Abstract. It has been reported that rat growth hormone releasing factor (rat GRF-43), similarly to the two human GRFs (GRF-40 and 44) stimulates adenylate cyclase activity in pituitary cells. Controversial findings have been presented by two different groups on the action of GRF on phosphoinositides (PI) metabolism, a phenomenon linked to Ca++ – mediated intracellular mechanisms. In the work to be reported, we evaluated the accumulation of inositol phosphates induced by GRF exposure in primary cultures of rat and human pituitary cells. Addition of rat GRF-43 to rat pituitary cells at doses up to 1 μm had no effect on inositol phosphates accumulation, while already at a dose as low as 0.05 nm it increased growth hormone secretion in the incubation medium significantly. In the same cell system, TRH, a known activator of PI breakdown, significantly increased [3H]inositol phosphates. In primary cultures of human somatotrophs from acromegalic subjects as in rats, addition of hpGRF-40 and also of TRH did not elicit any modification in the accumulation of [3H]inositol phosphates. Consistent with in vivo findings, both peptides induced a significant release of GH in the medium. Our results show that the GH releasing effect of GRF does not involve the hydrolysis of phosphatidylinositol in normal rat as well as in tumoral human somatotrophs. In addition it appears that the anomalous response of TRH on adenomatous cells from acromegalic patients is differently mediated in respect to the action of the tripeptide on normal lactotrophs and thyrotrophs.
Dolores Collado Escobar, Lucia M. Vicentini, Ezio Ghigo, Enrica Ciccarelli, Luciana Usellini, Carlo Capella, and Daniela Cocchi
Enrico Mazza, Stefania Goffi, Paolo Barchi, Emanuela Arvat, Jaele Bellone, Paolo Limone, Ezio Ghigo, and Franco Camanni
Mazza E, Goffi S, Barchi P, Arvat E, Bellone J, Limone P, Ghigo E, Camanni F. Enhanced adrenocorticotrophic hormone and cortisol responses to corticotrophin-releasing hormone in central idiopathic diabetes insipidus. Eur J Endocrinol 1994;130:121–4. ISSN 0804–4643
It is well known that arginine vasopressin (AVP) exerts a stimulatory effect on adrenocorticotrophic hormone (ACTH) secretion. Moreover, there is consistent evidence that the hypothalamic AVP-secreting neurons are involved in the neuroregulation of ACTH secretion. With the aim to throw further light on the interaction between AVP and corticotrophin-releasing hormone (CRH) in the neuroregulation of ACTH secretion, in this study we compared the ACTH and cortisol responses to human CRH (100 μg iv as a bolus) in 18 normal subjects (15 females and three males, age 22–35 years) and seven patients with central isolated diabetes insipidus (six females and one male, age 16–40 years). Two patients were newly diagnosed and five had discontinued substitution therapy with desamino-D-AVP 24 h before testing. All had free access to water before and during the test period. The ACTH and cortisol responses to CRH were higher in subjects with diabetes insipidus than in controls, either when evaluated as peak values (ACTH, mean±sem: 17.0±1.2 vs 7.7±0.7 pmol/l, p=0.0003; cortisol: 611.3±59.4 vs 450.7±21.2 nmol/l, p=0.01) or area under curve values (ACTH: 672.5±75.7 vs 364.0±33.6 pmol·1−1·h−1. p=0.002; cortisol: 29158.0±2937.0 vs 23236.7±1052.1 nmol·l−1 · h−1, p=0.03). These results show that patients with diabetes insipidus have an exaggerated pituitary-adrenal response to CRH. This may be due to the fact that in diabetes insipidus AVP secretion from parvocellular neurons of the paraventricular nucleus in the hypophysial portal system is not impaired. Alternatively, AVP secretion may be defective in both magnocellular and parvocellular hypothalamic AVP-secreting neurons. In this case, it could be hypothesized that adjustment is made to the feedback regulatory mechanisms of the hypothalamic–pituitary–adrenal axis, so that the CRH–ACTH axis assumes a main role with respect to the AVP–ACTH axis.
Franco Camanni, Divisione di Endocrinologia, Ospedale Molinette, corso Dogliotti 14, 10126 Torino. Italy
Roberta Giordano, Marcella Balbo, Andreea Picu, Lorenza Bonelli, Rita Berardelli, Alberto Falorni, Ezio Ghigo, and Emanuela Arvat
Objective: In autoimmune polyglandular syndrome types 1, 2, and 4 primary adrenal insufficiency is present, but its diagnosis is often late. We investigated the function of the hypothalamic–pituitary–adrenal axis in a group of patients with autoimmune diseases (AP) without any symptoms and signs of hypoadrenalism.
Design: In 10 AP and 12 normal subjects (NS), we studied cortisol (F), aldosterone (A), and DHEA responses to 0.06 μg adrenocorticotropin (ACTH) (1–24) followed by 250 μg, ACTH and F responses to human corticotropin-releasing hormone (hCRH; 100 μg) and insulin tolerance test (ITT) (0.1 UI/kg).
Results: Basal F, A, DHEA, as well as urinary free cortisol and plasma renin activity levels in AP and NS were similar, whereas ACTH levels in AP were higher (P<0.05) than in NS. NS showed F, A, and DHEA response to both consecutive ACTH doses. In AP, the F, A, and DHEA responses to 250 μg ACTH were similar to those in NS, whereas the 0.06 μg ACTH dose did not elicit any significant response. The ACTH responses to hCRH and ITT in AP were higher (P<0.05) than in NS. The F response to hCRH in AP was lower (P<0.05) than in NS, whereas the F response to ITT in AP did not significantly differ from NS.
Conclusions: Enhancement of both basal and stimulated corticotrope secretion coupled with reduced adrenal sensitivity to low ACTH dose is present in AP patients without symptoms and signs of hypoadrenalism. This functional picture suggests that normal adrenal secretion is maintained due to corticotrope hyperfunction, suggesting the existence of some subclinical primary hypoadrenalism.
Ezio Ghigo, Gianluca Aimaretti, Laura Gianotti, Jaele Bellone, Emanuela Arvat, and Franco Camanni
Ghigo E, Aimaretti G, Gianotti L, Bellone J, Arvat E, Camanni F. New approach to the diagnosis of growth hormone deficiency in adults. Eur J Endocrinol 1996;134:352–6. ISSN 0804–4643
Pyridostigmine (PD), a muscarinic cholinergic agonist, and arginine (ARG) clearly increase the growth hormone (GH) response to growth hormone-releasing hormone (GHRH) in man. The current study was undertaken to investigate the value and safety of PD + GHRH and ARG + GHRH tests as well as the measurement of serum insulin-like growth factor I (IGF-I) in diagnosing GH deficiency in adults. Fifty-four patients considered GH deficient from extensive organic or idiopathic pituitary disease and 326 healthy adults were studied. The IGF-I concentrations were lower than the 3rd percentile of normal values in only 31 of the 54 (57.4%) patients with hypopituitarism. However, the IGF-I levels in hypopituitary patients and in normal subjects overlapped more frequently between 41 and 60 years (50%) and between 61 and 80 years (92.3%) as opposed to between 20 and 40 years (8.6%). In contrast to the IGF-I measurement, the ranges of peak GH responses to PD + GHRH and ARG + GHRH tests were clearly differentiated between the hypopituitary (0.2–6.8 and 0.1–9.5 μg/l, respectively) and normal subjects 17.7–114 and 16.1–119 μg/l, respectively). However, the PD + GHRH test was reliable only in subjects of 20–40 years of age. In conclusion, IGF-I measurement had no value in the diagnosis of GH deficiency in adults aged over 40 years, but is reliable enough when young adults of 20–40 years of age are considered. Both PD + GHRH and ARG + GHRH testing should be considered more reliable biochemical measurements of GH deficiency. In contrast to the PD + GHRH test, the ARG + GHRH test is reliable throughout the adult lifespan and appears to be the most appropriate for patient compliance and safety.
F Camanni, Divisione di Endocrinologia, Ospedale Molinette, C.so Dogliotti 14, 10126 Torino, Italy
Roberta Giordano, Daniela Forno, Fabio Lanfranco, Chiara Manieri, Lucia Ghizzoni, and Ezio Ghigo
Turner's syndrome (TS) is a rare genetic disorder caused by complete or partial X chromosome monosomy in a phenotypic female, and it is associated with increased morbidity and mortality for cardiovascular diseases, impaired glucose tolerance, and dyslipidemia.
Subjects and methods
In 30 adult TS patients under chronic hormonal replacement therapy (HRT), 17β-estradiol (E2), body mass index (BMI), waist circumference, fasting glucose and insulin, homeostatic model assessment (HOMA) index, serum lipids, oral glucose tolerance test (OGTT), 24 h ambulatory blood pressure monitoring (ABPM), and intima–media thickness (IMT) were evaluated and compared with those in 30 age- and sex-matched controls (CS).
No difference was found between TS and CS in E2 and BMI, whereas waist circumference was higher (P<0.05) in TS (77.7±2.5 cm) than in CS (69.8±1.0 cm). Fasting glucose in TS and in CS was similar, whereas fasting insulin, HOMA index, and 2 h glucose after OGTT were higher (P<0.0005) in TS (13.2±0.8 mUI/l, 2.5±0.2, and 108.9±5.5 mg/dl respectively) than in CS (9.1±0.5 mUI/l, 1.8±0.1, and 94.5±3.8 mg/dl respectively). Total cholesterol was higher (P<0.05) in TS (199.4±6.6 mg/dl) than in CS (173.9±4.6 mg/dl), whereas no significant differences in high-density lipoprotein, low-density lipoprotein, and triglycerides were found between the two groups. In 13% of TS, ABPM showed arterial hypertension, whereas IMT was <0.9 mm in all TS and CS. A negative correlation between insulin levels, HOMA index, or 2 h glucose after OGTT and E2 was present in TS.
Our results indicate that adult patients with TS under HRT are connoted by higher frequency of central obesity, insulin resistance, hypercholesterolemia, and hypertension.
Ferdinando Massara, Ezio Ghigo, Pia Molinatti, Enrico Mazza, Vittorio Locatelli, Eugenio E. Müller, and Franco Camanni
Abstract. It is known that in normal subjects repeated administrations of the growth hormone-releasing factor (GRF) induces a state of partial refractoriness of the somatotropes to GRF. Studies were conducted to verify whether the cholinergic system plays a role in the mechanism(s) underlying the reduced GH responsiveness to the neuropeptide. In five healthy men, the GH response to three consecutive injections of GRF (50 μg iv), administered at 2 h intervals, was considerably blunted after the second and third GRF bolus. Administration of the inhibitor of cholinesterase, pyridostigmine bromide (120 mg orally) 30 min before the second GRF bolus, not only restored but greatly potentiated the GH responsiveness to the second GRF bolus. The GH response to the third GRF bolus was not apparently influenced by pre-treatment with pyridostigmine. These data reinforce the view that cholinergic neurotransmission plays an important role in the control of GH secretion in human.
Andrea Benso, Fabio Broglio, Gianluca Aimaretti, Barbara Lucatello, Fabio Lanfranco, Ezio Ghigo, and Silvia Grottoli
Chronic hypoxia induces complex metabolic and endocrine adaptations. High-altitude (HA) exposure is a physiological model of hypoxia.
To further investigate the endocrine and metabolic responses to extreme HA.
We studied nine male elite climbers at sea level and at 5200 m after climbing Mt. Everest.
After 7 weeks at HA, body weight was reduced (P<0.05); regarding endocrine variables we observed: a) an increase of 2-h mean GH concentration (P<0.05) as well as of total IGF-I and IGF binding protein-3 levels (P<0.05 for both); b) a prolactin increase (P<0.05) coupled with testosterone decrease (P<0.01) and progesterone increase (P<0.05) without any change in estradiol levels: c) no change in cortisol, ACTH, and dehydroepiandrosterone sulfate (DHEAS) levels; d) an increase in free thyroxine (P<0.05) and free tri-iodothyronine (T3) decrease (P<0.05) but no change in TSH levels; e) a plasma glucose decrease (P<0.05) without any change in insulin levels; f) an increase in mean free fatty acid levels (P<0.05); g) despite body weight loss, leptin levels showed non-significant trend toward decrease, while ghrelin levels did not change at all.
The results of the present study in a unique experimental human model of maximal exposure to altitude and physical exercise demonstrate that extreme HA and strenuous physical exercise are coupled with specific endocrine adaptations. These include increased activity of the GH/IGF-I axis and a low T3 syndrome but no change in ghrelin and leptin that was expected taking into account body weight decrease. These findings would contribute to better understanding human endocrine and metabolic physiology in hypoxic conditions.
Sergio Bernasconi, Cecilia Volta, Antonella Cozzini, Mariangela Ziveri, Lucia Ghizzoni, Costantino Panza, and Ezio Ghigo
To determine whether differences in the neuroendocrine control of GH are present between children and adult subjects, the GH response to GHRH (1 μg/kg) (group 1), insulin-induced hypoglycemia (0.1 U/kg iv) (group 2), clonidine (150 μg/m2 po) (group 3) and iv arginine (0.5 g/kg in 30 min) (group 4) after GHRH pretreatment (1 μg/kg) was studied in 26 short-stature normal children (mean age 10.2 years). The results were compared with historical data in adults. No differences were present among mean peak GH levels after the first and second stimuli in groups 1, 2 and 3, while in group 4 the GH response to arginine administration was lower than that obtained after the initial GHRH (0.43±0.04 vs 0.9±0.13 nmol/l). Moreover, comparing the GH peak values following the second stimulus, it appears that the greatest GH responses were elicited by GHRH (1.31±0.23 nmol/l) and clonidine (1.11±0.22 nmol/l), while the lowest was elicited by arginine (0.43±0.04 nmol/l). In adults, sequential GHRH administration leads to inhibition of the response of the somatotropes, probably mediated by an increase in hypothalamic somatostatin. Our results confirm that after GHRH prestimulation GHRH elicits a significant GH response suggesting that activation of the somatostatinergic tone is less effective in children. This hypothesis also explains the low GH response to arginine which acts selectively through somatostatin inhibition.
Rita Berardelli, Ioannis Karamouzis, Elisa Marinazzo, Elisa Prats, Andreea Picu, Roberta Giordano, Ezio Ghigo, and Emanuela Arvat
Mineralocorticoid receptors (MRs) in the hippocampus display an important role in the control of the hypothalamic–pituitary–adrenal (HPA) axis, mediating the proactive feedback of glucocorticoids, which maintains the basal HPA activity. The systemic administration of MR antagonists enhances spontaneous and CRH-stimulated ACTH, cortisol, and DHEA secretion, while the effects of chronic treatment with MR antagonists are scanty. Our study was performed in order to clarify this point.
ACTH, cortisol, and DHEA levels were studied during the infusion of placebo, canrenoate, a MR antagonist (CAN, 200 mg i.v. bolus at 1600 h followed by 200 mg infused over 4 h), and human CRH (hCRH; 2.0 μg/kg i.v. bolus at 1800 h) before and during the last week of 28-day treatment with CAN (200 mg/day p.o.) in eight young women.
Pre-treatment sessions: CAN and hCRH administration increased ACTH, cortisol, and DHEA levels versus placebo (P<0.05). Post-treatment sessions: during placebo infusion, cortisol and DHEA were significantly amplified versus pre-treatment session (P<0.05), while ACTH levels were not modified; CAN infusion, differently from pre-treatment session, was not able to significantly increase ACTH, cortisol, and DHEA levels; ACTH, cortisol, and DHEA responses to hCRH were amplified with respect to pre-treatment session, although statistical significance was obtained for cortisol and DHEA only.
MR blockade by acute CAN administration significantly enhances the HPA activity in the afternoon, during the quiescent phase of the circadian rhythm. At the same period, prolonged treatment with CAN amplifies both spontaneous and CRH-stimulated activities of the HPA axis, while it blunts the HPA responsiveness to a further MR-mediated stimulation.
Simona Bo, Anna Castiglione, Ezio Ghigo, Luigi Gentile, Marilena Durazzo, Paolo Cavallo-Perin, and Giovannino Ciccone
Available data about mortality of type 2 diabetic patients treated with different sulphonylureas are scarce and contradictory.
We evaluated the associations between all-cause and cause-specific mortality and treatments with different sulphonylureas in a retrospective cohort of type 2 diabetic patients from a diabetes clinic.
All 1277 patients treated with sulphonylureas during 1996–1997 were enrolled: 159 patients were treated with tolbutamide, 977 glibenclamide and 141 gliclazide. The baseline data (centralised laboratory parameters, anthropometric data and presence of chronic complications) were abstracted from the clinical records. Information on vital status was collected from demographic files after 14-year follow-up. Adjusted hazard ratios (HR) were estimated with Cox (all-cause mortality) or Fine and Gray models (cause-specific mortality), including several potential confounders.
Five hundred and fifty-six patients died during the follow-up: 262 from cardiovascular causes, 158 from cancer and 136 from other causes. When compared with the glibenclamide users, the gliclazide and tolbutamide users showed a significantly lower cancer mortality (HR=0.30; 95% CI 0.16–0.55, and HR=0.48; 95% CI 0.29–0.79 respectively). These results were strongly confirmed in the 555 patients on sulphonylurea monotherapy. None of the patients who were treated with gliclazide monotherapy died from cancer during the follow-up, and the patients on tolbutamide treatment exhibited a lower cancer mortality than the glibenclamide users (HR=0.40; 95% CI 0.22–0.71). Data did not change after stratification for the duration of sulphonylurea treatment from diabetes diagnosis to the study enrolment.
Cancer mortality was markedly reduced in the patients on gliclazide and tolbutamide treatment. These results suggest additional benefits for these drugs beyond their blood glucose-lowering effect and strongly advocate for further investigation.