Short-term growth hormone (GH) treatment of GH-deficient adults increases body sodium and extracellular water, but not blood pressure

Ambulatory blood pressure monitorisation in children with recombinant growth hormone treatment

OBJECTIVES

It is safe to use recombinant growth hormone in children. Studies have shown it to be effective and safe, except for a few side effects in the short and long term after treatment. The present study investigated the presence of hypertension in pediatric patients receiving growth hormone treatment using 24 h ambulatory blood pressure monitoring (ABPM).

METHODS

This study is a single-center, retrospective study. Eighty-four patients aged 5-16 years who received growth hormone treatment for at least 3 months, who underwent 24 h ABPM were analyzed. They were compared with 67 patients who had no risk factors for hypertension.

RESULTS

In the study, 84 rhGH-treated patients (45.2 % male, 54.8 % female) and 67 healthy control groups (49.3 % male, 50.7 % female) were analyzed. The mean age of the patient group was 10.83±2.85 years and the mean age of the healthy control group was 13.1±2.93 years. The diagnostic classification of the patients receiving treatment was as follows: 66.6 % (n=56) partial growth hormone deficiency, 22.6 % (n=19) growth hormone deficiency, 7.1 % (n=6) bioactive growth hormone, 2.3 % (n=2) idiopathic short stature, 1.1 % (n=1) low birth weight for gestational age (SGA). Body mass index was significantly lower in the treated group (p=0.013). The duration of treatment was 6.04±4.9 months. Daytime diastolic blood pressure was significantly lower in the treated group (p=0.001). There was no correlation between BMI and ABPM parameters in the treatment group and the control group.

CONCLUSIONS

The present study shows that growth hormone treatment is safe in terms of high blood pressure.

Delayed postoperative hyponatremia in patients with acromegaly: incidence and predictive factors

PURPOSE

Delayed postoperative hyponatremia (DPH) is a unique complication of transsphenoidal surgery (TSS) in pituitary tumors. Growth hormone (GH) enhances renal sodium reabsorption; however, the association between postoperative GH reduction and DPH in acromegaly is unclear. This study was performed to clarify the incidence of and the predictive factors for DPH in patients with acromegaly who underwent TSS.

METHODS

Ninety-four patients with active acromegaly were examined retrospectively. During the postoperative course, patients with serum sodium levels ≤ 134 mEq/L were classified into the DPH group. We compared basic clinical characteristics, tumor characteristics, and preoperative and postoperative examination findings between the DPH and non-DPH groups.

RESULTS

DPH occurred in 39 patients (41.5%), and the lowest serum sodium levels were generally observed during postoperative days (PODs) 7-9. They needed a 3-day longer hospital stay than those without DPH. The DPH group had lower preoperative body weight and body mass index. In addition, a transient increase in body weight during PODs 5-7 occurred with a transient decrease in urinary volume in the DPH group. Preoperative and postoperative GH and insulin-like growth factor-1 levels did not differ between the two groups.

CONCLUSION

The findings suggested that lower preoperative weight and a postoperative transient gain in body weight are associated with an increased risk of DPH in acromegaly patients undergoing transsphenoidal surgery.

Renal effects of growth hormone in health and in kidney disease

Growth hormone (GH) and its mediator insulin-like growth factor-1 (IGF-1) have manifold effects on the kidneys. GH and IGF receptors are abundantly expressed in the kidney, including the glomerular and tubular cells. GH can act either directly on the kidneys or via circulating or paracrine-synthesized IGF-1. The GH/IGF-1 system regulates glomerular hemodynamics, renal gluconeogenesis, tubular sodium and water, phosphate, and calcium handling, as well as renal synthesis of 1,25 (OH)2 vitamin D3 and the antiaging hormone Klotho. The latter also acts as a coreceptor of the phosphaturic hormone fibroblast-growth factor 23 in the proximal tubule. Recombinant human GH (rhGH) is widely used in the treatment of short stature in children, including those with chronic kidney disease (CKD). Animal studies and observations in acromegalic patients demonstrate that GH-excess can have deleterious effects on kidney health, including glomerular hyperfiltration, renal hypertrophy, and glomerulosclerosis. In addition, elevated GH in patients with poorly controlled type 1 diabetes mellitus was thought to induce podocyte injury and thereby contribute to the development of diabetic nephropathy. This manuscript gives an overview of the physiological actions of GH/IGF-1 on the kidneys and the multiple alterations of the GH/IGF-1 system and its consequences in patients with acromegaly, CKD, nephrotic syndrome, and type 1 diabetes mellitus. Finally, the impact of short- and long-term treatment with rhGH/rhIGF-1 on kidney function in patients with kidney diseases will be discussed.

Downregulation of the ACE2/Ang-(1-7)/Mas axis in transgenic mice overexpressing GH

The renin-angiotensin system (RAS) plays a crucial role in the regulation of physiological homeostasis and diseases such as hypertension, coronary artery disease, and chronic renal failure. In this cascade, the angiotensin-converting enzyme (ACE)/angiotensin II (Ang II)/AT1 receptor axis induces pathological effects, such as vasoconstriction, cell proliferation, and fibrosis, while the ACE2/Ang-(1-7)/Mas receptor axis is protective for end-organ damage. The altered function of the RAS could be a contributing factor to the cardiac and renal alterations induced by GH excess. To further explore this issue, we evaluated the consequences of chronic GH exposure on the in vivo levels of Ang II, Ang-(1-7), ACE, ACE2, and Mas receptor in the heart and the kidney of GH-transgenic mice (bovine GH (bGH) mice). At the age of 7-8 months, female bGH mice displayed increased systolic blood pressure (SBP), a high degree of both cardiac and renal fibrosis, as well as increased levels of markers of tubular and glomerular damage. Angiotensinogen abundance was increased in the liver and the heart of bGH mice, along with a concomitant increase in cardiac Ang II levels. Importantly, the levels of ACE2, Ang-(1-7), and Mas receptor were markedly decreased in both tissues. In addition, Ang-(1-7) administration reduced SBP to control values in GH-transgenic mice, indicating that the ACE2/Ang-(1-7)/Mas axis is involved in GH-mediated hypertension. The data indicate that the altered expression profile of the ACE2/Ang-(1-7)/Mas axis in the heart and the kidney of bGH mice could contribute to the increased incidence of hypertension, cardiovascular, and renal alterations observed in these animals.

Comparative study of the effects of different growth hormone doses on growth and spatial performance of hypophysectomized rats

This study was designed to examine the effects of recombinant human growth hormone replacement on somatic growth and cognitive function in hypophysectomized (HYPOX) female Sprague-Dawley rats. Rats (5 per group) were randomized by weight to 3 experimental groups: group 1, administered 200 microg/kg of GH once daily for 9 days; group 2, administered 200 microg/kg of GH twice daily; and group 3, administered saline daily. Somatic growth was evaluated by measurement of body weight daily and of the width of the proximal tibial growth plate of the HYPOX rats. Cognitive function was evaluated using the Morris water maze (MWM) test. The results indicated that GH replacement therapy in HYPOX rats promoted an increase in the body weight and the width of the tibial growth plate in a dose-dependent manner. On the third day of the MWM test, the escape latency in the GH-treated groups 1 and 2 was significantly shorter than that in the control rats (P<0.001 and P=0.032, respectively), suggesting that rhGH improved spatial memory acquisition in the MWM test. Therefore it is concluded that rhGH replacement therapy in HYPOX rats stimulates an increase in somatic growth in a dose-dependent manner and also has beneficial effects on cognitive functions.

Chronic growth hormone excess is associated with increased aldosterone: a study in patients with acromegaly and in growth hormone transgenic mice

Acromegaly is a disease characterized by chronic growth hormone (GH) excess. Since hypertension is a common finding in patients with acromegaly, interactions between GH and the renin-angiotensin-aldosterone system (RAAS) are under controversial debate. We examined GH, IGF-I, aldosterone, and renin in a well-defined group of acromegalic patients before and after cure by surgery. In addition, we analyzed the impact of chronic GH excess on the RAAS in mouse models over-expressing GH alone (G) or in combination with insulin-like growth factor-binding protein-2 (IGFBP-2; GB). Normalization of GH secretion after cure by surgery was accompanied by significant decreases of serum aldosterone in acromegalic patients (pre-op: 96.5 +/- 37.1 pg/mL, post-op: 41.3 +/- 28.2 pg/ mL; P < 0.001; n = 13), but renin concentrations were unaffected. In addition, aldosterone concentrations were positively correlated to GH levels (Spearman r = 0.39; P = 0.025; n = 26). To further study this association, we analysed two transgenic mouse models and found a similar relationship between GH and aldosterone in G mice, which showed about 3-fold elevated serum aldosterone levels in comparison to non-transgenic controls (males: 442 +/- 331 pg/mL vs. 151 +/- 84 pg/mL; P = 0.002; n > or = 12; females: 488 +/- 161 pg/mL vs. 108 +/- 125 pg/mL; P = 0.05; n > or = 4). Expression of aldosterone synthase was similar in adrenal glands of C and G mice. Aldosterone levels in G and GB mice of both genders were not different, indicating that the elevated aldosterone was due to GH excess and not caused by elevated IGF-I, which is known to be blocked by IGFBP-2 overexpression. Also in the mouse models, changes in aldosterone were independent from renin. In summary, we show that chronic GH excess is associated with increased aldosterone in humans and mice. GH-induced increases of aldosterone potentially contribute to the increased cardiovascular risk in acromegalic patients. The underlying mechanism is likely to be independent of renin, excess IGF-I, or adrenal aldosterone synthase expression.

Arterial pulse wave velocity, inflammatory markers, pathological GH and IGF states, cardiovascular and cerebrovascular disease

Blood pressure (BP) measurements provide information regarding risk factors associated with cardiovascular disease, but only in a specific artery. Arterial stiffness (AS) can be determined by measurement of arterial pulse wave velocity (APWV). Separate from any role as a surrogate marker, AS is an important determinant of pulse pressure, left ventricular function and coronary artery perfusion pressure. Proximal elastic arteries and peripheral muscular arteries respond differently to aging and to medication. Endogenous human growth hormone (hGH), secreted by the anterior pituitary, peaks during early adulthood, declining at 14% per decade. Levels of insulin-like growth factor-I (IGF-I) are at their peak during late adolescence and decline throughout adulthood, mirror imaging GH. Arterial endothelial dysfunction, an accepted cause of increased APWV in GH deficiency (GHD) is reversed by recombinant human (rh) GH therapy, favorably influencing the risk for atherogenesis. APWV is a noninvasive method for measuring atherosclerotic and hypertensive vascular changes increases with age and atherosclerosis leading to increased systolic blood pressure and increased left ventricular hypertrophy. Aerobic exercise training increases arterial compliance and reduces systolic blood pressure. Whole body arterial compliance is lowered in strength-trained individuals. Homocysteine and C-reactive protein are two inflammatory markers directly linked with arterial endothelial dysfunction. Reviews of GH in the somatopause have not been favorable and side effects of treatment have marred its use except in classical GHD. Is it possible that we should be assessing the combined effects of therapy with rhGH and rhIGF-I? Only multiple intervention studies will provide the answer.

Epithelial sodium channel is a key mediator of growth hormone-induced sodium retention in acromegaly

Acromegalic patients present with volume expansion and arterial hypertension, but the renal sites and molecular mechanisms of direct antinatriuretic action of GH remain unclear. Here, we show that acromegalic GC rats, which are chronically exposed to very high levels of GH, exhibited a decrease of furosemide-induced natriuresis and an increase of amiloride-stimulated natriuresis compared with controls. Enhanced Na(+),K(+)-ATPase activity and altered proteolytic maturation of epithelial sodium channel (ENaC) subunits in the cortical collecting ducts (CCDs) of GC rats provided additional evidence for an increased sodium reabsorption in the late distal nephron under chronic GH excess. In vitro experiments on KC3AC1 cells, a murine CCD cell model, revealed the expression of functional GH receptors and IGF-I receptors coupled to activation of Janus kinase 2/signal transducer and activator of transcription 5, ERK, and AKT signaling pathways. That GH directly controls sodium reabsorption in CCD cells is supported by: 1) stimulation of transepithelial sodium transport inhibited by GH receptor antagonist pegvisomant; 2) induction of alpha-ENaC mRNA expression; and 3) identification of signal transducer and activator of transcription 5 binding to a response element located in the alpha-ENaC promoter, indicative of the transcriptional regulation of alpha-ENaC by GH. Our findings provide the first evidence that GH, in concert with IGF-I, stimulates ENaC-mediated sodium transport in the late distal nephron, accounting for the pathogenesis of sodium retention in acromegaly.

Short-term administration of growth hormone (GH) lowers blood pressure by activating eNOS/nitric oxide (NO)-pathway in male hypophysectomized (Hx) rats

Background

The aim of the study was to evaluate the acute and continuous (up to 14 days of treatment) effect of growth hormone (GH) on blood pressure (BP) regulation and to investigate the interplay between GH, nitric oxide (NO) and BP.

In un-supplemented and GH supplemented hypophysectomized (Hx) male rats as well as intact rats, continuous resting mean arterial blood pressure (MAP) was measured using telemetry. Baroreceptor activity and the influences of NO on BP control were assessed during telemetric measurement. Furthermore, basal plasma and urine nitrate levels and aortic endothelial nitric oxide synthase (eNOS) expression were analysed. Endothelial function as well as vascular structure in the hindquarter vascular bed was estimated using an in vivo constant-flow preparation.

Results

Hypophysectomy was associated with decreased MAP (Hx: 83 ± 3 vs Intact: 98 ± 6 mmHg, p < 0.05) and heart rate (HR) (Hx: 291 ± 4 vs Intact: 351 ± 7 beat/min, p < 0.05). Endothelial dysfunction and reduced vasculature mass in the hindquarter vascular bed was found in Hx rats. GH substitution caused a further transient decrease in MAP and a transient increase in HR (14% and 16% respectively, p < 0.05). The reduction in MAP appeared to be NO dependent. Aortic eNOS expression was unchanged. GH substitution resulted in an impaired baroreceptor function. Two weeks of GH treatment did not normalise the BP, vascular structure and the endothelial function in the resistance vessels.

Conclusion

GH substitution seems to have a short lasting effect on lowering blood pressure via activation of the NO-system. An interaction between GH, NO-system and BP regulation can be demonstrated.

Growth hormone regulation of glomerular AT1 angiotensin receptors in adult uninephrectomized male rats

Sex differences exist in the mechanisms initiating early compensatory renal growth after unilateral nephrectomy (UNX); remnant kidney growth is growth hormone (GH) independent in adult female rats and GH dependent in adult male rats. The present study determined whether sex differences also exist in angiotensin type 1 receptor (AT1R) regulation during early remnant kidney (REM) growth after UNX, and if so, whether GH modulates AT1R expression after UNX in the male rat. Scatchard analysis of radioligand binding in glomeruli demonstrated that 48 h post-UNX, AT1R density (Bmax) was significantly decreased by 20% in female REM compared with control kidneys. In contrast, male REM glomerular Bmax was significantly increased by 28% compared with control kidneys. Furthermore, GH-suppressed male rats displayed attenuated REM growth, which was associated with a 35% decrease in AT1R Bmax. Losartan treatment also decreased REM AT1R Bmax by 55%. The activity of mRNA binding proteins that bind to the 5' leader sequence of the AT1R was regulated by UNX and GH treatment in an inverse manner to AT1R expression. These findings suggest that in rats 1) there are sex differences in the regulation of glomerular AT1R expression after UNX; 2) the increase in AT1R binding sites in the male REM is regulated by GH and mediates early remnant kidney growth; and 3) AT1R 5' leader sequence mRNA binding proteins play a role in UNX and GH regulation of glomerular AT1Rs in both males and females.

Claims for the anabolic effects of growth hormone: a case of the emperor's new clothes?

This review examines the evidence that growth hormone has metabolic effects in adult human beings. The conclusion is that growth hormone does indeed have powerful effects on fat and carbohydrate metabolism, and in particular promotes the metabolic use of adipose tissue triacylglycerol. However, there is no proof that net protein retention is promoted in adults, except possibly of connective tissue. The overexaggeration of the effects of growth hormone in muscle building is effectively promoting its abuse and thereby encouraging athletes and elderly men to expose themselves to increased risk of disease for little benefit.

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

We studied the effects of recombinant growth hormone on systemic nitric oxide (NO) formation and hemodynamics in a double-blind, placebo-controlled trial in adult patients with acquired growth hormone deficiency. 30 patients were randomly allocated to either recombinant human growth hormone (r-hGH; 2.0 IU/d) or placebo for 12 mo. In the subsequent 12 mo, the study was continued with both groups of patients receiving r-hGH. In months 1, 3, 6, 9, and 12 of each year, urine and plasma samples were collected for the determination of urinary nitrate and cyclic GMP as indices of systemic NO production, and of plasma IGF-1 levels. Cardiac output was measured in months 1, 12, and 24 by echocardiography. r-hGH induced a fourfold increase in plasma IGF-1 concentrations within the first month of treatment. Urinary nitrate and cyclic GMP excretion rates were low at baseline in growth hormone-deficient patients (nitrate, 96.8+/-7.4 micromol/mmol creatinine; cyclic GMP, 63.6+/-7.1 nmol/mmol creatinine) as compared with healthy controls (nitrate, 167.3+/-7.5 micromol/mmol creatinine; cyclic GMP, 155.2+/-6.9 nmol/mmol creatinine). These indices of NO production were significantly increased by r-hGH, within the first 12 mo in the GH group, and within the second 12 mo in the placebo group. While systolic and diastolic blood pressure were not significantly altered by r-hGH, cardiac output significantly increased by 30-40%, and total peripheral resistance decreased by approximately 30% in both groups when they were assigned to r-hGH treatment. In the second study year, when both groups were given r-hGH, there were no significant differences in plasma IGF-1, urinary nitrate, or cyclic GMP excretion, or hemodynamic parameters between both groups. In conclusion, systemic NO formation is decreased in untreated growth hormone-deficient patients. Treatment with recombinant human growth hormone normalizes urinary nitrate and cyclic GMP excretion, possibly via IGF-1 stimulation of endothelial NO formation, and concomitantly decreases peripheral arterial resistance. Increased NO formation may be one reason for improved cardiovascular performance of patients with acquired hypopituitarism during growth hormone therapy.