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Query: UMLS:C0020538 (hypertension)
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Hyperinsulinemia and insulin resistance have been postulated to link obesity and hypertension. Evidence supporting this concept derives mainly from epidemiological studies showing a correlation between insulin resistance, hyperinsulinemia, and blood pressure and from short-term studies suggesting that insulin has renal and cardiovascular actions that, if sustained, could elevate blood pressure. However, a cause-and-effect relation between insulin and hypertension has not been clearly established. Recent studies indicate that chronic hyperinsulinemia, similar to that found in obese hypertensive patients, did not raise blood pressure in normal dogs, even when renal excretory capability was reduced by prior removal of kidney mass. Chronic insulin infusion also failed to elevate blood pressure in dogs maintained on a high sodium intake and did not potentiate the long-term blood pressure responses to angiotensin II or norepinephrine. The presence or absence of insulin resistance may not be a major factor in determining the blood pressure response to hyperinsulinemia since chronic insulin infusion also failed to cause hypertension in obese, insulin-resistant dogs. Although hyperinsulinemia causes transient sodium retention, sustained decreases in renal excretory capability sufficient to cause chronic hypertension did not occur in dogs. In rats, insulin infusion causes small increases in blood pressure, although several characteristics of the hypertension (e.g., salt-sensitivity) differ from those observed in obese human hypertensive patients. Whether humans more closely resemble dogs or rats with respect to their long-term cardiovascular responses to insulin remains to be determined. However, very high insulin levels in humans with insulinoma do not cause hypertension, and several studies suggest that there is only a weak correlation between plasma insulin concentration and blood pressure in normal humans. Therefore, additional factors besides hyperinsulinemia per se may be responsible for a major component of obesity-associated hypertension.
Hypertension 1992 Jan
PMID:Obesity-associated hypertension. Hyperinsulinemia and renal mechanisms. 173 Apr 54

Essential hypertension is often accompanied by metabolic abnormalities which commonly include hyperinsulinemia/insulin resistance. Even in the absence of these metabolic disorders, high blood pressure tends to be associated with insulin resistance. These observations raise two orders of questions: 1) whether hyperinsulinemia and insulin resistance are simply innocent bystanders or are causally involved in the initiation and/or promotion of hypertension; 2) whether blood pressure elevation is eventually caused by excess of insulin or whether it is a manifestation of the complex metabolic state responsible for insulin resistance. The purpose of this paper is to survey the clinical, epidemiological and experimental data that have led to the above generalizations and to address the potential significance of this coexistence. First, it could be argued that the relationship between high blood pressure and the associated metabolic defects is incidental. In this case, insulin resistance and hypertension may represent two independent consequences of a same metabolic disorder. On the other hand, there is evidence that suggests that insulin resistance (by itself or by insulin) may play a role in the etiology and/or the clinical course of hypertension. Although insulin has complex actions on the circulation (including a vasodilator effect), plausible mechanisms by which insulin might raise blood pressure include stimulation of the sympathetic nervous system, alteration of ion transport kinetics, increase of renal sodium retention and stimulation of vascular smooth cells growth. The pathways that could link insulin resistance, through hyperinsulinemia, with essential hypertension are based on the concept that a defect of insulin action on glucose utilization, does not imply that all other effects of insulin are equally blunted. However, in patients with insulinoma, hypertension has not been associated, and the acute administration of insulin does not cause an increase in blood pressure. It is also possible, on the contrary, that hypertension may be the cause of insulin resistance, but in various forms of secondary hypertension, impaired insulin sensitivity has not been found. It is probable that insulin resistance may represent, in a subgroup of individuals characterized by genetic predisposition (ethnicity, familiarity, etc.), simply a marker for susceptibility to hypertension. Hyperinsulinemia, in these subjects, may directly contribute to a raise in blood pressure by several mechanisms. In conclusion, despite the clinical importance of this association the nature of the relationship between insulin resistance and blood pressure remains obscure. Since hypertension does not develop in all insulin resistant subjects and hyperinsulinemia does not always cause a raise in blood pressure, the relationship must be modulated by other genetic or environmental factors.
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PMID:[Hyperinsulinism/insulin resistance: cause, effect or marker of essential arterial hypertension?]. 764 26

Hypertension is a well-recognized complication of obesity. However, the mechanisms for the development of obesity hypertension are not known. One mechanism proposed is that the hyperinsulinemia present in obese hypertensive patients causes hypertension via sodium retaining and/or sympathetic nervous system stimulatory effects. However, numerous studies in dogs have revealed no evidence for such chronic pressor actions of hyperinsulinemia. This is in close agreement with studies in human insulinoma patients that show marked hyperinsulinemia and normal blood pressure. The appropriateness of the dog as an experimental model is strengthened by reports from our laboratory and others that inducing obesity in dogs reproduces many of the characteristics of obesity in humans, including insulin resistance, hyperinsulinemia, sodium retention, hypertriglyceridemia and hypertension. Recent studies in obese dogs have indicated that significant increases in renal medullary cellularity and intercellular matrix deposition could contribute to the sodium retention and hypertension. Additional evidence suggests that sympathetic nervous system stimulation also may contribute to the elevated blood pressure. However, the mechanisms through which obesity induces these changes and the temporal relationship between these factors and the development of the hypertension remains to be determined.
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PMID:Obesity and hypertension: roles of hyperinsulinemia, sympathetic nervous system and intrarenal mechanisms. 778 35

Hyperinsulinaemia and insulin resistance have been hypothesized to be the common pathophysiological factor of hypertension, NIDDM and obesity. To evaluate the possible role of hyperinsulinaemia and insulin resistance on hypertension, we studied a group of 37 patients with insulinoma who were admitted to our department in the period from 1966 to 1990. We recorded blood pressure and assayed blood glucose, plasma insulin, plasma triglycerides and serum uric acid levels, before and after surgery, in these patients and in a 37-subject control group. No significant increase in blood pressure and triglyceride plasma levels was recorded in the chronic hyperinsulinaemic hypoglycaemic patients, suggesting the lack of a direct role of hyperinsulinaemia on hypertension.
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PMID:Effect of endogenous organic hyperinsulinaemia on blood pressure and serum triglycerides. 808 12

Hyperinsulinemia has been assumed to contribute to the pathogenesis of atherosclerosis. To assess the reliability of such claim we planned a retrospective study on a cohort of patients with pancreatic insulin producing neoplasm. A correlation was sought between fasting insulin plasma levels and the metabolic profile emerging from those parameters known to be cardiovascular risk factors, i.e. plasma triglycerides and cholesterol, insulin resistance, hypertension. Special attention was paid to the duration of disease, because the time exposure to hyperinsulinemia could play an important role in developing cardiovascular disease. Seventy patients, 41 females and 29 males, aged 44.9 +/- 1.96 yr (range 15-80), with surgically proved insulinoma were included in the study. Chronic exposure to hyperinsulinemia was documented through the measurement of insulin plasma levels either in the fasting state or post-prandially, resulting in 44.7 +/- 3.28 and 149.9 +/- 12.22 microU/ml, respectively. Fasting glycemia in average was 45.3 +/- 1.34 mg/dl. Plasma triglycerides and cholesterol concentrations were 136.3 +/- 7.93 and 195.8 +/- 5.18 mg/dl, respectively, their distribution overlapping that anticipated for the general population. No correlation arose between the degree of hyperinsulinemia and the lipidic profile. Preoperative blood pressure was 136.9 +/- 2.87 mmHg, systolic and 81.9 +/- 1.32 mmHg, diastolic. Hypertension was present in 5 (7.1%) out of 70 patients and persisted after tumor removal. A condition of insulin resistance (M = 4.06 +/- 0.4 mg/kg min vs 7.41 +/- 0.21) was documented through the euglycemic hyperinsulinemic clamp technique in 20 patients and showed a positive and significant correlation with fasting insulinemia.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Absence of clinically overt atherosclerotic vascular disease and adverse changes in cardiovascular risk factors in 70 patients with insulinoma. 814 64

Hyperinsulinemia is alleged to contribute to the pathogenesis of hypertension and dyslipidemia (hypertriglyceridemia) in the setting of insulin resistance. To assess the association among hyperinsulinemia, hypertension, and hypertriglyceridemia in the absence of insulin resistance, we determined their prevalence in a large cohort of patients with insulinoma (N = 250). In this retrospective case-control study, patients with insulinoma were matched by age, gender, race, and year of operation with 217 control patients admitted to the hospital for elective cholecystectomy. Mean preoperative blood pressure measurements were compared between study patients and control patients. In addition, age-, gender-, and race-specific percentiles of blood pressure were compared with data from the National Health and Nutrition Examination Survey I, and those of triglycerides (N = 65) and cholesterol (N = 70) were compared with Mayo Clinic normal reference data. The study group consisted of 105 men and 145 women; the median age was 41 years (range, 8 to 82). The median duration of symptoms before operation was 1.9 years (range, 0.05 to 40 years). After adjustment for body mass index, no statistically significant differences in systolic and diastolic blood pressure were noted between patients with insulinoma and matched control patients (131 +/- 19 versus 128 +/- 18 mm Hg and 81 +/- 11 versus 79 +/- 9 mm Hg, respectively). No relationship was observed between duration of hyperinsulinemia (as long as 40 years) and blood pressure. The age- and gender-specific percentiles of systolic and diastolic blood pressure of the patients with insulinoma did not differ from the age- and gender-specific percentiles for the general white population.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Hypertension and dyslipidemia in patients with insulinoma. 842 94

Hypertension and diabetes mellitus are common chronic conditions which frequently coexist. Diabetic nephropathy is a major cause of elevated blood pressure in patients with insulin-dependent diabetes mellitus (IDDM). Diabetic nephropathy, arterial sclerosis, obesity and association of essential hypertension can be the causes of hypertension in patients with non-insulin-dependent diabetes mellitus (NIDDM). Ambulatory blood pressure monitoring has revealed that the nocturnal fall of blood pressure is blunted in patients with diabetic nephropathy. A blunted diurnal blood pressure variation is seen in microalbuminuric diabetic patients and even in some normoalbuminuric patients. Accumulating data suggest that normalisation of blood pressure in hypertensive IDDM patients is most important to minimise the loss of kidney function. Angiotensin converting enzyme (ACE) inhibitors have been reported to be effective in postponing the development of nephropathy and in slowing its progression. Whether only ACE inhibitors have such beneficial renal effects on diabetic nephropathy is under discussion. While many studies have suggested that insulin resistance and hyperinsulinaemia are related to an elevated blood pressure in hypertensive patients, there does not seem to be enough evidence to prove that insulin per se can raise blood pressure in humans. Neither an insulin infusion within a physiological range nor sustained hyperinsulinaemia and insulin resistance (e.g. patients with insulinoma, cystic ovary syndrome) have been associated with an elevated blood pressure. Insulin resistance in some hypertensive patients may be a consequence of a decreased blood flow due to an increased peripheral resistance. Preliminary evidence suggests that low birth weight or impaired fetal growth is related to hypertension and NIDDM. Familial clustering of diabetic nephropathy suggests the contribution of genetic susceptibility and/or environmental inheritance. The frequent association of nephropathy with hypertension has led to research on the genes related to hypertension (ACE, angiotensinogen). Nevertheless, to date no reliable and clinically useful genetic marker has been found. Attempts to correct the metabolic abnormalities derived from diabetes are a new topic in the treatment of diabetic nephropathy. The effects of HMG CoA reductase inhibitors (antihypercholesterolaemic drugs), aldose reductase inhibitors (inhibitors of the polyol pathway) and glycation inhibitors (inhibitors of formation of advanced glycosylation end-products) on diabetic nephropathy have been evaluated in animal studies and in some clinical trials. Thus far, results with HMG CoA reductase and aldose reductase inhibitors have been somewhat conflicting. The potential therapeutic role of glycation inhibition in the treatment of diabetes deserves further study.
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PMID:Diabetic nephropathy. Its relationship to hypertension and means of pharmacological intervention. 925 79

Central or visceral obesity is recognized as a main risk factor for cardiovascular disease and type 2 diabetes mellitus. The co-existence of visceral obesity, increased blood lipid levels, hypertension and impaired glucose tolerance defines the metabolic syndrome that today is widely recognized as one of the prime factors behind cardiovascular morbidity and mortality. Endocrine disorders such as insulinoma, hypothyroidism and hypercortisolism are known to cause obesity. However, it is only hypercortisolism that is associated with increased abdominal fat accumulation. Recently, new findings have shed light on subtle endocrinopathies that are prevalent in individuals presenting with the metabolic syndrome. Such derangements are of borderline character and often fall within the normal reference range. Intervention studies demonstrate that correction of relative hypogonadism in men with visceral obesity and other manifestations of the metabolic syndrome seem to decrease the abdominal fat mass and reverse the glucose intolerance, as well as lipoprotein abnormalities in the serum. Further analysis of the underlying mechanism has also disclosed a regulatory role for testosterone in counteracting visceral fat accumulation. Longitudinal epidemiological data demonstrates that relatively low testosterone levels are a risk factor for development of visceral obesity. The primary event that triggers the initial development of visceral obesity is not known, but it seems plausible that increased activity in the hypothalamus-pituitary-adrenal axis can be of major importance.
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PMID:Androgens and abdominal obesity. 1033 65

The preoperative evaluation and safe anesthetic treatment of patients with endocrine gland tumors mandate an understanding of the physiologic dysfunctions attributable to these tumors. Some patients will exhibit various signs and symptoms characteristic of the MEN syndromes. In the patient with acromegaly, a fiberoptic-guided intubation of the trachea to secure the airway before induction of general anesthesia must be anticipated. Anesthetic treatment of the patient with hyperadrenocorticism requires knowledge of the physiologic effect of excess cortisol. In the patient with severe hyperparathyroidism, we attempt to correct the markedly elevated plasma calcium levels and maintain adequate hydration and urine output perioperatively. Following thyroidectomy for MCT, 2 potential problems of concern are upper airway obstruction and aspiration resulting from injury (unilateral or bilateral) to the recurrent laryngeal nerve and the superior laryngeal nerve, respectively. The major focus during excision of an insulinoma is prevention of wide swings in blood glucose concentrations. In the gastrinoma patient, the anesthesiologist not only must correct any intravascular fluid volume deficit or electrolyte imbalance but must also consider the patient to have a full stomach at the time of anesthetic induction. Correction of hypokalemia and control of hypertension may be required in the preoperative preparation of the patient with an adrenal cortex tumor. Preoperative alpha-adrenergic blockade must be initiated in the patient with a pheochromocytoma to prevent dangerous elevations in blood pressure during anesthesia and surgery for the tumor's removal. Vasodilators with rapid onset and short duration are used to treat intraoperative hypertension. After ligation of the tumor's blood supply, falls in blood pressure may require treatment with fluids and vasopressors. Carcinoid syndrome patients should be treated with somatostatin to prevent stimuli such as anxiety, abdominal scrubbing, or tumor manipulation from precipitating severe hypotension, hypertension, bronchospasm, or tachycardia. In both pheochromocytoma and carcinoid patients, a smooth anesthetic induction and tracheal intubation plus avoidance of drugs that release histamine or activate the sympathetic nervous system may also prevent intraoperative crises.
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PMID:Anesthetic implications for surgical patients with endocrine tumors. 1081 14

Larger studies had shown improved patient outcome and lower probability of coronary artery disease in insulin treated groups. The classical lipid abnormalities associated with type 2 diabetes are low HDL-cholesterol concentration and high triglyceride concentration. Insulin usage leads to a decrease in triglyceride concentration, primarily by its effect on the enzyme adipose tissue lipoprotein lipase. Insulin suppresses the enzyme, thereby controlling lipolysis in uncontrolled diabetes. Insulins therapy also improves the endothelial dysfunction especially in people with evident macrovascular complications. Though insulin is noted to increase adrenergic tone and may cause elevation of blood pressure, still patients with insulinoma do not have high blood pressure. Some studies suggest weight gain with insulin therapy, others contradict it. One study suggests that insulin does not affect treatment satisfaction. Insulin is known to improve the glycaemic scenario and also the insulin secretory pattern by reducing the glucotoxicity.
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PMID:Insulin therapy--role beyond glucose control. 1588 27


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