Altered circadian blood pressure profile in patients with active acromegaly. Relationship with left ventricular mass and hormonal values

HOMA-IR in acromegaly: a systematic review and meta-analysis

PURPOSE

This review is aimed at examining whether the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) is higher in Caucasian, adult, treatment-naïve patients with acromegaly (ACRO) than in the reference population independently of diabetes presence and to evaluate the impact of treatment [surgery and somatostatin analogues (SSAs)] on its assessment.

METHODS

We systematically reviewed in PubMed and Web of Science from July 1985 to December 2019, registered with the code number CRD42020148737. The inclusion criteria comprised studies conducted in Caucasian adult treatment-naïve patients with active ACRO in whom HOMA-IR or basal insulin and glucose were reported. Three reviewers screened eligible publications, extracted the outcomes, and assessed the risk of biases.

RESULTS

Of 118 originally selected studies, 15 met the inclusion criteria. HOMA-IR was higher in ACRO than the reference population, with mean difference and (95% confidence intervals) of 2.04 (0.65-3.44), even in ACRO patients without diabetes, 1.89 (1.06-2.73). HOMA-IR significantly decreased after treatment with either surgery or SSAs - 2.53 (- 3.24- - 1.81) and - 2.30 (- 3.05- - 1.56); respectively. However, the reduction of HOMA-IR due to SSAs did not improve basal glucose.

CONCLUSION

HOMA-IR in treatment-naïve ACRO patients is higher than in the reference population, even in patients without diabetes. This finding, confirms that insulin resistance is an early event in ACRO. Our results also suggest that HOMA-IR is not an adequate tool for assessing insulin resistance in those patients treated with SSAs.

Acromegaly: The Research and Practical Value of Noninvasive Hemodynamic Assessments via Impedance Cardiography

BACKGROUND

Arterial hypertension (AH) that accompanies acromegaly (AC) may lead to cardiovascular dysfunction. Such consequences may be detected with impedance cardiography (ICG), which is a noninvasive method of hemodynamic assessment. Early detection of subclinical hemodynamic alterations in AC patients may be crucial for optimizing treatment and preventing cardiovascular remodeling. The purpose of this study was to identify the hemodynamic parameters of the cardiovascular system that differentiate patients with AC from those in the control group (CG), with a particular emphasis on potential targets for medical therapy.

METHODS

This observational, prospective, clinical study involved a comparative analysis of 33 AC patients with no significant comorbidities and the controls selected via propensity score matching based on a set of baseline characteristics (age, sex, body mass index, mean blood pressure [MBP]), with comparable proportions of AH patients. The assessed hemodynamic parameters included the stroke volume index (SI), cardiac index, systemic vascular resistance index, velocity index (VI), acceleration index, Heather index (HI), and thoracic fluid content (TFC).

RESULTS

Both the AC group and the CG had well-controlled AH (mean blood pressure of 121/77 mmHg and 119/76 mmHg, respectively). In terms of baseline characteristics, the AC group was characterized by a higher hear rate and lower creatinine levels than the CG (76.2 bpm vs. 66.8 bpm [p = 0.001] and 0.755 mg/dL vs. 0.850 mg/dL [p = 0.035], respectively). ICG assessment of AC patients and CG patients showed the former to have higher heart rates (73.5 bpm vs. 65.2 bpm; p = 0.003), lower SI (43.8 mL/m² vs. 53.4 mL/m²; p = 0.0001), lower VI (42.1 1/1000/s vs. 49.3 1/1000/s; p = 0.037), lower HI (8.49 Ohm/s² vs. 13.4 Ohm/s², p ≤ 0.0001), and higher thoracic fluid content (TFC) (38.4 1/kOhm vs. 28.1 1/kOhm; p ≤ 0.0001), respectively.

CONCLUSIONS

Even with well-controlled hypertension, AC is associated with a high TFC, increased heart rate, and decreased indices of cardiac contractility. Hemodynamic changes in AC patients may be detected with the modern, noninvasive diagnostic tool, ICG.

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.

Clinical Conditions and Predictive Markers of Non-Dipper Profile in Hypertensive Patients

Hypertension remains one of the primary causes of premature cardiovascular mortality representing a major independent risk factor.

The importance of ambulatory blood pressure monitoring in clinical evaluation of hypertensive patients, beyond diagnosis, is the identification of circadian dipping/non-dipping profile. The non-dipper pattern in hypertensive and normotensive patients is associated with significant target organ damage and worse outcomes, as an increased cardiovascular risk condition. Non-dipping pattern has been found to be associated with specific clinical conditions. Obesity, diabetes mellitus, metabolic syndrome, obstructive sleep apnea syndrome, chronic kidney disease, autonomic and baroreflex dysfunctions, salt sensitivity, hormonal changes, gender and age were extensively studied. Research efforts are focused on recognizing and exploring predictive markers of abnormal blood pressure circadian pattern. Previous studies acknowledge that red cell distribution width, mean platelet volume, fibrinogen level, C-reactive protein, serum uric acid and gamma-glutamyltransferase, are independently significant and positive associated to non-dipping pattern. Moreover, research on new biomarkers are conducted: Chitinase 3-Like-Protein 1, atrial and B-type natriuretic peptide, brain-derived neurotrophic factor, chemerin, sphingomyelin and the G972R polymorphism of the insulin receptor substrate-1 gene. This review summarizes the current knowledge of different clinical conditions and biomarkers associated with the non-dipper profile in hypertensive patients.

The beneficial effect of acromegaly control on blood pressure values in normotensive patients

OBJECTIVE

Control of acromegaly may ameliorate blood pressure (BP) in hypertensive (HT) patients. We evaluated the impact of acromegaly control on BP values of normotensive (NT) acromegalics.

DESIGN

Retrospective cohort study.

PATIENTS

Fifty-eight naïve patients with acromegaly (39 F; age range, 30-69 years), including 28 NT and 30 HT subjects, participated in the study.

MEASUREMENTS

Blood pressure was measured by clinical measurement and 24-h ambulatory monitoring at diagnosis and after 24 months of medical therapy for acromegaly.

RESULTS

Acromegaly was controlled by medical therapy in 15 NT and 17 HT patients at 24 months. In the NT group, systolic (SBP) or diastolic (DBP) BP significantly increased (all P < 0·005) when acromegaly was uncontrolled, but did not change when the disease was controlled. Changes in SBP and DBP were also significantly different between uncontrolled and controlled NT patients. At 24 months, clinical hypertension was detected only in uncontrolled NT patients (46% vs 0%, P < 0·001), whereas ambulatory hypertension was found in 38% of uncontrolled and in 7% of controlled NT subjects (P = 0·035). In the HT group, ambulatory SBP increased in patients with uncontrolled acromegaly (24-h SBP P = 0·046, day SBP P = 0·005, night SBP P = 0·005), whereas ambulatory DBP decreased in subjects with controlled disease (24-h DBP P = 0·008, day DBP P = 0·026).

CONCLUSIONS

Control of acromegaly has a beneficial effect on BP regulation either in HT or NT subjects; in the latter, it may prevent progression towards hypertension.

Causes and mechanisms of nondipping hypertension

Growing evidence indicates that nondippers have worsened cardiovascular outcomes than dippers. Ambulatory blood pressure monitoring with a lack of nocturnal BP fall (nondipping) have also been shown to be more closely associated with target organ damage and worsened cardiovascular outcome than in patients with essential hypertension with dipping pattern. The underlying pathogenetic mechanisms potentially linking nondipping with cardiovascular disease are not fully understood. There are multiple possible underlying pathophysiologic mechanisms in the impaired BP decline during the night. Extrinsic and intrinsic factors including abnormal neurohormonal regulation, lack of physical activity, nutritional factors such as increased dietary sodium intake, and smoking of tobacco have been implicated for blunted circadian rhythm of BP. Certain diseases such as diabetes and chronic renal diseases also affect the circadian BP rhythm. Currently, the clinical importance of nondipping is known well; however, the relationship between certain disease states and nondipping has not been fully explained yet. This paper will attempt to address to clarify the underlying basis for nondipping and the specific associations with various disease states.

GH and IGF-I excess control contributes to blood pressure control: results of an observational, retrospective, multicentre study in 105 hypertensive acromegalic patients on hypertensive treatment

CONTEXT

Approximately one-third of patients with acromegaly have concomitant hypertension. The outcome of hypertension after treatment of acromegaly is unknown.

OBJECTIVE

To evaluate the role of GH and IGF-I control on systolic (SBP) and diastolic blood pressure (DBP) levels.

PATIENTS

One hundred and five hypertensive patients (60 women, 45 men) with active disease receiving treatment for hypertension at their diagnosis of acromegaly.

DESIGN

Observational, retrospective, multicentre.

MEASUREMENTS

At diagnosis and after 24 months (median) of treatment we measured serum GH and IGF-I levels, blood pressure levels, left ventricular (LV) mass index (LVMi), early-to-late mitral flow velocity (E/A, as a measure of diastolic function) and LV ejection fraction (LVEF, as a measure of systolic function).

RESULTS

At the diagnosis of acromegaly, hypertension was mild in 41.1% and severe in 58.9%. Serum GH and IGF-I levels did not differ in patients with mild or severe hypertension. After 24 months of treatment, all patients had a notable decrease in both GH and IGF-I levels, and achieved significantly lower levels of DBP, heart rate and LVMi; 76 patients (71%) had achieved control of GH and IGF-I levels. Only the patients with controlled acromegaly achieved significantly lower SBP levels and significantly improved cardiac systolic and diastolic function. A higher dose of antihypertensive drugs and/or an increased number of drugs to control hypertension were significantly greater in patients with uncontrolled (32.3%) than in those with controlled acromegaly (7.8%; P = 0.004).

CONCLUSION

Hypertensive patients with controlled acromegaly achieved improved control of hypertension and of cardiac diastolic and systolic function. The use of antihypertensive drugs was significantly less in patients achieving control of acromegaly.

Identification, treatment and management of cardiovascular risks in patients with acromegaly

Acromegaly, a syndrome related to growth hormone/IGF-1 excess, is frequently complicated by cardiovascular abnormalities (acromegalic cardiomyopathy). Extremely frequent are left ventricular hypertrophy and alterations of diastolic filling, which may progress to systolic dysfunction and eventually heart failure. Cardiac abnormalities may normalize after successful medical or surgical treatment of acromegaly, particularly in young patients with short-lasting disease, but this is less likely to occur in elderly patients. Both hypertension and cardiac valve disease are frequently encountered in acromegaly, but neither seems to be favorably influenced by disease control. The prevalence of coronary heart disease (CHD) is controversial but is probably not increased in acromegaly. Arrhythmias are relatively common in untreated acromegalic patients, although their clinical relevance is unknown. A cardiac evaluation of acromegalic patients should include echocardiography, basal electrocardiogram and blood pressure measurement, and evaluation of common risk factors for CHD. Appropriate and prompt treatment allowing a rapid control of growth hormone/IGF-1 hypersecretion is warranted because many features of acromegalic cardiomyopathy may be reverted, particularly in younger patients. In view of the lack of association with acromegaly, common risk factors for CHD, hypertension, arrhythmias or valve disease should be managed independently, irrespective of control of disease activity.

Assessment of the awareness and management of cardiovascular complications of acromegaly in Italy. The COM.E.T.A. (COMorbidities Evaluation and Treatment in Acromegaly) Study

BACKGROUND

During the course of acromegaly, cardiovascular, respiratory, and metabolic co-morbidities contribute to enhanced mortality. In 2002, the Pituitary Society and the European Neuroendocrine Association sponsored a Consensus Workshop in Versailles during which guidelines for diagnosis and treatment of co-morbidities in acromegaly were defined. However, as for other guidelines previously issued in the field, no data are available on their clinical application.

AIM

The aim of this work coordinated by the Italian Study group on co-morbidities evaluation and treatment in acromegaly (COM.E.T.A.) was to assess, on a national basis, the application in the clinical practice of the Versailles criteria for diagnosis and treatment of cardiovascular comorbities in acromegaly.

MATERIALS AND METHODS

In January 2007 an ad hoc designed questionnaire was sent by mail to 130 endocrine Centers in Italy.

RESULTS

The guidelines have been generally well perceived and translated in clinical practice. Specifically: 1) echocardiography is considered the mainstay for the diagnosis and follow-up; 2) ambulatory blood pressure monitoring and blood lipid assessment are performed in most hypertensive patients; 3) most endocrinologists directly manage hypertension and are aware of the uncertainty of the effect of the control of the disease on blood pressure levels; 4) ACE inhibitors and angiotensin receptors blockers are first-choice anti-hypertensive treatment; 5) approximately half of the centers consider somatostatin analogues of paramount relevance for biochemical control of disease; 6) awareness that left ventricular hypertrophy and heart failure are the most relevant cardiovascular complications is high although the impact of ischemic, arrhythmic, and valvular complications on prognosis is less well perceived.

CONCLUSION

The results of the present survey suggest that previuosly issued guidelines are generally carefully followed in the clinical practice. On the other side, a certain lack of awareness of emerging aspects of the cardiovascular comorbities of acromegaly confirms the necessity of periodically updating the guidelines based on the availability of new clinical information.

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.

Acute and chronic effects of growth hormone on renal regulation of electrolyte and water homeostasis

For decades, growth hormone (GH) has been known to influence electrolyte and water handling in humans and animals. However, the molecular mechanisms underlying the GH-induced anti-natriuretic and anti-diuretic effects have remained elusive. This review will examine the existing literature on renal electrolyte and water handling following acute and chronic GH-exposure. Renal responses to GH differ in acute and chronic models. Acute application of GH results in a reduced urinary electrolyte and water excretion, whereas the chronic effects of GH are more diverse, as this state likely represents a complex mixture of primary and secondary actions of GH as well as compensatory mechanisms. During chronic GH-exposure an initial sodium retaining state often occurs, followed by a normalization of the urinary sodium excretion, although extracellular volume expansion still persists. We recently described a possible mechanism by which GH acutely increases renal electrolyte and water reabsorption, by modulation of the kidney specific Na(+), K(+), 2Cl(-) co-transporter (NKCC2). The primary aim of this review is to investigate how GH-induced regulation of NKCC2 may be involved in the complex renal changes previously described during acute and chronic GH. We propose, that the GH-induced increase in NKCC2 activity may explain the initial water and sodium retention seen in a number of studies. Moreover, renal changes seen during prolonged GH-exposure may now be seen on the background of the acute stimulation of NKCC2. Additionally, GH also promotes renal acidification, thus influencing renal acid/base handling. The GH-induced renal acidification is partly compatible with changes in NKCC2 activity. Finally, we review the available data on changes in hormonal systems affecting tubular transport during acute and chronic GH-exposure.

CYP11B2 -344T/C gene polymorphism and blood pressure in patients with acromegaly

CONTEXT

The pathogenesis of increased blood pressure (BP) in acromegaly is unclear, and the role of IGF-I levels and the renin-angiotensin-aldosterone system (RAAS) in this disease remains controversial.

OBJECTIVE AND DESIGN

The aim of this study was to investigate the role of gene polymorphisms of the RAAS and involved in sodium handling on BP in acromegaly.

SETTING AND PATIENTS

We conducted a multicentric retrospective study that included 100 consecutive patients with acromegaly referred during the period 2000-2003.

INTERVENTION

All patients were genotyped for ACE I/D, AGT M235T, CYP11B2 -344T/C, B2R -58T/C, and alpha-adducin G460W polymorphisms.

MAIN OUTCOME MEASURE

We assessed the prevalence of hypertension and BP according to the genotype.

RESULTS

Patients with the CYP11B2 -344CC genotype displayed a significant increase in the risk of hypertension compared with patients with CT/TT genotypes (odds ratio = 4.0; 95% confidence interval = 1.4-11.6; P = 0.01). Consistently, a significant proportion of patients with the CYP11B2 -344CC genotypes were under antihypertensive treatment (73.1%) compared with patients with the TT/TC genotypes (38.2%; P = 0.003). Patients with the -344CC genotype displayed a significant increase in systolic BP (10.2 +/- 4.3 mm Hg; P = 0.02) but not a significant increase in diastolic BP (2.6 +/- 2.6 mm Hg; P = 0.32) compared with patients with the CT/TT genotype.

CONCLUSIONS

We have shown an association of the -344T/C CYP11B2 gene polymorphism with BP in patients affected by acromegaly. These findings suggest that the RAAS is implicated in the pathogenesis of hypertension in acromegaly.

Acute growth hormone administration induces antidiuretic and antinatriuretic effects and increases phosphorylation of NKCC2

Growth hormone (GH) has antidiuretic and antinatriuretic effects in rats and humans, but the molecular mechanisms responsible for these effects are unknown. The aim of this study was to investigate the mechanisms behind the acute renal effects of GH in rats. Female rats received rat (r)GH (2.8 mg/kg sc) or saline and were placed in metabolic cages for 5 h. Urinary excretion of electrolytes and urinary volume were reduced after rGH injection, while urine osmolality was increased. Creatinine and lithium clearance remained unchanged, suggesting that rGH increases reabsorption in segments distal to the proximal tubule. Total plasma insulin-like growth factor I (IGF-I) levels did not change, while cortical IGF-I mRNA abundance was increased. The relative abundance of total and Ser(256)-phosphorylated aquaporin 2 was found to be unchanged by immunoblotting, whereas a significant increase of Thr(96) and Thr(101)-phosphorylated NKCC2 (renal Na(+), K(+), 2Cl(-) cotransporter) was found in the inner stripe of outer medulla thick ascending limbs (mTAL). Additionally, an increased NKCC2 expression was observed in the cortical region. Immunohistochemistry confirmed these findings. The density of NKCC2 molecules in the apical membrane of mTAL cells appeared to be unchanged after rGH injection evaluated by immunoelectron microscopy. Basolateral addition of rGH or IGF-I to microperfused rat mTAL segments did not change transepithelial voltage. In conclusion, GH appears to exert its acute antinatriuretic and antidiuretic effects through indirect activation of NKCC2 in the mTAL.

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.