Cardiovascular effects of high-dose growth hormone treatment in growth hormone-deficient children

Evaluation of cardiac structure, exercise capacity and electrocardiography parameters in children with partial and complete growth hormone deficiency and their changes with short term growth hormone replacement therapy

PURPOSE

To evaluate cardiac structure, exercise capacity and electrocardiography (ECG) parameters of children with complete and partial growth hormone (GH) deficiency (GHD) and the effect of 12 months GH treatment on these.

METHODS

M-mode echocardiography, ECG and exercise test expressed as metabolic equivalent (MET) were performed in children with GHD, aged 9-14 years, divided into those with a peak GH response < 7 µg/L (complete GHD; n = 30) and 7-10 µg/L (partial GHD; n = 17) after two GH stimulation tests, at baseline and 12 months after GH initiation. Forty-eight healthy peers underwent the same tests once.

RESULTS

Left ventricular mass (LVM) was significantly lower before treatment in both groups with GHD compared to healthy peers (p = 0.015 and p = 0.032) but LVM in the GHD groups was similar to controls after 12 months of treatment. The increase in LVM in the complete GHD group was significant (p = 0.044). LVM index was significantly reduced with treatment in children with partial GHD (p = 0.035). Max METs, VO_2max and exercise duration were significantly increased in children with complete GHD after treatment (p = 0.022, p = 0.015 and p = 0.002, respectively). Significant changes in P wave and QTc dispersion on ECG between groups were within physiological limits.

CONCLUSION

This study showed that children with both partial and complete GHD had smaller cardiac structures and less exercise capacity compared to their healthy peers prior to GH treatment but this improved with 12 months of treatment. The cardiac trophic effect of GH, as well as the effect of increasing exercise capacity, is greater in those with complete GHD than in those with partial GHD.

Cardiac functions in children with growth hormone deficiency: Effects of one year of GH replacement therapy

INTRODUCTION

Children with Growth Hormone deficiency (GHD) are prone to heart dysfunction and, if left untreated, will result in marked cardiac dysfunction in adulthood. The aim was to evaluate the effect of GHD and growth hormone (GH) therapy on cardiac structure in children and adolescents, and to investigate the role of insulin like growth factor-1 (IGF-1) in this.

METHODS

M-mode, pulse-wave Doppler echocardiography and tissue Doppler imaging (TDI) were performed in 49 children with GHD who were divided into those with a peak GH response < 7 μg/L and 7-10 μg/L after two GH stimulation tests, aged 8-16 years at baseline and at six and 12 months after GH initiation, and 49 healthy peers. IGF-1 concentration was measured.

RESULTS

Although the left ventricular end diastolic and systolic diameters in both GH deficient groups were significantly lower than controls (p < 0.01), both diameters increased significantly with one year of treatment and achieved normal values (p > 0.05). Using TDI in both two patients group revealed increased E/A, prolonged isovolumic relaxation time, shortened ejection time, and a significant increase in myocardial performance index compared to controls (p < 0.001). Significant improvement was observed in these parameters from the sixth month of GH treatment (p < 0.001), this improvement does not match parameters measured in healthy peers, even after one year of treatment in both patients group. (p < 0.001). No correlation was found between IGF-1 concentration and any echocardiographic parameter.

CONCLUSION

Echocardiographic parameters were similar in children with a GH peak < 7 μg/L and 7-10 μg/L. In TDI, both systolic and diastolic function was impaired in GHD children compared to controls. These parameters improved after one year of GH therapy but did not recover to healthy control levels.

The effect of recombinant human growth hormone therapy on left-ventricular chamber size and function in children with growth hormone deficiency

This study was designed to assess the effect of recombinant human growth hormone (rhGH) therapy on left-ventricular (LV) chamber size and function in children with idiopathic isolated growth hormone deficiency (GHD) using conventional echocardiography and tissue Doppler imaging (TDI). Thirty patients (19 boys and 11 girls) with idiopathic isolated GHD were followed-up for 12 months. Mean age of patients was 11.0 ± 2.6 years (range 6.3-15.5). At baseline and at 3, 6, and 12 months of treatment, the structure of the left ventricle was assessed by conventional echocardiography and myocardial rates and time intervals by TDI. There was a significant increase in LV mass (LVM) compared with pretreatment values. Like LVM, relative wall thickness (RWT) was also increased significantly. The significant increase in LVM indexed to body surface area and RWT became apparent at month 3 of treatment with a significant increase in LVM indexed to height(2.7) at treatment month 6. Normalized LVM increased as early month 3 of treatment, and a steady increase was observed until month 12. However, no patient had LVM > +2 standard deviation scores at month 12 of treatment. No significant differences were observed in functional parameters of the left ventricle and the interventricular septum. The results of this study showed that rhGH therapy causes an increase in myocardial mass without changing the geometry or function of the myocardium. Therefore, the increase in myocardial mass appears to be concentric, thus causing remodeling instead of hypertrophy.

Cardiac functions in children with growth hormone deficiency before and during growth hormone-replacement therapy

Childhood growth hormone deficiency (GHD) decreases left-ventricular (LV) mass, but impairment of cardiac function has never been documented. The objective of this study was to assess the cardiac effects of GHD and recombinant human growth hormone (rhGH) treatment using conventional echocardiography and tissue Doppler imaging. Complete two-dimensional, M-mode, pulse-wave Doppler echocardiography and pulse-wave tissue Doppler imaging were performed in 12 children (6 male and 6 female patients) with GHD at baseline and at 5.86 ± 1.61 months after rhGH therapy. Recombinant human growth hormone treatment was associated with a significant increase in LV mass index (63.8 ± 27.1 to 79.3 ± 30.3 g/m(2); P < 0.01) and LV internal dimensions (21.4 ± 2.63 to 24.0 ± 4.13 mm in systole [P = 0.03] and 36.5 ± 3.90 to 39.5 ± 4.94 mm in diastole [P < 0.01]). There were statistical differences of parameters, such as deceleration time of early peak velocity of mitral, isovolumic relaxation time, and myocardial performance index (103 ± 15.4 to 139 ± 21.2 ms [P < 0.01], 55.5 ± 9.24 to 69.2 ± 3.74 ms [P < 0.01], and 37.8 ± 4.46 to 44.9 ± 5.44% [P < 0.01], respectively). Before and during rhGH therapy, there were no significant differences in fractional shortening of the left ventricle, peak mitral, and tricuspid wave velocities with ratios determined using conventional echocardiography and tissue Doppler imaging. In children, GHD affects heart morphology by inducing a decrease in cardiac size, but it does not modify cardiac function. Recombinant human growth hormone treatment increases cardiac mass, deceleration time of early peak velocity of the mitral valve, isovolumic relaxation time, and myocardial performance index, but it does not make a difference in other parameters of conventional echocardiography and tissue Doppler imaging.

Cardiac status after childhood growth hormone treatment of Turner syndrome

CONTEXT

In Turner syndrome (TS), GH treatment is well established. Data on cardiac status after discontinuation of treatment are scarce. This study aimed to assess biventricular size and function in TS at least 6 months after discontinuation of GH treatment.

METHODS

TS patients and healthy women prospectively underwent cardiac magnetic resonance imaging. Ventricular two-dimensional tomographic cine data were acquired to obtain biventricular volume, mass, and ejection fraction. Atrioventricular valve flow measurements were performed using a two-dimensional flow-sensitized sequence. Flow velocity curves were calculated and indices of biventricular diastolic filling were derived.

RESULTS

Thirty-one patients [mean (sd) age 20 (2) yr, body surface area 1.75 (0.15) m(2), 5 (2) yr after GH discontinuation] and 23 normal control women [age 21 (2) yr, body surface area 1.80 (0.13) m(2)] were included. Compared with controls, patients had smaller mean end-diastolic volumes [right ventricle (RV), 84 (11) ml/m(2) vs. 79 (10), P = 0.02; left ventricle (LV), 81 (10) vs. 72 (9), P < 0.001], end-systolic volumes [RV 38 (7) ml/m(2) vs. 36 (6), P = 0.04; LV 34 (5) vs. 29 (4), P < 0.001], and stroke volumes [RV 46 (6) ml/m(2) vs. 43 (6), P = 0.03; LV, 47 (7) vs. 44 (4), P = 0.02]. Patients had a higher mean heart rate [79 (13) beats/min vs. 71 (10), P < 0.05]. Biventricular ejection fraction, mass, cardiac output, and diastolic filling pattern were comparable.

CONCLUSION

After discontinuation of GH treatment TS patients showed no myocardial hypertrophy and well-preserved biventricular function. Ventricular volumes were smaller in Turner patients, compared with controls, whereas mean heart rate was higher. These last observations may be part of the natural development in TS and not linked to GH treatment, which at this point we consider safe.

M-mode echocardiographic evaluation of systolic function, LV volume and mass in children on growth hormone therapy

Since abnormal endogenous growth hormone (GH) secretion in adults is associated with cardiac dysfunction, it is important to ensure that GH therapy in children and adolescents does not cause similar effects. Forty-two growth hormone-deficient children (Group 1) (19 girls, 23 boys) were evaluated. Six girls and seven boys were prepubertal with a mean age of 6.65 yr (range 4.37-9.73 yr). Twenty-nine were pubertal (13 girls, 16 boys), mean age 13.57 yr (range 10.08-16.76 yr). The patients had been on long-term GH therapy for 34.97 +/- 18.78 months with an average weekly dose of 17.61 IU/m2/wk. The mean height SDS was -2.85 +/- 1.22 for boys and -2.5 +/- 0.64 for girls at the onset of therapy, and at the time of examination -1.8 +/- 1.32 for the boys and 1.87 +/- 0.94 for the girls. Thirty-four normal control subjects (Group 2) matched for age, sex and body size were also studied. Left ventricular volume (LV), mass and systolic function [shortening fraction (FS)] were evaluated by two-dimensional guided M-mode echocardiography. Blood pressure was also measured. No differences in blood pressure were observed between patients and controls. There was no correlation of GH dose and duration of therapy with LV measurements. No significant differences were found between Group 1 and Group 2. These observations suggest that long term administration of GH does not produce adverse cardiac effects in GH deficient children. Nevertheless, longer follow-up studies are still needed to confirm the safety of long-term rhGH treatment.

Lack of effects of recombinant human growth hormone in a child with a complex cardiovascular malformation and dilated cardiomyopathy

Recent studies have suggested the beneficial effects of GH treatment in patients with dilated cardiomyopathy. We have treated with recombinant human growth hormone (rhGH) a 6-year-old female with a complex congenital heart defect (severe tricuspid hypoplasia and malposition of the great arteries), who developed a progressive dilated cardiomyopathy of unknown etiology. rhGH treatment (0,1 U/kg/day, for 3 months) did not improve cardiac function, nor clinical symptoms, although we have no clear explanations for this. However, a trial with rhGH may be offered to children with dilated cardiomyopathy and waiting for heart transplantation.

Increased insulin-like growth factor-1 protein in human left ventricular hypertrophy

Animal models of cardiac hypertrophy demonstrated increased expression of insulin-like-growth factor-1 (IGF-1) in the heart. To study protein expression of insulin-like-growth factor 1 in left ventricular hypertrophy (LVH) in humans 11 hearts of autopsy cases with LVH were compared to 11 controls using immunohistochemical staining with anti-human IGF-1. LVH was defined as thickening of the left ventricular wall which ranged from 1.6 to 2.5 cm with hearts weights from 400 to 900 g. Immunohistochemical staining for IGF-1 was increased in the presence of LVH. In cases of LVH 37.9 +/- 3.5% of the cross-sectional myocardial area stained positively for IGF-1 compared to 6.8 +/- 2.9% in controls (P < 0.001). The findings support the hypothesis that IGF-1 has a role in the pathogenesis of LVH in humans. The increase of IGF-1 protein with LVH suggests reactivation of the cardiac IGF-1 genes in the hypertrophied adult cardiomyocyte.

Is growth hormone good for the heart?

Growth hormone (GH), probably acting indirectly through locally produced insulin-like growth factor I, stimulates myocardial hypertrophy and increases myocyte contractility. In experimental models insulin-like growth factor I appears to be a key regulator of ventricular hypertrophy. Many adults with growth hormone deficiency (GHD) have reduced left ventricular mass, a lower ejection fraction, and reduced exercise tolerance. Elevated serum lipid levels, increased visceral fat, and early atheroma formation may contribute to an increased mortality rate from cardiovascular disease in these persons, but GH replacement therapy appears to correct many of these abnormalities. GH excess (acromegaly) results in cardiac hypertrophy that can progress to cardiac failure. Treatment with octreotide at least partially reverses cardiac hypertrophy and dysfunction. GH treatment may induce beneficial cardiac hypertrophy in adults without GHD who have dilated cardiomyopathy. Significant cardiac dysfunction has not been reported in children with GHD who are treated with GH, nor have adverse cardiac effects been reported with GH in short children without GHD, including those with Turner syndrome. We now have extensive experience with the therapeutic use of GH in children with cardiac structural abnormalities (e.g., Turner and Noonan syndromes, congenital heart disease), and such use appears to be safe. Furthermore, cardiac complications of GH in children without cardiac disease are rare. Continued observation to ensure that GH therapy has no long-term effects on cardiac anatomy or function in children is necessary.