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G Aimaretti, G Fanciulli, S Bellone, M Maccario, E Arvat, G Delitala, F Camanni and E Ghigo

OBJECTIVE: Adults with severe GH deficiency (GHD) need recombinant human growth hormone (rhGH) replacement to restore body composition, structure functions and metabolic abnormalities. The optimal rhGH dose for replacement has been progressively reduced to avoid side effects. The aim of the present study was to define the minimal rhGH dose able to increase both IGF-I and IGF binding protein (BP)-3 levels in GHD and to verify the possible change in GH sensitivity. DESIGN AND PATIENTS: To this goal, we studied the effect of 4-day treatment with 3 rhGH doses (1.25, 2.5 and 5.0 microg/kg/day) on IGF-I and IGFBP-3 levels in 25 panhypopituitary adults with severe GHD (12 males and 13 females, age: 44.5+/-3.0 years, body mass index (BMI): 27.0+/-0.9 kg/m(2)) and 21 normal young adult volunteers (NV, 12 males and 9 females, age: 30.5+/-2.0 years, BMI: 20.8+/-0.5 kg/m(2)). RESULTS: Basal IGF-I and IGFBP-3 levels in GHD were lower (P<0.001) than in NV. In NV the 1.25 microg/kg dose of rhGH did not modify IGF-I levels. The dose of 2.5 microg/kg rhGH significantly increased IGF-I levels in men (P<0.001) but not in women, while the 5.0 microg/kg dose increased IGF-I levels in both sexes (P<0.001). IGFBP-3 levels were not modified by any of the administered rhGH doses. In GHD patients, all rhGH doses increased IGF-I levels 12 h after both the first (P<0.01) and the fourth rhGH dose (P<0.001). At the end of treatment percentage increases in IGF-I were higher (P<0.001) in GHD patients than in NV. In contrast with NV, in GHD patients the IGF-I response to short-term stimulation with rhGH was independent of gender. Moreover, GHD patients showed increases in IGFBP-3 after the fourth administration of both 2.5 and 5.0 microg/kg rhGH. CONCLUSION: The results of the present study demonstrate that the minimal rhGH dose able to increase IGF-I and IGFBP-3 levels in GHD patients is lower than in normal subjects, at least after a very short treatment. This evidence suggests an enhanced peripheral GH sensitivity in GH deprivation.

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G Radetti, B Pasquino, E Gottardi, I Boscolo Contadin, G Aimaretti and F Rigon

OBJECTIVE: Excessive GH secretion may lead to secondary diabetes mellitus, while prolonged GH treatment may accelerate the onset of type 2 diabetes mellitus in predisposed individuals. Turner's syndrome (TS) patients are a population at risk since they have reduced glucose tolerance (GT) spontaneously and because they are usually treated with high doses of GH. DESIGN AND METHODS: The aim of the study was to evaluate insulin sensitivity (IS) and glucose tolerance (GT) in a group of TS patients treated with GH for a period of 6 years. Forty-seven TS girls were included in the study. GH was administered at a mean weekly dosage of 0.35 mg/kg, injected subcutaneously over 6-7 days. GT was assessed according to the criteria of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. IS was evaluated with the quantitative insulin sensitivity check index (QUICK-I). RESULTS: No significant increase of impaired GT was observed in the patients during the follow-up period, while a reduced IS was detected. IS in TS patients was already lower than in prepubertal controls (P<0.001) before starting treatment and further decreased during the first year of therapy (P<0.05), and then remained stable over the following years. No correlation was found between QUICK-I, body mass index, years of treatment, onset and duration of puberty. One patient became diabetic during the course of treatment. CONCLUSIONS: GH treatment in TS girls does not significantly increase the prevalence of impaired GT or type 2 diabetes mellitus, while it does, however, decrease IS.

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D Vivenza, A Rapa, N Castellino, S Bellone, A Petri, G Vacca, G Aimaretti, F Broglio and G Bona

BACKGROUND: Previous investigations on the ghrelin gene reported three common polymorphisms (Arg51Gln, Leu72Met, and Gln90Leu), but their role in overweight and obese individuals remains to be clarified. OBJECTIVE: To ascertain whether these genetic variants could influence ghrelin secretion and play a part in predisposing to earlier onset of obesity or in modulating the overweight phenotype in childhood. DESIGN AND METHODS: Mutational analysis of the entire ghrelin gene and total and acylated plasma determinations were performed in 81 obese or overweight children and adolescents (46 were obese and 35 overweight: Ob/Ow). We also recruited 168 normal-weight healthy controls (72 young adults and 96 children) for mutational or plasma ghrelin analysis. RESULTS: Median total and acylated plasma ghrelin concentrations were significantly lower in Ob/Ow individuals than in controls (175 pg/ml compared with 345 pg/ml, P<0.0001, and 95 pg/ml compared with 114 pg/ml, P<0.0001, respectively). The ghrelin gene variants showed similar allele frequencies in the Ob/Ow individuals and in controls; in the former, they were not associated with any change in total and acylated circulating ghrelin concentrations or anthropometric data. The Leu72Met status was associated with a positive family history for obesity (75% for Leu72Met compared with 39% for Leu72Leu, P=0.03) and with a greater percentage of newborns born 'large for gestational age' (33% for Leu72Met compared with 5% for Leu72Leu, P=0.03), but in the control group it was related to a lower mean body mass index z-score (-0.03 for Leu72Met and -0.47 for Leu72Leu, P=0.04). CONCLUSION: Our present findings do not support the hypothesis that the ghrelin gene polymorphisms have a relevant impact in the secretion of total and acylated ghrelin.

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V Gasco, G Corneli, G Beccuti, F Prodam, S Rovere, J Bellone, S Grottoli, G Aimaretti and E Ghigo

GH deficiency (GHD) in adults has to be shown by a single provocative test, provided that it is validated. Insulin tolerance test (ITT) has been indicated as the test of choice; now also glucagon test is validated and represents an alternative. The GHRH plus arginine (ARG) test and testing with GHRH plus a GH secretagogue are equally reliable diagnostic tools, and are now considered as ‘golden’ standards as ITT. Childhood-onset (CO) GHD needs retesting in late adolescence or young adulthood; this is a major clinical challenge and raises questions about the most appropriate method and cut-off value. Appropriate re-evaluation of GH status is represented by simple measurement of IGF1 concentration off rhGH treatment. Clearly, low IGF1 levels are evidence of persistent severe GHD in subjects with genetic GHD or panhypopituitarism. However, normal IGF1 levels never rule out severe GHD and CO-GHD with normal IGF1 levels must undergo a provocative test. The appropriate GH cut-off limit is specific for each provocative test. As shown by the ROC curve analysis, in late adolescents and young adults, the lowest normal GH peak response to ITT is 6.1 μg/l while that to GHRH+ARG test is 19.0 μg/l. These cut-off limits, however, are just indicative as being variable as a function of the assay used. No other test is validated for retesting. As GHRH+ARG test mostly explores the GH-releasable pool, normal GH response would be verified by a second ITT in order to rule out subtle hypothalamic defect.

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J Bellone, L Ghizzoni, G Aimaretti, C Volta, MF Boghen, S Bernasconi and E Ghigo

Bellone J, Ghizzoni L, Aimaretti G, Volta C, Boghen MF, Bernasconi S, Ghigo E. Growth hormonereleasing effect of oral growth hormone-releasing peptide 6 (GHRP-6) administration in children with short stature. Eur J Endocrinol 1995;133:425–9. ISSN 0804–4643

Growth hormone-releasing peptide 6 (GHRP-6) is a synthetic hexapeptide with a potent GH-releasing activity after intravenous, subcutaneous, Intranasal and oral administration in man. Previous data showed its activity also in some patients with GH deficiency. The aim of our study was to verify the GH-releasing activity of oral GHRP-6 administration on GH secretion in children with normal short stature. The effect of oral GHRP-6 (300 μg/kg) was compared with that of the maximally effective dose of intravenous GH-releasing hormone (GHRH-29, 1 μg/kg). As the GHRH-induced GH rise in children is potentiated by arginine (ARG), even when administered by oral route at low dose (4 g), we studied also the interaction of oral GHRP-6 and ARG administration. We studied 13 children (nine boys and four girls aged 6.2–10.5 years, pubertal stage I) with normal short stature (height less than –2 sd score; height velocity more than –2 sd score; normal bone age; insulin-like growth factor I > 70 μg/l), In a first group of children (N = 7), oral GHRP-6 administration induced a GH response (mean ± sem, peak at 60 min vs baseline: 18.8 ±3.0 vs 1.1 ± 0.3 μg/l, p < 0.0006; area under curve: 1527.3 ± 263.9 μgl−1 h) which was similar to that elicited by GHRH (peak at 45 min vs baseline: 20.8 ±4.5 vs 2.2±0.9 μg/l, p <0.007; area under curve: 1429.4 ± 248.2 μgl−1 h−1). In a second group of children (N = 6), the GH response to oral GHRP-6 administration (peak at 75 min vs baseline: 18.5 ±5.1 vs 1.5 ± 0.6 μg/l, p < 0.01; area under curve: 1598.5 ± 289.3 μgl−1 h−1) was not modified by co-administration of oral ARG (peak at 90 min vs baseline: 15.2 ±5.6 vs 0.9±0.3 μg/l, p < 0.002; area under curve: 1327.8 ± 193.2 μgl−1 h−1). The amount of GH released and the timing of the somatotrope response after the oral administration of GHRP-6 were similar in the two groups. In conclusion, the present data show that in normal short children the oral administration of GHRP-6 is able to increase GH secretion to an extent similar to that observed after intravenous administration of the maximally effective GHRH dose. Moreover, in contrast to GHRH, the effect of GHRP-6 is not enhanced by low-dose oral ARG. As this amino acid likely acts via inhibition of hypothalamic somatostatin release, our data suggest that a decrease in the somatostatinergic activity does not improve the GH-releasing effect of GHRP-6 in childhood, at variance with that observed after GHRH. Our results suggest that GHRP-6 could be clinically useful to stimulate GH secretion in short children.

E Ghigo, Divisione di Endocrinologia, Ospedale Molinette, C. so. AM Dogliotti 14, 10126 Torino, Italy

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H J Schneider, S Rovere, G Corneli, C G Croce, V Gasco, R Rudà, S Grottoli, G K Stalla, R Soffietti, E Ghigo and G Aimaretti

Objective: Hypopituitarism frequently follows pituitary neurosurgery (NS) and/or irradiation. However, the frequency of hypothalamic–pituitary dysfunction after NS of non-pituitary intracranial tumors is unclear. The aim of this study was to assess the presence of endocrine alterations in patients operated on for intracranial tumors.

Design: This is a retrospective study.

Methods: We studied 68 consecutive adult patients (28 female, 40 male, age 45.0 ± 1.8 years; body mass index (BMI): 26.5 ± 0.6) with intracranial tumors who underwent NS only (n = 17) or in combination with radiotherapy (RT) and/or chemotherapy (CT) (n = 51). In all subjects, basal endocrine parameters and the GH response to GHRH + arginine test (using BMI-dependent cut offs) were evaluated.

Results: In 20.6% of the patients, peripheral endocrinopathy related to CT and/or RT was present. Hypopituitarism was found in 38.2% of the patients. Total pituitary hormone, multiple pituitary hormone, and isolated pituitary hormone deficits were present in 16.2, 5.8, and 16.2% respectively. The most common pituitary deficits were, in decreasing order: LH/FSH 29.4%, GH 27.9%, ACTH 19.1%, TSH 17.7%, and diabetes insipidus 4.4%. Hyperprolactinemia was present in 13.2%. The prevalence of hypopituitarism was higher in patients who underwent NS only and with tumors located closely to the sella turcica, but a substantial proportion of patients with tumors not directly neighboring the sella also showed hypopituitarism.

Conclusions: Hypopituitarism frequently occurs after NS for intracranial tumors. Also, exposure of these patients to CT and/or RT is frequently associated with peripheral endocrinopathies. Thus, endocrine evaluation and follow-up of patients treated for intracranial tumors should be performed on a regular basis.

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J Bellone, G Aimaretti, MR Valetto, S Bellone, C Baffoni, E Arvat, S Seminara, F Camanni and E Ghigo

Bellone J. Aimaretti G, Valetto MR, Bellone S, Baffoni C, Arvat E, Seminara S, Camanni F, Ghigo E, Acute administration of recombinant human growth hormone inhibits the somatotrope responsiveness to growth hormone-releasing hormone in childhood. Eur J Endocrinol 1996:135: 421–4. ISSN 0804–4643

In adulthood the growth hormone (GH) response to growth hormone-releasing hormone (GHRH) is inhibited by previous acute administration of either GH or GHRH and it is restored by substances that inhibit hypothalamic somatostatin release. Because in children the GH response to GHRH is not affected by previous neurohormone administration, it has been suggested that in childhood a GH increase is not able to trigger the somatostatin-mediated negative GH autofeedback mechanism. To verify this hypothesis, in 25 children (8 girls and 17 boys; 15 prepubertal and 10 in pubertal stages II–IV) with familial short stature (normal height velocity and insulin-like growth factor I levels) we studied the effect of acute iv administration of different recombinant human GH doses (group 1, N = 5, 0.06U/kg; group 2, N = 6, 0.01 U/kg; group 3, N = 7, 0.005 U/kg at −150 min or saline on the GH response to GHRH (1 μg/kg iv at 0 min). In another group (N = 7), we studied the effect of 0.005 U/kg iv recombinant human GH or saline on the GH response to GHRH combined with arginine (0.5 g/kg iv over 30 min), which likely inhibits hypothalamic somatostatin release. Serum GH increases after recombinant human GH were dose-dependent (GH peak, mean±sem, 171.7 ± 24.4, 33.3 ± 3.9 and 21.8 ± 5.1 μg/l, respectively). The administration of recombinant human GH strongly inhibited the GHRH-induced GH rise in all groups (group 1, 7.1 ± 1.7 vs 23.1 ± 7.6 μg/l, p < 0.05; group 2, 9.5 ±2.8 vs 26.9±8.5 μg/l, p < 0.05; group 3, 9.1 ±2.7 vs 34.8 ± 7.2 μg/l, p< 0.02). The GH response to arginine + GHRH (56.9 ± 13.3 μg/l) was higher than that to GHRH alone recorded in group 1 (p < 0.005), group 2 (p < 0.01) and group 3 (p < 0.01), while exogenous recombinant human GH failed to inhibit it (45.0 ± 9.4 μg/l). Our results demonstrate that in childhood, as well as in adulthood, recombinant human GH administration inhibits the somatotrope responsiveness to GHRH. This inhibitory effect is likely to be mediated by hypothalamic somatostatin release.

Ezio Ghigo, Divisione di Endocrinologia, Ospedale Molinette, Dogliotti 14, 10126 Torino, Italy

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F Broglio, A Benso, C Gottero, LD Vito, G Aimaretti, A Fubini, E Arvat, M Bobbio and E Ghigo

OBJECTIVE: Altered function of the GH/IGF-I axis in patients with dilated cardiomyopathy (DCM) has been reported. In fact, DCM patients show reduction of IGF-I levels, which could reflect slight peripheral GH resistance or, alternatively, reduced somatotroph secretion. Spontaneous GH secretion has been reported to be altered by some but not by other authors, whereas the GH response to GHRH, but not that to GH-releasing peptides, seems reduced in DCM patients. On the other hand, it is well known that the GH response to GHRH in humans is markedly potentiated by arginine (ARG), which probably acts via inhibition of hypothalamic somatostatin release; in fact the GHRH+ARG test is known as one of the most reliable to evaluate the maximal secretory capacity of somatotroph cells. METHODS: In order to further clarify the somatotroph function in DCM, in well-nourished patients with DCM (34 male, 4 female; age (mean+/-s.e. m.) 57.8+/-1.1 years; body mass index (BMI) 24.6+/-0.6kg/m(2); left ventricular ejection fraction 23.2+/-1.6%; New York Heart Association classification I/1, II/17, III/18, IV/2) we studied the GH response to GHRH (1.0 microgram/kg i.v.) alone or combined with ARG (0.5g/kg i.v.). The results in DCM patients were compared with those in age-matched control subjects (CS) (39 male, 7 female; age 58.9+/-1.0 years; BMI 23.2+/-0.3kg/m(2)). RESULTS: Mean IGF-I levels in DCM patients were lower than in CS (144.3+/-6.9 vs 175.1+/-8. 4 microgram/l, P<0.05) whereas basal GH levels were similar in both groups (1.7+/-0.3 vs 1.7+/-0.3 microgram/l). The GH response to GHRH in DCM patients was lower (P<0.05) than that in CS (GH peak 6.5+/-1.2 vs 10.7+/-2.1 microgram/l). In both groups the GH response to GHRH+ARG was higher (P<0.001) than that to GHRH alone. However, the GH response to GHRH+ARG in DCM patients remained clearly lower (P<0.01) than that in CS (18.3+/-3.2 vs 34.1+/-4.6 microgram/l). The GH response to GHRH alone and combined with ARG was not associated with the severity of the disease. CONCLUSION: DCM patients show blunted GH responses to GHRH both alone and combined with ARG. Evidence that ARG does not restore the GH response to GHRH in DCM patients makes it unlikely that the somatotroph hyporesponsiveness to the neurohormone reflects hyperactivity of hypothalamic somatostatinergic neurons.

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M Maccario, F Tassone, C Gauna, SE Oleandri, G Aimaretti, M Procopio, S Grottoli, CD Pflaum, CJ Strasburger and E Ghigo

OBJECTIVE: To verify the hypothesis of an increased sensitivity to GH in obesity (OB) and Cushing's syndrome (CS). DESIGN: We studied the effects of short-term administration of low-dose rhGH on circulating IGF-I levels in patients with simple OB or CS and in normal subjects (NS). METHODS: Nineteen women with abdominal OB aged (mean +/- s.e.m.) 38.2+/-3.1 years, body mass index 40.7+/-2.5 kg/m(2), waist to hip ratio 0.86+/-0.02, ten with CS (50.4+/-4.2 years, 29.7 +/- 3.3 kg/m(2)) and 11 NS (35.0+/-3.6 years, 20.5+/-0.5 kg/m(2)) underwent s.c. administration of 5 microg/kg per day rhGH at 2200 h for four days. Serum IGF-I, IGF-binding protein-3 (IGFBP-3), GH-binding protein (GHBP), insulin and glucose levels were determined at baseline and 12 h after the first and the last rhGH administration. RESULTS: Basal IGF-I levels in NS (239.3+/-22.9 microg/l) were similar to those in OB (181.5+/-13.7 microg/l) and CS (229.0+/-29.1 microg/l). Basal IGFBP-3, GHBP and glucose levels in NS, OB and CS were similar while insulin levels in NS were lower (P<0.01) than those in OB and CS. In NS, the low rhGH dose induced a sustained rise of IGF-I levels (279.0+/-19.5 microg/l, P<0.001), a non-significant IGFBP-3 increase and no change in GHBP, insulin and glucose levels. In OB and CS, the IGF-I response to rhGH showed progressive increase (246.2+/-17.2 and 311.0+/-30.4 microg/l respectively, P<0.01 vs baseline). Adjusting by ANCOVA for basal values, rhGH-induced IGF-I levels in CS (299.4 microg/l) were higher than in OB (279.1 microg/l, P<0.01), which, in turn, were higher (P<0.05) than in NS (257.7 microg/l). In OB, but not in CS, IGFBP-3 and insulin levels showed slight but significant (P<0.05) increases during rhGH treatment, which did not modify glucose levels in any group; thus, in the OB patient group a significant fall in glucose/insulin ratio was observed. CONCLUSIONS: Short-term treatment with low-dose rhGH has enhanced stimulatory effect on IGF-I levels in OB and, particularly, in hypercortisolemic patients. These findings support the hypothesis that hyperinsulinism and hypercortisolism enhance the sensitivity to GH in humans.

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G Aimaretti, C Baffoni, L DiVito, S Bellone, S Grottoli, M Maccario, E Arvat, F Camanni and E Ghigo

Classical provocative stimuli of GH secretion such as insulin-induced hypoglycaemia, arginine, clonidine, glucagon and levodopa have been widely used in clinical practice for approximately 30 years. On the other hand, in the last 10 years new potent stimuli of GH secretion have been proposed, but an extensive comparison with the classical ones has rarely been performed, at least in adults. In order to compare the GH-releasing activity of old and new provocative stimuli of GH secretion, and to define the normative values of the GH response, in 178 normal adults (95 males, 83 females; age range: 20-50 years, all within +/-15% of their ideal body weight), we studied the GH response to: insulin-induced hypoglycaemia (ITT, 0.1IU/kg i.v.), arginine (ARG, 0.5g/kg i.v.), clonidine (CLO, 300 microg/kg p.o.), glucagon (GLU, 1mg i.m.), pyridostigmine (PD, 120mg p.o.), galanin (GAL, 80pmol/kg per min), GH-releasing hormone (GHRH, 1 microg/kg i.v.), GHRH+ARG, GHRH+PD, hexarelin, a GH-releasing protein (HEX, 2 microg/kg i.v.) and GHRH+HEX (0.25 microg/kg i.v.). The mean (+/-s.e.m.) peak GH response to ITT (21.8+/-2.8, range: 3.0-84.0 microg/l) was similar to those to ARG (18.0+/-1.6, range: 2.9-39.5 microg/l) or GLU (20. 5+/-2.2, range: 10.6-36.9 microg/l) which, in turn, were higher (P<0. 001) than those to CLO (8.2+/-1.6, range: 0.3-21.5 microg/l), PD (9. 6+/-1.1, range: 2.2-33.0 microg/l) and GAL (9.3+/-1.1, range: 3.9-18. 3 microg/l). The GH response to GHRH (19.1+/-1.5, range: 2.7-55.0 microg/l) was similar to those after ITT, ARG or GLU but clearly lower than those after GHRH+ARG (65.9+/-5.5, range: 13.8-171.0 microg/l) and GHRH+PD (50.2+/-4.6, range: 17.7-134.5 microg/l) which, in turn, were similar. The GH response to HEX (55.3+/-5.5, range: 13.9-163.5 microg/l) was similar to those after GHRH+ARG and GHRH+PD but lower (P<0.001) than that after GHRH+HEX (86.0+/-4.3, range: 49. 0-125.0 microg/l) which was the most potent stimulus of GH secretion. In this adult population the third centile limits of peak GH response to various stimuli were the following: ITT: 5.3; ARG: 2.9; CLO: 1.5; GLU: 7.6; PD: 2.2; GAL: 4.0; GHRH: 5.0; GHRH+ARG: 17.8; GHRH+PD: 17.9; HEX: 21.6; GHRH+HEX: 57.1. These results confirm that, among classical provocative tests of GH secretion, ITT followed by ARG and GLU are the most potent ones and possess clear limits of normality. GHRH+ARG or PD and HEX are strong stimuli of GH secretion which, however, is maximally stimulated by a combination of GHRH and a low dose of HEX. It is recommended that each test is used with appropriate cut-off limits.