Controversies regarding the effects of growth hormone on the heart

Endocrine system dysfunction and chronic heart failure: a clinical perspective

Chronic heart failure (CHF) leads to an excess of urgent ambulatory visits, recurrent hospital admissions, morbidity, and mortality regardless of medical and non-medical management of the disease. This excess of risk may be attributable, at least in part, to comorbid conditions influencing the development and progression of CHF. In this perspective, the authors examined and described the most common endocrine disorders observed in patients with CHF, particularly in individuals with reduced ejection fraction, aiming to qualify the risks, quantify the epidemiological burden and discuss about the potential role of endocrine treatment. Thyroid dysfunction is commonly observed in patients with CHF, and sometimes it could be the consequence of certain medications (e.g., amiodarone). Male and female hypogonadism may also coexist in this clinical context, contributing to deteriorating the prognosis of these patients. Furthermore, growth hormone deficiency may affect the development of adult myocardium and predispose to CHF. Limited recommendation suggests to screen endocrine disorders in CHF patients, but it could be interesting to evaluate possible endocrine dysfunction in this setting, especially when a high suspicion coexists. Data referring to long-term safety and effectiveness of endocrine treatments in patients with CHF are limited, and their impact on several "hard" endpoints (such as hospital admission, all-cause, and cardiovascular mortality) are still poorly understood.

Recurrent hypoglycaemia and dilated cardiomyopathy: delayed presentation of Sheehan's syndrome

Sheehan's syndrome (SS) is ischaemic necrosis of the pituitary gland due to massive postpartum haemorrhage. The clinical manifestations may vary from subtle to life-threatening and may present immediately after delivery or many years later. We present a case history of a 58-year-old non-diabetic woman who had undetected SS and presented with two unusual manifestations, including recurrent hypoglycaemia and dilated cardiomyopathy 34 years after delivery. The dilated cardiomyopathy reversed partially after treatment.

Polygenic adaptation and convergent evolution on growth and cardiac genetic pathways in African and Asian rainforest hunter-gatherers

Different human populations facing similar environmental challenges have sometimes evolved convergent biological adaptations, for example, hypoxia resistance at high altitudes and depigmented skin in northern latitudes on separate continents. The "pygmy" phenotype (small adult body size), characteristic of hunter-gatherer populations inhabiting both African and Asian tropical rainforests, is often highlighted as another case of convergent adaptation in humans. However, the degree to which phenotypic convergence in this polygenic trait is due to convergent versus population-specific genetic changes is unknown. To address this question, we analyzed high-coverage sequence data from the protein-coding portion of the genomes of two pairs of populations: Batwa rainforest hunter-gatherers and neighboring Bakiga agriculturalists from Uganda and Andamanese rainforest hunter-gatherers and Brahmin agriculturalists from India. We observed signatures of convergent positive selection between the rainforest hunter-gatherers across the set of genes with "growth factor binding" functions ([Formula: see text]). Unexpectedly, for the rainforest groups, we also observed convergent and population-specific signatures of positive selection in pathways related to cardiac development (e.g., "cardiac muscle tissue development"; [Formula: see text]). We hypothesize that the growth hormone subresponsiveness likely underlying the adult small body-size phenotype may have led to compensatory changes in cardiac pathways, in which this hormone also plays an essential role. Importantly, in the agriculturalist populations, we did not observe similar patterns of positive selection on sets of genes associated with growth or cardiac development, indicating our results most likely reflect a history of convergent adaptation to the similar ecology of rainforests rather than a more general evolutionary pattern.

Illicit drugs and cardiac arrhythmias in athletes

The current management of athletes with cardiac arrhythmias has become complicated by the widespread use of illicit drugs, which can be arrhythmogenic.

The World Anti-Doping Agency annually updates a list of prohibited substances and methods banned by the International Olympic Committee that includes different classes of substances namely, anabolic androgenic steroids, hormones and related substances, β2-agonists, diuretics, stimulants, narcotics, cannabinoids, glucocorticosteroids, alcohol, β-blockers and others. Almost all illicit drugs may cause, through a direct or indirect arrhythmogenic effect, a wide range of cardiac arrhythmias (focal or reentry type, supraventricular and/or ventricular) that can even be lethal and which are frequently sport activity related.

A large use of illicit drugs has been documented in competitive athletes, but the arrhythmogenic effect of specific substances is not precisely known. Precipitation of cardiac arrhythmias, particularly in the presence of a latent electrophysiologic substrate including some inherited cardiomyopathies, at risk of sudden death or due to long-term consumption of the substances, should raise the suspicion that illicit drugs may be a possible cause and lead cardiologists to investigate carefully this relationship and appropriately prevent the clinical consequences.

Panhypopituitarism presenting as life-threatening heart failure caused by an inherited microdeletion in 1q25 including LHX4

Clinical presentation of hypopituitarism in the neonate may be variable, ranging from absent to severe nonspecific symptoms and may be life-threatening in patients with adrenocorticotropic hormone deficiency. The LIM homeobox gene 4 (LHX4) transcription factor regulates early embryonic development of the anterior pituitary gland. Autosomal dominant mutations in LHX4 cause congenital hypopituitarism with variable combined pituitary hormone deficiency (CPHD). We report on a neonate with unexplained heart failure and minor physical anomalies, suggesting a midline defect. She was diagnosed with complete CPHD. Cardiac function was rescued by replacement with hydrocortisone and thyroxine; hypoglycaemia stopped under growth hormone therapy. Magnetic resonance imaging revealed a dysgenetic pituitary gland suggesting an early developmental defect. Array comparative genomic hybridization showed a maternally inherited 1.5-megabase microdeletion in 1q25.2q25.3, including the LHX4 gene. Haploinsufficiency of LHX4 likely explains the predominant pituitary phenotype in the proposita and we suggest variable intrafamilial penetrance of the inherited microdeletion. To the best of our knowledge, we are the first to report on heart failure as a rare nonspecific symptom of treatable CPHD in the newborn. Variably penetrant pituitary insufficiency, including this severe and atypical presentation, can be correlated with LHX4 insufficiency and highlights the role of LHX4 for pituitary development.

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.

Growth hormone and physical performance

There has been limited research and evidence that GH enhances physical performance in healthy adults or in trained athletes. Even so, human growth hormone (GH) is widely abused by athletes. In healthy adults, GH increases lean body mass, although it is possible that fluid retention contributes to this effect. The most recent data indicate that GH does not enhance muscle strength, power, or aerobic exercise capacity, but improves anaerobic exercise capacity. In fact, there are adverse effects of long-term GH excess such that sustained abuse of GH can lead to a state mimicking acromegaly, a condition with increased morbidity and mortality. This review will examine GH effects on body composition and physical performance in health and disease.

Growth hormone administration: is it safe and effective for athletic performance

Human growth hormone (GH) is widely abused by athletes; however, there is little evidence that GH improves physical performance. Replacement of GH in GH deficiency improves some aspects of exercise capacity. There is evidence for a protein anabolic effect of GH in healthy adults and for increased lean body mass following GH, although fluid retention likely contributes to this increase. The evidence suggests that muscle strength, power, and aerobic exercise capacity are not enhanced by GH administration, however GH may improve anaerobic exercise capacity. There are risks of adverse effects of long-term abuse of GH. Sustained abuse of GH may lead to a state mimicking acromegaly, a condition with increased morbidity and mortality.

Low-dose growth hormone is cardioprotective in uremia

Growth hormone (GH) is required to maintain normal cardiac structure and function and has a positive effect on cardiac remodeling in experimental and possibly human disease. Cardiac resistance to GH develops in the uremic state, perhaps predisposing to the characteristic cardiomyopathy associated with uremia. It was hypothesized that administration of low-dosage GH may have a salutary effect on the cardiac remodeling process in uremia, but because high levels of GH have adverse cardiac effects, administration of high-dosage GH may worsen uremic cardiomyopathy. In rats with chronic renal failure, quantitative cardiac morphology revealed a decrease in total capillary length and capillary length density and an increase in mean intercapillary distance and fibroblast volume density evident. Low-dosage GH prevented these changes. Collagen and TGF-beta immunostaining, increased in chronic renal failure, were also reduced by GH, suggesting a mechanism for its salutary action. Low-dosage GH also prevented thickening of the carotid artery but did not affect aortic pathology. In contrast, high-dosage GH worsened several of these variables. These results suggest that low-dosage GH may benefit the heart and possibly the carotid arteries in chronic renal failure.

Relationship between insulin-like growth factor-I and brain natriuretic peptide in patients with acromegaly after surgery

BACKGROUND

Increased cardiac insulin-like growth factor (IGF)-I production is associated with physiological cardiac hypertrophy in athletes, and IGF-I has been recognized as a cardioprotective agent in experimental animal studies. On the other hand, acromegaly which is characterized by an excess of IGF-I has been linked to impaired cardiac function.

METHODS AND RESULTS

Both the relationship between the serum levels of IGF-I and brain natriuretic peptide (BNP), which is released from the cardiac ventricles in response to ventricular stress, and that between IGF-I and the concentrations of the plasma amino-terminal propeptide of procollagen type III (P-III-P), which is associated with myocardial fibrosis, were evaluated in 19 patients after surgical treatment for acromegaly. Echocardiography revealed that left ventricular systolic function and dimensions were within normal range in all patients. Significant inverse correlations were found between IGF-I and the BNP (r=-0.5, p=0.02) and P-III-P levels (r=-0.62, p=0.005).

CONCLUSION

We observed an inverse significant relationship between IGF-I and both the BNP and P-III-P value in surgically treated acromegaly patients. These observations suggest that appropriate levels of IGF-I have beneficial cardioprotective effects after surgery in patients with acromegaly.

Effect of growth hormone on cardiac contractility in patients with adult onset growth hormone deficiency

This study was conducted to investigate the effect of growth hormone (GH) replacement on cardiac function assessed by standard or tissue Doppler echocardiography in GH deficiency. Ten patients (mean age 47+/-14 years) received GH at a dose of 1.0 IU/day (6 times/week). After 6 months of GH replacement, GH substitution was discontinued. Echocardiography was performed at baseline, after 6 months of therapy, and 1 year after the withdrawal of GH replacement. All parameters were compared with those from 11 healthy controls matched for age, gender, and left ventricular (LV) mass index. After GH replacement, LV ejection fractions were nonsignificantly increased. However, fractional shortening, LV dimensions, and LV volumes did not change. Compared with controls, peak strain (-18.9+/-4.8% vs -15.7+/-6.9%, p<0.01) and strain rate (-1.3+/-0.4/s vs -1.0+/-0.5/s, p<0.01) at baseline were significantly decreased in patients with GH deficiency. Strain and strain rate increased significantly after 6 months of replacement but returned to baseline levels after 12 months off therapy. In conclusion, GH replacement in adult-onset GH deficiency demonstrated beneficial effects on cardiac contractility assessed by strain and strain rate, but these parameters returned to baseline levels after the withdrawal of GH. Strain and strain rate can be used to evaluate subtle changes in myocardium after GH replacement.

Cardiovascular toxicities of performance-enhancing substances in sports

Athletes commonly use drugs and dietary supplements to improve athletic performance or to assist with weight loss. Some of these substances are obtainable by prescription or by illegal means; others are marketed as supplements, vitamins, or minerals. Nutritional supplements are protected from Food and Drug Administration regulation by the 1994 US Dietary Supplement Health and Education Act, and manufacturers are not required to demonstrate proof of efficacy or safety. Furthermore, the Food and Drug Administration lacks a regulatory body to evaluate such products for purity. Existing scientific data, which consist of case reports and clinical observations, describe serious cardiovascular adverse effects from use of performance-enhancing substances, including sudden death. Although mounting evidence led to the recent ban of ephedra (ma huang), other performance-enhancing substances continue to be used frequently at all levels, from elementary school children to professional athletes. Thus, although the potential for cardiovascular injury is great, few appropriately designed studies have been conducted to assess the benefits and risks of using performance-enhancing substances. We performed an exhaustive OVID MEDLINE search to Identify all existing scientific data, review articles, case reports, and clinical observations that address this subject. In this review, we examine the current evidence regarding cardiovascular risk for persons using anabolic-androgenic steroids including 2 synthetic substances, tetrahydrogestrinone and androstenedione (andro), stimulants such as ephedra, and nonsteroidal agents such as recombinant human erythropoietin, human growth hormone, creatine, and beta-hydroxy-beta-methylbutyrate.

Cardiac changes associated with growth hormone therapy among children treated with anthracyclines

OBJECTIVE

The objective was to assess the cardiac effects of growth hormone (GH) therapy. Anthracycline-treated childhood cancer survivors frequently have reduced left ventricular (LV) wall thickness and contractility, and GH therapy may affect these factors.

METHODS

We examined serial cardiac findings for 34 anthracycline-treated childhood cancer survivors with several years of GH therapy and baseline cardiac z scores similar to those of a comparison group (86 similar cancer survivors without GH therapy).

RESULTS

LV contractility was decreased among GH-treated patients before, during, and after GH therapy (-1.08 SD below the age-adjusted population mean before therapy and -1.88 SD 4 years after therapy ceased, with each value depressed below normal). Contractility was higher in the control group than in the GH-treated group, with this difference being nearly significant. The GH-treated children had thinner LV walls before GH therapy (-1.38 SD). Wall thickness increased during GH therapy (from -1.38 SD to -1.09 SD after 3 years of GH therapy), but the effect was lost shortly after GH therapy ended and thickness diminished over time (-1.50 SD at 1 year after therapy and -1.96 SD at 4 years). During GH therapy, the wall thickness for the GH-treated group was greater than that for the control group; however, by 4 years after therapy, there was no difference between the GH-treated group and the control group.

CONCLUSIONS

GH therapy among anthracycline-treated survivors of childhood cancer increased LV wall thickness, but the effect was lost after therapy was discontinued. The therapy did not affect the progressive LV dysfunction.

IGF-I is a matter of heart

An intriguing relationship between IGF-I action and cardiac function has been noted for some time, but exactly how IGF-I modulates myocardial function remained obscure. Recent research shed novel insight into potential mechanisms of IGF-I actions in cardiac muscle. New discoveries help elucidate the role of IGF-I signaling in protecting cardiac muscle against injuries, and support potential therapeutic roles for IGF-I in cardiomyopathy. Multiple actions of IGF-I has been described in cardiac muscle cells, including the well-documented anti-apoptosis effect and the newly emerged action on cardiac muscle regeneration. Furthermore, interplay between heat shock protein and IGF-I receptor signaling has been identified and this new paradigm might be involved in the development of diabetic cardiomyopathy. This article reviews recent research findings and outlines potential therapeutic implications of IGF-I in heart failure.

Cardiac resistance to growth hormone in uremia

BACKGROUND

Cardiovascular disease is a major cause of death in end-stage renal disease (ESRD). Since growth hormone is required for maintaining normal cardiac structure and function and as growth hormone has a salutary effect on cardiac remodeling in disease, we postulated that if cardiac resistance to growth hormone develops in chronic renal failure (CRF) this may predispose to the cardiomyopathy of uremia. We set out to test whether in CRF there is resistance to the cardiac action of growth hormone and whether this defect might be caused by altered growth hormone signaling.

METHODS

Growth hormone-deficient (dw/dw) rats and growth hormone-intact Sprague-Dawley rats underwent a subtotal nephrectomy or sham operation and pair feeding.

RESULTS

In dw/dw rats treated with growth hormone for 8 days there was a significant increase in insulin-like growth factor-1 (IGF-1) mRNA levels in controls but this response was attenuated in CRF. Next, growth hormone-stimulated Janus kinase-signal transducers and activators of transcription (JAK2-STAT5) signaling was studied 15 minutes after intravenous growth hormone in dw/dw and Sprague-Dawley rats. Growth hormone receptor, JAK2, STAT5a, and STAT5b protein levels were unaltered in CRF. Growth hormone-induced JAK2, growth hormone receptor (GHR), and STAT5 tyrosine phosphorylation was significantly depressed in CRF as was nuclear translocation of phosphorylated STAT5. When rats were treated with pharmacologic dose growth hormone, STAT5 phosphorylation increased similarly in CRF and control rats.

CONCLUSION

Uremic rats develop cardiac resistance to growth hormone caused at least, in part, by a postreceptor defect in growth hormone-induced signaling that is characterized by impaired phosphorylation and nuclear translocation of STAT5. These findings raise the question whether growth hormone resistance contributes to the cardiac changes of uremia.

Growth hormone deficiency in Costello syndrome

We report on three patients with Costello syndrome and isolated growth hormone (GH) deficiency treated with biosynthetic GH. To our knowledge, these are the only patients with Costello syndrome who have been successfully treated for GH deficiency. We review the pathophysiology of Costello syndrome and highlight the recent recommendations of tumor screening and cardiac surveillance in this population, of particular relevance to those receiving GH therapy.