Effects of octreotide on lipid metabolism in acromegaly

Effects of endocrine disorders on lipids and lipoproteins

Endocrine diseases may be associated with dyslipidaemia and may increase atherosclerotic cardiovascular disease (ASCVD) risk. This chapter describes changes in lipids and lipoproteins in diseases of the pituitary, thyroid, adrenal glands, ovaries, and testes, the mechanisms for these changes, ASCVD risk in these endocrine disorders, and whether treatment of the endocrine disorder improves the lipid profile and reduces ASCVD risk. Acromegaly, GH deficiency, Cushing syndrome, chronic glucocorticoid replacement, hypothyroidism, PCOS and male hypogonadism can increase LDL-C and/or TG. Marked reductions in LDL-C are associated with hyperthyroidism, and extremely low HDL-C levels with testosterone and/or other anabolic steroid abuse. Acromegaly, GH deficiency, Cushing syndrome, and chronic glucocorticoid replacement are associated with increased ASCVD risk. Treatment of acromegaly, GH deficiency, hypothyroidism, Cushing syndrome, and testosterone deficiency reduce LDL-C, although statin therapy may still be needed. Effects on ASCVD are not known.

Lipid Management in Patients with Endocrine Disorders: An Endocrine Society Clinical Practice Guideline

OBJECTIVE

This guideline will provide the practicing endocrinologist with an approach to the assessment and treatment of dyslipidemia in patients with endocrine diseases, with the objective of preventing cardiovascular (CV) events and triglyceride-induced pancreatitis. The guideline reviews data on dyslipidemia and atherosclerotic cardiovascular disease (ASCVD) risk in patients with endocrine disorders and discusses the evidence for the correction of dyslipidemia by treatment of the endocrine disease. The guideline also addresses whether treatment of the endocrine disease reduces ASCVD risk.

CONCLUSION

This guideline focuses on lipid and lipoprotein abnormalities associated with endocrine diseases, including diabetes mellitus, and whether treatment of the endocrine disorder improves not only the lipid abnormalities, but also CV outcomes. Based on the available evidence, recommendations are made for the assessment and management of dyslipidemia in patients with endocrine diseases.

Effects of growth hormone deficiency on body composition and biomarkers of cardiovascular risk after definitive therapy for acromegaly

BACKGROUND

Both growth hormone (GH) excess and GH deficiency are associated with abnormalities in body composition and biomarkers of cardiovascular risk in patients with pituitary disorders. However, the effects of developing GH deficiency after definitive treatment of acromegaly are largely unknown.

OBJECTIVE

To determine whether development of GH deficiency after definitive therapy for acromegaly is associated with increased visceral adiposity and biomarkers of cardiovascular risk compared with GH sufficiency after definitive therapy for acromegaly.

DESIGN

Cross-sectional.

PATIENTS

We studied three groups of subjects, all with a history of acromegaly (n = 76): subjects with subsequent GH deficiency (GHD; n = 31), subjects with subsequent GH sufficiency (GHS; n = 25) and subjects with active acromegaly (AA; n = 20). No study subjects were receiving somatostatin analogues, dopamine agonists or hGH.

MEASUREMENTS

Body composition (by DXA), abdominal adipose tissue depots (by cross-sectional CT), total body water (by bioimpedance analysis) and carotid intima-media thickness (IMT) were measured. Fasting morning serum was collected for high-sensitivity C-reactive protein (hsCRP), lipids and lipoprotein levels. An oral glucose tolerance test was performed, and homoeostasis model of assessment-insulin resistance (HOMA-IR) was calculated.

RESULTS

Abdominal visceral adipose tissue, total adipose tissue and total body fat were higher in subjects with GHD than GHS or AA (P < 0·05). Subcutaneous abdominal fat was higher, and fibrinogen and IMT were lower in GHD (but not GHS) than AA (P < 0·05). Patients with GHD had the highest hsCRP, followed by GHS, and hsCRP was lowest in AA (P < 0·05). Fasting glucose, 120-min glucose, fasting insulin, HOMA-IR and per cent total body water were lower in GHD and GHS than AA (P < 0·05). Triglycerides were higher in GHS than AA (P < 0·05). Lean body mass, mean arterial pressure, total cholesterol, HDL and LDL were comparable among groups.

CONCLUSIONS

Development of GHD after definitive treatment of acromegaly may adversely affect body composition and inflammatory biomarkers of cardiovascular risk but does not appear to adversely affect glucose homoeostasis, lipids and lipoproteins, or other cardiovascular risk markers.

The treatment with growth hormone receptor antagonist in acromegaly: effect on vascular structure and function in patients resistant to somatostatin analogues

BACKGROUND

Acromegaly is known to be associated to vascular damage characterized by an increase of vascular wall thickness and an impairment of vascular function.

AIM

The aim of this study was to evaluate the effect of medical treatment with the GH receptor antagonist pegvisomant on vascular structure and function in acromegalic patients resistant to somatostatin analogues.

PATIENTS

Ten patients (4 males and 6 females, 28-58 yr) and 20 sex-, age-, and body mass index-matched healthy controls entered the study. All patients were treated for 18 months with pegvisomant at doses ranging from 10 to 40 mg/day.

OUTCOME MEASURES

Primary outcome measures were measurement of carotid arteries intima-media thickness (IMT), and brachial arteries flow mediated dilation (FMD); secondary outcome measures were blood pressure, blood glucose and lipids levels.

RESULTS

Carotid arteries maximal IMT was significantly higher in patients than in controls at baseline (1.18±0.59 vs 0.69±0.13, p=0.001) and slightly, but not significantly, decreased after treatment (0.97±0.17). Brachial arteries FMD was significantly lower in patients than controls at baseline (7.5±2.5 vs 13.1±1.4, p<0.001) and significantly increased after treatment (8.8±3.7, p=0.016). Systolic (SBP) and diastolic (DBP) blood pressure values, serum glucose and insulin levels and homeostasis model assessment (HOMA) index were higher, whereas HDL-cholesterol levels were lower in patients than controls at baseline. After treatment, SBP and DBP, as well as serum glucose and insulin levels and HOMA index significantly decreased whereas no significant change was found in serum lipid profile.

CONCLUSIONS

The results of the current study suggested that long-term treatment with pegvisomant induced a slight reduction of carotid arteries wall thickness and a significant improvement of brachial arteries vascular function in patients with acromegaly resistant to somatostatin analogues.

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.

The effect of atorvastatin on serum lipoproteins in acromegaly

OBJECTIVE

Acromegaly is associated with long-term adverse effects on cardiovascular mortality and morbidity. Reducing growth hormone secretion improves well-being and symptoms, but may not significantly improve the lipoprotein profile. An additional approach to cardiovascular risk reduction in acromegaly may therefore be to target lipoprotein metabolism directly. In this study we investigated the effect of statin treatment.

DESIGN

Double blind, placebo-controlled, crossover study of the effects on circulating lipoproteins of atorvastatin 10 mg daily vs. placebo. Each treatment was given for 3 months in random order.

SUBJECTS

Eleven patients with acromegaly.

MEASUREMENTS

Lipids, lipoproteins, apolipoproteins, enzyme activity and calculated cardiovascular risk.

RESULTS

Atorvastatin treatment compared to placebo resulted in a significant decrease in serum cholesterol (5.85 +/- 1.04 mmol/l vs. 4.22 +/- 0.69 mmol/l; mean +/- SD; P < 0.001), low-density lipoprotein (LDL) cholesterol (2.95 +/- 1.07 mmol/l vs. 1.82 +/- 0.92 mmol/l; P < 0.001), very low-density lipoprotein (VLDL) cholesterol (0.31 (0.21-0.47) mmol vs. 0.23 (0.13-0.30) mmol/l median (interquartile range); P < 0.05), apolipoprotein B (111 +/- 28 mg/dl vs. 80 +/- 18 mg/dl; P < 0.001), and calculated coronary heart disease risk (6.8 (3.3-17.9) vs. 2.8 (1.5-5.7)% over next 10 years; P < 0.01). Serum triglyceride was 1.34 (1.06-1.71) mmol/l on placebo and 1.14 (0.88-1.48) mmol/l on atorvastatin (ns). HDL cholesterol, apolipoprotein A1 and Lp(a) concentrations and cholesteryl ester transfer protein and lecithin: cholesterol acyl transferase activities were also not significantly altered.

CONCLUSION

Atorvastatin treatment was safe, well tolerated and effective in improving the atherogenic lipoprotein profile in acromegaly.

Clinical indicators of biochemical remission in acromegaly: does incomplete disease control always mean therapeutic failure?

OBJECTIVE

Correction of GH and IGF-I levels are associated with improvements in insulin secretion, cardiac performance and body composition in patients with acromegaly, but whether these parallel post-treatment levels of GH-IGF-I axis activity is undefined. We investigate whether various biochemical outcomes after transsphenoidal pituitary surgery (TSS) in these patients are associated with clinically relevant differences in cardiac performance, insulin resistance and body composition.

DESIGN

Cross-sectional study of consecutive patients with acromegaly admitted to the hospital between 2001 and 2002.

PATIENTS AND METHODS

Forty-one patients after TSS for somatotroph pituitary adenoma and 23 patients with naive acromegaly serving as positive controls were enrolled in the study. Mean daily GH levels (mGH), IGF-I, leptin and lipid levels, glucose, insulin and GH concentrations during oral glucose tolerance test (oGTT) were measured in all study participants. Insulin resistance was measured by homeostatic model index (R(HOMA)). Body composition was assessed by dual-energy X-ray absorptiometry. Left ventricular mass index (LVM(i)) and cardiac index (C(i)) were determined by echocardiography.

RESULTS

We found no difference in cardiac indices, insulin resistance, body composition and leptin levels between patients with complete biochemical remission and those with inadequately controlled disease (P > 0.05 for all) after TSS. Cured patients had lower values (mean +/- SD) of cardiac index (2.2 +/- 0.7 vs. 3.0 +/- 1.0 l/min/m(2); P = 0.04) compared with naive patients. A similar decrease in LVM(i) was observed in controlled (108.4 +/- 30.0 g/m(2); P = 0.015) and inadequately controlled disease (108.8 +/- 30.7 g/m(2); P = 0.03) in comparison with naive disease (160.3 +/- 80.6 g/m(2)). Insulin resistance and leptin changed in opposite ways. In controlled and inadequately controlled disease, R(HOMA) index was lower (2.2 +/- 1.4; P = 0.001 and 3.1 +/- 2.0; P = 0.05 vs. 5.1 +/- 3.1) while leptin concentration was higher (14.9 +/- 8.7 microg/l, P = 0.004 and 12.8 +/- 7.8 microg/l, P = 0.05 vs. 7.4 +/- 3.8 microg/l) than in naive disease. In all patients, leptin correlated negatively with cardiac index (r = -0.46; P = 0.001) and IGF-I levels (r = -0.45; P < 0.001). Independent predictors of biochemical remission, based on normal IGF-I levels only, were cardiac [P = 0.04, odds ratio (OR) 0.4; 95% confidence interval (CI) 0.2-0.9] and R(HOMA) index (P = 0.009, OR 0.6; 95% CI 0.4-0.8). Similar results were obtained if the definition of cure included both normal IGF-I levels and the ability to achieve GH nadir < 1 microg/l during oGTT. Insulin resistance (P = 0.02, OR 0.6; 95% CI 0.4-0.9) and leptin level (P = 0.002, OR 1.3; 95% CI 1.1-1.6) were independent predictors of normalized mGH values.

CONCLUSION

This study shows that cardiac indices, insulin resistance and body composition were not different between patients with complete biochemical remission and those with discordant GH and IGF-I levels. It appears that even incomplete disease control after TSS can result in improvement of these clinical markers.

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.

Effects of treatment with Sandostatin LAR on small dense LDL and remnant-like lipoproteins in patients with acromegaly

OBJECTIVE

Acromegalic patients have been shown to have an increase in the concentrations of small dense low-density lipoprotein (LDL) and remnant-like lipoprotein particles (RLP). These lipoproteins are atherogenic and may contribute to the cardiovascular risk of these patients. The aim of this study was to determine whether treatment of acromegaly using Sandostatin LAR could lower these atherogenic lipoproteins.

METHODS

Fourteen patients with active acromegaly were recruited and Sandostatin LAR, a long-acting somatostatin analogue, was given every 4 weeks by intramuscular injection for 6 months. Fasting lipids, lipoproteins, lipolytic enzymes were determined at baseline, 12 and 24 weeks after treatment. Small dense LDL was measured using density gradient ultracentrifugation and RLP-cholesterol (RLP-C) by an immunoseparation assay.

RESULTS

There was already a marked reduction in GH and IGF-1 by week 8 and, in all subjects, IGF-1 levels within their respective age-specific normal range were achieved. At week 12, plasma triglyceride significantly decreased (P < 0.01) and both HDL2 (P < 0.01) and HDL3 (P < 0.01) subfractions increased. A reduction was seen in small dense LDL concentration (P < 0.05) and RLP-C (P < 0.05). Lipoprotein lipase (LPL) activity increased (P < 0.01) and the magnitude of the increase in LPL activity correlated with the increase in HDL at 3 months (r = 0.55, P < 0.05) but not with the changes in plasma triglyceride, small dense LDL or RLP-C. The improvement in plasma lipids and lipoproteins persisted until the end of the study.

CONCLUSION

Sandostatin LAR is effective in the treatment of acromegaly and is associated with favourable changes in plasma lipids and a reduction in small dense LDL and RLP-C.

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.

Cardiovascular risk factors in acromegaly before and after normalization of serum IGF-I levels with the GH antagonist pegvisomant

Acromegaly is associated with premature cardiovascular mortality. GH replacement therapy decreases inflammatory markers of cardiovascular risk, but little is known about these markers in patients with acromegaly. The GH receptor antagonist, pegvisomant, reduces IGF-I levels in 98% of patients treated. We investigated the effects of GH receptor blockade on inflammatory and other cardiovascular risk markers in active acromegaly. Forty-eight patients with acromegaly and 47 age- and body mass index-matched controls were included. The study consisted of 3 parts: a cross-sectional study, a prospective randomized 12-wk placebo-controlled study, and a longitudinal open-label study of up to 18 months of pegvisomant treatment. After baseline evaluation, patients with acromegaly were randomized to placebo (n = 14), 10 mg (n = 12), 15 mg (n = 10), or 20 mg (n = 12) daily pegvisomant for 12 wk. Subsequently, all patients received at least 10 mg pegvisomant daily for up to 18 months, with dose adjustments to achieve a normal IGF-I level. Anthropometry, GH, IGF-I, and pegvisomant levels were measured monthly. C-reactive protein (CRP), IL-6, homocysteine, lipoprotein(a), glucose, insulin, triglycerides, total cholesterol, and high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol were determined at baseline, 4 and 12 wk in the placebo-controlled study and at 3-month intervals (during which IGF-I levels were normal) in the longitudinal study. In the cross-sectional study, patients had lower CRP than did controls [median, 0.3 (range, 0.2-0.8) vs. 2.0 (0.6-3.7) mg/liter; P < 0.0001] and had higher insulin [78.6 (55.8-130.2) vs. 54.5 (36.6-77.5) pM, P = 0.0051]. IL-6, homocysteine, triglycerides, lipoprotein(a), LDL cholesterol and HDL cholesterol were not different between groups. In the placebo-controlled study, CRP increased in patients treated with 20 mg pegvisomant, compared with placebo (mean +/- SEM, 13.7 +/- 3.6 vs. 0.5 +/- 3.3 mg/liter; P = 0.010). There were no significant differences in IL-6, homocysteine, glucose, insulin, triglyceride, total cholesterol, LDL cholesterol and HDL cholesterol levels. In the longitudinal open-label study (median duration, 15.6 months), CRP increased by 2.0 +/- 0.5 mg/liter (P = 0.0002). Total cholesterol and triglycerides increased (0.22 +/- 0.11 mM, P = 0.050; and 0.25 +/- 0.09 mM, P = 0.007, respectively), whereas lipoprotein(a) decreased (-70 +/- 33 mg/liter, P = 0.039). Glucose, insulin, homocysteine, HDL cholesterol, and IL-6 did not change. We conclude that patients with active acromegaly have lower CRP and higher insulin levels than healthy controls. Administration of pegvisomant increases CRP levels. We propose that GH secretory status is an important determinant of serum CRP levels, although additional studies are needed to determine the mechanism and significance of this finding.

Serum lipoprotein changes following IGF-I normalization using a growth hormone receptor antagonist in acromegaly

OBJECTIVE

Active acromegaly is associated with altered lipid metabolism. The purpose of this study was to investigate the effect of serum IGF-I normalization on serum lipoproteins and insulin, in patients with acromegaly receiving the GH receptor antagonist pegvisomant.

PATIENTS

Twenty patients (9 male, mean age 58.7 years, range 28-79) with active acromegaly (baseline serum IGF-I > 130% the age-related upper limit of normal) received pegvisomant and achieved a normal serum IGF-I [585.2 +/- 54.3 (mean +/- SEM) to 169.2 +/- 13.9 ng/ml, P < 0.0001].

MEASUREMENTS

Total cholesterol (TC), high-density lipoprotein (HDL) cholesterol, triglyceride (TG), apolipoprotein B (apo B), apolipoprotein A1 (apo A1), lipoprotein a [Lp(a)] and insulin were measured in a single batch analysis on samples obtained at baseline and the first occasion of serum IGF-I normalization. Low-density lipoprotein (LDL) was calculated using the Friedewald formula. Paired analysis was performed using Student's paired t-test and the Wilcoxon signed rank test.

RESULTS

Normalization of serum IGF-I resulted in an increase in TC (5.0 +/- 0.3 to 5.7 +/- 0.4 mmol/l, P = 0.0068), an increase in LDL (3.0 +/- 0.25 to 3.7 +/- 0.31 mmol/l, P = 0.0093) and an increase in apo B (110.6 +/- 7.76 to 127.1 +/- 8.86 mg/l, P = 0.014). TC and LDL increased in all but four patients. Despite a significant fall in fasting insulin levels (9.9 to 8.3 mU/l, range 8.85-19.8 to 6.33-11.6, P < 0.001) and insulin resistance (2.7 to 1.9, range 1.2-10.4 to 1-6.2, P < 0.001), mean serum TG and HDL levels were unaffected by IGF-I normalization. The protein component of HDL, apo A1, increased (153 +/- 4 to 166.4 +/- 5.43 mg/l, P = 0.026) and Lp(a) declined (median 342 to 235 mg/l, range 60-1013 to 74-671), P = 0.0035). Baseline serum TC and LDL were below the age- and sex-matched mean population value but after normalization of serum IGF-I the distribution of serum TC and LDL values was similar to that of the general population.

CONCLUSIONS

Active acromegaly is associated with lowered mean serum TC and LDL. Successful management using pegvisomant increases lowered baseline serum TC and LDL levels, restoring the distribution of values to that of the general population, and improves insulin resistance. These findings are consistent with the reported lipoprotein changes following GH administration to normal and GH-deficient individuals.

Effects of normalization of GH hypersecretion on lipoprotein(a) and other lipoprotein serum levels in acromegaly

BACKGROUND & AIMS

Lipoprotein(a) has been recognized as an important risk factor for cardiovascular disease. Lipoprotein(a) has been found to be elevated in sera of acromegalic patients, possibly contributing to the increased incidence of coronary heart disease found in these patients. In the present study we sought to determine the effects of GH hormonal status on lipoprotein(a) and other lipid parameters, including lipoprotein lipase (LPL) activity.

DESIGN

Cross-sectional study.

PATIENTS

Twenty acromegalic patients, with either active (n = 12) or controlled (n = 8) acromegaly, were studied. Twenty-nine healthy subjects served as control group for serum lipid measurements.

MEASUREMENTS

Serum GH, IGF-1, IGF binding protein-3 (IGFBP-3) and insulin levels were measured in patients. Insulin resistance was measured by the homeostatic model assessment (HOMA). Plasma total cholesterol, triglycerides, HDL-lipids, apolipoproteins A-I and B, lipoprotein(a) and lipoprotein lipase activity were also measured.

RESULTS

The highest lipoprotein(a) levels were observed in patients with active acromegaly, followed by patients with controlled acromegaly, whose lipoprotein(a) concentrations were still significantly higher than those of the control group (means +/- SEM: active acromegaly, 0.67+/-0.13 g/l; controlled acromegaly, 0.41+/-0.12 g/l; controls 0.17+/-0.02 g/l; P<0.05). There were no differences in other lipid and lipoprotein values among the groups. In patients, significant correlations were observed between lipoprotein(a) and basal GH levels (r = 0.56, P<0.02), mean GH levels (r = 0.48, P<0.05) and with insulin resistance estimated by HOMA (r = 0.62, P<0.01). No correlations were found between lipoprotein(a) and IGF-1 or IGFBP-3 levels.

CONCLUSIONS

Our present results demonstrate that both active acromegalic patients and those with controlled disease have elevated serum lipoprotein(a) concentrations. The findings might suggest that the present biochemical criteria for cure of acromegaly are not strict enough to result in the normalization of all the undesirable metabolic changes found in this disease, and also that significant cardiovascular risk may persist despite successful treatment of acromegaly.

LDL physical properties, lipoprotein and Lp(a) levels in acromegalic patients. Effects of octreotide therapy. Italian Multicenter Octreotide Study Group

High vascular morbidity and mortality is associated with acromegaly. The aim of the present study was to assess the effects of octreotide therapy on several known cardiovascular risk factors and to correlate them with octreotide-induced hormonal changes. Lipid levels, LDL particle size distribution as evaluated by single vertical spin density gradient ultracentrifugation, apolipoproteins AI and B, lipoprotein (a) [Lp(a)] concentrations and apo(a) phenotypes were evaluated in 20 non-diabetic acromegalic patients (6 M, 14 F), with normal thyroid, adrenal and gonadal function, aged 29-66 years. Normal subjects (20), matched for age, sex and BMI served as control for lipid variables. Acromegalic patients were characterized by lower HDL cholesterol (and apoA-I) and by higher Lp(a) concentrations in comparison to controls. Treatment with octreotide (100 microg t.i.d. for 3 months) led to: an increase in HDL cholesterol (median: + 22%), a decrease in LDL cholesterol (-14%) and a decrease of the Lp(a) levels (all phenotypes) (-28%). The expected decreases of IGF-I levels (median: -48%) and 7-h AUC of GH (-50%), insulin (-40%) and glucagon (-20%) were observed. Only Lp(a) modifications showed a correlation with GH modifications. The study of LDL physical properties showed that acromegalic patients had smaller and/or more dense LDL particles, in comparison with normal controls (relative flotation rate, Rf: 0.40 +/- 0.03 versus 0.42 +/- 0.02 P < 0q05), an alteration that might contribute to the high vascular risk of acromegalic patients. However, the LDL subfraction distribution remained unmodified during octreotide therapy (Rf 0.39 +/- 0.03). In conclusion, this study shows that in acromegalic patients octreotide treatment is indeed associated with an amelioration of some lipoprotein parameters, i.e. LDL, HDL, and Lp(a) concentrations. However, this treatment has no effect on the small and/or dense LDL particles present in these patients.

Epidemiology of acromegaly

Acromegaly is a consequence of chronic growth hormone (GH) excess, due in the majority of cases to a GH-secreting pituitary adenoma, and occurring with a population prevalence of 60 per million and an incidence of 3-4 per million per year. Males and females appear to be equally affected with an average age of presentation of 44 years. Younger patients may have more aggressive tumours and higher GH concentrations. There is co-existent hyperprolactinaemia in about one third of cases, and a variable proportion of [figure: see text] tumours appear to have activating mutations of the gsp gene or other genetic abnormalities. Acute complications such as carpal tunnel syndrome, sweating and obstructive sleep apnoea are usually readily reversible with treatment of the condition, but chronic complications such as hypertension, diabetes and heart disease are less readily corrected and post-treatment GH levels of < 2.5 ug/L (5 mU/L) are needed to achieve the prevalence found in the general community. Such 'curative' levels of GH are achieved in only about 50% of patients with current therapies, and as a result there is an ongoing excess of patients with chronic complications of acromegaly leading to increased morbidity and mortality from the disorder, with observed-to-expected mortality ratios ranging from 1.6-3.3 and only approaching unity in those with growth hormone levels < 2.5 ug/L following treatment. Prognostic factors include in some studies the presence of diabetes and [table: see text] hypertension prior to diagnosis as well as measures of exposure to excessive growth hormone derived from the product of preoperative serum GH and the time from first symptoms to treatment. Overall, however, the most important prognostic variable appears to be the serum GH concentration achieved by treatment, with an increasing consensus that this needs to be < 2.5 ug/L (5 mU/L) to achieve cure of the condition.

Medical therapy for acromegaly

Both somatostatin analogues, which bind to the somatostatin receptor subtypes 2 and 5, and dopamine agonists, which are specific for the D2 receptor, have been used to treat acromegaly. Each of these classes of drugs contains several compounds that vary in duration of action, efficacy, and side effect profile. Although somatostatin analogues reduce GH levels and alleviate symptoms in most patients and restore IGF-1 levels to normal in 60% to 65% of patients, tumor shrinkage is limited to 40% of patients. evidence in the literature supports the use of these medications as secondary therapy in patients with acromegaly who have had surgery and who continue to have elevated GH levels (above 2 ng/mL during an oral glucose tolerance test) with or without IGF-1 concentrations that are above the upper limit of normal for age. In addition, medical therapy indicated in patients who refuse surgery and in patients who are poor surgical candidates. The controversial question is whether medical therapy should be an option for primary treatment of the acromegalic patient. Currently, ther are no data from prospective randomized trials comparing the effects of surgery versus somatostatin analogues as first-line therapy for for newly diagnosed acromegalic patients. Limited data from nonrandomized studies demonstrate that somatostatin analogues are effective long-term in suppressing GH and reducing IGF-1 into the normal range in approximately two-thirds of patients who have never undergone previous treatment. It is still the consensus that patients with GH-secreting microadenomas should undergo surgical resection, because the likelihood of complete cure by an experience neurosurgeon is high, at least 70% or greater. Successful surgical treatment has the advantage of completely removing the tumor in contrast to medical therapy, which rarely produces shrinkage greater than 50% despite the fact that IGF-1 and GH levels may be normal. In patients with macroadenomas of a size and location that suggest that the chance of complete resection is 40% or less, primary treatment with a somatostatin analogue should be considered as one option in the initial management of the patient. Another option in such an individual would be surgical debulking followed by medical therapy, because it is theoretically possible that biochemical cure with medical therapy after surgical debulking might be achieved with lower doses. The cost-effectiveness of these approaches has not yet been determined. Once the decision has been made to begin medical therapy, a choice must be made between dopamine agonists and somatostatin analogues. Most evidence suggests that somatostatin analogues are more effective than dopamine agonists and therefore would be the therapy of choice. In select patients, dopamine agonists, particularly the long-acting agonist cabergoline, may be preferred initially if the patient is unwilling to take injections or if the GH elevations are relatively modest (< 10 ng/mL). Biochemical cure should be assessed by measurement of GH (which can be performed 2 hours after an octreotide injection) and IGF-1 concentrations. The goal of treatment include reduction of of GH below 2 ng/mL and reduction of IGF-1 into the normal range. In patients who do not reach these goals, the dose or frequency of injection of the somatostatin analogue or both should be increased. If such measures are unsuccessful, a dopamine agonist may be added to the medical regimen because some studies suggest that combination therapy may be more effective in select cases than octreotide therapy alone. If such measures are still unsuccessful, other options should be considered, including surgery, pituitary radiation, and medical treatment with investigational drugs.

Effect of short-term treatment with recombinant human growth hormone on lipids and lipoproteins in women and men without growth hormone disturbances

The effect of recombinant human growth hormone (rHGH) on cholesterol, high- and low-density lipoprotein (HDL and LDL) cholesterol, triglycerides (TG), apolipoprotein (apo) B, apo A-I, and lipoprotein(a) [Lp(a)] was studied in 40 postmenopausal women treated with 0.05, 0.1, or 0.2 IU/kg/d rHGH or placebo for 7 days. Cholesterol, LDL cholesterol, and HDL cholesterol decreased in a dose-dependent manner (P = .001, P = .001, and P = .003, respectively), whereas apo B decreased insignificantly (P = .15). Apo A-I decreased significantly only among women treated with rHGH at a dose of 0.1 IU/kg/d (P = .03). When all rHGH-treated women were grouped together, Lp(a) increased (P = .001). We also studied 20 young men treated with either 0.2 IU/kg/d rHGH or placebo. As in women, cholesterol and apo B decreased P = .005 and P = .02, respectively), whereas Lp(a) increased (P = .05). There was no detectable effect of rHGH on TG concentrations in men. As in women, there was no significant effect of 0.2 IU/kg/d rHGH on apo A-I concentrations. All lipid and lipoprotein measures reached pretreatment levels during the first week after treatment was stopped, except Lp(a), which remained elevated 2 weeks after rHGH cessation.

Serum lipoproteins in acromegaly before and 6-15 months after transsphenoidal adenomectomy

OBJECTIVES

Acromegaly is a rare disorder characterized by over-secretion of GH, most often because of a pituitary adenoma. The disease is associated with disturbances in lipoprotein metabolism and an increased cardiovascular mortality. The aim of the present study was to investigate whether treatment of acromegaly results in changes in serum concentrations of lipids and apolipoproteins, including lipoprotein(a) (Lp(a)).

DESIGN

Fourteen patients with clinical features of acromegaly and increased GH secretion were studied 1-10 months before and 6-15 months after transsphenoidal adenomectomy in an open study.

PATIENTS

Three patients had diabetes mellitus before surgery and two of these patients had normalized serum glucose levels post-operatively. Mean and baseline plasma GH levels were determined from 24-hour GH profiles. Serum samples were taken in the morning after an overnight fast. All patients were normocholesterolaemic, and four patients were hypertriglyceridaemic before treatment.

RESULTS

Mean plasma GH levels decreased from 34.5 +/- 7.4 to 2.1 +/- 0.4 mU/l (mean +/- SEM). Serum IGF-I, insulin and free T3 levels decreased and serum SHBG concentrations increased post-operatively. There was no effect of treatment on serum cholesterol concentrations, but serum triglyceride concentrations decreased. Serum apolipoprotein (apo) B and apoE levels were unaffected by treatment. Serum apoA-I levels increased and Lp(a) levels decreased post-operatively.

CONCLUSIONS

Successful treatment of acromegaly, resulting in normal mean GH values (< 5 mU/l) and/or normal responsiveness to TRH, have beneficial effects on serum lipoproteins with increased serum apoA-I levels and decreased serum levels of triglycerides and Lp(a). These effects seem to be independent of improvement in glucose tolerance, since patients with diabetes mellitus before surgery and normal fasting blood glucose levels post-operatively had similar lipoprotein responses to treatment as those with normal fasting blood glucose levels before surgery.

Body composition in active acromegaly during treatment with octreotide: a double-blind, placebo-controlled cross-over study

OBJECTIVE

In active acromegaly body composition is characteristically altered by an increase in lean body mass and a corresponding reduction in fat mass. These changes are induced by an excessive secretion of GH and insulin-like growth factor I (IGF-I). Growth hormone is an anabolic hormone and leads to stimulation of protein synthesis and an increased lipolysis in adipose tissue. Treatment with the somatostatin analogue, octreotide, has been shown to reduce GH levels causing reduced hormonal effects on target tissues. We have studied changes in body composition during short-term reduction in GH level by octreotide in active acromegaly.

DESIGN

Octreotide was compared to placebo in a double-blind, cross-over trial. Dual-energy X-ray absorptiometry scanning was employed to calculate body composition. Relations between body composition parameters and clinical signs of acromegaly (finger circumference and foot volume) were studied.

PATIENTS

Twelve patients with active acromegaly, confirmed by lack of GH suppression during oral glucose loading, were included. All had pituitary adenomas diagnosed by computed tomography.

MEASUREMENTS

Serum GH and IGF-I. Lean body mass, fat mass and total weight, foot volume and finger circumference.

RESULTS

Four weeks of octreotide treatment caused a 75% decrease in GH levels (n = 10), a reduction in IGF-I from 476 +/- 51.9 (mean +/- SEM) to 233 micrograms/l +/- 46.3 (P < 0.005) and a corresponding decrease in both body weight (2.51 kg +/- 0.41) (P < 0.005) and lean body mass (2.44 kg +/- 0.48) (P < 0.005). No significant changes in fat mass were observed. These findings were paralleled by significant reductions in foot volume (44.50 ml +/- 17) (P < 0.05) and finger circumference (1.3 mm +/- 0.3) (P < 0.05).

CONCLUSIONS

Short-term octreotide therapy reduces growth hormone levels leading to a significant reduction in lean body mass as assessed by dual-energy X-ray absorptiometry. Alterations in lean body mass were positively correlated with reductions in foot volume. Thus, simple clinical tests may be valuable in judging the effects of treatment in active acromegaly.