المؤلفون: Aimaretti G; Department of Internal Medicine, University of Turin, Italy., Corneli G, Razzore P, Bellone S, Baffoni C, Arvat E, Camanni F, Ghigo E

المصدر: The Journal of clinical endocrinology and metabolism [J Clin Endocrinol Metab] 1998 May; Vol. 83 (5), pp. 1615-8.

نوع المنشور: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't

بيانات الدورية: Publisher: Oxford University Press Country of Publication: United States NLM ID: 0375362 Publication Model: Print Cited Medium: Print ISSN: 0021-972X (Print) Linking ISSN: 0021972X NLM ISO Abbreviation: J Clin Endocrinol Metab Subsets: MEDLINE

مواضيع طبية MeSH: Arginine* , Growth Hormone-Releasing Hormone*/adverse effects , Insulin*/adverse effects, Human Growth Hormone/*deficiency , Hypoglycemia/*physiopathology, Adult ; Female ; Human Growth Hormone/metabolism ; Human Growth Hormone/therapeutic use ; Humans ; Hypoglycemia/chemically induced ; Hypopituitarism/physiopathology ; Insulin-Like Growth Factor I/metabolism ; Male

مستخلص: There is now wide consensus that, within an appropriate clinical context, GH deficiency (GHD) in adults must be shown biochemically by provocative testing of GH secretion and that appropriate cut-off limits have to be defined for each provocative test. Insulin-induced hypoglycemia (ITT) is indicated as the test of choice, and severe GHD, to be treated with recombinant human GH replacement, is defined by a GH peak response to ITT of less than 3 micrograms/L. GHRH + arginine (GHRH + ARG) is one of the most promising tests in alternative to ITT. In fact, it has been reported as a potent, reproducible, and age-independent test and that it is able to distinguish between GHD and normal adults. The aim of the present study was to compare the GH response to ITT and GHRH + ARG in a large group of hypopituitary adults (n = 40; 29 male and 11 female; age: 36.4 +/- 2.1 yr). The third centile limit of the peak GH response to ITT has been reported as 5 micrograms/L, whereas in our lab, that to GHRH + ARG is 16.5 micrograms/L. In hypopituitary adults, the mean peak GH response to ITT (1.5 +/- 0.2 micrograms/L, range: 0.1-8.5 micrograms/L) was lower (P < 0.001) than that to GHRH + ARG (3.0 +/- 0.4 micrograms/L, range 0.1-12.0 micrograms/L), though there was positive correlation (r = 0.61, P < 0.001) between the GH responses to the 2 tests. The peak GH response to GHRH + ARG, but not that to ITT, was positively (though weakly) associated with insulin-like growth factor-I levels (r = 0.35, P < 0.03). Childhood and adult onset GHD patients, as well as patients with single and multiple pituitary insufficiencies, had similar peak GH responses to ITT or GHRH + ARG. Analyzing individual GH responses, 4/40 (10%) of the hypopituitary patients had GH peaks higher than 5 micrograms/L after ITT; moreover, 3 other patients (7%) had GH peaks, after ITT, higher than 3 micrograms/L. On the other hand, after GHRH + ARG, all patients had GH peaks lower than 16.5 micrograms/L, whereas 21/40 (52.5%) had GH peaks higher than 3 micrograms/L. Because 3 micrograms/L is the arbitrary cut-off for ITT, the third centile limit of which is 5 micrograms/L, we arbitrarily considered 9 micrograms/L as the cut-off point for GHRH + ARG. It is noteworthy that 37/40 (92.5%) patients had a GH peak, after GHRH + ARG, below this limit. In conclusion, our present results confirm that the ITT test is a reliable provocative test for the diagnosis of adult GHD, whereas they show that the GHRH + ARG test is, at least, as sensitive as the ITT test (provided that appropriate cut-off limits are considered). Note that even the arbitrary cut-off point below which severe GHD is demonstrated has to be appropriate to the potency of the test.

المؤلفون: Grottoli S; Dipartimento di Medicina Interna, Università di Torino, Italy., Razzore P, Arvat E, Oleandri SE, Rossetto R, Ciccarelli E, Camanni F, Ghigo E

المصدر: Journal of endocrinological investigation [J Endocrinol Invest] 1997 Nov; Vol. 20 (10), pp. 597-602.

نوع المنشور: Journal Article; Research Support, Non-U.S. Gov't

بيانات الدورية: Publisher: Springer Country of Publication: Italy NLM ID: 7806594 Publication Model: Print Cited Medium: Print ISSN: 0391-4097 (Print) Linking ISSN: 03914097 NLM ISO Abbreviation: J Endocrinol Invest Subsets: MEDLINE

مواضيع طبية MeSH: Arginine/*pharmacology , Growth Hormone-Releasing Hormone/*pharmacology , Human Growth Hormone/*metabolism , Hyperprolactinemia/*physiopathology , Oligopeptides/*pharmacology , Pituitary Gland/*drug effects , Pituitary Gland/*metabolism, Adenoma/metabolism ; Adolescent ; Adult ; Arginine/administration & dosage ; Drug Interactions ; Female ; Growth Hormone-Releasing Hormone/administration & dosage ; Humans ; Hypothalamus/drug effects ; Hypothalamus/metabolism ; Oligopeptides/administration & dosage ; Pituitary Neoplasms/metabolism ; Somatostatin/metabolism

مستخلص: Aim of the present study was to verify the maximal secretory capacity of somatotrope cells in patients with pathological hyperprolactinemia (HPRL) comparing it with that in normal age-matched women (NW). To this goal in 12 HPRL normal weight patients (age 28.6 +/- 2.6 yr, BMI 23.1 +/- 1.1 kg/m2) and 8 NW (27.2 +/- 0.8 yr, 22.8 +/- 0.8 kg/m2) we studied the GH response to GHRH (1 microgram/kg i.v.), GHRH plus arginine (ARG, 0.5 g/kg i.v.), an amino acid probably acting at the hypothalamic level inhibiting somatostatin release, and Hexarelin (HEX, 2 micrograms/kg i.v.), a synthetic hexapeptide belonging to GHRP family, which acts concomitantly at the pituitary and the hypothalamic level. IGF-I levels in HPRL were similar to those in NW (179.2 +/- 16.5 micrograms/l and 218.5 +/- 30.8 micrograms/l). In NW the GH response to GHRH (AUC: 1299.5 +/- 186.9 micrograms 90 min/l) was lower (p < 0.02) than those to GHRH + ARG (5252.7 +/- 846.3 micrograms 90 min/l) and HEX 3216.6 +/- 462.3 micrograms 90 min/l) which, in turn, were similar. In HPRL the GH response to GHRH (894.7 +/- 242.4 micrograms 90 min/l) was lower (p < 0.03) than that to HEX (1586.5 +/- 251.3 micrograms 90 min/l) and both were lower (p < 0.03) than that to GHRH + ARG (4468.8 +/- 941.7 micrograms 90 min/l). In HPRL the GH responses to GHRH and HEX were lower than those that in NW (p < 0.03) while that to GHRH + ARG was similar in both groups. These results demonstrate that the somatotrope responsiveness to GHRH and HEX is clearly reduced in patients with pathological hyperprolactinemia. On the other hand, in this condition the GH response to GHRH + ARG is normal. As arginine likely acts via inhibition of hypothalamic somatostatin release, these findings show that the maximal secretory capacity of somatotrope cells in hyperprolactinemia is preserved and indicate that partial refractoriness of somatotrope cells to GHRH and HEX could be due to somatostatinergic hyperactivity.

المؤلفون: Maccario M; Department of Internal Medicine, University of Turin, Italy., Grottoli S, Razzore P, Procopio M, Oleandri SE, Ciccarelli E, Camanni F, Ghigo E

المصدر: European journal of endocrinology [Eur J Endocrinol] 1996 Aug; Vol. 135 (2), pp. 205-10.

نوع المنشور: Journal Article; Research Support, Non-U.S. Gov't

بيانات الدورية: Publisher: Oxford University Press Country of Publication: England NLM ID: 9423848 Publication Model: Print Cited Medium: Print ISSN: 0804-4643 (Print) Linking ISSN: 08044643 NLM ISO Abbreviation: Eur J Endocrinol Subsets: MEDLINE

مواضيع طبية MeSH: Arginine/*pharmacology , Glucose/*administration & dosage , Growth Hormone/*metabolism , Hyperprolactinemia/*metabolism , Insulin/*metabolism , Obesity/*metabolism, Adolescent ; Adult ; Blood Glucose/analysis ; Female ; Glucose/pharmacology ; Growth Hormone/blood ; Humans ; Insulin/blood ; Insulin Secretion ; Middle Aged ; Prolactin/blood

مستخلص: In hyperprolactinemic patients an exaggerated glucose-induced insulin secretion has been reported, but these results have not been confirmed by other researchers. On the other hand, there are few data concerning somatotrope secretion in this condition. In order to clarify these points, in seven normal weight hyperprolactinemic female patients (HP: age 18-46 years, body mass index = 21.8 +/- 0.6 kg/m(2), basal prolactin = 91.7 +/- 16.5 micrograms/l) we studied the effects of glucose load (100 g orally) and/or arginine (0.5 g/kg infused over 30 min) on insulin glucose and growth hormone (GH) levels. These results were compared with those obtained in seven patients with simple obesity (OB: age 23-48 years, body mass index = 38.3 +/- 2.6 kg/m(2)) in whom exaggerated insulin and low GH secretion are well known. Seven normal women (NS: age 26-32 years, body mass index = 20.6 +/- 1/9 kg/m(2)) were studied as controls. The insulin response to glucose in HP (area under curve = 11,460.8 +/- 1407.5 mU x min x l(-1)) was not significantly different from NS (7743.7 +/- 882.9 mU x min x l(-1)) and OB (14,504.8 +/- 1659.9 mU x min x l(-1)). The arginine-induced insulin release in HP and OB was similar (4219.4 +/- 631.7 and 4107.3 +/- 643.2 mU x min x l(-1), respectively), both being higher (p < 0.02) than in NS (2178.1 +/- 290.9 mU x min x l(-1). Glucose and arginine had an additive effect on insulin release in HP and NS (19,769.1 +/- 3249.6 and 10,996.6 +/- 1201.0 mU x min 1(-1), respectively) and a synergistic effect in OB (28 117.3 +/- 5224.7 mU x min x l(-1)). In HP the insulin response to the combined administration of glucose and arginine was not significantly different from the one in OB, and both were higher (p < 0.05) than in NS. The increase in glucose levels after glucose administered on its own or combined with arginine was higher (p < 0.02) and longer lasting in OB than in NS and HP. After arginine in OB, the glucose levels did not show the late decrease under baseline values observed in HP and NS. Glucose inhibited GH secretion both in HP and NS (p < 0.05), while arginine stimulated it in all groups, although the GH response in HP and NS was higher (p < 0.03) than in OB. The arginine-induced GH secretion was inhibited by glucose in HP and NS but not in OB. These results demonstrate that both in hyperprolactinemic patients and in obesity there is a clear increase in insulin secretion. The insulin hyperresponsiveness in hyperprolactinemia is more clearly demonstrated by combined stimulation with glucose and arginine. In spite of similar insulin hypersecretion in hyperprolactinemic and obese patients, GH secretion is reduced only in the latter; with these data the hypothesis that somatotrope insufficiency in obesity is due to hyperinsulinism is unlikely.

المؤلفون: Maccario M; Department of Clinical Pathophysiology, University of Turin, Italy., Procopio M, Grottoli S, Oleandri SE, Razzore P, Camanni F, Ghigo E

المصدر: The Journal of clinical endocrinology and metabolism [J Clin Endocrinol Metab] 1995 Dec; Vol. 80 (12), pp. 3774-8.

نوع المنشور: Journal Article; Research Support, Non-U.S. Gov't

بيانات الدورية: Publisher: Oxford University Press Country of Publication: United States NLM ID: 0375362 Publication Model: Print Cited Medium: Print ISSN: 0021-972X (Print) Linking ISSN: 0021972X NLM ISO Abbreviation: J Clin Endocrinol Metab Subsets: MEDLINE

مواضيع طبية MeSH: Arginine/*pharmacology , Growth Hormone/*metabolism , Growth Hormone-Releasing Hormone/*pharmacology , Obesity/*metabolism , Pirenzepine/*pharmacology , Pituitary Gland, Anterior/*metabolism , Somatostatin/*pharmacology, Adult ; Female ; Glucose/pharmacology ; Growth Hormone/antagonists & inhibitors ; Humans ; Male ; Muscarinic Antagonists/pharmacology ; Reference Values

مستخلص: It is known that spontaneous and stimulated GH secretion is reduced in obesity. On the other hand, it has been recently reported that, in obese subjects, plasma GH levels did not change during a hyperglycemic clamp. To further study the sensitivity of somatotrope cells to inhibitory influences in obesity, we studied the effect of somatostatin, pirenzepine, or glucose on the GH response to GHRH or arginine in 32 obese patients and 30 controls. Basal GH levels were lower in obese than in normal subjects (1.0 +/- 0.6 vs. 4.8 +/- 0.7 micrograms/L, P < 0.05), while insulin-like growth factor-I levels were similar in both groups (137.3 +/- 13.2 vs. 138.8 +/- 12.2 micrograms/L). In obese as well as in control subjects pirenzepine abolished the GH response to either GHRH (AUC0-120: 43.7 +/- 9.6 vs. 258.3 +/- 59.9 micrograms/L/h, P < 0.04 and 113.0 +/- 75.0 vs. 870.5 +/- 255 micrograms/L.h, P < 0.01, respectively) or arginine (6.5 +/- 2.5 vs. 118.7 +/- 55.9 micrograms/L.h, P < 0.05 and 47.7 +/- 7.3 vs. 334.0 +/- 157.5 micrograms/L.h, P < 0.01, respectively). Differently from pirenzepine, glucose blunted the GH response to either GHRH or arginine in control subjects (260.8 +/- 38.3 vs. 479.5 +/- 83.9 micrograms/L.h, P < 0.03 and 294.8 +/- 46.3 vs. 625.1 +/- 139.1 micrograms/L.h, P < 0.05, respectively), but failed to modify it in obese patients (193.7 +/- 39.4 vs. 172.4 +/- 33.6 micrograms/L.h and 121.1 +/- 43.4 vs. 155.1 +/- 39.7 micrograms/L.h, respectively). On the other hand, somatostatin deeply blunted the GHRH-induced GH release in obese patients (58.5 +/- 25.4 vs. 548.7 +/- 196.6 micrograms/L.h, P < 0.05) as well as in controls (181.4 +/- 44.4 vs. 759.7 +/- 46.6 micrograms/L.h, P < 0.04). In conclusion, our results show that, in obesity, the stimulated GH release is refractory to the inhibitory effect of glucose but not of pirenzepine, in spite of their likely common mechanism of action, i.e. increase of hypothalamic somatostatin release. Exogenous somatostatin is able to abolish GH secretion both in normal and obese subjects. These data suggest the existence of a peculiar inhability of hyperglycemia to trigger somatostatinergic release in obesity.

المؤلفون: Ciccarelli E; Dipartimento di Fisiopatologia Clinica, Università di Torino, Italy., Zini M, Grottoli S, Razzore P, Portioli I, Valcavi R

المصدر: Clinical endocrinology [Clin Endocrinol (Oxf)] 1994 Sep; Vol. 41 (3), pp. 371-4.

نوع المنشور: Journal Article

بيانات الدورية: Publisher: Blackwell Publishing Country of Publication: England NLM ID: 0346653 Publication Model: Print Cited Medium: Print ISSN: 0300-0664 (Print) Linking ISSN: 03000664 NLM ISO Abbreviation: Clin Endocrinol (Oxf) Subsets: MEDLINE

مواضيع طبية MeSH: Arginine/*administration & dosage , Hyperthyroidism/*blood , Prolactin/*blood, Adult ; Female ; Humans ; Male ; Radioimmunoassay

مستخلص: Objective: Reduced PRL responses to TRH or dopamine antagonists have been described in hyperthyroid patients. Arginine stimulates PRL secretion through pathways other than the activation of TRH receptors or dopamine-dependent mechanisms. We therefore investigated PRL responses to arginine in patients with hyperthyroidism.
Design: L-Arginine (30 g infused over 30 minutes) was administered at time zero.
Subjects: Sixteen patients with untreated hyperthyroidism due to Graves' disease (8 female and 8 male), with a mean age (+/- SE) of 31.3 +/- 1.4 years (range 23-42), and 12 normal subjects (6 female and 6 male, ages 30.1 +/- 2.1 years, range 22-47) were studied.
Measurements: Prolactin was measured by RIA between -30 and 120 minutes, at 15-minute intervals.
Results: Basal PRL levels were similar in the hyperthyroid patients and normal control subjects. The hyperthyroid women showed blunted PRL responses compared to normal women (peak PRL levels, 364 +/- 44 mU/l, vs 760 +/- 156, P < 0.02). PRL responses to arginine, small but clearly detectable in normal men, were completely abolished in hyperthyroid men (peak PRL levels, 248 +/- 48 mU/l, vs 112 +/- 14, P < 0.01).
Conclusions: PRL responses to arginine are impaired in hyperthyroid patients. Therefore, arginine should be added to the list of PRL stimuli whose responses are blunted in hyperthyroidism. Inhibition of PRL gene expression, and thus reduced pituitary PRL synthesis and storage, may explain why PRL responses to all secretagogues are reduced in these patients.

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