Serum Leptin and Ghrelin Levels in Active and Inactive Acromegalic Patients During an Oral Glucose Tolerance Test

The acromegaly lipodystrophy

Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) are essential to normal growth, metabolism, and body composition, but in acromegaly, excesses of these hormones strikingly alter them. In recent years, the use of modern methodologies to assess body composition in patients with acromegaly has revealed novel aspects of the acromegaly phenotype. In particular, acromegaly presents a unique pattern of body composition changes in the setting of insulin resistance that we propose herein to be considered an acromegaly-specific lipodystrophy. The lipodystrophy, initiated by a distinctive GH-driven adipose tissue dysregulation, features insulin resistance in the setting of reduced visceral adipose tissue (VAT) mass and intra-hepatic lipid (IHL) but with lipid redistribution, resulting in ectopic lipid deposition in muscle. With recovery of the lipodystrophy, adipose tissue mass, especially that of VAT and IHL, rises, but insulin resistance is lessened. Abnormalities of adipose tissue adipokines may play a role in the disordered adipose tissue metabolism and insulin resistance of the lipodystrophy. The orexigenic hormone ghrelin and peptide Agouti-related peptide may also be affected by active acromegaly as well as variably by acromegaly therapies, which may contribute to the lipodystrophy. Understanding the pathophysiology of the lipodystrophy and how acromegaly therapies differentially reverse its features may be important to optimizing the long-term outcome for patients with this disease. This perspective describes evidence in support of this acromegaly lipodystrophy model and its relevance to acromegaly pathophysiology and the treatment of patients with acromegaly.

Acromegaly, inflammation and cardiovascular disease: a review

Acromegaly is characterized by Growth Hormone (GH) and Insulin-like Growth Factor 1 (IGF-1) excess. Uncontrolled acromegaly is associated with a strongly increased risk of cardiovascular disease (CVD), and numerous cardiovascular risk factors remain present after remission. GH and IGF-1 have numerous effects on the immune and cardiovascular system. Since endothelial damage and systemic inflammation are strongly linked to the development of CVD, and have been suggested to be present in both controlled as uncontrolled acromegaly, they may explain the presence of both micro- and macrovascular dysfunction in these patients. In addition, these changes seem to be only partially reversible after remission, as illustrated by the often reported presence of endothelial dysfunction and microvascular damage in controlled acromegaly. Previous studies suggest that insulin resistance, oxidative stress, and endothelial dysfunction are involved in the development of CVD in acromegaly. Not surprisingly, these processes are associated with systemic inflammation and respond to GH/IGF-1 normalizing treatment.

Evaluation and diagnostic potential of serum ghrelin in feline hypersomatotropism and diabetes mellitus

Background

Ghrelin is a growth hormone secretagogue. It is a potent regulator of energy homeostasis. Ghrelin concentration is down‐regulated in humans with hypersomatotropism (HS) and increases after successful treatment. Additionally, ghrelin secretion seems impaired in human diabetes mellitus (DM).

Hypothesis

Serum ghrelin concentration is down‐regulated in cats with HS‐induced DM (HSDM) compared to healthy control cats or cats with DM unrelated to HS and increases after radiotherapy.

Animals

Cats with DM (n = 20) and with HSDM (n = 32), 13 of which underwent radiotherapy (RT‐group); age‐matched controls (n = 20).

Methods

Retrospective cross‐sectional study. Analytical performance of a serum total ghrelin ELISA was assessed and validated for use in cats. Differences in serum ghrelin, fructosamine, IGF‐1 and insulin were evaluated.

Results

Ghrelin was significantly higher (P < .001) in control cats (mean ± SD: 12.9 ± 6.8 ng/mL) compared to HSDM‐ (7.9 ± 3.3 ng/mL) and DM‐cats (6.7 ± 2.3 ng/mL), although not different between the HSDM‐ and DM‐cats. After RT ghrelin increased significantly (P = .003) in HSDM‐cats undergoing RT (from 6.6 ± 1.9 ng/mL to 9.0 ± 2.2 ng/mL) and the after RT ghrelin concentrations of HSDM cats were no longer significantly different from the serum ghrelin concentration of control cats. Serum IGF‐1 did not significantly change in HSDM‐cats after RT, despite significant decreases in fructosamine and insulin dose.

Conclusion and Clinical Importance

Ghrelin appears suppressed in cats with DM and HSDM, although increases after RT in HSDM, suggesting possible presence of a direct or indirect negative feedback system between growth hormone and ghrelin. Serum ghrelin might therefore represent a marker of treatment effect.

Outcome of complications in acromegaly patients after long-term disease remission

Acromegaly patients suffer from pathologically high growth hormone (GH) and IGF-1 levels that in 99% of cases is due to a GH-producing pituitary adenoma. During active disease, GH excess is associated with a number of pathological conditions, such as hypertension, hypertrophic cardiomyopathy, sleep apnea, arthropathy, vertebral fractures and insulin resistance. After adequate treatment in the form of transsphenoidal surgery, radiotherapy, medical treatment or by a combination of these treatment modalities, several comorbid conditions improve considerably. However, despite long-term biochemical disease control, the prevalence of late manifestations of GH excess is high and significantly impair quality of life. In addition, there is evidence that adequate treatment is not able to normalize mortality risk in these patients. In this review, we critically evaluate the long-term consequences of acromegaly after treatment, focusing on comorbid conditions, quality of life and mortality. We also discuss ongoing challenges in the management of acromegaly patients.

Prospective study of surgical treatment of acromegaly: effects on ghrelin, weight, adiposity, and markers of CV risk

CONTEXT

Although epidemiological studies have found that GH and IGF-1 normalization reduce the excess mortality of active acromegaly to expected rates, cross-sectional data report some cardiovascular (CV) risk markers to be less favorable in remission than active acromegaly.

OBJECTIVE

The objective of the study was to test the hypothesis that remission of acromegaly after surgical therapy increases weight and adiposity and some CV risk markers and these changes are paralleled by a rise in ghrelin.

DESIGN

Forty-two adults with untreated, active acromegaly were studied prospectively. Changes in outcome measures from before to after surgery were assessed in 26 subjects achieving remission (normal IGF-1) and 16 with persistent active acromegaly (elevated IGF-1) after surgery.

SETTING

The study was conducted at tertiary referral centers for pituitary tumors.

MAIN OUTCOME MEASURES

Endocrine, metabolic, and CV risk parameters, anthropometrics, and body composition by dual-energy X-ray absorptiometry were measured.

RESULTS

Remission increased total ghrelin, body weight, waist circumference, C-reactive protein, homocysteine, high-density lipoprotein, and leptin and reduced systolic blood pressure, homeostasis model assessment score, triglycerides, and lipoprotein (a) by 6 months and for 32 ± 4 months after surgery. The ghrelin rise correlated with the fall in the levels of GH, IGF-1, and insulin and insulin resistance. Weight, waist circumference, and ghrelin did not increase significantly in the persistent active acromegaly group. Total body fat, trunk fat, and perentage total body fat increased by 1 year after surgery in 15 remission subjects: the increase in body fat correlated with the rise in total ghrelin.

CONCLUSIONS

Although most markers of CV risk improve with acromegaly remission after surgery, some markers and adiposity increase and are paralleled by a rise in total ghrelin, suggesting that these changes may be related. Understanding the mechanisms and long-term implications of the changes that accompany treatment of acromegaly is important to optimizing management because some aspects of the postoperative profile associate with the increased metabolic and CV risk in other populations.

Food intake regulating hormones in adult craniopharyngioma patients

INTRODUCTION

Patients with craniopharyngioma (CP) have disturbances of the hypothalamic-pituitary axis and serious comorbidities such as obesity. We hypothesized that the secretion of hormones regulating the nutritional status is altered in adult patients with CP compared with patients with non-functioning pituitary adenoma (NFPA).

METHODS

WE INCLUDED 40 CP (50% MALES, MEAN AGE: 49.6±14.3 years) and 40 NFPA (72.5% males, mean age: 63.4±9.8 years) patients. We measured glucose, insulin, leptin, total ghrelin, peptide-YY (PYY) and cholecystokinin (CCK) during oral glucose tolerance test (OGTT). Fat mass (FM) was determined by dual X-ray absorptiometry.

RESULTS

Gender distribution was not significantly different, but CP patients were significantly younger (P<0.001). CP patients had significantly higher BMI and FM than NFPA patients (BMI 32±8 vs 28±4 kg/m(2), P=0.009 and FM 37±9 vs 33±9%, P=0.02). Fasting glucose level (84±12 vs 78±11 mg/dl, P=0.03), leptin (27.9±34.2 vs 11.9±11.6 μg/l, P=0.008) and leptin levels corrected for percentage FM (0.66±0.67 vs 0.32±0.25 μg/l%, P=0.005) were significantly higher in CP than in NFPA patients, whereas ghrelin was significantly lower (131±129 vs 191±119 ng/l, P=0.035). Insulin, PYY and CCK did not differ significantly between groups. After glucose load, leptin decreased significantly in CP patients (P=0.019). In both groups, ghrelin decreased significantly during OGTT (both P<0.001). The percentage decline was significantly smaller for CP. PYY and CCK increased equally after glucose in both groups.

CONCLUSION

Our patients with CP have more metabolic complications than our patients with NFPA. The levels of leptin and ghrelin at fasting status and after glucose seem to be altered in CP, whereas changes in insulin, PYY and CCK do not seem to be responsible for the metabolic changes in these patients.

Influence of pegvisomant on serum ghrelin and leptin levels in acromegalic patients

INTRODUCTION

Pegvisomant (peg) is a GH receptor antagonist. In de novo acromegalic patients with high GH levels, ghrelin and leptin levels are reduced, suggesting a direct GH-mediated effect. The aim of our study was to evaluate whether peg treatment in acromegalic patients may abolish the GH impact on ghrelin and leptin levels.

METHODS

Ghrelin, leptin and endogenous GH were measured in ten peg-treated acromegalic patients (three females/seven males, 47 years (28-57)), ten patients with active (act) and ten patients with inactive disease (inact) as well as in ten gender-, age- and body mass index (BMI)-matched healthy volunteers (controls). Endogenous GH was measured using a special in-house assay without interference by peg; total ghrelin and leptin were determined using a commercial RIA and an immunofluorometric in-house assay respectively.

RESULTS

Age and BMI did not differ significantly between groups. Endogenous GH was significantly higher in peg (6.3 μg/l (1.5-41)) and act (9.3 μg/l (1.7-70)) compared with controls (0.1 μg/l (0.1-3.1)) and inact (0.35 μg/l (0.1-2.0), P<0.001). Ghrelin was significantly higher in peg (232  ng/l (96-351)) compared with act (102 ng/l (33-232), P<0.01), whereas ghrelin was not significantly different between the other groups. Leptin was highest in controls (19 μg/l (4-57)) and lowest in act (6 μg/l (2-21)), but this difference did not reach significance.

CONCLUSION

Treatment with peg seems to disrupt the feedback loop of ghrelin and GH, leading to elevated ghrelin levels. Furthermore, peg therapy appears not to have a strong impact on leptin levels, as acromegalic patients with and without peg treatment showed similar leptin levels.

Influence of long-term growth hormone replacement on leptin and ghrelin in GH deficiency before and after glucose load

INTRODUCTION

This cross-sectional study was performed to evaluate the effect of long-term GH substitution on leptin and ghrelin in GH deficiency (GHD).

METHODS

Leptin and ghrelin were measured after glucose load for 3 h in 52 pat and 10 age- and BMI-matched healthy controls. 22 GHD pat were on GH substitution (GH-Sub) for a median of 10 yr (range 2-27 yr). 30 age- and BMI-matched GHD pat were not substituted for at least 2 yr (non-Sub).

RESULTS

Basal leptin (8 microg/l (1-130) vs. 16 microg/l (3-89), p<0.05) and AUC of leptin (p<0.05) was significantly lower in GH-Sub compared to non-Sub. In the control group, leptin was higher compared to GH-Sub and similar to non-Sub (19 microg/l (4-57)). Ghrelin (baseline: non-Sub 113 ng/l (61-270), GH-Sub 145 ng/l (83-280), controls 131 ng/l (83-274)) were slightly but not significantly lower for non-Sub. After glucose load, a significant decrease in leptin appeared in both GHD groups, but not in the control group. Ghrelin decreased significantly in all groups.

CONCLUSION

Lipolytic GH causes lower leptin in GH-Sub. The reason for similar ghrelin might be the compensating effect of acute GH suppression and stimulating low fat mass on ghrelin. Leptin regulation after glucose load is impaired in GHD, whereas ghrelin regulation seems to be not effected.