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Biomedical subjects

R Volpi

Publications and source records attributed to R Volpi.

At least 163 records · Page 9Linked to original sources
PubMed1984

Different effects of metoclopramide and domperidone on GH release in type I male diabetics.

Dopamine (DA) has a physiological role in the control of GH release from the pituitary. Studies have been carried out using DA agonist or antagonist, since in normal subjects DA does not cross the blood-brain-barrier (BBB). In contrast, the BBB is altered in type I diabetics, who respond to DA with a significant increase of GH release. In these patients Metoclopramide (MCP), an antidopaminergic drug, is also capable of stimulating GH release. In a previous paper, we suggested that this effect could be related to enhanced blood concentrations of DA, due to a reduced peripheral DA catabolism determined by MCP. However, since MCP crosses the BBB, an effect of this drug on other hypothalamic neurotransmitters could not be excluded. The purpose of the present study was to determine whether Domperidone (DOM) a drug which does not cross the BBB, but as well as MCP is thought to increase blood levels of DA, is also capable of inducing GH release in diabetics. Sixteen type I male diabetics were injected intravenously with MCP (6) or DOM (10) and a week later with normal saline. Ten normal subjects participated as controls to all three tests. MCP and DOM did not produce any effects in the normal controls; as expected, MCP induced a marked increase in serum levels of GH in the diabetics, while in contrast DOM did not stimulate GH secretion in diabetics. These data suggest that the effect of MCP is not due to the dopaminergic pathway previously described, but rather to a modulation of some other neurotransmitter at hypothalamic level, or to a direct effect on the pituitary in diabetics.

Adult↗
PubMed1984

Effect of pharmacological doses of oxytocin on insulin response to glucose in normal man.

In this study we have examined the effect of the administration of oxytocin on basal blood concentrations of insulin, glucagon, cortisol, growth hormone, and on the dynamic secretory response of these hormones to intravenous glucose administration (0.33 g/kg) in basal condition and after the injection of 3 IU (1 plus 2 IU/1 h) or 6 IU (2 plus 4 IU/1 h) of oxytocin (6 subjects for each group). The highest dose of oxytocin (6 IU) used significantly increased insulin secretion in response to intravenously administered glucose. No significant change of insulin secretion was observed with 3 IU of oxytocin. Glucagon, cortisol, and growth hormone response to intravenous injection of glucose was not affected by oxytocin (3 or 6 IU) administration. These results suggest that high doses of oxytocin affect beta-cell function in normal man.

Adult↗
PubMed1984

The growth hormone response to thyrotropin-releasing hormone in insulin-dependent diabetics involves a cholinergic mechanism.

In order to establish whether cholinergic receptors mediate GH secretion induced by TRH in insulin-dependent diabetes, 10 patients were treated with pirenzepine, an anticholinergic agent, and tested with TRH. Basal concentrations of GH were elevated in these patients and 8 of 10 patients responded to TRH with a significant rise in GH levels. Pretreatment with pirenzepine (40 mg given iv 10 min before TRH) suppressed the TRH-induced GH rise. Pirenzepine had no effect on TRH-induced TSH release. This finding suggests that a cholinergic mechanism is involved in the paradoxical response of GH to TRH in diabetic patients.

Adult↗
PubMed1984

Histaminergic H1 and H2 receptors do not mediate cortisol release in response to naloxone in normal men.

In order to evaluate the role of histamine as a possible mediator of the ACTH-cortisol response to naloxone, a specific opioid receptor antagonist, 12 normal men were treated with naloxone before and after the administration of dexchlorpheniramine and cimetidine, respectively H1 and H2 histamine receptor antagonists. Cortisol levels in the plasma were measured before and after drug injections. Naloxone significantly stimulated the secretion of cortisol in all subjects; the administration of dexclorpheniramine or cimetidine failed to modify this response. These data confirm the stimulatory effect of naloxone on cortisol secretion, but do not support the hypothesis that a histaminergic pathway mediates this response.

Adrenocorticotropic Hormone↗
PubMed1983

Naloxone does not alter the effect of gamma aminobutyric acid derivative, baclofen, on GH release in man.

To evaluate the interaction between opioid peptides and GABAergic system in regulating GH secretion we administered 5 mg of baclofen, a GABA derivative, to eight normal male subjects. The results were compared to those obtained in the same subjects treated with naloxone (10 mg/2 h) plus baclofen. GH levels increased significantly above basal value either after baclofen and naloxone plus baclofen without any significant difference between GH responses during the two tests. It is suggested that the two substances do not act at the level of the same receptor site. The evaluation of a possible interaction between opioid peptides and GABAergic system on GH release requires further investigation.

Adult↗
PubMed1983

Effect of metoclopramide on serum growth hormone levels in cirrhotic men.

Growth hormone (GH) secretory response to metoclopramide (MCP) administration was evaluated in 9 male patients with liver cirrhosis and in 6 normal controls. As expected, MCP did not modify serum GH concentrations in normal subjects. In contrast, a striking GH secretory response to MCP was observed in 5 out of 9 cirrhotics. In the other four patients serum GH levels did not show any variation after MCP. The different behavior between cirrhotic "responders" and "non responders" can not be interpreted on the basis of the medical history or the clinical and laboratory data. Three hypothesis are proposed: i) The effect of MCP could be promoted by estrogens and inhibited by androgens. ii) False neurochemical transmitters could affect dopaminergic system of some cirrhotics, allowing or inhibiting the GH response to MCP. iii) MCP could stimulate GH secretion by a serotonergic mechanism. These findings provide further evidence of a modification of the GH secretory pattern in patients with cirrhosis of the liver.

Adult↗
PubMed1981

[Urinary levels of dehydroepiandrosterone in a group of male patients with functional hyperprolactinemia].

On 22 male patients diagnosed as "functional hyperprolactinemia" (the Prolactin (PRL) basal value, was higher than the basal PRL means +/- 2 DS of a control group) we have measured the urinary excretion of Dehydroepiandrosterone (DHEA) mainly produced by adrenal cortex. Our results haven't shown no difference in the urinary excretion of DHEA values in hyperprolactinemic patients has been documented.

Adult↗
PubMed1980

[Study of GH in patients suffering from sexual impotence and abnormal glucose tolerance test (author's transl)].

The correlation between dopamine-serotonin systems and sexual behaviour and the influence of these two amines on GH secretion is well known. We evaluated GH responses (maximum increase (delta) after OGTT and mean increase (delta M) after insulin test) in a group of 32 males suffering from erective impotence with impotence with abnormal reaction to a glucose tolerance test. Results were compared with those obtained in a group of 13 normal controls. No significant difference in basal values and dynamic responses between the two groups was present. Our data suggest that GH doesn't decrease the tolerance to glucose in these patients. The abnormal values observed during a glucose tolerance test may be due to some agent involved in the interactions between limbic system, ventral lateral and ventral medial hypothalamic nuclei and dopamine-serotonin systems. No influence by this system on GH secretion is evident.

Adult↗
PubMed1979

Gonadotropin-releasing hormone test for hypogonadic men.

Gonadotropin patterns before and after stimulation with gonadotropin-releasing hormone (GnRH) have been studied in 69 hypogonadic men of various types: patients with expansive hypothalamus--pituitary disorders before and after surgery, patients with hypogonadotropic hypogonadism, and patients with oligozoospermia or azoospermia who have primary partial or total testicular deficiency. Three characteristic gonadotropin patterns were found: (a) low basal values of LH and FSH with either absent or decreased and delayed responses; (b) normal basal values and pituitary responses above the normal range; or (c) high basal values and pituitary responses above the normal range. These gonadotropin patterns were correlated with disorders of the hypothalamus--pituitary--testis axis. The advantages and disadvantages of the GnRH test for the clinical evaluation of male hypogonadism are discussed.

Adolescent↗
PubMedDate not supplied

The GABAergic control of prolactin release is not affected by insulin-dependent diabetes mellitus: evidence from studies with sodium valproate.

In order to evaluate the influence of the GABAergic system in the regulation of PRL secretion in patients with IDDM, serum PRL levels were measured in 7 diabetics and in 7 normal men with sodium valproate (400 mg per os), a drug capable of increasing cerebral GABA concentrations. A significant decrease of serum PRL concentrations was observed between 30 and 120 min after sodium valproate administration in both control and diabetic subjects. The time course and magnitude of the sodium valproate effect were similar in all subjects. These data confirm the inhibitory control of the GABAergic system on PRL secretion in man as evidenced by the GABAergic drug sodium valproate. It is suggested that this system is not altered in diabetic patients.

Adult↗
PubMedDate not supplied

Prolactin secretion and nodular goiter. (Hypothetical correlations).

In a group of 129 female patients with nodular goiter, Graves' disease and primary hypothyroidism, the PRL and TSH secretions were studied in parallel. Concurrent changes in the two hormones were evident only in conditions of marked hyper- or hypothyroidism. In the patients with non-toxic nodular (single or multiple) goiter the TSH showed low or normal values, while the PRL appeared normal or elevated. From these results two important conclusions can be drawn: 1. the T3 and T4 levels interact with PRL secretion concomitantly with TSH only when they undergo a huge deviation from the normal range; 2. the goitrogenic action of PRL that has been reported in experimental animals cannot be excluded in man.

Adolescent↗
PubMedDate not supplied

Thyrotropin and prolactin in patients with hypothalamus-pituitary diseases.

Seventy patients with hypothalamus-pituitary diseases were studied. 13 of them were studied before surgical treatment and then 15-20 days and 6 months later. A comparison was made with 59 controls. In all these subjects PRL and TSH were studied under basal conditions and after TRH stimulation. As for TSH the highest percentage of abnormal responses was found in the group of patients with chromophobe adenoma and parasellar dysplasias. This area of the pituitary appears relatively undamaged in acromegalic patients. In clinically hypothyroid patients, normal or high TSH responses to TRH were often found. As for PRL, a hyperprolactinaemia was mostly found in the group of patients with chromophobe adenoma, parasellar dysplasias and craniopharyngioma, although there was a different pattern in the TSH responses. No correlation was found between the basal PRL levels and the TSH responses to TRH. There was no significant difference in the TSH responses of the patients with PRL secreting and non-secreting chromophobe adenomas. The hypothesis of two autonomous systems is supported by the finding of differences in the functional recovery of the two pituitary areas studied at different times after surgical treatment.

Acromegaly↗