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Biomedical subjects

I Gil-Ad

Publications and source records attributed to I Gil-Ad.

At least 55 records · Page 3Linked to original sources
PubMed1984

Effect of aging on human plasma growth hormone response to clonidine.

The effect of the oral administration of 0.150 mg/m2 clonidine on the plasma level of human growth hormone (hGH) was studied in 53 adults (25 males and 28 females) aged from 28 to 68 years, of which 15 were healthy volunteers and 38 were hypertensive. Both the normal and hypertensive subjects of both sexes showed an age-related responsiveness of hGH to clonidine, with a normal or partial response in the younger subjects and blunting or lack of response in the more elderly subjects. In the females the blunting of the hGH response appeared at an earlier age than in the males. It is speculated that an alteration in the sensitivity of the central alpha-adrenergic receptors and a decrease in the sex steroid hormones may account for the progressive reduction in hGH secretion with advancing age.

Adult↗
PubMed1984

Plasma growth hormone response to oral clonidine as compared to insulin hypoglycemia in obese children and adolescents.

The response of plasma growth hormone (hGH) to a single oral dose of clonidine (0.15 mg/m2) was compared with that obtained with insulin hypoglycemia (ITT) induced by administration of double the usual dose (0.2 U/kg i.v.) in 13 obese subjects aged 5-17 years (7 males, 6 females) with a subscapular skinfold greater than 20 mm and a weight greater than 2 SD of the median. Six healthy subjects (3 males, 3 females), aged 8-14 years who served as controls received the usual dose of 0.1 U/kg i.v. in the ITT. Clonidine induced an increase of more than 10 ng/ml in the plasma hGH levels in 10 (4 males, 6 females) of the 13 obese subjects and in all of the healthy controls, with peak levels ranging from 14.3 to 31.0 ng/ml (m +/- SD 21.0 +/- 5.2 ng/ml); the ITT elicited a similar rise in only 6 of the 13 subjects and 3 of the healthy controls, with peak levels ranging from 9.8 to 20.0 ng/ml (m +/- SD 14.4 +/- 4.5 ng/ml). Clonidine decreased plasma insulin levels in all the obese female subjects (by a mean of 65%) whereas in the obese males the insulin pattern was variable. There was no change in blood glucose levels following the administration of clonidine; during the ITT all subjects showed a decrease to less than 50 mg/dl. Blood pressure decreased by a mean of 20 mmHg during the clonidine test. This study demonstrates that clonidine is a more effective hGH stimulus than insulin induced hypoglycemia in normal and in obese children and that the lower hGH secretion of the obese is confirmed by the clonidine test.

Adolescent↗
PubMed1984

Basal plasma HGH and cortisol levels and the effect of clonidine administration in female migrainous patients.

Clonidine, a central alpha-adrenergic agent and prophylactic antimigraine drug is known to stimulate human growth hormone (HGH) release and to suppress cortisol secretion. A possible association between basal hormonal levels and response to either acute clonidine test or chronic treatment in female migrainous patients was investigated. 15 females, aged 18-43 years, suffering from migraine, underwent an acute clonidine test by administration of a single oral dose of 0.15 mg. High basal HGH levels (greater than or equal to 9 ng/ml) were observed in 6 patients, while the other 9 patients demonstrated normal low basal HGH levels. Acute clonidine administration induced a marked rise of HGH in 8 of the 9 patients with low basal HGH. In 4 of the 8 responders HGH levels exceeded 20 ng/ml and 3 subjects reached the acromegalic range (greater than 90 ng/ml). The mean response in this group was higher than in a reference group consisting of children and adolescents. It is suggested that the basal hypersecretion and the hyperresponsiveness of HGH to clonidine provocation test in some migrainous patients results from a hypersensitivity of the central alpha-adrenergic receptors. 12 of the 15 females were treated for 10 weeks with clonidine at gradually increased doses of 0.05 mg/day up to a maximal dose of 0.15 mg/day. A marked suppressive effect on cortisol secretion was observed in the migrainous patients after acute and chronic administration of clonidine. No correlation was observed between HGH and cortisol response to acute or chronic clonidine administration and the prophylactic effect of clonidine on migraine.

Adolescent↗
PubMed1981

Rise in plasma growth hormone in response to exogenous LRH in Klinefelter's syndrome.

In a group of sixteen patients with Klinefelter's syndrome (KS) aged from 2 years 8 months to 31 years, a study was made of the plasma growth hormone (hGH) response to LRH (50 micrograms/m2 i.v.; n=16), TRH (200 micrograms i.v.; n=14) and insulin-induced hypoglycaemia (0.1 u R.I,/kg i.v.; n=6). There was a rise in hGH following LRH from a level below 5 ng/ml during fasting to a level above 8 ng/ml (P less than 0.001) in nine (56.3%) of the sixteen patients tested; a similar response was found in only one of a control group of fifteen boys matched for age. TRH stimulation led to a rise in hGH in one of the fourteen KS patients tested, with none in the control group. Insulin-induced hypoglycaemia elicited a normal response of hGH in the six KS patients tested, from 1.8 +/- 0.7 to 16.5 +/- 3.7 ng/ml, (M +/- SD, P less than 0.001). Basal prolactin (PRL) levels were normal in the KS patients (9.4 +/- 4.1 ng/ml, M +/- SD) but the response to TRH stimulation was significantly higher (63.3 +/- 40 ng/ml; P less than 0.01) than that of the control group (30 +/- 15 ng/ml). Plasma gonadotrophin levels and the response to LRH stimulation were increased in all of the KS patients except those below the age of 13. Plasma TSH levels and the response to TRH stimulation as well as the levels of serum thyroxine were found to be normal in all the KS patients tested. The abnormal rise of hGH following LRH stimulation and of PRL following TRH stimulation suggests a disturbance in the neuroendocrine regulation mechanisms of these hormones in KS.

Adolescent↗
PubMed1981

Abnormal growth hormone response to LRH and TRH in adolescent schizophrenic boys.

The authors studied the effect of LRH and TRH on HGH in 10 adolescent schizophrenic boys and 9 age-matched normal boys. Before antipsychotic treatment, LRH and TRH induced a marked rise in hGH in 8 of 10 patients and 4 of 6 patients, respectively. No effect on HGH was observed in the normal controls. After 3 months of treatment with chlorpromazine, thioridazine, or haloperidol, LRH failed to induce a rise in HGH in 5 of the 6 patients tested, but TRH induced a significant rise in HGH in 3 of 4 patients tested. The authors postulate that these results indicate a dysfunction in the mechanism regulating HGH secretion in schizophrenia.

Adolescent↗
PubMed1979

Oral clonidine as a growth hormone stimulation test.

A single oral dose of 0.15 mg/m2 of clonidine was given to eighteen healthy children and adolescents and to seven patients with hypopituitarism. In healthy subjects there was a pronounced increase in plasma growth hormone from 4.9 +/- 1.3 ng/ml (+/- SEM) to 34.4 +/- 4.5 ng/ml. In the patients with hypopituitarism there was no change in growth-hormone concentrations. Clonidine induced a slight increase in blood glucose in healthy subjects and a slight decrease in patients with hypopituitarism. During the test systolic blood-pressure decreased by a mean of 20 mm Hg in the healthy subjects and by 25 mm Hg in the patients with hypopituitarism. The only side-effect observed was drowsiness. Oral administration of clonidine, a well-tolerated drug, seems to be a simple test for of GH reserves in children and adolescents.

Administration, Oral↗
PubMed1978

Pituitary hormones and ergot alkaloids.

From the data presented it appears that ergot drugs are both a useful tool for use in the study of neuroendocrine control of pituitary hormone secretion and a valid pharmacologic weapon for treatment of hyperprolactinemic states, GH and, probably, ACTH and MSH hypersecretion. In fact, they are capable of a long-lasting disruption of PRL secretion from a normal or tumoral pituitary gland, are unable to affect directly the somatotrophs of an intact AP, but inhibit GH and, possibly, ACTH secretion from a hyperplastic or tumoral gland. Ergolines also exert clear-cut PRL-lowering effects and are capable of suppressing GH secretion in acromegaly. The intimate mechanism(s) and hence site(s) of action of some of these compounds await clarification.

Acromegaly↗
PubMed1977

Effect of 5-hydroxytryptophan on prolactin and growth hormone release in the infant rat: evidence for different neurotransmitter mediation.

In 10 day-old female and male rats, administration of 5-hydroxytryptophan (5-HTP) induced a prompt elevation in plasma prolactin (Prl) and growth hormone (GH) levels. Pretreatment with 2 serotonin (5-HT) receptor blockers, methysergide (Meth) and metergoline (MCE), markedly reduced the 5-HTP-induced Prl rise but failed to alter the GH response to 5-HTP. Administration of 2 selective inhibitors of presynaptic 5-HT reuptake, 3-(p-trifluoromethylphenoxy)-N-methyl-3-phenyl-propylamine and chlorimipramine (CIM), potentiated the 5-HTP-stimulated Prl rise but significantly reduced the 5-HTP-induced GH release. Blockade of dopaminergic or alpha-adrenergic receptors by pretreatment with pimozide (Pim) or phentolamine (Phent), respectively, or central sympathectomy by intraventricularly (i.vt.) injected 6-hydroxydopamine (6-OHDA) were capable of reducing the 5-HTP-induced GH release without affecting the 5-HTP-induced Prl rise. These data indicate that in the infant rat the 5-HTP-induced Prl release is mediated via the brain 5-HT system and that a nonspecific activation of the catecholaminergic system is responsible for the GH response to the drug.

5-Hydroxytryptophan↗
PubMed1977

Growth hormone releasing activity of thyrotropin-releasing hormone in rats with hypothalamic lesions.

The growth hormone (GH)-releasing effect of thyrotropin-releasing hormone (TRH) was investigated in rats in which central nervous system (CNS)-anterior pituitary (AP) connections had been experimentally interrupted. Sprague-Dawley (SD) female and male rats, underwent bilateral electrolytic lesions in the median eminence (ME) or the ventromedial nuclei (VMN) or were sham-operated (sham-op). Fifteen days after surgery, 0.9% NAACl or TRH was injected iv into sham-op rats or those with lesions in the CNS, anesthetized with urethane, and blood was drawn at 5 and 10 min posttreatment. In the rats with ME lesions, TRH at all the doses used (0.1, 0.4 and 0.8 microng/100 g BW) induced a marked, although not dose-related GH rise, which was not present in sham-op rats after TRH, or after NaCl administration to either rats with ME lesions or sham-op rats. In SD male rats lesioned in the VMN, TRH at doses of 0.4 and 0.8 microng/100 g BW induced significant GH rises, while the lowest TRH dose (0.1 microng/100 g BW) was ineffective; again, TRH was ineffective at all doses used in sham-op rats. Concomitant evaluation of the prolactin (PRL)-releasing effect of TRH (0.1-0.8 microng/100 g BW), showed a striking elevation of plasma PRL in both female and male sham-op controls, but no PRL rise in the rats with ME lesions. The results reveal that in the rat with surgical separation of the anterior pituitary from the CNS, a direct GH-releasing effect of TRH can be obtained, whereas its PRL-releasing effect is no longer observed, and suggest that, by analogy, the GH-releasing effect of TRH present in some disease states of the human may be due to an impairment of CNS-AP connections.

Animals↗
PubMed1977

Thyrotrophin releasing hormone-induced growth hormone and prolactin release: physiological studies in intact rats and in hypophysectomized rats bearing an ectopic pituitary gland.

To determine how the sensitivity of the ectopic anterior pituitary gland to the GH-releasing effect of thyrotrophin releasing hormone (TRH) might be affected by the time lapse from transplantation, TRH (0-15 and 0-6 microng) was injected i.v. into hypophysectomized (hypox)-transplanted rats under urethane anaesthesia 1,3,8,15,30 and 60 days after transplantation, and plasma samples were taken 5 and 10 min later. Baseline GH values gradually decreased with time from about 16-0 ng/ml (1 day) to about 3-0 ng/ml (30 and 60 days). The TRH-induced GH release was absent 1 day after transplantation, present only with the higher TRH dose 3 and 8 days after transplantation, and clearly elicitable, also with the lower TRH dose (0-15 microng), from 15 up to 60 days. Determination of plasma prolactin concentrations showed a decline from about 85-0 ng/ml (1 day) to about 32-0 ng/ml (8 days); subsequently (15-60 days) prolactin values stabilized. Plasma prolactin levels increased 15 and 60 days after transplantation only when a dose of 0-6 microng TRH was given. In intact weight-matched rats, TRH induced a GH response only at the dose of 1-2 microng while a short-lived but clear-cut prolactin response could be obtained even with the 0-3 microng dose. The present results indicate that: (1) disconnexion between the central nervous system and the anterior pituitary gland greatly enhances GH responsiveness while blunting prolactin responsiveness to TRH; (2) the sensitivity of the anterior pituitary gland to the GH-releasing effect of TRH increases with time from transplantation; (3) TRH is a more effective prolactin- than GH-releaser on the pituitary gland in situ.

Animals↗