Glucose metabolism and visceral fat in GH deficient adults: 1 year of GH replacement

Effect of long-term growth hormone replacement on glucose metabolism in adults with growth hormone deficiency: a systematic review and meta-analysis

PURPOSE

This systematic review and meta-analysis was performed to summarize the long-term (more than 6 months) effect of growth hormone (GH) replacement therapy (GHRT) on glucose metabolism among adults growth hormone deficiency (AGHD) patients.

METHODS

We searched MEDLINE, EMBASE and the Cochrane Library databases from inception till March 2020 for relevant studies evaluating the effect of GHRT on glucose metabolism in AGHD patients. Results were stratified into two periods (6-12 months and more than12 months) according to the length of follow-up.

RESULTS

Thirty-three studies including 11 randomized controlled trials (RCTs) and 22 prospective open-label studies (POLs) were included in the meta-analysis. The findings of this meta-analysis showed that GH supplementation with a duration of 6-12 months among adults with growth hormone deficiency (GHD) significantly increased fasting plasma glucose (FPG) (SMD 0.37; 95% CI 0.25 to 0.49; I² = 0%; P < 0.00001), fasting insulin (FI) (SMD 0.2; 95% CI 0.08 to 0.33; I² = 9%; P = 0.001), glycated hemoglobin (HbA1c) (SMD 0.31; 95% CI 0.17 to 0.46; I² = 10%; P < 0.0001) and homeostasis model of assessment-insulin resistance (HOMA-IR) (SMD 0.28; 95% CI 0.08 to 0.47; I² = 13%; P = 0.006). Notably, GH intervention with a duration of more than 12 months showed no significant effect on FI (SMD 0.14; 95% CI - 0.09 to 0.37; I² = 0%; P = 0.24), HbA1c (SMD - 0.02; 95% CI - 0.3 to 0.26; I² = 72%; P = 0.89) and HOMA-IR levels (SMD 0.04; 95% CI - 0.24 to 0.31; I² = 0%; P = 0.80) in adults with GHD. However, FPG levels in AGHD were still significantly increased with more than one year intervention period (SMD 0.41; 95% CI 0.29 to 0.53; I² = 0%; P < 0.00001).

CONCLUSION

Overall, the current meta-analysis demonstrated that GHRT with a shorter duration (6-12 months) led to a deterioration in glucose metabolism including FPG, FI, HbA1c and HOMA-IR in AGHD patients. However, the negative effects of GH therapy on these glucose homeostasis parameters were not seen in longer duration of GHRT, except for FPG.

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

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

A long-acting human growth hormone with delayed clearance (VRS-317): results of a double-blind, placebo-controlled, single ascending dose study in growth hormone-deficient adults

BACKGROUND

Administration of daily recombinant human GH (rhGH) poses a considerable challenge to patient compliance. Reduced dosing frequency may improve treatment adherence and potentially overall treatment outcomes.

OBJECTIVES

This study assessed the safety and tolerability and the potential for achieving IGF-I levels within the target range in adults with GH deficiency after a single dose of the long-acting rhGH analog, VRS-317.

DESIGN

This was a randomized, double-blind, placebo-controlled, single ascending dose study.

PATIENTS

Fifty adults with growth hormone deficiency (mean age, 45 years) were studied in 5 treatment groups of 10 subjects each (8 active drug and 2 placebo).

SETTING

The study was conducted in 17 adult endocrinology centers in North America and Europe.

MAIN OUTCOME MEASURES

Adverse events, laboratory safety assessments, and VRS-317 pharmacokinetics and pharmacodynamics (IGF-I and IGF binding protein-3) were analyzed.

RESULTS

At 0.80 mg/kg, VRS-317 had a mean terminal elimination half-life of 131 hours. Single VRS-317 doses of 0.05, 0.10, 0.20, 0.40, and 0.80 mg/kg (approximately equivalent to daily rhGH doses of 0.3-5.0 μg/kg over 30 d) safely increased the amplitude and duration of IGF-I responses in a dose-dependent manner. After a single 0.80 mg/kg dose, serum IGF-I was maintained in the normal range between -1.5 and 1.5 SD values for a mean of 3 weeks. No unexpected or serious adverse events were observed.

CONCLUSIONS

The elimination half-life for VRS-317 is 30- to 60-fold longer and stimulates more durable IGF-I responses than previously studied rhGH products. Prolonged IGF-I responses do not come at the expense of overexposure to high IGF-I levels. The pharmacokinetics and pharmacodynamics combined with the observed safety profile indicate the potential for safe and effective monthly dosing.

Pathophysiology of human visceral obesity: an update

Excess intra-abdominal adipose tissue accumulation, often termed visceral obesity, is part of a phenotype including dysfunctional subcutaneous adipose tissue expansion and ectopic triglyceride storage closely related to clustering cardiometabolic risk factors. Hypertriglyceridemia; increased free fatty acid availability; adipose tissue release of proinflammatory cytokines; liver insulin resistance and inflammation; increased liver VLDL synthesis and secretion; reduced clearance of triglyceride-rich lipoproteins; presence of small, dense LDL particles; and reduced HDL cholesterol levels are among the many metabolic alterations closely related to this condition. Age, gender, genetics, and ethnicity are broad etiological factors contributing to variation in visceral adipose tissue accumulation. Specific mechanisms responsible for proportionally increased visceral fat storage when facing positive energy balance and weight gain may involve sex hormones, local cortisol production in abdominal adipose tissues, endocannabinoids, growth hormone, and dietary fructose. Physiological characteristics of abdominal adipose tissues such as adipocyte size and number, lipolytic responsiveness, lipid storage capacity, and inflammatory cytokine production are significant correlates and even possible determinants of the increased cardiometabolic risk associated with visceral obesity. Thiazolidinediones, estrogen replacement in postmenopausal women, and testosterone replacement in androgen-deficient men have been shown to favorably modulate body fat distribution and cardiometabolic risk to various degrees. However, some of these therapies must now be considered in the context of their serious side effects. Lifestyle interventions leading to weight loss generally induce preferential mobilization of visceral fat. In clinical practice, measuring waist circumference in addition to the body mass index could be helpful for the identification and management of a subgroup of overweight or obese patients at high cardiometabolic risk.

Comparison of two dose regimens of growth hormone (GH) with different target IGF-1 levels on glucose metabolism, lipid profile, cardiovascular function and anthropometric parameters in gh-deficient adults

OBJECTIVE

To compare the effects of two regimens of GH therapy with different target IGF-1 levels on anthropometric parameters, glucose metabolism, lipid profile and cardiac function in adults with GH deficiency (GHD).

PATIENTS AND METHODS

Retrospective analysis of 14 GHD adults from Clementino Fraga Filho University Hospital, Rio de Janeiro, Brazil, who were treated with a GH regimen aimed at maintaining serum IGF-1 levels between the median and upper reference limit (high dose group - HDGH) and 18 GHD adults from Federal University Hospital, Curitiba, Brazil, who received a fixed GH dose of 0.2mg/day in the first year of treatment, followed by titration to maintain serum IGF-1 levels between the median and lower reference limit (low dose group - LDGH). All patients were followed for 2 years with analysis of anthropometric parameters, serum levels of IGF-1, glucose, insulin, HOMA-IR, lipid profile, and transthoracic echocardiography.

RESULTS

Changes on weight, BMI and waist circumference were similar between the two groups. Insulin levels increased and HOMA-IR worsened in the LDGH group at 1year and improved thereafter. Total cholesterol and triglycerides did not change with therapy. LDL cholesterol reduced in both groups, while HDL-cholesterol significantly increased only in the HDGH group (p=0.007 vs LDGH). No significant variations on echocardiographic parameters were observed.

CONCLUSION

The HDGH and LDGH regimens resulted in similar changes on anthropometric, echocardiographic, glucose and lipid parameters in GHD adults, except for increase in HDL cholesterol that was only observed in the HDGH regimen.

Comparison of glucose and lipid metabolism and bone mineralization in patients with growth hormone deficiency with and without long-term growth hormone replacement

The effects of long-term growth hormone (GH) substitution in pituitary-insufficient patients with GH deficiency (GHD-pats) on glucose and lipid metabolism and bone mineral density (BMD) have yet to be ascertained. We performed this cross-sectional study comparing GHD-pats with and without long-term GH substitution. We measured lipid parameters at baseline and glucose and insulin concentrations for 3 hours during oral glucose tolerance test in 52 GHD-pats (21 female and 31 male; median age, 51.5 years [27-82]). Twenty-two GHD-pats were on constant GH substitution (GH-Subs) for a median of 10 years (2-42 years). Thirty GHD-pats had not been substituted for at least 2 years (non-Subs). For analyses of beta-cell function, insulin resistance (IR), and sensitivity, homeostatic model assessment (HOMA)-beta , HOMA-IR, and insulin sensitivity index were used, respectively. Body composition and BMD were measured by dual-energy x-ray absorptiometry. Age and body mass index did not differ significantly between groups. Fasting glucose was significantly lower for GH-Subs than non-Subs (87 mg/dL [71-103] vs non-Subs 89 mg/dL [71-113], P < .05), whereas basal insulin did not differ significantly (10 muU/mL (4-42) vs non-Subs 10 microU/mL [4-63]). Glucose and insulin levels at 120 minutes as well as patients' area under the curve, C-peptide, hemoglobin A(1c), waist-hip ratio, HOMA-beta, HOMA-IR, insulin sensitivity index, lipid parameters, and BMD did not differ significantly; but total fat mass was significantly higher in non-Subs (37% [20%-52%] vs GH-sub 31% [13%-54%], P < .01). More non-Subs had abnormal glucose tolerance (19 [63%] vs GH-Subs 9 [41%]). Long-term GH substitution trends to beneficially influence fasting glucose and glucose tolerance, although differences are sparse. Growth hormone substitution alone does not seem to significantly impact on insulin sensitivity, lipid metabolism, and BMD in patients with pituitary insufficiency.

Impact of 5 years of growth hormone replacement therapy on cardiovascular risk factors in growth hormone-deficient adults

The benefits of long-term effects of growth hormone (GH) substitution on carbohydrate and lipid metabolism in GH-deficient (GHD) adults are still controversial. The purpose of this study was to evaluate the effects of 5 years of GH substitution on body composition, glucose and lipid metabolism, and carotid artery intima-media thickness (IMT) in GHD adults. Fourteen patients were clinically assessed every 3 months for 5 years. Serum insulin-like growth factor 1 levels, lipid profile, oral glucose tolerance test, and ultrasonography of the carotid arteries were performed at baseline, 6 months, and every year during replacement. Visceral fat was measured by computed tomographic scan at baseline and at 6, 12, 24, and 60 months. The waist circumference was reduced after 6 months but increased during the next months toward baseline values. Visceral fat decreased during the study. Fasting glucose and insulin levels did not change, as well as the homeostasis model assessment of insulin resistance index. Despite an initial increase in frequency of abnormal glucose tolerance, mean 2-hour oral glucose tolerance test glucose levels decreased during the last 2 years. There was an increase in apolipoprotein A-1 levels during the treatment. Apolipoprotein B levels were reduced after 6 months and remained stable thereafter. A reduction in carotid artery IMT was observed during replacement. We concluded that 5 years of GH replacement therapy promoted positive effects on visceral fat, lipid profile, and carotid artery IMT in GHD adults. Long-term therapy improves insulin sensitivity through a reduction in visceral fat, and continuing monitoring is mandatory in terms of glucose metabolism.

Association of insulin resistance and nocturnal fall of blood pressure in GH-deficient adults during GH replacement

The GH deficiency syndrome in adults is characterized by changes in body composition, metabolic, cardiovascular and psychological profile. Such alterations fit the metabolic syndrome. Changes of blood pressure (BP) levels related to the presence of insulin resistance (IR) may be present in the GH-deficient adult prior to or after therapy with recombinant GH (hGH). The purpose of the study was to assess the relationship between BP and IR in GH-deficient adults after 24 months of replacement with hGH. Thirteen GH-deficient adults were studied [7 men and 6 women, with an average age of 38.6+/-14.14 yr body mass index (BMI) 25.83+/-2.26 kg/m2]. The BP was assessed by means of ambulatory monitoring of BP (AMBP), prior to the treatment and 12 and 24 months after replacement with hGH. Glucose metabolism was assessed by the homeostatic model assessment (HOMA), during the same periods. The average dosage of hGH utilized was 0.67+/-0.15 mg/day. In the analysis of BP levels, we observed a decrease of the diurnal systolic BP (SB P) (p=0.043) and a reduction of the diurnal systolic (p=0.002) and diastolic pressure loads (p=0.038). During the night there were no changes in BP levels. We observed an increase in the percentage of patients with a non-physiological nocturnal fall (non dippers) after replacement with hGH (61.53%). The mean HOMA, insulin and glucose in the fasting state did not present any statistically significant changes. Although the patients within the nondipper group had higher HOMA and insulin levels throughout the study, there were no changes in any of these parameters after GH replacement. All patients with HOMA >2.5 were within the non-dipper group, whereas all dippers had HOMA <2.5. In conclusion, 24 months of therapy with hGH do not seem to have affected glucose homeostasis, and since there is no relationship with the increase of the percentage of non-physiological nocturnal fall, we will need a longer observation time to discover the effects of this finding.

Therapeutic aspects of growth hormone and insulin-like growth factor-I treatment on visceral fat and insulin sensitivity in adults

Growth hormone (GH) is generally considered to exert anti-insulin actions, whereas insulin-like growth factor I (IGF-I) has insulin-like properties. Paradoxically, GH deficient adults and those with acromegaly are both predisposed to insulin resistance, but one cannot extrapolate from these pathological conditions to determine the normal metabolic roles of GH and IGF-I on glucose homeostasis. High doses of GH treatment have major effects on lipolysis, which plays a crucial role in promoting its anti-insulin effects, whereas IGF-I acts as an insulin sensitizer that does not exert any direct effect on lipolysis or lipogenesis. Under physiological conditions, the insulin-sensitizing effect of IGF-I is only evident after feeding when the bioavailability of circulating IGF-I is increased. In contrast, many studies in GH deficient adults have consistently shown that GH replacement improves the body composition profile although these studies differ considerably in terms of age, the presence or absence of multiple pituitary hormone deficiency, and whether GH deficiency was childhood or adult-onset. However, the improvement in body composition does not necessarily translate into improvements in insulin sensitivity presumably due to the anti-insulin effects of high doses of GH therapy. More recently, we have found that a very low dose GH therapy (0.1 mg/day) improved insulin sensitivity without affecting body composition in GH-deficient adults and in subjects with metabolic syndrome, and we postulate that these effects are mediated by its ability to increase free 'bioavailable' IGF-I without the induction of lipolysis. These results raise the possibility that this low GH dose may play a role in preventing the decline of beta-cell function and the development of type 2 diabetes in these "high risk" subjects.

Effects of resistance exercise and growth hormone administration at low doses on lipid metabolism in middle-aged female rats

hGH (human growth hormone) is a key factor for metabolism as well as for growth. Lack of hGH usually increases LDL (low-density lipoprotein) while impairing exercise capacity and cardiac function [Amato G., Carella C., Fazio S., La Montagna G., Cittadini A., Sabatini D., Marciano-Mone C., Sacca L., and Bellastella A., 1993. Body composition, bone metabolism, and heart structure and function in growth hormone (GH)-deficient adults before and after GH replacement therapy at low doses. J. Clin. Endocrinol. Metab. 77, 1671-1676.]. It is still unclear, however, whether the administration of hGH to humans or animals has a synergic effects on body composition and the desired metabolic parameters with endurance resistance exercise. Therefore, the present study seeks to establish whether or not lipid metabolism is altered by both recombinant GH (growth hormone) and X (resistance exercise) in middle-aged female rats. GH administration resulted in greater weight gain compared with control and exercised animals, but the effect was reduced when combined with exercise. The increased body weight was largely due to increased muscle mass. Exercise did not result in any additional effect of GH on muscle mass. In the exercise group, hepatic HDL (high density lipoprotein) increased compared to the C (control group). The GX (growth hormone+exercise) group's serum and X group's kidney IGF-I (Insulin-like growth factor-I) concentration increased compared to the C group. In G and GX groups, serum insulin and leptin concentrations were higher than in the control, suggesting that GH may induce an insulin resistant state. Any gains in muscle mass were minimal and were not synergistic with exercise. These results suggest that hGH may not be useful for increasing performance in athletes and may induce and acquired insulin resistance.

Two years of growth hormone replacement therapy in a group of patients with Sheehan's syndrome

To investigate the effects of GH replacement on lipid profile, carotid artery intima-media thickness (IMT), glucose metabolism and visceral fat in patients with Sheehan's syndrome, ten patients, mean age 44.8+/-9.5 yr, compared with 10 controls matched for age and body mass index were studied. Total cholesterol, Triglycerides (TG), HDL-c, LDL-c, Apolipoprotein A and B (apoA and apoB) and Lipoprotein (a), serum IGF-1, ultrasonography of the carotid arteries, oral glucose tolerance test (OGTT), HOMA insulin resistance index, insulin sensitivity index (ISI)-composite and abdominal CT scan were performed. When compared to a control group, patients presented lower HDL concentrations (p=0.05) and 2-h OGTT insulin levels (p<0.04) and increased TG levels (p<0.04). After 24 months of GH replacement a reduction in the relation ApoB/ApoA (p=0.04) was observed, as well as an increase in HDL (p<0.004). A decrease in carotid artery IMT and in visceral fat over time was found, p<0.03 and p<0.04 respectively, though without any significant differences during post hoc comparisons of means, which may be explained by the small number of cases studied, but there was a tendency, p=0.08 and p=0.09 respectively. The 2-h OGTT insulin levels increased (p<0.02) as well as the prevalence of glucose intolerance (prevalence = 42.8%, p<0.05). GH replacement therapy promoted favorable effects on carotid artery IMT, lipid profile and visceral fat in patients with Sheehan's syndrome. On the other hand, patients developed abnormal glucose tolerance probably due to an increase in insulin resistance, demonstrated by higher insulin levels, despite favorable changes in body composition.

Cardiovascular disease and risk factors: the role of growth hormone

Clinical studies in patients with acromegaly have shown that growth hormone (GH) exerts both short- and long-term effects on the structure and function of the heart. Moreover, chronic growth hormone deficiency (GHD) has been associated with impaired cardiac performance, low heart rate and impaired left ventricular systolic function. Exercise capacity in patients with GHD is significantly reduced and in some severely affected individuals, dilated cardiomyopathy and heart failure has been reported. GHD has also been associated with a number of risk factors for cardiovascular disease. Altered lipoprotein metabolism and elevated fibrinogen and plasminogen activator inhibitor-1 activity are associated with GHD, and the risk of hypertension is increased in GH-deficient men. Subcutaneous and intra-abdominal fat mass have also been found to be abnormally high in these patients. These effects may contribute to an increased risk of death from cardiovascular disease. GH is therefore an important factor in the development and function of the cardiovascular system. In this paper, the effects of GH on the physiological mechanisms of the cardiovascular system are discussed, including the effect of GHD on cardiovascular disease risk. We will also discuss the effects of long-term GH replacement therapy in this patient population.

Glucose metabolism and visceral fat in GH deficient adults: two years of GH-replacement

The aim of this study was to evaluate the effect of 24 months of growth hormone (GH) replacement on glucose metabolism and visceral fat in 17 adults with GH deficiency: 9 men and 8 women; age 40 +/- 1.8 yr. [range 20-61] and body mass index 25 +/- 0.8 Kg/m2. Glucose metabolism was evaluated by a standard oral glucose tolerance test (OGTT), by the homeostatic model assessment (HOMA) insulin resistance index and by the insulin sensitivity index (ISI)-composite derived from the OGTT. Visceral fat was evaluated by CT scan.Twenty-four months of GH replacement induced an increase in the prevalence of abnormal glucose tolerance, with significant progressive increment in 2h-OGTT insulin levels at 3, 12 and 24 months (p = 0.005). Plasma glucose levels and ISI-composite did not alter during the study. HOMA-IR index increased only in the group of patients (n = 8) who had abnormal OGTT at 24 months (p = 0.012). Visceral fat reduced at month 12 and remained decreased until the end of the study (p = 0.009). In conclusion, the present study suggests that adults with GH deficiency after twenty-four months of GH replacement developed abnormal glucose tolerance, probably due to an increase in insulin resistance, associated with higher insulin levels, despite favorable alterations in body composition.