Central Alpha-2 Adrenergic Function in Patients with Essential Hypertension

Giustina, Andrea; Doga, Mauro; Bossoni, Simonetta; Bodini, Corrado; Legati, Fabio; Pizzocolo, G; Romanelli, G

doi:10.1055/s-2007-1004944

Cited by 6 publications

(2 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In general, functional secretory capacity of the pituitary gland is large in humans; the finding of a normal growth hormone response to the administration of growth hormone-releasing hormone in HT patients 27 also does not support the possibility that secretory defect underlies different hormonal responses in HT and NT subjects. Several investigators 9,[28][29][30] proposed an important role of the nervous system in the aetiology and pathogenesis of essential hypertension, particularly of the abnormalities of the sympathetic nervous system in the early phases of hypertension.…”

Section: Discussionmentioning

confidence: 85%

“…40,41 This hypothesis is supported by the data showing decreased response of growth hormone to a central pre-synaptic alpha-2 adrenergic agonist clonidine in HT patients. 27,42 Clonidine stimulates growth hormone secretion from the pituitary gland through the endogenous release of growth hormone-releasing hormone by the hypothalamus. 43,44 Therefore, the decreased growth hormone response to hypoglycaemia seen in our study may be explained by the desensitization of alpha-2 adrenergic receptors on growth hormone-releasing hormone neurons in the hypothalamus.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Decreased pituitary response to insulin-induced hypoglycaemia in young lean male patients with essential hypertension

Rádiková

Penesová

Cizmárová³

et al. 2006

J Hum Hypertens

View full text Add to dashboard Cite

Essential hypertension is associated with changes in central catecholaminergic pathways which might also be reflected in the pituitary response to stress stimuli. The aim of this study was to determine whether the response of pituitary hormones, cortisol, plasma renin activity, aldosterone and catecholamines to insulininduced hypoglycaemia is changed in hypertension. We studied 22 young lean male patients with newly diagnosed untreated essential hypertension and 19 healthy normotensive, age-and body mass index (BMI)-matched controls. All subjects underwent an insulin tolerance test (0.1 IU insulin/kg body weight intravenously) with blood sampling before and 15, 30, 45, 60 and 90 min after insulin administration. Increased baseline levels of norepinephrine (Po0.05), increased response of norepinephrine (Po0.001) and decreased response of growth hormone (Po0.001), prolactin (Po0.001), adrenocorticotropic hormone (Po0.05) and cortisol (Po0.001) were found in hypertensive patients when compared to normotensive controls. Increased norepinephrine levels and a decreased pituitary response to metabolic stress stimuli may represent another manifestation of chronically increased sympathetic tone in early hypertension.

show abstract

Section: Discussionmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Decreased pituitary response to insulin-induced hypoglycaemia in young lean male patients with essential hypertension

Rádiková

Penesová

Cizmárová³

et al. 2006

J Hum Hypertens

View full text Add to dashboard Cite

show abstract

The inhibitory effect of glucose on growth hormone secretion is lost in obesity but not in hypertension

Limone

Oleandri

Catt

et al. 1997

J Endocrinol Invest

View full text Add to dashboard Cite

In obesity there is a clear reduction of both spontaneous and stimulated GH secretion. Furthermore, in obese patients the somatotrope responsiveness to provocative stimulation is selectively refractory to the inhibitory effect of glucose load. It has been hypothesized that hyperinsulinism of obese patients could play a role in the pathogenesis of these alterations. Aim of the present study was to verify the GH response to GHRH and the ability of glucose load to inhibit it in patients with essential hypertension in whom hyperinsulinism and insulin resistance are frequently present. To this goal, 7 patients with essential hypertension (HP, age, mean +/- SE: 29.6 +/- 2.4 yr, 3 females and 4 males, BMI: 21.7 +/- 1.2 kg/m2), 7 obese (OB, 4 females and 3 males, 31.9 +/- 4.1 yr, 35.6 +/- 2.0 kg/m2) and 7 normal subjects (NS, 4 females and 3 males, 28.3 +/- 3.9 yr, 21.0 +/- 1.6 kg/m2) underwent the following tests: GHRH (1 microgram/kg i.v. at time 0) alone and preceded by oral glucose load (OGTT, 100 g po at -45 min). Basal insulin levels were similar in HP and OB (11.3 +/- 0.5 and 12.7 +/- 2.2 microU/ml, respectively); these, in turn, were higher (p < 0.005) than those in NS (6.8 +/- 0.8 microU/ml). Basal plasma glucose levels in HP were similar to those in OB and NS (80.3 +/- 3.6, 86.9 +/- 6.7 and 84.4 +/- 1.7 mg/dl, respectively). In HP and OB and NS basal GH (1.0 +/- 0.5, 1.0 +/- 0.6 and 0.3 +/- 0.1 micrograms/l, respectively) and IGF-I levels (132.6 +/- 14.8, 137.3 +/- 13.2 and 138.8 +/- 12.2 micrograms/l, respectively) were similar. In HP the GH response to GHRH (AUC: 1058.8 +/- 347.8 micrograms/l/min) was similar to that observed in NS (959.0 +/- 167.8 micrograms/l/min) and higher than that in OB (344.8 +/- 67.2 micrograms/l/min, p < 0.01). OGTT clearly blunted (p < 0.01) the GHRH-induced GH response in HP as well as in NS (401.8 +/- 104.4 and 521.6 +/- 76.6 (g/l/min, respectively) but not in OB (387.4 +/- 78.8 (g/l/min). The OGTT-induced insulin levels in HP did not differ from those of OB, both being higher (p < 0.05) than those recorded in NS. Glucose levels after OGTT were similar in the three groups. In conclusion, this study demonstrates that, like in normal subjects but differently from in obese patients the GH response to GHRH is normal in patients with essential hypertension and it is normally inhibited by oral glucose load even when these patients show high insulin levels. Thus, it is unlikely that the low somatotrope secretion and its refractoriness to inhibition by glucose load in obesity is due to hyperinsulinism.

show abstract

Effect of two β2-agonist drugs, salbutamol and broxaterol, on the growth hormone response to exercise in adult patients with asthmatic bronchitis

Giustina

Malerba

Bresciani

et al. 1995

J Endocrinol Invest

View full text Add to dashboard Cite

The aim of our study was to evaluate the effect of the iv administration of two different beta 2- receptors agonists, salbutamol and broxaterol, on the growth hormone (GH) response to maximal exercise in 11 patients (8 males and 3 females; age range 18-65 yr; mean +/- SE age 56 +/- 13 yr; BMI 26.2 +/- 1.4 kg/m2) with chronic asthmatic bronchitis. All the subjects underwent four cycloergometric exercise tests (incremental workload until maximal predicted heart rate). At baseline, at maximal exercise, at the end of the recovery period and 60 min after the end of each exercise, blood samples were drawn for the assay of GH, glucose, insulin, lactates, norepinephrine and epinephrine. Two exercises were performed without treatment while the remaining two were performed 60 min after the administration of 400 micrograms of either salbutamol or broxaterol (both diluted in 10 ml of saline) according to a randomized double blind cross-over design. Both exercise tests performed without treatment caused a significant (p < 0.05) and similar GH peak with respect to baseline values (from 0.3 +/- 0.1 micrograms/L to 2.8 +/- 1.3 micrograms/L, mean of the two exercise tests). Salbutamol pretreatment blunted the GH response to exercise which caused a no more significant serum GH peak over the baseline levels (from 0.6 +/- 0.2 micrograms/L to 1.4 +/- 0.6 micrograms/L,). Moreover, broxaterol completely abolished the GH response to exercise (baseline level 0.6 +/- 0.2 micrograms/L; peak levels 0.4 +/- 0.1 micrograms/L). The serum GH peak after exercise + broxaterol was significantly (p < 0.05) lower as compared to exercise + salbutamol. In conclusion, we have demonstrated for the first time that beta 2 stimulation blunts the physiological GH response to maximal exercise in adult human subjects. It can be suggested that changes in brain neurotransmitters, possibly an increase in the alpha-adrenergic tone, are likely to be involved in this endocrine effects of exercise.

show abstract

Central Alpha-2 Adrenergic Function in Patients with Essential Hypertension

Cited by 6 publications

References 8 publications

Decreased pituitary response to insulin-induced hypoglycaemia in young lean male patients with essential hypertension

Decreased pituitary response to insulin-induced hypoglycaemia in young lean male patients with essential hypertension

The inhibitory effect of glucose on growth hormone secretion is lost in obesity but not in hypertension

Effect of two β2-agonist drugs, salbutamol and broxaterol, on the growth hormone response to exercise in adult patients with asthmatic bronchitis

Contact Info

Product

Resources

About