Cardiovascular effects of prolonged growth hormone replacement in adults

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.

Reviewing the safety of GH replacement therapy in adults

CONTEXT

Systematic data on safety of growth hormone (GH) replacement therapy in adult GH deficiency is lacking.

OBJECTIVE

To systematically describe safety of adult GH replacement therapy on glucose metabolism and long term safety.

DESIGN

A systematic web-based search of PubMed was performed guided by the Standard Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

OUTCOME

Randomised controlled trials of ≥3 months and open trials for ≥12 months with more than 50 adult patients (50 patient years, prospective and retrospective) including adverse event reporting as well as articles on mortality primarily on adult onset patients, reporting mortality ratios on GH treated patients, were included for the review.

RESULTS

Based on the defined selection criteria 94 studies were included. The short-term early placebo controlled trials did not demonstrate an increased frequency of diabetes mellitus (DM) and the long-term open studies did not consistently show an increased incidence of DM during GH replacement. The concern that long-term GH replacement might increase the risk of primary cancer, secondary neoplasia after tumour treatment and recurrence of previous tumours was not evident in the study data.

CONCLUSION

Based on available data, short- and long-term adult GH replacement in patients with severe GH deficiency and hypopituitarism is safe. However, the small number of subjects, limitation of long-term of GH treatment data and absence of an adequate control population is still a limitation for the interpretation of these data.

Early-onset growth hormone deficiency results in diastolic dysfunction in adult-life and is prevented by growth hormone supplementation

OBJECTIVE

The primary goal of growth hormone (GH) replacement is to promote linear growth in children with growth hormone deficiency (GHD). GH and insulin-like growth factor-1 (IGF-1) are also known to have roles in cardiac development and as modulators of myocardial structure and function in the adult heart. However, little is known about cardiac diastolic function in young adults with childhood onset GH deficiency in which GH treatment was discontinued following puberty. The aim of the study was to evaluate the effects of long standing GHD and peri-pubertal or continuous GH replacement therapy on diastolic function in the adult dwarf rat.

DESIGN

The dwarf rat, which possesses a mutation in a transcription factor necessary for development of the somatotroph, does not exhibit the normal peri-pubertal rise in GH around day 28 and was used to model childhood or early-onset GHD (EOGHD). In another group of male dwarfs, GH replacement therapy was initiated at 4 weeks of age when GH pulsatility normally begins. Ten weeks after initiation of injections, GH-treated dwarf rats were divided into 2 groups; continued treatment with GH for 12 weeks (GH-replete) or treatment with saline for 12 weeks. This latter group models GH supplementation during adolescence with GHD beginning in adulthood (adult-onset GHD; AOGHD). Saline-treated heterozygous (HZ) rats were used as age-matched controls. At 26 weeks of age, cardiac function was assessed using invasive or noninvasive (conventional and tissue Doppler) indices of myocardial contractility and lusitropy.

RESULTS

Systolic function, as determined by echocardiography, was similar among groups. Compared with HZ rats and GH-replete dwarfs, the EOGHD group exhibited significant reductions in myocardial relaxation and increases in left ventricular filling pressure, indicative of moderate diastolic dysfunction. This was further associated with a decrease in the cardiac content of sarcoplasmic reticulum Ca(2+) ATPase (SERCA2), one of the important cardiac calcium regulatory proteins. Dwarfs supplemented with GH during the peri-adolescence stage, but not beyond (AOGHD), exhibited a subtle prolongation in the deceleration time to early filling. In contrast, continual GH replacement preserved diastolic function such that the cardiac phenotype of the GH-replete dwarfs resembled that of their age-matched HZ counterpart.

DISCUSSION

Our data indicate that GHD during adolescence leads to overt diastolic dysfunction in early adulthood and this is prevented by continual GH replacement therapy. Since discontinuation of GH replacement following adolescence only mitigated the lusitropic deficits that were observed in untreated dwarfs, GH treatment into adulthood could be beneficial.

Doping and musculoskeletal system: short-term and long-lasting effects of doping agents

Doping is a problem that has plagued the world of competition and sports for ages. Even before the dawn of Olympic history in ancient Greece, competitors have looked for artificial means to improve athletic performance. Since ancient times, athletes have attempted to gain an unfair competitive advantage through the use of doping substances. A Prohibited List of doping substances and methods banned in sports is published yearly by the World Anti-Doping Agency. Among the substances included are steroidal and peptide hormones and their modulators, stimulants, glucocorticosteroids, β₂-agonists, diuretics and masking agents, narcotics, and cannabinoids. Blood doping, tampering, infusions, and gene doping are examples of prohibited methods indicated on the List. Apart from the unethical aspect of doping, as it abrogates fair-play's principle, it is extremely important to consider the hazards it presents to the health and well-being of athletes. The referred negative effects for the athlete's health have to do, on the one hand, by the high doses of the performance-enhancing agents and on the other hand, by the relentless, superhuman strict training that the elite or amateur athletes put their muscles, bones, and joints. The purpose of this article is to highlight the early and the long-lasting consequences of the doping abuse on bone and muscle metabolism.

The influence of growth hormone replacement on peripheral inflammatory and cardiovascular risk markers in adults with severe growth hormone deficiency

BACKGROUND

Adult GHD syndrome is associated with clustering of adverse cardiovascular (CV) risk factors such as abnormal body composition, dyslipidemia, insulin resistance and abnormal haemostatic factors. There is a wealth of evidence linking CV events with elevated levels of inflammatory markers (hs-CRP and IL-6) in the general population; however data on their abnormalities in GHD and specially the effects of GH replacement (GHR) on these inflammatory markers are limited.

OBJECTIVE

To study the effects of GHR on inflammatory markers, glucose homeostasis and body composition in a cohort of adults with recently diagnosed severe GHD due to hypothalamic pituitary disease.

DESIGN

Fifteen hypopituitary adults (11 males, mean age 48.5 years) with recently diagnosed, severe GHD were recruited. Patients received GHR (in addition to other pituitary hormone replacements) titrated to clinical response and to normalize age and gender adjusted IGF-1 levels. Weight, waist hip ratio (WHR), body composition, fasting plasma glucose and insulin, insulin resistance index (HOMA-IR), fasting serum lipid levels, hs-CRP, IL-6 and TNF-alpha were measured at baseline and following a minimum 6 months of stable maintenance GHR.

RESULTS

GHR resulted in a physiological increase in IGF-1 SDS [median -0.6 to +0.39, P<0.0001], improved quality of life (mean pre-treatment AGHDA score 16 vs. post-treatment score 7, P<0.0001) and reduction in WHR (0.94 vs. 0.92, P=0.01). There were no significant changes in body weight and composition. Levels of hs-CRP (log transformed, mean (SD)) were significantly reduced following GHR (pre 1.21 (0.9) vs. post 0.27 (0.9), P<0.0001) but TNF-alpha and IL-6 levels remained unchanged. Fasting glucose (mmol/L) [4.6 (0.1) vs. 5.1 (0.1), P=0.003], fasting insulin (muU/mL) [9.4 (8.1) vs. 12.1 (9.2), P=0.03] and HOMA-IR [1.2 (1.0) vs. 1.5 (1.1) P=0.02] (all pre-GHR vs. post-GHR and mean (SD)) significantly increased following GHR indicating increased insulin resistance. Significant improvements were noted in fasting LDL-cholesterol (LDL-C) and HDL-cholesterol (HDL-C) levels following GHR [3.4 (0.9) vs. 2.9 (0.7), P=0.03 and 1.2 (0.2) vs. 1.3 (0.2), P=0.02, respectively] (all pre-GHR vs. post-GHR and mean (SD)). Levels of total cholesterol and triglycerides did not change following GHR.

CONCLUSIONS

Physiological GHR for at least 6 months in hypopituitary adults with recently diagnosed severe GHD resulted in favourable changes in hs-CRP, WHR, fasting LDL-C and HDL-C levels all of which are recognised CV risk markers. However, there remains a high prevalence of obesity in this population and given the worsening of insulin sensitivity in the short term with GHR, monitoring and aggressive treatment of established CV risk factors is essential to reduce premature atherosclerotic CVD in this patient population.

The GH-IGF-I axis and the cardiovascular system: clinical implications

BACKGROUND

GH and IGF-I affect cardiac structure and performance. In the general population, low IGF-I has been associated with higher prevalence of ischaemic heart disease and mortality. Both in GH deficiency (GHD) and excess life expectancy has been reported to be reduced because of cardiovascular disease.

OBJECTIVE

To review the role of the GH-IGF-I system on the cardiovascular system.

RESULTS

Recent epidemiological evidence suggests that serum IGF-I levels in the low-normal range are associated with increased risk of acute myocardial infarction, ischaemic heart disease, coronary and carotid artery atherosclerosis and stroke. This confirms previous findings in patients with acromegaly or with GH-deficiency showing cardiovascular impairment. Patients with either childhood- or adulthood-onset GHD have cardiovascular abnormalities such as reduced cardiac mass, diastolic filling and left ventricular response at peak exercise, increased intima-media thickness and endothelial dysfunction. These abnormalities can be reversed, at least partially, after GH replacement therapy. In contrast, in acromegaly chronic GH and IGF-I excess causes a specific cardiomyopathy: concentric cardiac hypertrophy (in more than two-thirds of the patients at diagnosis) associated to diastolic dysfunction is the most common finding. In later stages, impaired systolic function ending in heart failure can occur, if GH/IGF-I excess is not controlled. Abnormalities of cardiac rhythm and of cardiac valves can also occur. Successful control of acromegaly is accompanied by decrease of the left ventricular mass and improvement of cardiac function.

CONCLUSION

The cardiovascular system is a target organ for GH and IGF-I. Subtle dysfunction in the GH-IGF-I axis are correlated with increased prevalence of ischaemic heart disease. Acromegaly and GHD are associated with several abnormalities of the cardiovascular system and control of GH/IGF-I secretion reverses (or at least stops) cardiovascular abnormalities.

Exercise echocardiography reveals subclinical cardiac dysfunction in young adult survivors of childhood acute lymphoblastic leukemia

OBJECTIVE

Anthracyclines (AC) have contributed significantly to increased survival rate in acute lymphoblastic leukemia (ALL), although the use of these drugs is limited due to cardiotoxicity. The aim was to evaluate heart muscle function in asymptomatic adult survivors of ALL treated in early childhood in relation to the combined effects of AC and other potential cardiotoxic factors.

PROCEDURE

Twenty-three young adult ALL survivors who had all received treatment with median 120 (120-400) mg AC/m(2) before the onset of puberty were examined median 21 years after remission and compared with 12 healthy controls. Basal echocardiography including two-dimensional (2D) M-mode and Doppler examination was performed, followed by a maximal exercise stress test and stress echocardiography immediately after stress test and after 5 min recovery.

RESULTS

We found significant differences in systolic function between patients and controls at maximal exercise despite absence of reported symptoms from the patients. The most marked difference was in ejection fraction at stress 59.5% (32.6-81.1) and 77.3% (66.2-85.3), respectively (P < 0.00006). Ten out of 23 patients reduced their ejection fraction at stress compared with at rest; this was not found in any of the controls. Cardiovascular risk factors such as GH deficiency and a high proportion of trunk fat did not have an impact on cardiac function.

CONCLUSIONS

With very long follow up in a homogenous cohort of ALL survivors, we found subclinical cardiac dysfunction with exercise stress echocardiography even after low doses of AC.

Beginning to end: cardiovascular implications of growth hormone (GH) deficiency and GH therapy

Both growth hormone (GH) and insulin-like growth factor I (IGF-I) are involved in heart development and in maintenance of cardiac structure and performance. Cardiovascular disease has been reported to reduce life expectancy in both GH deficiency (GHD) and GH excess. Patients with GHD suffer from a cluster of abnormalities associated with increased cardiovascular risk, including abnormal body composition, unfavorable lipid profile, increased fibrinogen and C-reactive protein levels, insulin resistance, early atherosclerosis and endothelial dysfunction, and impaired left ventricular (LV) performance (i.e., reduced diastolic filling and impaired response to peak exercise). Long-term GH replacement therapy reverses most of these abnormalities. More consistently, GH replacement reduces body fat and visceral adipose tissue, reduces low-density lipoprotein cholesterol and triglyceride levels, and improves endothelial function. GH replacement also reduces intima media thickness at major arteries and improves LV performance, but these results have been observed only in small series of patients treated on a short-term basis. This review discusses the roles of GHD and GH replacement therapy in the development of cardiovascular disease.

Human Placental Lactogen Decreases Regional Blood Flow in Anesthetized Pigs

In 22 pigs anesthetized with sodium pentobarbitone, changes in blood flow caused by infusion of human placental lactogen into the left renal, external iliac, and anterior descending coronary arteries were assessed using electromagnetic flowmeters. In 17 pigs, infusion of human placental lactogen whilst keeping the heart rate and arterial pressure constant decreased coronary, renal and iliac flow. In 5 additional pigs, increasing the dose of human placental lactogen produced a dose-related decrease in regional blood flow. The mechanisms of the above response were studied in 15 of the 17 pigs by repeating the experiment of infusion. The human placental lactogen-induced decrease in regional blood flow was not affected by blockade of cholinergic receptors (5 pigs) or of alpha-adrenergic receptors (5 pigs), but it was abolished by blockade of beta2-adrenergic receptors (5 pigs). The present study showed that intra-arterial infusion of human placental lactogen primarily decreased coronary, renal and iliac blood flow. The mechanism of this response was shown to be due to the inhibition of a vasodilatory beta2-adrenergic receptor-mediated effect.

Influence of growth hormone on cardiovascular health and disease

Experimental and clinical studies indicate that growth hormone (GH) and insulin-like growth factor-1 (IGF-1) are involved in heart development. Impaired cardiovascular function, as recently demonstrated, could potentially reduce life expectancy both in GH deficiency (GHD) and excess. Patients with childhood- or adult-onset GHD may have both cardiac structural and functional abnormalities, i.e. reduced cardiac mass, reduced diastolic filling, and impaired left ventricular response to peak exercise. In addition, GHD patients may present with an increase in vascular intima-media thickness and a higher occurrence of atheromatous plaques that can further aggravate the hemodynamic conditions and contribute to the increased cardiovascular and cerebrovascular risk. However, some evidence has been provided to show that cardiovascular abnormalities can be partially reversed after somatropin (recombinant GH) therapy in patients with GHD. Recently, somatropin administration was shown to induce improvement in hemodynamics and clinical status in some patients with heart failure. Although these data need to be confirmed in more extensive studies, such promising results open new perspectives for somatropin therapy. The role of GH secretagogues in heart failure is still unknown.

The effects of 12 months of growth hormone replacement therapy on cardiac autonomic tone in adults with growth hormone deficiency

OBJECTIVES

Growth hormone deficiency (GHD) in adults is associated with a cluster of cardiovascular risk factors. Some abnormalities of cardiac structure and function have been reported in adult patients with GHD, but there are few data related to cardiac autonomic tone. Non-invasive assessment of cardiac autonomic status can be achieved by heart rate variability (HRV), which can be measured by using time-domain or frequency-domain variables. To our knowledge, short-term (6 months) effects of GH replacement therapy (GHRT) on HRV in a limited number of patients have been evaluated prospectively in only two previous studies. The present study was therefore designed to investigate the effects of GHD and 12 months of GHRT on cardiac autonomic tone in a larger number of adult patients with severe GHD.

PATIENTS AND METHODS

HRV measurement, by using time-domain variables, was performed in 22 patients with GHD (eight men, 14 women; mean age 45.4 +/- 2.4 years) and 22 healthy controls (nine men, 13 women; mean age 40.8 +/- 1.8 years) at baseline. The time-domain variables (sympathetically influenced parameters SDNN and SDANN and parasympathetically influenced parameters RMSSD and PNN50) were derived from 24-h electrocardiogram (ECG) recordings. In the patient group, cardiac autonomic tone was re-evaluated after 6 and 12 months of GHRT.

RESULTS

Mean baseline values of SDNN and SDANN were significantly higher (higher values mean lower sympathetic activity) in GHD patients than in healthy controls (P < 0.05), but mean baseline values of RMSSD and PNN50 did not differ significantly in healthy controls and patients. After 6 and 12 months of GHRT, mean SDNN and SDANN were decreased significantly when compared with the baseline values before GHRT (P < 0.05). However, mean RMSSD and PNN50 did not differ significantly from baseline. When SDNN and SDANN measurements were evaluated individually for each patient, after 12 months of GHRT both of the sympathetically influenced parameters decreased in 90% of the patients.

CONCLUSIONS

These data indicate that sympathetic tone is decreased in adult patients with severe GHD. Additionally, an increment in sympathetic activity and normalization of sympathovagal balance have been demonstrated after 6 and 12 months of GHRT. This result suggests that, at least at the doses used in this study, GHRT improves sympathetic tone, without an obvious arrhythmogenic effect.

Cardiovascular Effects of Growth Hormone Treatment: Potential Risks and Benefits

Growth hormone (GH) and insulin-like growth factor-I are involved in heart development and in maintaining cardiac structure and performance. Cardiovascular disease has been reported to reduce life expectancy both in GH deficiency (GHD) and in GH excess. Patients with GHD suffer from abnormalities of left ventricular performance, i.e. reduced diastolic filling and impaired response to peak exercise. Patients with GHD also have increased intima-media thickness at the common carotid arteries, associated with a higher occurrence of atherosclerotic plaques, which may further aggravate the haemodynamic conditions. This may contribute to increased cardiovascular and cerebrovascular risk. These cardiovascular abnormalities can be reversed, at least partially, with GH replacement therapy. In recent years, GH therapy has been used to increase cardiac mass in ischaemic or dilated cardiomyopathy, but the results have produced contradictory data.

Complications in adults with growth hormone deficiency--a survey study in Japan

It has been reported that adult patients with growth hormone deficiency (GHD) have increased risk factors for cardiovascular disorders in Western countries. However, data on this issue in Japan have not been fully investigated. To clarify the situation on this issue in Japan, a nationwide questionnaire survey was conducted by Study Group of Hypothalamo-Pituitary Disease, and medical records of 863 adult patients were recruited. The incidences of complications and risk factors for cardiovascular diseases were compared between GH deficient patients (GHD, n = 494) and GH intact patients (GHI, n = 369). The incidence of myocardial infarction was higher in GHD (1.2%) than in GHI (0.8%), but not significantly. The incidences of angina pectoris and liver dysfunction were significantly higher in GHD than in GHI (2.8 vs 0.8%, p = 0.048, and 11.9 vs 5.5%, p<0.0001, respectively). The prevalences of obesity and hyperlipidemia (HL) were significantly higher in GHD (p = 0.004, p<0.001, respectively). Combinations of HL plus diabetes mellitus (DM) or hypertension (HT) were more common in GHD than in GHI (HL + DM; 7.2 vs. 2.9%, HL + HT; 10.9 vs. 2.9%). These results indicated that GH deficiency have an increased prevalence of cardiovascular risk factors in Japanese similar to Western countries, and suggested that GH supplement therapy may be needed to reduce those complications.

Structural, functional and autonomic changes in the cardiovascular system in growth hormone deficient patients

BACKGROUND

Growth hormone deficiency (GHD) is known to cause higher rates of cardiovascular mortality. The purpose of the study was to analyze the structural and functional changes in the heart and investigate their relation to autonomic function as assessed with heart rate variability (HRV).

METHODS

Eleven untreated GHD patients (mean age 50.4 +/- 10.7 years, M/F: 3/8) and 15 age- and sex-matched healthy persons (mean age 45.3 +/- 10.4 years, M/F: 5/10) were compared. Both groups were examined with echocardiography, HRV, and exercise testing and findings were analyzed.

RESULTS

The groups were similar in height, weight, body mass index, body surface area, systolic and diastolic blood pressure, heart rate. The GHD patients had lower exercise duration and metabolic equivalent (MET) compared to controls (7.94 +/- 1.26 vs. 9.8 +/- 1.9 min, P < 0.001, for MET 8.85 +/- 0.86 vs. 10.7 +/- 2.23, P = 0.03). On echocardiography, GHD patients had lower interventricular septum diastolic diameter (9 +/- 0.89 vs. 10.7 +/- 0.88 mm, P < 0.001) and posterior wall thickness (8.4 +/- 0.93 vs. 9.8 +/- 0.91 mm, P = 0.002), and lower left ventricle mass index (90.9 +/- 20 vs. 112 +/- 8 g/m2, P = 0.01). Left ventricular ejection fraction was lower in the GHD patients (57.4 +/- 5.12% vs. 65.5 +/- 4.1%, P < 0.001). Time and frequency domain heart rate variability parameters, SDNN, SDANN, VLF, LF ve LF/HF were lower in GHD patients compared to controls. There was a significant correlation between left ventricle diastolic diameter and LF (r = 0.62, P = 0.02).

CONCLUSION

GHD seemed to cause decreased left ventricle mass and decreases in the sympathetic components of HRV that may have a bearing on the increased cardiovascular risk seen in these patients.

Myostatin is a skeletal muscle target of growth hormone anabolic action

Myostatin is a cytokine that has recently been shown to selectively and potently inhibit myogenesis. To investigate the mechanisms of anabolic actions of GH on skeletal muscle growth, we examined the in vitro and in vivo effects of GH on myostatin regulation. Twelve GH-deficient hypopituitary adult subjects were treated with recombinant GH (5 micro g/kg.d) in a double-blind, placebo-controlled fashion. Body composition and physical function were assessed and skeletal muscle biopsies from the vastus lateralis performed at 6-monthly intervals during 18 months of treatment. Myostatin mRNA expression was significantly inhibited to 31 +/- 9% (P < 0.001) of control by GH but not by placebo administration (79 +/- 11%) as determined by quantitative real-time PCR normalized for the housekeeping glyceraldehyde-3-phosphate dehydrogenase gene. The inhibitory effect of GH on myostatin was sustained after 12 and 18 months of GH treatment. These effects were associated with increases in lean body mass and translated into enhanced aerobic performance as determined by maximal oxygen uptake and ventilation threshold. Parallel in vitro studies of skeletal muscle cells demonstrated significant reduction of myostatin expression by myotubes in response to GH, compared with vehicle treatment. Conversely, GH receptor antagonism resulted in up-regulation of myostatin in myoblasts. Given the potent catabolic actions of myostatin, our data suggest that myostatin represents a potential key target for GH-induced anabolism.

Three weekly injections (TWI) of low-dose growth hormone (GH) restore low normal circulating IGF-I concentrations and reverse cardiac abnormalities associated with adult onset GH deficiency (GHD)

GH replacement therapy given 3 times weekly (TWI) and adjusted to allow serum IGF-I concentrations in the mid-normal range for sex and age has been shown to be as effective as the daily regimen in improving lipid profile, body composition, bone mass and turnover in adult GH deficient (GHD) patients. Only one study has investigated so far the short-term (6 months) effect of a fixed weight-based TWI dosing schedule on heart structure and function in childhood onset (CO) GHD patients, whereas such a schedule in adult onset (AO) GHD patients has not been studied as yet. Aim of this study was to investigate whether a 1-yr low-dose titrated TWI GH-replacement regimen aimed at achieving and maintaining IGF-I levels within the low normal limits for age and sex is able to affect cardiovascular and heart parameters in a group of AO GHD patients. Eight adult patients (4 women and 4 men, age 35.8 +/- 3.37 yr, body mass index, BMI, 28.7 +/- 2.62 kg/m2) with AO GHD were included in the study, along with 10 healthy subjects, matched for age, sex, BMI and physical activity (6 women and 4 men, age 35.2 +/- 4.05 yr, BMI 28.4 +/- 2.34 kg/m2). M- and B- mode ecocardiography and pulsed doppler examination of transmitral flow were performed in GHD patients at baseline and after 3 and 12 months of GH therapy (mean GH dose 6.7 +/- 0.8 microg/kg/day given thrice a week), while normal subjects were studied once. Treatment with GH for 1 yr induced a significant increase in left ventricular (LV) diastolic and systolic volumes (+11.1 and +16.5%, respectively). Systolic LV posterior wall thickness and LV mass were increased (+10.2 and +7.7%, respectively) by GH administration. Systemic vascular resistance was significantly decreased by 1-yr GH therapy (-13.8% after 1 yr), while stroke volume, cardiac output and cardiac index were increased (+9.4, +11.6 and + 11.9%, respectively). LV end-systolic stress was decreased at the end of GH therapy (-11.2%). E and A wave, significantly reduced at baseline, were increased by 1 yr of GH therapy (+23.3% and +28.1%, respectively); likewise, the abnormally high E peak deceleration time was partially reversed by GH administration (-10.7%). Our study, though conducted in a small sample size, demonstrates that a TWI GH treatment schedule is able to reverse the cardiovascular abnormalities in AO GHD patients and to improve body composition and lipid profile. The maintenance of circulating IGF-I concentrations within the low normal range allows to avoid most of the side-effects reported with higher GH doses while being cost-effective and improving the patient's compliance.

Link of nonhemodynamic factors to hemodynamic determinants of left ventricular hypertrophy

Despite current evidence suggesting that hemodynamic load is the fundamental stimulus to begin the sequence of biological events leading to the development of left ventricular hypertrophy, genotype, gender, body size, and less easily recognizable environmental factors may contribute to generate the cascade of molecular changes that eventually yield the increase in protein synthesis needed to increase left ventricular mass. However, even nonhemodynamic factors such as gender and body size eventually regulate the growth of left ventricular mass by at least in part influencing loading conditions. Consideration of measurable factors, such as gender, body size, and hemodynamic load, allows evaluation of individual echocardiographic left ventricular mass as the deviation from the level that would be required to face a gender-specific hemodynamic load at a given body size. Values of left ventricular mass that are inappropriately high for individual gender, body size, and hemodynamic load are associated with a high cardiovascular risk phenotype, even independent of the presence of arterial hypertension. Thus, the condition of inappropriately high left ventricular mass may be recognized as a more advanced stage of pathological structural changes initially induced by overload, going beyond the compensatory needs. The biological process that yields inappropriate left ventricular mass is probably linked to the protracted activity over time of biological mediators of left ventricular hypertrophy, such as proto-oncogenes and other growth factors, neurohormones, and cytokines, inducing structural modifications that initially compensate imposed overload but eventually change the structure of myocardial tissue and the composition of motor units.

Growth hormone and exercise: physiology, use and abuse

This review summarizes the interactions between growth hormone (GH) and exercise. Exercise has profound effects upon the GH-insulin-like growth factor I axis per se. In addition, there is increasing evidence that such physiological perturbations might be influential in the performance responses to repeated training. However, the ergogenic effects of systemic administration of recombinant human GH by athletes and bodybuilders remain unproven. What is certain is that the prevalence of GH abuse by sportspeople will increase, not least because it is currently undetectable. The frequent and potentially severe side-effects associated with such 'doping' will be of increasing relevance to endocrinologists.

Growth hormone and the heart

Impaired cardiovascular function has recently been demonstrated to potentially reduce life expectancy both in GH deficiency and excess. Experimental and clinical studies have supported the evidence that GH and IGF-I are implicated in cardiac development. In most patients with acromegaly a specific cardiomyopathy, characterized by myocardial hypertrophy with interstitial fibrosis, lympho-mononuclear infiltration and areas of monocyte necrosis, results in biventricular concentric hypertrophy. In contrast, patients with childhood or adulthood-onset GH deficiency (GHD) may suffer both from structural cardiac abnormalities, such as narrowing of cardiac walls, and functional impairment, that combine to reduce diastolic filling and impair left ventricular response to peak exercise. In addition, GHD patients may have an increase in vascular intima-media thickness and a higher occurrence of atheromatous plaques, that can further aggravate the haemodynamic conditions and contribute to increased cardiovascular and cerebrovascular risk. However, several lines of evidence have suggested that the cardiovascular abnormalities can be partially reversed by suppressing GH and IGF-I levels in acromegaly or after GH replacement therapy in GHD patients. Recently, much attention has been focussed on the ability of GH to increase cardiac mass suggesting its possible use in the treatment of chronic nonendocrine heart failure. In fact, GH administration can induce an improvement in haemodynamic and clinical status in some patients. Although these data need to be confirmed in more extensive studies, such promising results seem to open new perspectives for GH treatment in humans.

Should we start and continue growth hormone (GH) replacement therapy in adults with GH deficiency?

During the last decade, growth hormone deficiency (GHD) in adults has been described as a clinical syndrome. Central features of this entity include increased fat mass, reduced muscle and bone mass, as well as impaired exercise capacity and quality of life. GH replacement therapy has been initiated on a wide scale, but patients do not profit equally from this expensive therapy. The decision to start and continue GH replacement should be made individually for each patient. An eligible patient should have a clear diagnosis of GHD. In addition, GH replacement therapy should be efficacious. Especially, the unique and valuable effects of GH replacement on exercise performance and quality of life are strong arguments in favour of continuation of therapy. In osteopenic patients, GH replacement increases bone mass. Also, GH induces improvements in the cardiovascular risk profile. However, it has not yet been proved whether GH replacement reduces the incidence of bone fractures and cardiovascular mortality and improves life expectancy. Thus far, long-term physiological GH replacement does not appear to be complicated by adverse effects. Therefore, available evidence warrants continuation of long-term GH replacement therapy in patients with a clear-cut diagnosis of GHD who demonstrate beneficial effects of this therapy, especially with regard to exercise performance and quality of life.

Myocardial hypertrophy in transgenic mice overexpressing the bovine growth hormone (bGH) gene

OBJECTIVES

The main purpose of the present study was to characterize cardiac muscle hypertrophy using both qualitative and quantitative microscopy in mice overexpressing the bovine growth hormone.

RESULTS

Measurements of 30 fibres from each group revealed that fibre diameter in transgenic hearts was significantly larger than in control hearts. There was a significant decrease in interfibrillar space in transgenic hearts as compared with control hearts. The enlarged transgenic hearts displayed unchanged organelles such as normal myofibrils and mitochondria in a normal pattern, suggesting balanced growth. Myelin structures were occasionally observed between normal myofibrils. Moreover, myocardial beta-adrenergic receptors and muscarinic receptors in the hearts of transgenic mice overproducing GH were studied to see whether they are involved in the hypertrophic process. It was shown that the density of muscarinic receptors had decreased and the super-high affinity of muscarinic receptors was lost, without any significant changes in either the density or the affinity of beta-adrenergic receptors, as compared with controls.

CONCLUSIONS

These results demonstrate that a GH excess was able to induce significant myocardial hypertrophy and that there was a downregulation of muscarinic receptors.

The relationship between aerobic exercise capacity and circulating IGF-1 levels in healthy men and women

OBJECTIVES

To determine whether aerobic capacity is associated independently with insulin-like growth factor-I (IGF-1) levels in healthy community-dwelling men and women.

SETTING

The Baltimore Longitudinal Study on Aging (BLSA).

DESIGN

A cross-sectional analysis of data from the population-based cohort of the Baltimore Longitudinal Study of Aging (BLSA).

PARTICIPANTS

We studied 181 men and 92 women aged 20 to 93 years, volunteers in the Baltimore Longitudinal Study on Aging (BLSA). Subjects were free of endocrine, renal, hepatic, gastrointestinal, or cardiac diseases, and they were taking no medications known to interfere with the growth hormone-IGF-1 axis.

MEASUREMENTS

All subjects underwent a single measurement of serum IGF-1 in the fasting state, as well as peak VO2 determinations during maximal treadmill exercise testing performed within one visit of the IGF-1 determination. Dual energy X-ray absorptiometry (DEXA) scans were performed in a subset of 171 subjects (64 women and 107 men) for determination of fat free mass (FFM).

RESULTS

In the pooled group of women and men, univariate regression analysis revealed that age was correlated strongly with decreasing IGF-1 levels (r = -0.53, P < .001) and with peak VO2r = -0.56, P < .001). IGF-1 levels were also significantly correlated with peak VO2 (r = 0.29, P < .001). There were no significant gender-related differences in these relationships. On multivariate analysis, age (beta = -0.54, P < .001), but not peak VO2 (P = -0.01, P = .840), remained strongly associated with IGF-1 levels. After adjustment of peak VO2 for FFM in subjects with DEXA scans, results were similar.

CONCLUSIONS

These findings indicate that although both peak aerobic capacity and circulating IGF-1 levels decline with age, aerobic capacity is not independently related to circulating IGF-1 in healthy men and women across the adult life span.

Growth hormone and exercise

This review summarizes the interactions between GH and exercise. Not only does exercise have profound effects upon the GH/IGF-I axis per se, but there is increasing evidence that such physiological perturbations might be influential in the performance responses to repeated training. However, the effects of systemic administration of rGH in restoring exercise capability and muscle strength in GH deficient adults and the ergogenic benefits of GH doping amongst athletes remain unproven. What is certain is that these issues will be of increasing relevance to clinical endocrinologists.

Treatment with growth hormone enhances contractile reserve and intracellular calcium transients in myocytes from rats with postinfarction heart failure

BACKGROUND

Recombinant human growth hormone (GH) improves in vivo cardiac function in rats with postinfarction heart failure (MI). We examined the effects of growth hormone (14 days of 3.5 mg. kg-1. d-1 begun 4 weeks after MI) on contractile reserve in left ventricular myocytes from rats with chronic postinfarction heart failure.

METHODS AND RESULTS

Cell shortening and [Ca2+]i were measured with the indicator fluo 3 in myocytes from MI, MI+GH, control, and normal animals treated with GH (C+GH) under stimulation at 0.5 Hz at 37 degrees C. Cell length was similar in MI and MI+GH rats (150+/-5 and 157+/-5 microm) and was greater in these groups than in the control and C+GH groups (140+/-4 and 139+/-4 microm, P<0.05). At baseline perfusate calcium of 1.2 mmol/L, myocyte fractional shortening and [Ca2+]i transients were similar among the 4 groups. We then assessed contractile reserve by measuring the increase in myocyte fractional shortening in the presence of high-perfusate calcium of 3.5 mmol/L. In the control and C+GH groups, myocyte fractional shortening and peak systolic [Ca2+]i were similarly increased in the presence of high-perfusate calcium. In the presence of high-perfusate calcium, both myocyte fractional shortening and peak systolic [Ca2+]i were depressed in the MI compared with the control groups. In contrast, myocyte fractional shortening (14.1+/-.9% versus 11.1+/-.9%, P<0.05) and peak systolic [Ca2+]i (647+/-43 versus 509+/-37 nmol/L, P<0.05) were significantly higher in MI+GH than in MI rats and were comparable to controls. Left ventricular myocyte expression of sarcoplasmic reticulum Ca2+ ATPase 2 (SERCA-2) and left ventricular SERCA-2 protein levels were increased in MI+GH compared with MI rats.

CONCLUSIONS

Calcium-dependent contractile reserve is depressed in myocytes from rats with postinfarction heart failure. Long-term growth hormone therapy increases contractile reserve by restoring normal augmentation of systolic [Ca2+]i in myocytes from rats with postinfarction heart failure.