Effects of two different somatostatin analogs on glucose tolerance in acromegaly

The effects of somatostatin analogues on glycaemia in the treatment of neuroendocrine tumours

Long-acting somatostatin analogues (SSAs) are the most commonly used drugs in the management of neuroendocrine tumours (NETs) because of their ability to control symptoms and prolong survival. SSA use is associated with changes in glucose metabolism. However, the impacts on glycaemic control and body mass index (BMI) caused by SSAs in NETs are largely unknown. In the present study, we evaluated the effects of SSA treatment on BMI and glycated haemoglobin (HbA1c) in our cohort of patients with NETs. We also assessed changes in glycaemic control and BMI before and after SSA treatment. In addition, we assessed the incidence of new diabetes or whether there was worsening of glycaemic control for patients with pre-existing diabetes. The study comprised a retrospective study of 279 patients with NETs who were treated with SSAs between January 2014 and January 2019. Glycaemic control was assessed by measuring changes in Hba1c. A number needed to harm analysis was used to look at new cases of diabetes within the study population. Treatment with SSAs was associated with a mean increase in HbA1c of 3.35 ± 6.30 mmol mol^-1 despite a mean decrease in BMI of -1.04 ± 2.79 kg m^-2 . There were 19 new cases of type 2 diabetes mellitus (T2DM) in the population of 209 with a number needed to harm of 12.5. Of the 34 patients with pre-existing T2DM, five had worsening of their mean HbA1c. Treatment with SSAs for NETs is associated with an increase in HbA1c, despite a reduction in BMI and, importantly, a risk of developing T2DM with a number needed to harm of 12.5. This project was registered with the National Health Service Clinical Audit and Registries. It has a CARMS number - 17666.

Octreotide long-acting release (LAR) in combination with other therapies for treatment of neuroendocrine neoplasia: a systematic review

BACKGROUND

In the last decades, the incidence of neuroendocrine neoplasia (NEN) increased from 1 to 5 new diagnoses/100,000 persons/year. The synthetic somatostatin analogues (SSAs) represent the first-choice treatment for both functionally active and inactive gastro-enteric-pancreatic NEN. This systematic review examines the role of octreotide long-acting release (LAR) in combination with other therapies for NEN management.

METHODS

Primary outcomes were the disease control rate and the progression free survival (PFS), defined as the time between treatment initiation and progression of disease. Secondary outcomes were overall survival (OS) and safety.

RESULTS

This systematic review identified 13 studies, concerning the use of octreotide LAR in association with other therapies in advanced NENs and included 1,206 patients. Patients were treated with octreotide LAR in combination with other drugs, mainly with everolimus (404 patients, 35%), but even with Peptide Receptor Radionuclide Therapy, bevacizumab, interferon or fluoride-derivatives. Disease control was observed in 85% cases with SSAs in combination with other therapies; PFS ranged from 15 to 16.4 months and OS from 25 to 61.9 months. SSAs are very well tolerated drugs, with few side effects which are usually mild, not requiring drug withdrawn.

CONCLUSIONS

The review summarizes the effectiveness and available safety data on octreotide LAR in combination with other therapies in patients with NEN and may provide suggestions to address the therapeutic strategy. Further comparative head-to-head studies are needed to understand which is the best combination treatment for patients with progressive NEN after failure of first-line therapy.

Driver versus navigator causation in biology: the case of insulin and fasting glucose

BACKGROUND

In biomedicine, inferring causal relation from experimental intervention or perturbation is believed to be a more reliable approach than inferring causation from cross-sectional correlation. However, we point out here that even in interventional inference there are logical traps. In homeostatic systems, causality in a steady state can be qualitatively different from that in a perturbed state. On a broader scale there is a need to differentiate driver causality from navigator causality. A driver is essential for reaching a destination but may not have any role in deciding the destination. A navigator on the other hand has a role in deciding the destination and the path but may not be able to drive the system to the destination. The failure to differentiate between types of causalities is likely to have resulted into many misinterpretations in physiology and biomedicine.

METHODS

We illustrate this by critically re-examining a specific case of the causal role of insulin in glucose homeostasis using five different approaches (1) Systematic review of tissue specific insulin receptor knock-outs, (2) Systematic review of insulin suppression and insulin enhancement experiments, (3) Differentiating steady state and post-meal state glucose levels in streptozotocin treated rats in primary experiments, (4) Mathematical and theoretical considerations and (5) Glucose-insulin relationship in human epidemiological data.

RESULTS

All the approaches converge on the inference that although insulin action hastens the return to a steady state after a glucose load, there is no evidence that insulin action determines the steady state level of glucose. Insulin, unlike the popular belief in medicine, appears to be a driver but not a navigator for steady state glucose level. It is quite likely therefore that the current line of clinical action in the field of type 2 diabetes has limited success largely because it is based on a misinterpretation of glucose-insulin relationship. The insulin-glucose example suggests that we may have to carefully re-examine causal inferences from perturbation experiments and set up revised norms for experimental design for causal inference.

Drug treatment strategies for secondary diabetes in patients with acromegaly

INTRODUCTION

Acromegaly is a rare disease due to oversecretion of growth hormone (GH). Even though the disease is often portrayed by its most apparent clinical features, given the abundance of GH receptors throughout the body, it truly is a systemic disease leading to numerous complications and comorbidities. A distinct medical issue in the context of acromegaly is diabetes: It can be a complication as a consequence of GH excess and its mediators, but it can also result from treatment of acromegaly.

AREAS COVERED

This review provides an overview of the effects of acromegaly pathophysiology on glucose homeostasis. Furthermore, it devotes an extensive section on the influence that acromegaly treatment has on glucose metabolism, including approved as well as currently investigated drugs. It also summarizes observations from the use of anti-diabetic medication in patients with acromegaly.

EXPERT OPINION

Glucose imbalance is an important aspect of acromegaly comorbidity and deserves more attention. Even though numerous studies have investigated glucose homeostasis in acromegaly, there is still a clear need for more basic, translational, and also clinical research to advance the understanding of the underlying mechanisms and how to best address them.

Changes in metabolic parameters and cardiovascular risk factors after therapeutic control of acromegaly vary with the treatment modality. Data from the Bicêtre cohort, and review of the literature

CONTEXT

Untreated acromegaly is associated with increased morbidity and mortality due to malignant, cardiovascular, and cerebrovascular disorders. Effective treatment of acromegaly reduces excess mortality, but its impact on cardiovascular risk factors and metabolic parameters are poorly documented.

AIM

We analyzed changes in cardiovascular risk factors and metabolic parameters in patients receiving various treatment modalities.

PATIENTS AND METHODS

We retrospectively studied 96 patients with acromegaly, both at diagnosis and after IGF-I normalization following surgery alone (n = 51) or medical therapy with first generation somatostatin analogues (SSA, n = 23), or pegvisomant (n = 22). Duration of follow-up was 77 (42-161) months, 75 (42-112) months, and 62 (31-93) months, in patients treated with surgery alone, SSA, and pegvisomant, respectively. In all the cases except four, patients treated medically had underwent previous unsuccessful surgery.

RESULTS

IGF-I normalization was associated with increased body weight, decreased systolic blood pressure (SBP) in hypertensive patients, decreased fasting plasma glucose (FPG) and HOMA-IR and HOMA-B levels, increased HDL cholesterol (HDLc); whereas, LDL cholesterol (LDLc) was not significantly different. Plasma PCSK9 levels were unchanged in patients with available values. Cardiovascular and metabolic changes varied with the treatment modality: surgery, but not pegvisomant, had a beneficial effect on SBP; FPG decreased after surgery but increased after SSA; the decline in HOMA-IR was only significant after surgery; pegvisomant significantly increased LDLc and total cholesterol; whereas SA increased HDLc and had no effect on LDLc levels.

CONCLUSION

Treatments used to normalize IGF-I levels in patients with acromegaly could have differential effects on cardiovascular risk factors and metabolic parameters.

Somatostatin Analogs and Glucose Metabolism in Acromegaly: A Meta-analysis of Prospective Interventional Studies

INTRODUCTION

Somatostatin analogs (SSAs) effectivelycontrol growth hormone secretion in first and second line treatmentof acromegaly. Their effect onglucose metabolism is still debated.

AIM

to address the following questions: 1) Do SSAs affect fasting plasma glucose (FPG), fasting plasma insulin (FPI), glycosylated hemoglobin (HbA1c), glucose load (2h-OGTT), HOMA-I, HOMA-β, triglycerides (TGD), weight (W) or body mass index (BMI)? 2) Do lanreotide (LAN) and octreotide LAR (OCT) affect metabolism differently? 3)Does their effect depend on disease control?

METHODS

We performed a meta-analysis of prospective interventional trialstreating acromegaly with SSAs. Inclusion criteria: all studies reporting glyco-metabolic outcomes before and after SSAs with a minimum 6-month follow-up.

RESULTS

The inclusion criteria were met by 47 studies treating 1297 subjects (631 F). SSA treatment effectively lowered FPI (effect size [ES] -6.67 mU/L, 95%CI: -8.38 to -4.95mU/L; p<0.001), HOMA-I (ES -1.57, CI: -2.42 to -0.72; p<0.001), HOMA-β (ES -47.45, CI: -73.15 to -21.76; p<0.001) and TGD (ES -0.37 mmol/L, CI: -0.47 to -0.27 mmol/L; p<0.001). SSAs worsened 2h-OGTT (ES 0.59 mmol/L, CI: 0.05 to 1.13 mmol/L; p=0.032), but not FPG. A mild but significant increase in HbA1c (ES 0.12%, CI: 0.00to 0.25%; p=0.044) was found in OCT treated subjects.

CONCLUSIONS

SSA treatment in acromegaly patients-while improving disease control- reduces insulin levels, increases after load glucose and, ultimately, increases HbA1c levels without affecting FPG. The findings suggest that clinicians treating acromegaly with SSAs should consider targeting post-prandial glucose.

Impact of Long-Acting Somatostatin Analogues on Glucose Metabolism in Acromegaly: A Hospital-Based Study

PURPOSE

To evaluate the change in glucose tolerance in treatment-naïve patients with acromegaly after administration of SSA and to identify predictive factors of glucose impairment during SSA therapy.

METHODS

Oral glucose tolerance testing (OGTT) was performed on 64 newly diagnosed and treatment-naïve patients with acromegaly both at pretreatment and 3 months after initiation of treatment with long-acting SSA. Insulin resistance (IR) was assessed by homeostatic model assessment- (HOMA-) IR and IS_OGTT. Insulin secretion was assessed by HOMA-β, INS₀/BG₀, IGI (insulinogenic index), IGI/IR, ISSI2, and AUC_INS/AUC_BG. Receiver-operating characteristic (ROC) curves were generated to determine the optimal cutoffs to predict the impact of SSA on glucose metabolism.

RESULTS

Pretreatment, 19, 24, and 21 patients were categorized as having normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and diabetes mellitus (DM), respectively. Posttreatment, IR, represented by IS_OGTT, was significantly improved in all 3 groups. Insulin secretion, represented by HOMA-β, declined in the NGT and IGT groups, but was unaltered in the DM group. The glucose tolerance status deteriorated in 18 (28.1%) patients, including 13 patients in the NGT group and 5 patients in the IGT group. Deterioration was associated with lower baseline BG₁₂₀ (plasma glucose 120 min post-OGTT), less reduction of growth hormone (GH), and greater reduction of insulin secretion after SSA therapy. BG₁₂₀ greater than 8.1 mmol/l provided the greatest sensitivity and specificity in predicting the stabilization and/or improvement of glucose tolerance status after SSA treatment (PPV 90.7%, NPV 66.7%, p < 0.001).

CONCLUSIONS

The deterioration of glucose metabolism induced by SSA treatment is caused by the less reduction of GH and the more inhibition of insulin secretion, which can be predicted by the baseline BG₁₂₀ during OGTT.

Diabetes in Patients With Acromegaly

Acromegaly is a clinical syndrome which results from growth hormone excess. Uncontrolled acromegaly is associated with cardiovascular mortality, due to an excess of risk factors including diabetes mellitus, hypertension and cardiomegaly. Diabetes mellitus is a frequent complication of acromegaly with a prevalence of 12-37%. This review will provide an overview of a number of aspects of diabetes mellitus and glucose intolerance in acromegaly including the following: 1. Epidemiology and pathophysiology of abnormalities of glucose homeostasis 2. The impact of different management options for acromegaly on glucose homeostasis 3. The management options for diabetes mellitus in patients with acromegaly RECENT FINDINGS: Growth hormone and IGF-1 have complex effects on glucose metabolism. Insulin resistance, hyperinsulinaemia and increased gluconeogenesis combine to produce a metabolic milieu which leads to the development of diabetes in acromegaly. Treatment of acromegaly should ameliorate abnormalities of glucose metabolism, due to reversal of insulin resistance and a reduction in gluconeogenesis. Recent advances in medical therapy of acromegaly have varying impacts on glucose homeostasis. These adverse effects influence management choices in patients with acromegaly who also have diabetes mellitus or glucose intolerance. The underlying mechanisms of disorders of glucose metabolism in patients with acromegaly are complex. The aim of treatment of acromegaly is normalisation of GH/IGF-1 with reduction of co-morbidities. The choice of therapy for acromegaly should consider the impact of therapy on several factors including glucose metabolism.

Somatostatin analogues in acromegaly and gastroenteropancreatic neuroendocrine tumours: past, present and future

Acromegaly is a hormonal disorder that arises when the pituitary gland secretes excess growth hormone (GH), which in turn stimulates a concomitant increase in serum insulin-like growth factor 1 (IGF-1) levels. Gastroenteropancreatic neuroendocrine tumours (GEP-NET) constitute a heterogeneous group of tumours that can secrete serotonin and a variety of peptide hormones that may cause characteristic symptoms known as carcinoid syndrome or other symptoms and hormonal hypersecretion syndromes depending on the tumour's site of origin. Current medical therapy for the treatment of acromegaly and GEP-NET involves the administration of somatostatin analogues that effectively suppress excess hormone secretion. After its discovery in 1979, octreotide became the first synthetic biologically stable somatostatin analogue with a short-acting formulation of octreotide introduced into clinical practice in the late 1980s. Lanreotide, another somatostatin analogue, became available in the mid-1990s initially as a prolonged-release formulation administered every 10 or 14 days. Long-acting release formulations of both octreotide (Sandostatin LAR and Novartis) and lanreotide (Somatuline Autogel, Ipsen), based on microparticle and nanoparticle drug-delivery technologies, respectively, were later developed, which allowed for once-monthly administration and improved convenience. First-generation somatostatin analogues remain one of the cornerstones of medical therapy in the management of pituitary and GEP-NET hormone hypersecretion, with octreotide having the longest established efficacy and safety profile of the somatostatin analogue class. More recently, pasireotide (Signifor), a next-generation multireceptor-targeted somatostatin analogue, has emerged as an alternative therapeutic option for the treatment of acromegaly. This review summarizes the development and clinical success of somatostatin analogues.

Disease activity and lifestyle influence comorbidities and cardiovascular events in patients with acromegaly

OBJECTIVE

The primary objective of this study is to identify the predictors of comorbidities and major adverse cardiovascular events (MACE) that can develop after diagnosis of acromegaly. The role of therapy for acromegaly in the event of such complications was also evaluated.

DESIGN AND METHODS

Retrospective cohort study was conducted on 200 consecutive acromegalic patients in a tertiary referral center. The following outcomes were evaluated: diabetes, hypertension and MACE. Each patient was included in the analysis of a specific outcome, unless they were affected when acromegaly was diagnosed, and further classified as follows: (i) in remission after adenomectomy (Hx), (ii) controlled by somatostatin analogues (SSA) (SSAc) or (iii) not controlled by SSA (SSAnc). Data were evaluated using Cox regression analysis.

RESULTS

After diagnosis of acromegaly, diabetes occurred in 40.8% of patients. The SSAnc group had a three-fold higher risk of diabetes (HR: 3.32, P = 0.006), whereas the SSAc group had a 1.4-fold higher risk of diabetes (HR: 1.43, P = 0.38) compared with the Hx group. Hypertension occurred in 35.5% of patients, after diagnosis. The determinants of hypertension were age (HR: 1.06, P = 0.01) and BMI (HR: 1.05, P = 0.01). MACE occurred in 11.8% of patients, after diagnosis. Age (HR: 1.09, P = 0.005) and smoking habit (HR: 5.95, P = 0.01) were predictors of MACE. Conversely, therapy for acromegaly did not influence hypertension or MACE.

CONCLUSION

After diagnosis of acromegaly, control of the disease (irrespective of the type of treatment) and lifestyle are predictors of comorbidities and major adverse cardiovascular events.

Current and Emerging Aspects of Diabetes Mellitus in Acromegaly

Diabetes mellitus is a frequent complication of acromegaly, a disease characterized by chronic hypersecretion of growth hormone (GH) by a pituitary adenoma. Diabetes occurs commonly but not only as a consequence of an insulin-resistant state induced by GH excess. The development of diabetes in patients with acromegaly is clinically relevant, since such a complication is thought to increase the already elevated cardiovascular morbidity and mortality risk of the disease. Emerging data suggest that a specific cardiomyopathy can be identified in acromegaly patients with diabetes. Moreover, the presence of diabetes may also influence therapeutic decision making in acromegaly, since traditional and newly developed drugs used in this clinical setting may impact glucose metabolism regardless of control of GH hypersecretion.

Italian Society for the Study of Diabetes (SID)/Italian Endocrinological Society (SIE) guidelines on the treatment of hyperglycemia in Cushing's syndrome and acromegaly

Hyperglycemia is a common feature associated with states of increased growth hormone secretion and glucocorticoid levels. The purpose of these guidelines is to assist clinicians and other health care providers to take evidence-based therapeutic decisions for the treatment of hyperglycemia in patients with growth hormone and corticosteroid excess. Both the SID and SIE appointed members to represent each society and to collaborate in Guidelines writing. Members were chosen for their specific knowledge in the field. Each member agreed to produce-and regularly update-conflicts of interest. The authors of these guidelines prepared their contributions following the recommendations for the development of Guidelines, using the standard classes of recommendation shown below. All members of the writing committee provided editing and systematic review of each part of the manuscript, and discussed the grading of evidence. Consensus was guided by a systematic review of all available trials and by interactive discussions.

Italian Society for the Study of Diabetes (SID)/Italian Endocrinological Society (SIE) guidelines on the treatment of hyperglycemia in Cushing's syndrome and acromegaly

BACKGROUND

Hyperglycemia is a common feature associated with states of increased growth hormone secretion and glucocorticoid levels.

AIMS

The purpose of these guidelines is to assist clinicians and other health care providers to take evidence-based therapeutic decisions for the treatment of hyperglycemia in patients with growth hormone and corticosteroid excess.

METHODOLOGY

Both the SID and SIE appointed members to represent each society and to collaborate in Guidelines writing. Members were chosen for their specific knowledge in the field. Each member agreed to produce--and regularly update--conflicts of interest. The Authors of these guidelines prepared their contributions following the recommendations for the development of Guidelines, using the standard classes of recommendation shown below. All members of the writing committee provided editing and systematic review of each part of the manuscript, and discussed the grading of evidence. Consensus was guided by a systematic review of all available trials and by interactive discussions.

Diagnosis, treatment and clinical perspectives of acromegaly

Acromegaly is an insidious disease of the pituitary caused by a growth hormone-secreting adenoma. Generally, the diagnosis is made rather late in the course of the disease. Currently, acromegaly can be cured in about half of the patients with the disease by expert surgery. The remainder of non-surgically cured patients often can be effectively treated with somatostatin analogs; either with the new generation of dopaminergic drugs or with Pegvisomant, a GH-receptor blocking agent. However, at the time of diagnosis many patients suffer from serious comorbidities, including hypertension, heart disease, arthrosis, sleep apnea and diabetes mellitus. Recent reports have shown that mortality risk can be normalized. Nevertheless, all efforts should be undertaken to treat comorbidities. New strategies for surgery and medical treatment are discussed.

Effects of medical therapies for acromegaly on glucose metabolism

OBJECTIVE

Abnormalities of glucose metabolism are common findings of acromegaly. However, robust evidence on whether therapy with somatostatin analogs (SSAs) or pegvisomant (PEG) differently affects glucose metabolism is lacking. The purpose of this study was to evaluate the effects of therapy with SSAs, PEG, or their combination on glucose metabolism in a large series of acromegalic patients.

DESIGN

This was a historical-prospective study. Among 50 consecutive acromegalic patients under SSA therapy, acromegaly in 19 patients was controlled. PEG used in combination with SSA therapy allowed the control of acromegaly in the remaining 31 patients and was then continued as monotherapy in 18 patients.

METHODS

The following parameters were evaluated at the diagnosis of acromegaly and during DIFFERENT TREATMENTS: fasting plasma glucose (FPG) and insulin concentrations, insulin sensitivity (QUICK-I), homeostasis model assessment of insulin resistance (HOMA2-IR), and plasma glucose and insulin concentrations during the oral glucose tolerance test (OGTT). Comparison was made using analysis for paired data.

RESULTS

Insulin resistance improved when acromegaly was controlled with therapy with SSAs, PEG, or SSA+PEG. However, FPG concentrations were higher during SSA therapy (alone or combined with PEG) than at the diagnosis of acromegaly, even when corrected for disease activity, whereas they were reduced during PEG therapy. Mean glucose concentrations during the OGTT were higher in patients receiving SSA therapy than in those receiving PEG therapy. In addition, the prevalence of diabetes or impaired glucose tolerance was higher during SSA therapy than at diagnosis or during PEG therapy and was not influenced by disease control.

CONCLUSIONS

Medical therapies for acromegaly reduce insulin resistance and increase insulin sensitivity; on the contrary, glucose indexes may be differently affected by SSA or PEG therapy.

Influence of glucocorticoids and growth hormone on insulin sensitivity in humans

The seminal concept proposed by Sir Harold Himsworth more than 75 years ago that a large number of patients with diabetes were 'insulin insensitive', now termed insulin resistance, has now expanded to include several endocrine syndromes, namely those of glucocorticoid excess, and growth hormone excess and deficiency. Synthetic glucocorticoids are increasingly used to treat a wide variety of chronic diseases, whereas the beneficial effects of recombinant growth hormone replacement therapy in children and adults with growth hormone deficiency have now been well-recognized for over 25 years. However, clinical and experimental studies have established that increased circulating levels of glucocorticoids and growth hormone can also lead to worsening of insulin resistance, glucose intolerance, overt diabetes mellitus and cardiovascular disease. Improved understanding of the physiological 24-h rhythmicity of glucocorticoid and growth hormone secretion and its influence on the dawn phenomenon and the Staub-Trauggot effect has therefore led to renewed interest in studies on the mechanisms of insulin resistance induced by exogenous administration of glucocorticoids and growth hormone in humans. In this review, we describe the physiological events that result from the presence of resistance to insulin action at the level of skeletal muscle, adipose tissue, and liver, describe the known mechanisms of glucocorticoid- and growth hormone-mediated insulin resistance, and provide an update of the contributions of glucocorticoids and growth hormone to understanding the pathophysiology of insulin resistance and its effects on several endocrine syndromes.

Glucose status in patients with acromegaly receiving primary treatment with the somatostatin analog lanreotide

To describe glucose status changes in patients with acromegaly receiving somatostatin analog lanreotide as primary treatment. This retrospective, single-center study conducted during 1996-2008, included acromegalic patients receiving primary lanreotide treatment. Baseline and last follow-up visit assessments included glucose status (according to American Diabetes Association criteria), growth hormone (GH), and insulin-like growth factor-1 (IGF-1) levels. Glucose control was considered improved when fasting plasma glucose or antidiabetic treatments were reduced, and deteriorated if fasting glucose was the same/higher but with increased antidiabetic treatments. 42 patients (median age 50 years; range 29-75 years) were included. At baseline, 26 (62%) were normoglycemic, eight (19%) had impaired glucose tolerance/fasting glycemia, and eight (19%) had diabetes mellitus; family history of diabetes mellitus was significantly associated with abnormal glucose status. At final visit, the mean (SE) lanreotide dose was 108 (21) mg/month. Median treatment duration was 23 months, range 3-138 months, and 74% of patients received the 120-mg dose. Median GH levels decreased significantly (baseline, 12 [5-20] μg/l; final visit, 2.1 [1.0-4.7] μg/l; P < 0.0001); IGF-1 levels were age- and sex-normalized in 33% of patients. Glucose control deteriorated in seven patients (17%) and improved from abnormal levels in 10 (24%). Deterioration was associated with smaller GH decreases (median change, -3.4 μg/l vs. -10.7 μg/l, P = 0.014) and improvement with trend to lower BMI and younger age. During primary lanreotide treated acromegalic patients 60% had no change, 24% had an improvement and 17% had a worsening of glucose status. Deterioration was significantly associated with smaller GH decreases during primary lanreotide treatment.

Octreotide long-acting repeatable for acromegaly

Acromegaly remains a therapeutic challenge for the endocrinologist. Among the available therapeutic options, octreotide long-acting repeatable (Sandostatin(®) LAR(®), Novartis) plays a chief role, both as a primary therapy and as an adjuvant treatment after unsuccessful surgery. A plethora of papers and a meta-analysis have demonstrated its efficacy in: control of clinical picture; achievement of safe growth hormone and normal age-matched IGF-I levels (both factors associated with restoration of normal life expectancy) in 60-70% of patients; control of tumor volume (with real shrinkage in over half of cases); and halt or reversal of most acromegaly-associated comorbidities. Treatment is well tolerated in most patients and can be safely prolonged for many years if required.

Acromegaly: presentation, morbidity and treatment outcomes at a single centre

OBJECTIVE

Analysis of patients with acromegaly followed-up at a single centre, focusing on baseline characteristics, morbidity and efficacy of treatment.

DESIGN AND METHODS

Retrospective review of electronic medical records of acromegalics from 1987 to 2009.

RESULTS

One hundred and fifteen patients (45 men), aged 47 ± 14 years, with a mean follow-up of 8.8 ± 0.8 years were studied. Twenty-five per cent had micro- and 75% macroadenomas. Forty-three per cent presented with visual field defects, 49% had hypertension, 25% diabetes mellitus and 35% dyslipidaemia. At follow-up, 50% had myocardial hypertrophy, 55% colon polypodiasis, 74% nodular thyroid disease and 18% adrenal masses. Surgery was performed in 79% (8% twice), followed by conventional radiotherapy in 27%. Fifty-two per cent of the patients achieved remission. Disease control was reported in 65% of microadenomas and 41% of macroadenomas. Remission rates with surgery alone were 41%. Improvement of remission rates was achieved with subsequent treatment with somatostatin analogues (SSA) (53%), or conventional radiotherapy (63%). Nevertheless, pituitary reserve was compromised with the latter. SSA significantly improved outcomes in microadenomas, even as a monotherapy (remission in 89%), in contrast to macroadenomas (0%), although these agents were associated with impaired glucose metabolism and cholelithiasis in half of the patients.

CONCLUSIONS

Acromegaly is associated with an increased morbidity. About half of the treated patients achieved remission (2/3 of microadenomas). The best outcomes were reported for the combination of surgery with radiotherapy, in spite of a higher risk of hypopituitarism. SSA led to remission in a significant percentage of microadenomas, but was associated with increased rates of cholelithiasis and impaired glucose homeostasis.

Octreotide long-acting release (LAR): a review of its use in the management of acromegaly

Octreotide long-acting release (LAR) [Sandostatin LAR] is a somatostatin analogue with a well established clinical profile in patients with acromegaly. It binds to somatostatin receptor subtypes 2 and 5 with high potency to reduce the production and secretion of growth hormone (GH) and insulin-like growth factor (IGF)-I. Octreotide LAR is administered intramuscularly once every 28 days, in contrast to the subcutaneous formulation which requires administration two to three times daily. In several noncomparative trials, octreotide LAR was effective as primary therapy in normalizing GH and IGF-I levels and reducing tumour volume in patients with acromegaly. In addition, no significant difference was seen between octreotide LAR and surgery or lanreotide long-acting (LA) or lanreotide Autogel(R) (ATG) in small, randomized or observational, primary therapy trials. In another small, randomized trial, preoperative octreotide LAR followed by surgery was no more effective than surgery alone in terms of normalizing IGF-I levels, except in patients with macroadenoma. Octreotide LAR has also demonstrated good efficacy as postoperative adjuvant therapy, alone or in combination with pegvisomant, in randomized or noncomparative trials. In patients with different treatment histories (mixed populations), the efficacy of octreotide LAR appears to be generally similar to that of lanreotide ATG and greater than that of lanreotide LA, according to data from switching or crossover studies. Also in mixed populations, the efficacy of octreotide LAR was not significantly different to that of pegvisomant in terms of normalizing IGF-I levels in a randomized trial, and octreotide LAR demonstrated good efficacy in combination with cabergoline in a small, sequential-treatment trial. Octreotide LAR was generally well tolerated in clinical trials, with the most commonly occurring adverse events being gastrointestinal or hepatobiliary in nature. Thus, octreotide LAR continues to be a valuable option in the treatment of acromegaly.

Octreotide LAR: safety and tolerability issues

BACKGROUND

Somatostatin analogues are the cornerstone in therapy of acromegaly and functioning neuroendocrine tumors. Long-acting retard formulations have improved patient survival and contributed considerably to quality of life. The first such compound was octreotide LAR ('long-acting release'), characterized by high affinity to somatostatin receptor subtypes 2 and 5, which has to be injected intramuscularly every 4 weeks.

OBJECTIVE

The aim was to screen all octreotide LAR-related literature and assess the compound's profile for safety and tolerability.

METHODS

An extensive literature search has been performed using the MEDLINE database to retrieve data from clinical studies evaluating the efficacy and tolerability of octreotide LAR.

RESULTS/CONCLUSION

Octreotide LAR is well tolerated; however, diarrhea and gallstone formation were identified as the main adverse events. Impairment of glucose homeostasis was a regular phenomenon, but its occurrence was unpredictable. General side effects such as headache, abdominal discomfort or fatigue were also reported. According to incidental case reports, administration during pregnancy appears to be safe for both mother and child; however, definitive evidence is missing. In addition, octreotide LAR has been evaluated for further indications including treatment of solid tumor entities, due to its antiproliferative effect. Currently, several compounds (lanreotide, SOM230) with a broader receptor spectrum are under evaluation and may improve treatment efficacy and lower incidence of side effects.

Effects of somatostatin analogs on glucose homeostasis: a metaanalysis of acromegaly studies

BACKGROUND

Somatostatin analogs (SSA) may influence glucose metabolism, but the clinical relevance of this effect is uncertain because trials performed so far are limited in terms of number of patients and heterogeneity for length and type of follow-up.

PURPOSE

The purpose of the study was to assess, via the metaanalysis of acromegaly studies, the clinical impact of SSA on glucose metabolism. The outcomes analyzed were fasting plasma glucose, fasting plasma insulin, hemoglobin A(1c), and plasma glucose concentrations during oral glucose tolerance test.

STUDY SELECTION

Eligibility criteria were: 1) duration of SSA treatment of at least 3 wk; 2) available numerical data for at least one of the four biochemical outcomes investigated; 3) measurement of the outcomes before and after SSA treatment; and 4) no selection of acromegalic patients for their responsivity to SSA. After revision, only 31 studies fulfilled eligibility criteria and were therefore selected for data extraction and analysis.

DATA SYNTHESIS

SSA treatment was found to induce statistically significant decrease in fasting plasma insulin [effect size -0.45, 95% confidence interval (CI) from -0.58 to -0.32, P < 0.001], without any significant change of fasting plasma glucose (effect size +0.04, 95% CI from -0.07 to +0.15, P = 0.52) and hemoglobin A(1c) (effect size +0.11, 95% CI from -0.02 to +0.23, P = 0.09). Serum glucose values during the oral glucose tolerance test were shown to significantly change during SSA treatment (effect size +0.31, 95% CI from +0.17 to +0.45, P < 0.001), although with high inconsistency among trials.

CONCLUSIONS

Our data suggest that modifications of glucose homeostasis induced by SSA may have an overall minor clinical impact in acromegaly.

[Evaluation of glucose metabolism in acromegalic patients before and after treatment with octreotide LAR]

AIM OF THE STUDY

To evaluate the glucose metabolism in acromegalic patients before and after treatment with octreotide LAR.

PATIENTS AND METHODS

This was a prospective and longitudinal study involving 30 patients from the acromegaly research outpatient clinic of the Endocrinology unit of the HUCFF/UFRJ. They underwent clinical and laboratorial evaluations, with measurements of growth hormone (GH), insulin-like growth factor type I (IGF-I), insulin, proinsulin, C peptide, glycosylated hemoglobin (HbA1c), IGF binding protein type 1 (IGFBP-1) and glucose, during oral glucose tolerance test (OGTT), before and after six months of treatment with octreotide LAR. The Wilcoxon signed-rank test was used and values of 5% were considered statistically significant.

RESULTS

We found 16 (54%) patients with normal glucose tolerance, 7 (23%) with impaired glucose tolerance and 7 (23%) diabetics. Twelve patients completed the six-month treatment, out of which three showed worsening of glucose tolerance and two (diabetics) had worse blood glucose control. Whereas there was an increase in waist circumference (p=0.03), there was a decrease in GH (p=0.04), with %IGF-I above the upper limit of reference values (% ULRV) [p=0.001], insulin (p=0.019), C peptide levels (p=0.002) and homeostatic model assessment (HOMA-IR) [p=0.039].

CONCLUSIONS

In this series, treatment with octreotide LAR led to a worsening of glucose tolerance in three non-diabetic patients and worsened glycemic control in two diabetics, in spite of reducing insulin resistance.

Octreotide-LAR vs lanreotide-SR as first-line therapy for acromegaly: a retrospective, comparative, head-to-head study

No head-to-head comparisons are available to analyze the efficacy of octreotide (LAR) and lanreotide (LAN) as first-line treatment of acromegaly.We compared the efficacy of these two drugs in 54 newly diagnosed patients (21 women, 33 men), 27 treated with LAR (10-30 mg every 28 days) and 27 with LAN (60-90 mg/28 days), for 12 months. Each LAR-treated patient was matched with one LAN-treated patient as for GH levels, sex, and age (+/-5 yr). Outcome measures were GH and IGF-I levels and tumor shrinkage and secondarily classical cardiovascular risk factors (total/HDL-cholesterol ratio, glucose tolerance), blood pressure and drug tolerability. In LAR- and in LAN-treated patients, respectively: GH and IGF-I were controlled in 21 (77.7%) and in 16 patients (59.3%; p=0.26); tumor shrinkage was absent (<25%) in 4 and 5 patients (p=1), mild (25.1-50%) in 9 and 12 (p=0.57), moderate (50.1-75%) in 10 and 6 (p=0.37) and notable (>75%) in 4 and 4 patients (p=1). The total/HDL-cholesterol ratio and insulin levels significantly decreased while glucose levels significantly increased in both groups. None of the patients with normal glucose tolerance at diagnosis developed diabetes mellitus. Side effects were mostly at the gastrointestinal level and were similar with both drugs. In conclusion, newly diagnosed patients with acromegaly treated with LAR and LAN have no significantly different prevalence of disease control, tumor shrinkage, improvement of cardiovascular risk markers and side effects. Therefore, both drugs can be safely employed as first-line therapy of acromegaly.

Somatostatin agonists for treatment of acromegaly

The discovery of somatotropin-release inhibitory factor (SRIF) in hypothalamic extract in 1970 led to the synthesis of the first somatostatin analog octreotide, discovery of five somatostatin receptor subtypes, and development of additional somatostatin receptor ligands (SRL) as pharmacotherapy for acromegaly and other neuroendocrine tumors. Long-acting formulations of SRL (octreotide LAR Depot, lanreotide SR and lanreotide autogel) assure improved patient compliance with weekly up to monthly injections, and are commonly used as primary or adjuvant treatment of acromegaly. We review SRL currently available, emphasizing long-acting compounds and their efficacy in controlling acromegaly. Disease control is evaluated by biochemical markers, tumor shrinkage, and disease-symptom improvement balanced against drug-related side effects.

Acromegaly

Acromegaly is caused by growth hormone hypersecretion, mostly from a pituitary adenoma, driving insulin-like growth factor 1 overproduction. Manifestations include skeletal and soft tissue growth and deformities; and cardiac, respiratory, neuromuscular, endocrine, and metabolic complications. Increased morbidity and mortality require early and tight disease control. Surgery is the treatment of choice for microadenomas and well-defined intrasellar macroadenomas. Complete resection of large and invasive macroadenomas rarely is achieved; hence, their low rate of disease remission. Pharmacologic treatments, including long-acting somatostatin analogs, dopamine agonists, and growth hormone receptor antagonists, have assumed more importance in achieving biochemical and symptomatic disease control.

Octreotide for acromegaly

Octreotide has dramatically changed the results of medical treatment of acromegaly. It is the reference drug for the pharmacological treatment of acromegaly, owing to its impressive efficacy in suppressing growth hormome secretion, and excellent compliance. Safe growth hormone and normal insulin-like growth factor I values are reached in 50-60% of unselected patients. Octreotide arrests the growth of the tumor and shrinks tumor in over half of all patients (namely, up to 88% of naive patients and to complete disappearance in anecdotic cases). The safety profile of octreotide is excellent, but in some patients, glucose metabolism worsens and cholelythiasis occurs. This review will address the primary treatment and the relative roles of pharmacological and surgical treatment, as well as the predictivity of octreotide results.

Medical treatment of acromegaly: comorbidities and their reversibility by somatostatin analogs

Relief of symptoms can be achieved following surgery for growth hormone (GH)-secreting adenomas, as well as after pharmacological therapy with somatostatin analogs. Recently, long-acting somatostatin analog depot formulations, octreotide LAR and lanreotide SR have become available. Somatostatin analogs control GH/insulin-like growth factor (IGF)-1 excess, induce tumor shrinkage in a high proportion of patients, improve symptoms of acromegaly with relatively limited side effects and are successfully administered in patients not suitable for surgery. Furthermore, preoperative somatostatin analogs have been suggested to improve outcome for tumors with limited invasiveness, while surgical tumor debulking in cases that are, at least partially, somatostatin resistant, increases the achievement of normal IGF-1 levels by postoperative somatostatin analog treatment. Effective control of hypertension, as well as diabetes, is mandatory in order to reduce the increased vascular morbidity/mortality. Control of GH/IGF-1 excess generally improves glucose metabolism. Somatostatin analogs improve insulin sensitivity, exerting, however, a concomitant direct inhibitory effect on insulin secretion, with a net balance leaning towards a deterioration in glucose homeostasis. As a result, oral insulin secretagogues (and/or insulin) should probably be preferred to insulin sensitizers in acromegalic patients developing diabetes while on somatostatin analogs. Nevertheless, glucose tolerance remains normal in most of the nondiabetic acromegalic patients, while diabetic acromegalic patients on insulin are at risk for hypoglycemia during initiation of somatostatin analog therapy. Although successful management of acromegaly has been associated with improvement in morphological and functional parameters of cardiomyopathy, limited and conflicting information is available regarding the effect on blood pressure control. Contradictory results have also been reported regarding sleep hypopnea or apnea in treated acromegalic patients. As acromegalic skeletal abnormalities are rather irreversible, apneic episodes may persist after normalization of hormonal levels. Aggressive therapy, including surgery, pharmacological treatment and, in some cases, pituitary irradiation, aiming at normalization of IGF-1 levels, is required for arthropathy management. Some improvement in pain, crepitus and range of motion has been observed after treatment with somatostatin analogs. Information on the impact of disease control, either by surgery or somatostatin analog treatment, on gonadal function is limited. Finally, the link between the hormonal/biochemical and the psychiatric/psychological features of acromegaly, as well as a potential basis for positive effects of somatostatin analog therapy remain unclear.

Etiologic aspects and management of acromegaly

Acromegaly is a systemic disease with various etiologies. It can occur as a sporadic or, more rarely, as a familial disease. Numerous complications such as endocrine, cardiovascular, respiratory, metabolic, osteoarticular and neoplastic disturbances occur and must be taken into account when establishing a therapeutic strategy. For this reason, the decision as to a treatment modality of acromegaly must be followed by a thorough evaluation of the patient and once the diagnosis of complications is settled, adequate treatment should be instituted. Follow up of the patients requires periodical re-assessment of complications’ status.

The long-term efficacy of conventional radiotherapy in patients with GH-secreting pituitary adenomas

OBJECTIVE

To assess the long-term efficacy and safety of conventional radiotherapy (RT) in the control of acromegaly according to recent stringent criteria of cure.

DESIGN

A retrospective longitudinal study.

PATIENTS AND METHODS

Forty-seven patients with active acromegaly were treated with conventional RT between 1982 and 1994. All patients were first operated on and successively irradiated at a dose of 45-50 Gy in 25-28 fractions for persistent (n = 40) or recurrent (n = 7) disease.

MEASUREMENTS

Long-term GH/IGF-I secretion and local tumour control were evaluated regularly, and possible side-effects were searched for systematically, especially in terms of secondary endocrine dysfunction. Biochemical cure of acromegaly was defined by glucose-suppressed plasma GH levels below 1 microg/l during an oral glucose tolerance test (OGTT) and normal age-corrected IGF-I values.

RESULTS

The 5-, 10- and 15-year overall survival rates were 98%, 95% and 93%, respectively. Suppression of GH during OGTT was seen in 9% of patients at 2 years, 29% at 5 years, 52% at 10 years, and 77% at 15 years. Age-corrected IGF-I levels were normal in 8% of patients 2 years after RT, and this proportion increased to 23%, 42% and 61% after 5, 10 and 15 years, respectively. Normalization of GH/IGF-I mainly depended on pre-RT levels. Local tumour control was 95% at 5, 10 and 15 years after treatment. Late toxicity was mainly represented by progressive hypopituitarism, which was present in 33% of patients at baseline and increased to 57%, 78% and in 85% of patients at 5 10 and 15 years after RT, respectively.

CONCLUSION

Conventional RT is effective in the long-term control of GH-secreting pituitary adenomas, although with a high prevalence of progressive hypopituitarism. At present, it remains a suitable option in acromegalic patients uncontrolled by surgery or medical therapy.

Pharmacologic Therapies for Acromegaly

Acromegaly is associated with insulin resistance and an increased incidence of cardiovascular disease. However, it remains unclear to what extent the effects of growth hormone (GH) excess on cardiovascular morbidity and mortality are mediated through insulin resistance versus through other direct or indirect effects of GH. Adequate control of GH excess by surgery or pharmacologic interventions is associated with decreased insulin resistance, reflected in decreased plasma insulin levels and fasting glucose levels or improved glucose tolerance. Despite divergent effects of both somatostatin and somatostatin analogs on GH, insulin and glucagon secretion, and glucose absorption, treatment with the somatostatin analogs octreotide and lanreotide has only limited effects on glucose metabolism. However, glucose sensitivity has only been formally examined using a hyperinsulinemic euglycemic clamp in a minority of these studies. Treatment with the GH-receptor antagonist pegvisomant ameliorates insulin sensitivity, reflected in decreased fasting plasma insulin levels and fasting glucose levels. Nonetheless, the effect of pegvisomant on glucose sensitivity has not been formally tested by hyperinsulinemic clamp conditions. In acromegaly, preliminary observations on new octreotide analogs with greater specificity for somatostatin-receptor subtypes indicate that these compounds achieve better control of GH hypersecretion than octreotide, but may also negatively influence insulin release. Assessment of insulin secretion and glucose levels in acromegalic patients during administration of these compounds is thus mandatory.

Octreotide long-acting release (LAR): a review of its use in the management of acromegaly

Octreotide long-acting release (LAR) is a somatostatin analogue designed for once monthly intramuscular injection. As with endogenous somatostatin, octreotide LAR inhibits secretion of growth hormone (GH) as well as various other peptide hormones. In the treatment of acromegaly, octreotide LAR effectively controlled the secretion of GH and insulin-like growth factor-1 (IGF-1) in about 55-70% of patients (n > 100) who had previously been treated with somatostatin analogues, a similar degree of control to that observed with subcutaneous octreotide and lanreotide slow release (SR). Progressive control of serum levels of GH and IGF-1 was achieved with octreotide LAR in clinical studies of up to 4 years' duration. In addition, primary therapy with octreotide LAR provided effective control of GH and IGF-1 secretion, particularly in patients with a pretreatment GH level <20 microg/L. The percentage of patients achieving a target serum GH level of <2-2.5 micro g/L or normal IGF-1 levels was significantly greater with octreotide LAR 10, 20 or 30 mg every 28 days than with lanreotide SR 30 mg every 7-14 days in a large (n = 125) sequential, 6-month study, but was not significantly different between treatment groups in a small, randomised, nonblind, parallel group study of previously untreated patients. The volume of pituitary tumour shrinkage achieved with octreotide LAR or lanreotide SR was also similar ( approximate, equals 33% after 24 months). Acromegaly symptoms, such as headache, increased perspiration, paraesthesia, fatigue and osteoarthralgia were improved during treatment with octreotide LAR or lanreotide SR. Overall, octreotide LAR is generally well tolerated by most patients. The incidence of gastrointestinal symptoms is about 30% but, in most cases, events are transient and mild to moderate. Gallbladder abnormalities (sediment, sludge, microlithiasis and gallstones) can occur, but only 1% have become symptomatic to date. The prevalence of biliary abnormalities did not change after switching from subcutaneous octreotide, or from lanreotide SR, to octreotide LAR. Glucose metabolism can be affected by octreotide LAR in some patients; about 15% become hyperglycaemic, usually mild in severity. In summary, octreotide LAR controls GH and IGF-1 secretion in about 55-70% of patients with acromegaly. Octreotide LAR is administered intramuscularly every 28 days, offering improved patient compliance and convenience over three-times-daily subcutaneous octreotide. Long-term therapy provides progressive control of serum GH and IGF-1 levels, and is generally well tolerated by most patients. Thus, for the medical management of acromegaly, octreotide LAR is an effective, well tolerated and convenient treatment option.

Systemic complications of acromegaly: epidemiology, pathogenesis, and management

This review focuses on the systemic complications of acromegaly. Mortality in this disease is increased mostly because of cardiovascular and respiratory diseases, although currently neoplastic complications have been questioned as a relevant cause of increased risk of death. Biventricular hypertrophy, occurring independently of hypertension and metabolic complications, is the most frequent cardiac complication. Diastolic and systolic dysfunction develops along with disease duration; and other cardiac disorders, such as arrhythmias, valve disease, hypertension, atherosclerosis, and endothelial dysfunction, are also common in acromegaly. Control of acromegaly by surgery or pharmacotherapy, especially somatostatin analogs, improves cardiovascular morbidity. Respiratory disorders, sleep apnea, and ventilatory dysfunction are also important contributors in increasing mortality and are advantageously benefitted by controlling GH and IGF-I hypersecretion. An increased risk of colonic polyps, which more frequently recur in patients not controlled after treatment, has been reported by several independent investigations, although malignancies in other organs have also been described, but less convincingly than at the gastrointestinal level. Finally, the most important cause of morbidity and functional disability of the disease is arthropathy, which can be reversed at an initial stage, but not if the disease is left untreated for several years.

Diagnosis and treatment of acromegaly complications

The Pituitary Society in conjunction with the European Neuroendocrine Association held a consensus workshop to develop guidelines for diagnosis and treatment of the co-morbid complications of acromegaly. Fifty nine pituitary specialists (endocrinologists, neurosurgeons and cardiologists) assessed the current published literature on acromegaly complications in light of recent advances in maintaining tight therapeutic control of GH hypersecretion. The impact of elevated GH levels on cardiovascular disease, hypertension, diabetes, sleep apnea, colon polyps, bone disease, reproductive disorders, and neuropsychologic complications were considered. Guidelines are proposed for effective management of these complications in the context of overall acromegaly control. When appropriate, requirements for prospective evidence-based studies and surveillance database development are enunciated. Effective management of co-morbid acromegaly complications will lead to improved morbidity and mortality in acromegaly.

Glucose homeostasis in acromegaly: effects of long-acting somatostatin analogues treatment

OBJECTIVE

Acromegaly is a syndrome with a high risk of impaired glucose tolerance (IGT) and diabetes mellitus (DM). Somatostatin analogues, which are used for medical treatment of acromegaly, may exert different hormonal effects on glucose homeostasis. Twenty-four active acromegalic patients were studied in order to determine the long-term effects of octreotide-LAR and SR-lanreotide on insulin sensitivity and carbohydrate metabolism.

DESIGN

Prospective study.

PATIENTS

We studied 24 patients with active acromegaly, 11 males and 13 females, aged 50.7 +/- 12.7 years, body mass index (BMI) 30.1 +/- 4.8 (kg/m2).

MEASUREMENTS

All patients underwent an oral glucose tolerance test (OGTT) and 12 also had an euglycaemic hyperinsulinaemic clamp. All patients were evaluated at baseline and after 6 months of somatostatin analogues therapy.

RESULTS

Acromegalic patients showed low M-values in respect to the control group at baseline (P<0.05), followed by a significant improvement after 6 months of therapy (P<0.005 vs. baseline). Serum glucose levels at 120 min during OGTT worsened (P<0.05) during somatostatin analogs therapy in patients with normal glucose tolerance, but not in those with impaired glucose tolerance or diabetes mellitus. This was associated with a reduced (P<0.05) and 30 min delayed insulin secretion during OGTT. Also, HbA1c significantly deteriorated in all subjects after treatment (4.7 +/- 0.6% and 5.1 +/- 0.5%, basal and after six months, respectively, P<0.005).

CONCLUSION

In acromegalic patients, somatostatin analogues treatment reduces insulin resistance, and also impairs insulin secretion. This may suggest that the use of oral secretagogue hypoglycaemic agents and/or insulin therapy should be considered rather than insulin sensitizers, as the treatment of choice in acromegalic patients who develop frank hyperglycaemia during somatostatin analogues therapy.

Evaluation of insulin resistance in acromegalic patients before and after treatment with somatostatin analogues

Many studies have recently shown that simple computer-solved indices, based on fasting glucose and insulin levels, closely mirror the euglycemic clamp technique in studying insulin resistance or pancreatic insulin secretion. Few data are at present available on the evaluation of these novel indices in acromegalic patients, known to be GH-dependent insulin-resistant subjects, in particular during medical treatment with somatostatin analogues. Indeed, these drugs are able to inhibit not only GH and IGF-I levels, but also insulin and glucagon pancreatic secretion, with contrasting effects on glucose metabolism. In this study, insulin resistance was evaluated by the homeostasis model assessment (HOMA-IR) and insulin sensitivity by quantitative insulin check index (QUICKI) in 27 normoglycemic acromegalic patients, before and after 6-month therapy with somatostatin analogues (lanreotide-SR 30-60 mg every 7-28 days in 15 and octreotide-LAR 20-30 mg every 28 days in 12). Thirty-five age- and sex-matched healthy subjects and 17 surgically treated acromegalic patients (5 cured and 12 not cured) were studied as control groups. Before medical treatment, HOMA-IR was higher in acromegalic patients than in healthy controls (4 +/- 3 vs 1.7 +/- 0.7, p < 0.05), while QUICKI was lower (0.33 +/- 0.04 vs 0.36 +/- 0.03, p < 0.05). During medical therapy, HOMA-IR decreased to 2.4 +/- 1.6 (p < 0.05) and became similar to that recorded in both healthy subjects and surgically treated patients. However, fasting glucose was increased and fasting insulin was decreased. QUICKI did not significantly change from basal values. No differences were observed between patients who normalized or not hormonal levels. The effects of the 2 drugs, though higher glucose levels were seen in patients treated with octreotide-LAR. In conclusion, this study demonstrates that medical treatment is able to improve insulin resistance, even if only successful surgery is able to completely normalize both HOMA-IR and QUICKI.