IGF-I, and testosterone (T) are directly involved in muscle adaptation to exercise because they promote muscle protein synthesis, whereas T and locally expressed IGF-I have been reported to activate muscle stem cells. Although exercise programs improve physical function, in the long-term most older men fail to comply. The GH/IGF-I axis and T levels decline markedly with aging, whereas accumulating evidence supports their indispensable role in maintaining physical function integrity. Several studies have reported that the administration of T improves lean body mass and maximal voluntary strength in healthy older men. On the other hand, most studies have shown that administration of GH alone failed to improve muscle strength despite amelioration of the detrimental somatic changes of aging. Both GH and T are anabolic agents that promote muscle protein synthesis and hypertrophy but work through separate mechanisms, and the combined administration of GH and T, albeit in only a few studies, has resulted in greater efficacy than either hormone alone. Although it is clear that this combined approach is effective, this review concludes that further studies are needed to assess the long-term efficacy and safety of combined hormone replacement therapy in older men before the medical rationale of prescribing hormone replacement therapy for combating the sarcopenia of aging can be established.

Effects of bench step exercise on arterial stiffness in post-menopausal women: contribution of IGF-1 bioactivity and nitric oxide production

OBJECTIVE

To examine the effect of bench step exercise on arterial pulse wave velocity (PWV) and the associated contribution of insulin-like growth factor (IGF)-1 bioactivity and nitric oxide (NO).

DESIGN

Twenty-six elderly (post-menopausal) women were randomly allocated to a bench step exercise group or a control group. The participants in the bench step exercise group practiced a 12-week home-based bench step exercise for 10-20min, 3 times daily (i.e., for a total of 140min/week at the intensity level of lactate threshold (LT)). In addition to conventional risk factors of atherosclerosis, PWV, IGF-1/IGF binding protein (IGFBP)-3 molar ratio (an index for IGF-1 bioactivity), and urinary nitrite/nitrate (NO(x)) excretion were measured before and after the intervention.

RESULTS

BMI, systolic blood pressure, fasting plasma glucose, low-density lipoprotein cholesterol, LT, and PWV were significantly improved in the bench step exercise group. A significant positive correlation between changes in PWV and IGF-1/IGFBP-3 molar ratio, and a significant negative correlation between changes in IGF-1/IGFBP-3 molar ratio and urinary NO(x) excretion were found in the bench step exercise group.

CONCLUSION

The bench step exercise leads to improvements in not only the classical risk factors of atherosclerosis but also the arterial stiffness in elderly women, partly through NO production via IGF-1 bioactivity.

Role of Growth Hormone Deficiency and Treatment in Chronic Kidney Disease

Malnutrition and inflammation are strong predictors of mortality in advanced kidney disease, especially in patients on renal replacement therapy. The complex relationship between kidney disease, uremia, and malnutrition significantly contributes to the increased morbidity and mortality in this patient population potentially through a relative deficiency in growth hormone (GH). With an approximate 26 million Americans currently affected by some stage of chronic kidney disease and a predicted 750,000 people to be on dialysis by 2020, there is a need to develop innovative strategies aimed at reducing the high mortality seen in dialysis patients. We will review evidence on one such intervention with infusion of recombinant GH to improve the nutritional and inflammatory state, thereby expecting to improve the mortality and morbidity in this patient population.

The GH/IGF-1 Axis and Heart Failure

The growth hormone (GH)/insulin-like growth factor 1 (IGF-1) axis regulates cardiac growth, stimulates myocardial contractility and influences the vascular system. The GH/IGF-1 axis controls intrinsic cardiac contractility by enhancing the intracellular calcium availability and regulating expression of contractile proteins; stimulates cardiac growth, by increasing protein synthesis; modifies systemic vascular resistance, by activating the nitric oxide system and regulating non-endothelial-dependent actions. The relationship between the GH/IGF-1 axis and the cardiovascular system has been extensively demonstrated in numerous experimental studies and confirmed by the cardiac derangements secondary to both GH excess and deficiency. Several years ago, a clinical non-blinded study showed, in seven patients with idiopathic dilated cardiomyopathy and chronic heart failure (CHF), a significant improvement in cardiac function and structure after three months of treatment with recombinant GH plus standard therapy for heart failure. More recent studies, including a small double-blind placebo-controlled study on GH effects on exercise tolerance and cardiopulmonary performance, have shown that GH benefits patients with CHF secondary to both ischemic and idiopathic dilated cardiomyopathy. However, conflicting results emerge from other placebo-controlled trials. These discordant findings may be explained by the degree of CHF-associated GH resistance. In conclusion, we believe that more clinical and experimental studies are necessary to exactly understand the mechanisms that determine the variable sensitivity to GH and its positive effects in the failing heart.

Serum vascular endothelial growth factor (VEGF) is elevated in GH deficient adults

OBJECTIVE

GHD adults exhibit a number of adverse surrogate markers of vascular risk culminating in excess vascular morbidity and mortality. Vascular endothelial growth factor (VEGF) and matrix metalloproteinases (MMPs) have been implicated in the pathogenesis of a number of vascular morbidities. Furthermore, serum levels decrease following GH replacement in GHD adults, though it remains unclear if levels are significantly elevated in untreated individuals.

DESIGN

A cross-sectional case-control study.

METHODS

We measured fasting serum VEGF, MMP2, and MMP9 in 27 patients with GHD, 24 with partial GHD (GHI), and 25 sex- and age-matched controls.

RESULTS

GHD (483±334 vs 326±180ng/l, P=0.04), but not GHI (354±192 vs 326±180ng/l, P=n/s) adults had significantly elevated VEGF levels compared with controls. Neither MMP2, nor MMP9 levels were elevated in the patient groups. Serum VEGF levels correlated positively with LDL-cholesterol (R=0.34, P=0.004) and serum MMP9 values (R=0.36, P=0.002), and negatively with IGF-I values, however, no correlation was observed with MMP2. Multiple regression analysis with VEGF levels as the dependent variable, and age, gender, % fat mass, LDL-C, insulin and IGF-I as independent variables revealed VEGF levels to be dependent on LDL-C alone (P=0.003, R=0.36).

CONCLUSION

GHD adults have elevated VEGF levels, which correlate with MMP9 levels. Both VEGF and MMP9 are associated with vascular pathologies and may provide insight in to the pathophysiological mechanisms underlying the increased vascular morbidity and mortality observed in GHD adults.

Postradiation therapy hypopituitarism

The increasing use of radiation treatment for head and neck cancers and other tumors, including pituitary adenomas, from the mid-20th Century onwards led to the recognition that pituitary function may be affected - often leading to some degree of pituitary insufficiency. Our knowledge is mostly based on observational or retrospective rather than randomized prospective studies. The various axes may be impacted at the hypothalamic or pituitary levels, or both. Some axes - the somatotropic and gonadotropic - appear to be especially vulnerable to radiation damage and may be affected quite early, whereas posterior pituitary function is rarely affected. Increased use of stereotactic radiosurgery, which focuses the radiation dose on the abnormal tissue, may be expected to reduce the impact on normal pituitary function, but such studies that are available are, as yet, relatively short term. Prospective studies of the effect of stereotactic radiosurgery on pituitary function would be valuable.

Regulation of inducible nitric oxide synthase activity/expression in rat hearts from ghrelin-treated rats

The purpose of this study was to examine the effects of ghrelin on protein kinase B (Akt) and mitogen-activated protein kinase p42/44 (ERK1/2) activation as well as ghrelin effects on inducible nitric oxide (NO) synthase (iNOS; for gene Nos2) activity/expression in rat hearts. Male Wistar rats were treated with ghrelin (0.3 nmol/5 μl) or an equal volume of phosphate-buffered saline, injected every 24 h into the lateral cerebral ventricle for 5 days and 2 h after the last treatment the animals were sacrificed. Serum NO, L-arginine (L-Arg), and arginase activity were measured spectrophotometrically. For phosphorylation of Akt, ERK1/2, and iNOS protein expression, Western blot method was used. The expression of Nos2 mRNA was measured by the quantitative real-time polymerase chain reaction (qRT-PCR). Treatment with ghrelin significantly increased NO production in serum by 1.4-fold compared with control. The concentration of L-Arg was significantly higher in ghrelin-treated rats than in control while arginase activity was significantly lower in ghrelin-treated than in control hearts. Ghrelin treatment increased phosphorylation of Akt by 1.9-fold and ERK1/2 by 1.6-fold and increased iNOS expression by 2.5-fold compared with control. In addition, ghrelin treatment increased Nos2 gene expression by 2.2-fold as determined by qRT-PCR. These results indicate that ghrelin regulation of iNOS expression/activity is mediated via Akt/ERK1/2 signaling pathway. These results may be relevant to understanding molecular mechanisms underlying direct cardiovascular actions of ghrelin.

The diagnosis and treatment of growth hormone deficiency in adults

PURPOSE OF REVIEW

This review summarizes the recent published information regarding efficacy and complications of growth hormone replacement therapy. Several recent reports have monitored patients for periods of up to 10 years. Additionally, a consensus conference has been held regarding needed improvements in diagnostic testing and the recommendations of consensus panels regarding diagnostic criteria and laboratory test utilization are summarized.

RECENT FINDINGS

Long-term studies show growth hormone can be administered safely and that muscle strength and function as well as lipoprotein abnormalities and low-bone mineral density show sustained improvement over extended periods of time. The complications that occur are generally dose-dependent and once attenuated do not tend to recur. Long-term safety studies regarding improvement in cardiovascular mortality and/or worsening prognosis for patients who develop malignancies are available only in the form of observational studies and randomized controlled long-term trial information is not yet available. The studies reported provide a means for clinicians to ascertain the patients who are likely to derive the greatest benefit from growth hormone when the appropriate diagnostic testing and treatment paradigms are utilized.

SUMMARY

The studies that are summarized provide useful information for assessing the response to treatment, selecting patients who are candidates for long-term replacement therapy and for selecting those in whom the need for therapy may need to be reassessed.

Non-invasive measurement of the haemodynamic effects of inhaled salbutamol, intravenous L-arginine and sublingual nitroglycerin

AIMS

To examine the effects of salbutamol and L-arginine, two compounds acting largely on the endothelium, and the endothelium-independent agent nitroglycerin on blood pressure, arterial compliance, cardiac function and vascular resistance.

METHODS

Continuous radial pulse wave analysis, whole-body impedance cardiography, and plethysmographic blood pressure from fingers in the supine position and during head-up tilt were recorded in nine healthy subjects. Data were captured before and after L-arginine (10 mg mg(-1) min(-1)) or saline infusion, salbutamol (400 microg) or placebo inhalation, and sublingual nitroglycerin (0.25 mg) or placebo resoriblet.

RESULTS

The results of all measurements were comparable before drug administration. The effects of inhaled salbutamol were apparent in the supine position: systemic vascular resistance (-9.2 +/- 2.6%) and augmentation index (-4.0 +/- 1.5%) decreased, and heart rate (8.6 +/- 2.5%) and cardiac output (8.8 +/- 3.1%) increased. L-arginine had no clear effects on supine haemodynamics, but during head-up tilt blood pressure was moderately decreased and reduction in aortic reflection time prevented, indicating improved large arterial compliance. Nitroglycerin reduced supine vascular resistance (-6.7 +/- 1.8%) and augmentation index (-7.4 +/- 1.6%), and increased cardiac output (+9.2 +/- 2.7%). During head-up tilt, nitroglycerin increased cardiac output (+10.6 +/- 5.6%) and heart rate (+40 +/- 7.5%), decreased vascular resistance (-7.8 +/- 5.8%) and augmentation index (-18.7 +/- 3.2%), and prevented the decrease in aortic reflection time.

CONCLUSIONS

Inhaled salbutamol predominantly changed supine haemodynamics, whereas the moderate effects of L-arginine were observed during the head-up tilt. In contrast, small doses of nitroglycerin induced major changes in haemodynamics both supine and during the head-up tilt. Altogether, these results emphasize the importance of haemodynamic measurements in both the supine and upright positions.

Hormonal modulation of endothelial NO production

Since the discovery of endothelium-derived relaxing factor and the subsequent identification of nitric oxide (NO) as the primary mediator of endothelium-dependent relaxations, research has focused on chemical and physical stimuli that modulate NO levels. Hormones represent a class of soluble, widely circulating chemical factors that impact production of NO both by rapid effects on the activity of endothelial nitric oxide synthase (eNOS) through phosphorylation of the enzyme and longer term modulation through changes in amount of eNOS protein. Hormones that increase NO production including estrogen, progesterone, insulin, and growth hormone do so through both of these common mechanisms. In contrast, some hormones, including glucocorticoids, progesterone, and prolactin, decrease NO bioavailability. Mechanisms involved include binding to repressor response elements on the eNOS gene, competing for co-regulators common to hormones with positive genomic actions, regulating eNOS co-factors, decreasing substrate for eNOS, and increasing production of oxygen-derived free radicals. Feedback regulation by the hormones themselves as well as the ability of NO to regulate hormonal release provides a second level of complexity that can also contribute to changes in NO levels. These effects on eNOS and changes in NO production may contribute to variability in risk factors, presentation of and treatment for cardiovascular disease associated with aging, pregnancy, stress, and metabolic disorders in men and women.

Investigation of early atherosclerotic changes in acromegalic patients

BACKGROUND

Functional and morphological changes of endothelium were risk factors for mortality attributed to atherosclerosis. Studies investigating early atherosclerotic alterations and the effect of the treatment of acromegaly on these alterations gave conflicting results.

OBJECTIVE

Surrogate markers of early atherosclerotic changes, i.e. brachial artery flow-mediated dilation (FMD) and carotid artery intima-media-thickness (IMT) in active and inactive acromegalic patients were compared with control subjects matched to patients for age, sex and cardiovascular risk factors to find out the direct effects of growth hormone (GH)/insulin-like growth factor-1 excess.

METHODS

In 14 active acromegalics and their 14 matched controls, 14 inactive acromegalics and their 14 matched controls, carotid artery IMT and FMD of brachial artery were measured. Inactive acromegalics were in remission for at least 1 year.

RESULTS

Active acromegalics had higher IMT than matched controls and inactive acromegalics (0.85 +/- 0.20 mm, 0.64 +/- 1.77 mm, 0.66 +/- 0.20 mm respectively; p < 0.005, p < 0.05) and IMT of inactive acromegalics was not different from their matched controls (0.61 +/- 0.12 mm). FMD was significantly lower in active acromegalics than in matched controls and inactive acromegalics (2.910 +/- 2.00 mm, 6.5 +/- 2.81 mm, 5.68 +/- 2.9 mm respectively; p < 0.005, p < 0.05). FMD of inactive acromegalics was not significantly different from their matched controls (7.96 +/- 3.12 mm). A significant inverse relationship was found between GH and FMD in active acromegalics (r = -0.659, p = 0.010).

CONCLUSION

In active acromegalics, early atherosclerotic changes are not only attributed to the high prevalence of risk factors, but also to the abnormal GH secretion itself.