Correlation between blood pressure and plasma insulin in acromegaly

Hypertension and Acromegaly

Hypertension is one of the most frequent complications in acromegaly, with a median frequency of 33.6% (range, 11%-54.7%). Although the pathogenesis has not been fully elucidated, it probably results from concomitant factors leading to expansion of extracellular fluid volume, increase of peripheral vascular resistance, and development of sleep apnea syndrome. Because the effect of normalization of growth hormone and insulinlike growth factor 1 excess on blood pressure levels is unclear, an early diagnosis of hypertension and prompt antihypertensive treatment are eagerly recommended, regardless of the specific treatment of the acromegalic disease and the level of biochemical control attained.

CARDIOVASCULAR COMPLICATIONS OF ACROMEGALY

Acromegaly is associated with increased mortality and decreased life expectancy. Cardiovascular disease is the principal cause of premature mortality in patients with acromegaly, accounting for about 60% of deaths. GH and/or IGF-I exert direct cardiac effects: enhance cardiac contractility, stimulate cardiomyocyte growth, influence calcium influx in cardiomyocytes. Cardiac remodelling is influenced by hypertension and insulin resistance. Among cardiovascular risk factors arterial hypertension, reported in 35% of patients with acromegaly, ranks among most important negative prognostic factors for mortality. Hypertension plays significant role in the development of cardiac hypertrophy, especially in older acromegalic patients and diastolic blood pressure is best predictive factor for cardiac hypertrophy. Therefore, early and aggressive hypertension treatment is essential for prognosis in acromegaly. Other important risk factors are: valvular defects, arrhythmias, endothelial dysfunction, heart failure, lipid abnormalities and coronary artery disease. Numerous studies suggest that patients with acromegaly are under threat of arrhythmias, especially those with structural heart abnormalities. Congestive heart failure as end-stage acromegalic cardiomyopathy occurs usually in older patients, with long-term uncontrolled disease and other cardiovascular and metabolic complications. Relation between acromegaly and coronary artery disease is controversial as it seems to be connected rather with classical cardiovascular risk factors than GH and IGF-1 overexpresion.

A case and review of acromegaly-induced cardiomyopathy and the relationship between growth hormone and heart failure: cause or cure or neither or both?

Growth hormone plays an integral role in the development and maintenance of structure and function of the heart. Specific involvement of the heart in acromegaly is termed acromegalic cardiomyopathy, manifested as concentric left ventricular hypertrophy and diastolic dys-function. Left untreated, it ultimately progresses to systolic heart failure. Heart failure from acromegalic cardiomyopathy is one of the most common causes of death in acromegaly. Current treatment options include different approaches to lower elevated growth hormone levels with improvement in symptoms, exercise tolerance, and echocardiographic improvement in regression of left ventricular hypertrophy and indices of diastolic dysfunction. On the other hand, growth hormone is essential for cardiac growth and function and exerts beneficial and protective effects on the cardiovascular system. Its potential role as adjunctive therapy in the treatment of heart failure as derived from experimental studies and clinical trials is discussed.

Hypertension in acromegaly and in the normal population: prevalence and determinants

BACKGROUND

The GH/IGF-I axis has a relevant role to play in the cardiovascular system but its implication in the pathogenesis of hypertension in the normal population and in acromegaly is not yet clear.

PATIENTS AND MEASUREMENTS

The aim of this retrospective and controlled study was to evaluate the prevalence and determinants of hypertension in 200 patients with acromegaly and 200 nonacromegalic subjects, matched for sex, age, body mass index (BMI) and smoking habits.

RESULTS

Hypertension was found in 46% of patients and in 25% of controls (P < 0.0001), without any difference between men and women. Family history of hypertension occurred in 30% of hypertensive acromegalic patients and in 62% of hypertensive controls (P < 0.0001). In both groups, hypertensive subjects were older than normotensive subjects. Systolic (SBP) and diastolic blood pressures (DBP) in hypertensive acromegalic patients were lower and higher, respectively, than in hypertensive controls. The risk of hypertension increased with age and was higher in the patients than in the controls [hazard ratio (HR) 1.9; P = 0.0002]. Independent predictors of SBP were age and glucose in the acromegalic population, and BMI, age and glucose levels in the controls. Independent predictors of DBP were age and glucose in the patients, and BMI, age and IGF-I in the controls.

CONCLUSIONS

In acromegaly, hypertension is more frequent than in the general population, involves predominantly DBP, and occurs earlier, is not related to gender, and is less frequently related to family history of hypertension and IGF-I levels. IGF-I may have a protective role for DBP in the general population.

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.

Cardiac Abnormalities in Acromegaly

Cardiovascular disease is claimed to be one of the most severe complications of acromegaly, contributing significantly to mortality in this disease. In fact, an excess of growth hormone (GH) and insulin-like growth factor 1 (IGF-I) causes a specific derangement of cardiomyocytes, leading to abnormalities in cardiac muscle structure and function, inducing a specific cardiomyopathy. In the early phase of acromegaly the excess of GH and IGF-I induces a hyperkinetic syndrome, characterized by increased heart rate and increased systolic output. Concentric hypertrophy is the most common feature of cardiac involvement in acromegaly, found in more than two thirds of patients at diagnosis. This abnormality is commonly associated with diastolic dysfunction and eventually with impaired systolic function ending in heart failure, if the GH/IGF-I excess is left untreated. In addition, abnormalities of cardiac rhythm and of heart valves have also been described in acromegaly. The coexistence of other complications, such as arterial hypertension and diabetes mellitus, aggravates acromegalic cardiomyopathy. Successful control of acromegaly induces a decrease in left ventricular mass and an improvement in diastolic function, while the effects of GH/IGF-I suppression on systolic function are more variable. However, since cardiovascular alterations in young patients with short disease duration are milder than in those with longer disease duration, it is likely to be easier to reverse and/or arrest acromegalic cardiomyopathy in young patients with early-onset disease. In conclusion, careful assessments of cardiac function, morphology, and activity are required in patients with acromegaly. An early diagnosis and prompt effective treatment are important in order to reverse acromegalic cardiomyopathy.

Pathogenesis and prevalence of hypertension in acromegaly

Hypertension is an important complication of acromegaly, contributing to the increased morbidity and mortality of this condition. Prevalence of hypertension in acromegalic patients is about 35%, ranging from 18 to 60% in different clinical series, and the incidence is higher than in the general population. The lowering of blood pressure observed concomitantly with the reduction in GH levels after successful therapy for acromegaly suggests a relationship between GH and/or IGF-I excess and hypertension. The exact mechanisms underlying the development of hypertension in acromegaly are still not clear but may include several factors depending on the chronic exposure to GH and/or IGF-I excess. Experimental and clinical studies suggest that the anti-natriuretic action of GH (due to direct renal action of GH or IGF-I and/or to indirect, systemic GH or IGF-I-mediated mechanisms) may play a role in the pathogenesis of hypertension. Acromegaly is frequently associated with insulin resistance and hyperinsulinaemia which may induce hypertension by stimulating renal sodium absorption and sympathetic nervous activity. Whether sympathetic tone is altered in acromegalic hypertensive patients remains a matter of debate. Recent studies indicate that an increased sympathetic tone and/or abnormalities in the circadian activity of sympathetic system could play an important role in development and/or maintenance of elevated blood pressure in acromegaly, and may partially account for the increased risk of cardiovascular complications. Acromegalic cardiomiopathy may also concur to elevate blood pressure and can be aggravated by the coexistence of hypertension. Finally, a role of GH and IGF-I as vascular growth factors cannot be excluded. In conclusion, acromegaly is associated with hypertension, but there is still no real consensus in the literature on the mechanisms behind the development of the high blood pressure.

Relationship between blood pressure and glucose tolerance in acromegaly

BACKGROUND

Hypertension represents a well-known risk factor for cardiovascular diseases. The pathogenesis of hypertension in acromegaly is commonly viewed as multifactorial, but the possible influence of metabolic disorders on blood pressure (BP) in affected patients is largely unknown.

OBJECTIVE

The aim of the present study was to evaluate the impact of glucose metabolism abnormalities on BP values in a series of patients with active acromegaly.

DESIGN

An open multicentre prospective study.

PATIENTS

Sixty-eight patients with active disease, aged 47.5 +/- 11.7 years, have been studied. Thirty-nine had normal glucose tolerance (NGT), 16 impaired glucose tolerance (IGT) and 13 suffered from diabetes mellitus (DM).

MEASUREMENTS

Mean clinical BP values were calculated as the mean of BP values obtained by sphygmomanometric measurement in three separate occasions and mean 24-h, diurnal and nocturnal systolic (SBP) and diastolic (DBP) values were obtained by 24-h ambulatory blood pressure monitoring (ABPM).

RESULTS

Patient's age and the degree of glucose tolerance abnormalities were found to significantly and independently influence BP values. All clinical and ABPM SBP and DBP values significantly increased with age by linear regression (P < 0.02 for all BP values, 0.30 < or = R < or = 0.43), and the independent influence of this parameter on BP values was confirmed by mutivariate analysis. Similarly, the independent influence of glucose tolerance abnormalities on BP values was confirmed when introducing age as a covariable in a multivariate analysis, and patients with DM presented significantly higher clinical SBP and 24-h, diurnal and nocturnal SBP and DBP than patients with NGT (P < 0.02 for clinical SBP, P < 0.015 for all ABPM values, respectively). In addition, patients with DM showed significantly higher 24-h, diurnal and nocturnal DBP than those with IGT (P < 0.05 in all cases). In contrast, no significant difference was found between NGT and IGT patients. No significant influence of disease duration, BMI, GH, IGF-I, or fasting and 2-h post glucose load insulinaemia on BP values was observed.

CONCLUSIONS

Abnormalities of glucose metabolism significantly contribute to increase systolic blood pressure and especially diastolic blood pressure in acromegalic patients. Careful control of blood pressure and of risk factors for developing systemic hypertension, with special reference to glucose tolerance, is mandatory to decrease cardiovascular morbidity and mortality in such patients.