Persisting effects on fasting glucose levels and insulin sensitivity after 6 months of discontinuation of a very low-dose GH therapy in adults with severe GH deficiency

Effects of 18 months of GH replacement on cardiovascular risk factors and quality of life in GH deficient adults; a randomized controlled trial using a fixed very low and a standard dose of GH

OBJECTIVE

Little is known of the effects of a fixed very low dose of growth hormone (GH) replacement on cardiovascular risk factors, bone mass, muscle strength and quality of life (QoL) in hypopituitary patients.

DESIGN/PATIENTS/METHODS

This was an open-label randomized study performed at a single center. Consecutive hypopituitary patients with adult onset GH deficiency (GHD) and BMI ≥ 27 kg/m² were randomized to receive a very low fixed dose of GH (LG, n = 9) or a standard dose of GH (SG, n = 9). Body composition, glucose and lipid metabolism, bone mineral content (BMC) and density (BMD), muscle strength, and QoL were measured at baseline and after 6, 12 and 18 months.

RESULTS

The fixed GH dose in LG was 0.1 mg/day. In SG, the mean baseline GH dose of 0.13 mg/day was gradually increased to 0.31 mg/day at study end. Lean body mass (LBM) as measured using DEXA as well as total body water (TBW) and extracellular water (ECW) were increased only in SG (P < 0.01, P < 0.05, and P < 0.01 vs. LG, respectively). There were no between-groups differences in BMD, BMC, insulin sensitivity, lipids, or muscle strength. Finally, although not significant compared with SG, a sustained improvement in QoL was seen in LG according to the QoL-AGHDA questionnaire.

CONCLUSION

In this pilot study, a fixed very low GH dose improved QoL in GHD adults without any induction of fluid retention. Other effects were comparable to those produced by the standard GH dose. Replacement with a very low GH dose could therefore be a treatment option in hypopituitary patients, especially in patients who do not tolerate higher GH dosage. Trial registration This study is registered at ClinicalTrials.gov, EU-nr 2009-016783-37.

GH Supplementation Effects on Cardiovascular Risk in GH Deficient Adult Patients: A Systematic Review and Meta-analysis

BACKGROUND AND OBJECTIVE

The current meta-analysis aims at evaluating whether the existing clinical evidence may ascertain the effects of growth hormone (GH) replacement therapy on cardiovascular risk, both in isolated GH deficiency (GHD) and in compensated panhypopituitarism including GH deficit.

METHODS

Original articles published from 1991 to 2015 were searched on Medline (Pubmed). Among an overall number of 181 potentially suitable studies, 24 fulfilled the selection criteria and were included in the analysis. Data aggregation was carried out through the calculation of the absolute risk reduction. The meta-analysis was then conducted by means of a fixed-effects model, according to the heterogeneity test (Chi-square statistic).

RESULTS

Fat-free mass (FFM) increase and fat mass (FM) reduction were found, together with a C-LDL reduction, a wide variation in glycaemia and a neutral effect on glycated haemoglobin (HbA1c) and blood pressure. These effects were valid both for isolated GHD patients and for those with compensated panhypopituitarism. The global outcome D showed a nonsignificant reduction of the overall cardiovascular risk (0.53; 95% C.I. -1.23, 2.85).

CONCLUSION

Our meta-analysis shows no signnificatly positive trend in cardiovascular risk after both short and long-term GH supplementation therapy in adult GHD patients. However, a reduction of LDL cholesterol levels has been found. No differences were found between isolated GHD participants and those affected by panhypopituitarism well compensated since at least 3 months.

Effects of growth hormone on glucose metabolism and insulin resistance in human

Growth hormone (GH) is important for promotion of somatic growth and the regulation of substrate metabolism. Metabolic action of GH occurs in multiple tissues including the liver, muscle, fat and pancreas either directly or indirectly through insulin-like growth factor 1. The diabetogenic action of GH has been well-described in previous in vivo studies. In this paper, we review the metabolic effects of GH on peripheral tissues focusing on glucose metabolism and insulin resistance, and discuss results from human studies on the long-term effects of GH administration on insulin resistance and hyperglycemia.

The effect of growth hormone (GH) replacement on blood glucose homeostasis in adult nondiabetic patients with GH deficiency: real-life data from the NordiNet® International Outcome Study

OBJECTIVE

To assess the effect of 4 years' growth hormone (GH) replacement on glucose homeostasis and evaluate factors affecting glycosylated haemoglobin (HbA_1c ) in adults with growth hormone deficiency (GHD).

DESIGN

NordiNet^® International Outcome Study, a noninterventional study, monitors long-term effectiveness and safety of GH replacement [Norditropin^® (somatropin), Novo Nordisk A/S] in real-life clinical practice.

PATIENTS

Nondiabetic patients (n = 245) with adult-onset GHD (age ≥20 years at GH start), ≥4 years' GH replacement and HbA_1c values at baseline and 4 years were included in the analysis.

MEASUREMENTS

Changes from baseline (∆) to 4 years in HbA_1c , fasting plasma glucose (FPG), IGF-I, lipids (high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, total cholesterol, triglycerides), waist circumference, glycaemic (HbA_1c <5·7%; HbA_1c , 5·7-6·5%; HbA_1c , ≥6·5%) and metabolic health status were evaluated. Effects of baseline HbA_1c , gender, baseline age, average GH dose and baseline body mass index (BMI) on ΔHbA_1c were investigated. The models were adjusted for concomitant medication use.

RESULTS

Mean (standard deviation) baseline HbA_1c was 5·13 (0·65)% and remained at the same level at 4 years. Age at treatment start (P = 0·0094) and BMI (P = 0·0008) had a significant impact on ∆HbA_1c . At 4 years, 85% of patients with HbA_1c <5·7% (normal levels) at baseline and 55% of patients with HbA_1c 5·7-6·5% (impaired glucose tolerance) at baseline remained in the same glycaemic health category. Nineteen patients improved from impaired glucose tolerance to normal HbA_1c . Seven patients developed diabetes.

CONCLUSIONS

These data demonstrate that 4 years' GH replacement therapy did not adversely affect glucose homeostasis in the majority of adults with GHD.

Effects of discontinuation of growth hormone replacement in adult GH-deficient patients: a cohort study and a systematic review of the literature

BACKGROUND

Recombinant human growth hormone (rhGH) replacement is advocated in adult growth hormone-deficient (GHD) patients to increase bone mass and improve lipid profile, body composition, and quality of life. The long-term effects of discontinuation of rhGh replacement are unknown.

METHODS

This cohort study and systematic review aim to evaluate the long-term metabolic effects of discontinuation of rhGh replacement in adult GHD patients, with a subgroup analyses according to age (< or > 60 years). Data on anthropometry, lipids, glucose, and bone mass density (BMD) were assessed for 3 years after discontinuation.

RESULTS

Cohort study included 64 patients who had discontinued rhGh replacement for >12 months. Fat percentage increased from 31.5±9.5% to 33.8±9.0% (mean difference 2.3, P=0.003). BMI decreased only in subjects <60 years (P=0.014). Glucose, total cholesterol, and LDL-cholesterol levels did not change; however, the percentage of patients on statins increased slightly from 39% to 44%. HDL-C concentration increased only in patients <60 years (mean difference 0.2, P=0.043). Lumbar spine BMD did not change; however, femoral neck BMD and bone turnover markers decreased in subjects <60 years (P=0.001). Systematic review included eight studies (n=166 patients) with a follow-up duration of 6-18 months. Of the Please check the edit of the sentence 'Of the eight studies "'.eight studies, three qualified as low risk of bias and five as having an intermediate risk of bias. None of the studies reported handling of statins, bisphosphonates, and glucose-lowering medication or excluded patients using these medications.

CONCLUSIONS

In this study, discontinuation of rhGh replacement resulted in metabolic changes only in patients <60 years after 3 years. Further research warrants to determine the optimal strategies for (dis)continuation of rhGh replacement in adult patients with GHD.

Short-term, low-dose GH therapy improves insulin sensitivity without modifying cortisol metabolism and ectopic fat accumulation in adults with GH deficiency

CONTEXT

Low-dose GH (LGH) therapy has been reported to improve insulin sensitivity in GH-deficient adults; however, the mechanism is unclear.

HYPOTHESIS

Effects of LGH therapy on insulin sensitivity are mediated through changes in cortisol metabolism and ectopic fat accumulation.

DESIGN AND SETTING

This was a double-blind, placebo-controlled, parallel, 3-month study.

PARTICIPANTS AND INTERVENTION

Seventeen GH-deficient adults were randomized to receive either daily LGH or placebo injections. Fasting blood samples were collected at baseline, and months 1 and 3, whereas hyperinsulinemic-euglycemic clamps, magnetic resonance spectroscopy scans, 24-hour cortisol production rates (CPRs), and sc abdominal fat biopsies were performed at baseline and month 3.

MAIN OUTCOME MEASURES

Clamp glucose infusion rate, intramyocellular, extramyocellular, and intrahepatic lipid content, 24-hour CPRs, adipocyte size, and adipocyte 11β-hydroxysteroid dehydrogenase activity in adults with GH deficiency were evaluated.

RESULTS

At month 1, LGH did not alter fasting levels of glucose, insulin, C-peptide, free fatty acid, adiponectin, total IGF-1, IGF-1 bioactivity, IGF-2, IGF binding protein (IGFBP)-2, or IGF-1 to IGFBP-3 molar ratio. At month 3, LGH increased clamp glucose infusion rates (P < .01) and IGF-1 to IGFBP-3 molar ratio (P < .05), but fasting glucose, insulin, C-peptide, free fatty acid, adiponectin, IGF-1 bioactivity, IGF-2, IGFBP-2, 24-hour CPRs, adipocyte size, adipocyte 11β-hydroxysteroid dehydrogenase activity, intrahepatic lipid, extramyocellular, or intramyocellular were unchanged. In the placebo group, all within-group parameters from months 1 and 3 compared with baseline were unchanged.

CONCLUSIONS

Short-term LGH therapy improves insulin sensitivity without inducing basal lipolysis and had no effect on cortisol metabolism and ectopic fat accumulation in GH-deficient adults. This may reflect an LGH-induced increase in IGF-1 to IGFBP-3 molar ratio exerting insulin-like effects through the abundant muscle IGF-1 receptors, but this hypothesis requires confirmation with further studies.

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.

The effect of polyethylene glycol recombinant human growth hormone on growth and glucose metabolism in hypophysectomized rats

OBJECTIVE

To study the effect of polyethylene glycol recombinant human growth hormone on growth and glucose metabolism in hypophysectomized rats, and compare the effect of treatment between recombinant human growth hormone (rhGH) and polyethylene glycol rhGH (PEG-rhGH).

METHODS

Hypophysectomy was performed in juvenile rats to build the animal model of GH deficiency. The hypophysectomized animals were randomly assigned into three groups and treated with saline (negative control, n=20), rhGH (n=20) and PEG-rhGH (n=20). A sham operation was performed to set up the normal control (n=20). Body weight, body length and tail length were recorded every 2days for a 14-day treatment and bone growth was measured at the end of therapy. Glucose infusion rate (GIR) determined by euglycemic hyperinsulinemic clamp was used to evaluate insulin sensitivity after GH treatment. We also examined plasma glucose and serum insulin levels

RESULTS

Compared with the negative control, the body weight, body length, tail length and bone growth increased significantly in hypophesectomized rats treated by GH (P<0.01). Although the weight gain in the first 10days was higher in the PEG-rhGH group than in the rhGH group (P<0.05), the growth promoting effect was similar between rhGH and PEG-rhGH (P>0.05). Neither rhGH nor PEG-rhGH impaired glucose tolerance of rats after hypophesectomy. Compared with negative controls, according to decreased serum insulin, reduced insulin expression in pancreatic cells and increased GIR in the clamp, both rhGH and PEG-rhGH groups had improved insulin sensitivity within 14 days (P<0.01). However, with prolonged treatment, the GIR in the rhGH-treated rats decreased significantly (P<0.05); while PEG-rhGH did not interfere with GIR, even after a doubled dose (P>0.05).

CONCLUSIONS

PEG-rhGH had the same linear growth promoting efficacy as unmodified rhGH. The short-term GH replacement could improve insulin sensitivity in hypophysectomized rats, especially after PEGylation.

Improved insulin sensitivity, preserved beta cell function and improved whole-body glucose metabolism after low-dose growth hormone replacement therapy in adults with severe growth hormone deficiency: a pilot study

AIMS/HYPOTHESIS

Growth hormone-deficient patients show deterioration of insulin sensitivity and beta cell function. High-dose growth hormone treatment often induces further impairment of insulin sensitivity, leading to an increase in insulin and glucose levels or even, in cases of preexisting beta cell defect, to overt diabetes. However, low-dose treatment may improve insulin sensitivity, although data in humans with detailed metabolic phenotyping are as yet not available. We postulated that long-term low-dose growth hormone replacement, restoring IGF-1 to the low-normal range, might beneficially affect glucose metabolism.

METHODS

We studied prospectively the metabolic responses to 24 and 48 weeks of growth hormone treatment in a small group of six adults with severe growth hormone deficiency (four men, two women; age 40-59 years; BMI 30.2 +/- 1 kg/m(2); mean growth hormone dose 0.3 +/- 0.04 mg/day). All participants underwent an oral glucose tolerance test, euglycaemic-hyperinsulinaemic clamp and hyperglycaemic-hyperinsulinaemic clamp plus i.v. L: -arginine on three occasions. Insulin sensitivity was measured by calculating the M value during the steady state of the euglycaemic-hyperinsulinaemic clamp. Insulin secretion and clearance were estimated from AUC(C-peptide), AUC(insulin) and their ratio at each phase of the hyperglycaemic-hyperinsulinaemic clamp.

RESULTS

Growth hormone significantly improved insulin sensitivity (M value 13.8 +/- 2.6 [baseline] vs 19.6 +/- 2.6 [24 weeks] and 23.7 +/- 1.9 [48 weeks] micromol kg(-1) min(-1); p < 0.01). Although the insulin response to glucose and arginine decreased slightly, the disposition index, integrating insulin sensitivity and secretion, significantly increased (p < 0.01), indicating an improvement in whole-body glucose metabolism. Insulin clearance was not affected during treatment (p > 0.05).

CONCLUSIONS/INTERPRETATION

Our data indicate that long-term low-dose growth hormone treatment may improve insulin sensitivity and whole-body glucose metabolism in adults with severe growth hormone-deficiency.

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.

Growth hormone (GH) treatment does not restore endothelial function in children with GH deficiency

BACKGROUND

In adults with growth hormone (GH) deficiency (GHD), GH treatment restores impaired endothelial function, a precursor of cardiovascular disease. Its effect in children with GHD is unknown.

METHODS

Three months of GH (0.3 mg/kg/wk) were given to nine children with GHD. Endothelial function was measured via reactive hyperemic response. Forearm blood flow (FBF, strain gauge plethysmography) was measured before and after 5 min of upper arm arterial occlusion. Blood pressure and lipid, insulin and glucose levels were measured. Pretreatment endothelial function was compared to 18 previously studied control children.

RESULTS

Percent fall in forearm vascular resistance was greater in controls (81.2 +/- 1.9%) than in children with GHD (69.6 +/- 5.3%, p = 0.021) but was not affected by GH (60.6 +/- 7.5%). GH markedly increased HOMAIR (21 +/- 7 versus 43 +/- 8, p = 0.004). Plasma lipid levels did not significantly differ.

CONCLUSION

These results indicate that endothelial function is impaired in children with GHD. GH therapy does not restore the impairment.