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Andrea Benso, Fabio Broglio, Gianluca Aimaretti, Barbara Lucatello, Fabio Lanfranco, Ezio Ghigo and Silvia Grottoli

Context

Chronic hypoxia induces complex metabolic and endocrine adaptations. High-altitude (HA) exposure is a physiological model of hypoxia.

Objective

To further investigate the endocrine and metabolic responses to extreme HA.

Methods

We studied nine male elite climbers at sea level and at 5200 m after climbing Mt. Everest.

Results

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.

Conclusions

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.

Restricted access

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

Free access

Valentina Gasco, Flavia Prodam, Silvia Grottoli, Paolo Marzullo, Salvatore Longobardi, Ezio Ghigo and Gianluca Aimaretti

Recombinant human GH has been licensed for use in adult patients with GH deficiency (GHD) for over 15 years. Early weight- and surface area-based dosing regimens were effective but resulted in supraphysiological levels of IGF1 and increased incidence of side effects. Current practice has moved towards individualised regimens, starting with low GH doses and gradually titrating the dose according to the level of serum IGF1 to achieve an optimal dose. Here we present the evidence supporting the dosing recommendations of current guidelines and consider factors affecting dose responsiveness and parameters of treatment response. The published data discussed here lend support for the use of low GH dosing regimens in adult GHD. The range of doses defined as ‘low dose’ in the studies discussed here (∼1–4 mg/week) is in accordance with those recommended in current guidelines and encompasses the dose range recommended by product labels.

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Maria Rosa Valetto, Jaele Bellone, Claudia Baffoni, Paola Savio, Gianluca Aimaretti, Laura Gianotti, Emanuela Arvat, Franco Camanni and Ezio Ghigo

Valetto MR, Bellone J, Baffoni C, Savio P, Aimaretti G, Gianotti L, Arvat E, Camanni F, Ghigo E. Reproducibility of the growth hormone response to stimulation with growth hormone-releasing hormone plus arginine during lifespan. Eur J Endocrinol 1996;135:568–72. ISSN 0804–4643

The reliability and reproducibility of provocative stimuli of growth hormone (GH) secretion in the diagnosis of GH deficiency are still controversial both in childhood and in adulthood. The combined administration of GH-releasing hormone (GHRH) and arginine (ARG), which likely acts via inhibition of hypothalamic somatostatin release, is one of the most potent stimuli known so far and has been proposed recently as the best test to explore the maximal somatotrope capacity of somatotrope cells. However, it is well known that, usually, provocative stimuli of GH secretion suffer from poor reproducibility and that of the GHRH + ARG test has still to be verified. We aimed to verify the between- and within-subject variability of the GH response to the GHRH + ARG test in normal subjects during their lifespan as well as in hypopituitaric patients with GH deficiency (GHD). In 10 normal children (C: six male and four female, age 12.3 ± 0.9 years, body mass index (BMI) = 16.6 ± 0.7 kg/m2, pubertal stages I-III), 18 normal young adults (Y: ten male and eight female, age 31.1 ± 1.3 years, BMI = 21.4 ± 0.4 kg/m2), 12 normal elderly subjects (E: two male and ten female, age 74.4 ± 1.8 years, BMI= 22.6 ± 0.6 kg/m2) and 15 panhypopituitaric GH-deficient patients (GHD: nine male and six female, age 40.9 ± 4.1 years, BMI= 22.7 ± 1.0 kg/m2), we studied the inter- and intra-individual variability of the GH response to GHRH (1 μg/kg iv) + ARG (0.5 g/kg iv) in two different sessions at least 3 days apart. The GH responses to GHRH + ARG in C (1st vs 2nd session: 61.6 ± 8.1 vs 66.5 ± 9.4 μg/l), Y (70.4 ± 10.1 vs 76.2 ± 10.7 μg/l) and E (57.9 ± 14.8 vs 52.1 ± 8.0 μg/l) were similar and reproducible in all groups. The somatotrope responsiveness to GHRH + ARG also showed a limited within-subject variability (r = 0.71, 0.90 and 0.89 and p < 0.02, 0.0005 and 0.0005 for C, Y and E, respectively). Similarly in GHD, the GH response to the GHRH + ARG test showed a good inter- (1st vs 2nd session: 2.3 ± 0.5 vs 2.2 ± 0.6 μg/l) and intra-individual reproducibility (r = 0.70, p < 0.005). The GHRH + ARG-induced GH responses in GHD were markedly lower (p < 0.0005) than those in age-matched controls and no overlap was found between GH peak responses in GHD and normal subjects. In normal subjects, the GH response to GHRH + ARG is very marked, independent of age and shows limited inter- and intra-individual variability. The GH response to the GHRH + ARG test is strikingly reduced in panhypopituitaric patients with GHD, in whom the low somatotrope responsiveness is reproducible. Thus, these findings strengthen the hypothesis that GHRH + ARG should be considered the most reliable test to evaluate the maximal secretory capacity of somatotrope cells and to distinguish normal subjects from GHD patients in adulthood.

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

Free access

Ginevra Corneli, Carolina Di Somma, Roberto Baldelli, Silvia Rovere, Valentina Gasco, Chiara Giulia Croce, Silvia Grottoli, Mauro Maccario, Annamaria Colao, Gaetano Lombardi, Ezio Ghigo, Franco Camanni and Gianluca Aimaretti

Objective: The diagnosis of growth hormone (GH) deficiency (GHD) in adults is based on a reduced peak GH response to provocative tests, such as the insulin tolerance test (ITT) and the GH-releasing hormone-arginine (GHRH-ARG) test. However, the cut-off limits of peak GH response in lean subjects are not reliable in obese patients; this is noteworthy since adult GHD is often associated with obesity. Aim of this study was to evaluate the diagnostic cut-off limits of peak GH response to the GHRH-ARG test in overweight and obese as well as in lean population.

Design and methods: The GH responses to the GHRH-ARG test were studied in 322 patients with organic hypothalamic-pituitary disease and in 318 control subjects. Patients were subdivided into two groups on the basis of the number of pituitary hormone deficits, except for GH deficiency: (a) patients with total pituitary hormone deficit (TPHD) and (b) patients without or with no more than two pituitary hormone deficits (PHD). Both patients and control subjects were divided into three subgroups according to body mass index (BMI): lean (BMI <25 kg/m2), overweight (BMI ≥25 and <30 kg/m2) and obese (BMI ≥30 kg/m2). TPHD patients were assumed to be GH deficient, whereas PHD patients may include subjects with either normal or impaired GH secretion. The statistical analysis was carried out by the Receiver-Operating Characteristic curve analysis (Medcalc 7.2). The diagnostic cut-off points were calculated for lean, overweight and obese subjects to provide optimal separation of GH-deficient patients and control subjects according to two criteria: (1) a balance between high sensitivity and high specificity; (2) to provide the highest pair of sensitivity/specificity values for GH deficiency.

Results: In the lean population the best pair of values, with highest sensitivity as 98.7% and highest specificity as 83.7%, was found using a peak GH cut-off point of 11.5 μg/l. In the overweight population the best pair of values, 96.7 and 75.5%, respectively, was found using a peak GH cut-off point of 8.0 μg/l. In the obese population the best pair of values, 93.5 and 78.3%, respectively, was found using a peak GH cut-off point of 4.2 μg/l. Applying the above mentioned cut-off points, among PHD patients we found that 80 subjects (72%) were GHD whereas 31 (28%) had normal GH secretion.

Conclusions: In conclusion the GHRH-ARG test is a reliable tool for the diagnosis of adult GH deficiency in lean, overweight and obese patients, provided that specific BMI-related cut-off limits are assumed.

Free access

Mohamad Maghnie, Maria Cristina Pennati, Elisa Civardi, Natascia Di Iorgi, Gianluca Aimaretti, Maria Loreta Foschini, Ginevra Corneli, Carmine Tinelli, Ezio Ghigo, Renata Lorini and Sandro Loche

Objectives: Evaluation of GH response to ghrelin in patients with GH deficiency (GHD) may help to elucidate the site and mechanism of action of ghrelin. We aimed to investigate the GH-releasing effect of ghrelin in children and young adults with childhood-onset GHD.

Design: All subjects underwent ghrelin testing and neuro-imaging examination. Magnetic resonance imaging evidenced the presence of a vascular pituitary stalk (VPS) or its complete absence (PSA).

Patients and methods: Seventeen prepubertal children and nine adult patients with childhood-onset GHD were selected for the study. The children were enrolled at a median age of 5.8 years. The adult subjects were included at a median age of 23.3 years. The diagnosis of GHD in the adult patients had been established at a median age of 8.5 years. Ghrelin was administered at a dose of 1 μg/kg body weight, i.v. at time zero, and blood for GH determination was obtained at 0, 15, 30, 45, 60, 75, 90, 105 and 120 min.

Results: Median GH response after ghrelin was similar between children and adults. Median peak GH response to ghrelin (7.45 μg/l, IQR: 3.9–11.3 μg/l) was significantly higher in patients with VPS (10.9 μg/l, IQR: 2.4–15.1 μg/l) than in those with PSA (IQR: 2.3–6.7 μg/l; P = 0.001). It was significantly higher in subjects with isolated GHD (12.5 μg/l, IQR: 10.8–15.5 μg/l) than in those with multiple pituitary hormone deficiencies (5.15 μg/l, IQR: 2.4–9.0 μg/l; P = 0.003). No correlation was found between the GH peak after ghrelin and body mass index.

Conclusion: The GH response to ghrelin in patients with congenital hypopituitarism depends on the degree of the anatomical abnormalities and lends further support to the assumption that the main action of the peptide is exerted at the hypothalamic level and requires the integrity of hypothalamic–pituitary connections.

Free access

Mohamad Maghnie, Gianluca Aimaretti, Simonetta Bellone, Gianni Bona, Jaele Bellone, Roberto Baldelli, Carlo de Sanctis, Luigi Gargantini, Roberto Gastaldi, Lucia Ghizzoni, Andrea Secco, Carmine Tinelli and Ezio Ghigo

Objective: A consensus exists that severe growth hormone deficiency (GHD) in adults is defined by a peak GH response to insulin-induced hypoglycemia (insulin tolerance test, ITT) of less than 3 μg/l based on a cohort of subjects with a mean age of 45 years.

Design and methods: By considering one of the following two criteria for the diagnosis of probable permanent GHD, i.e. the severity of GHD (suggested by the presence of multiple pituitary hormone deficiencies (MPHD)) or the magnetic resonance (MR) imaging identification of structural hypothalamic–pituitary abnormalities, 26 patients (17 males, 9 females, mean age 20.8±2.3 years, range 17–25 years) were selected for re-evaluation of the GH response to ITT and their IGF-I concentration. Eight subjects had isolated GHD (IGHD) and 18 had MPHD. Normative data for peak GH were obtained after ITT in 39 healthy subjects (mean age 21.2±4.4 years, range 15.1–30.0 years) and the reference range for IGF-I was calculated using normative data from 117 healthy individuals.

Results: Mean peak GH response to ITT was significantly lower in the 26 patients (1.8±2.0 μg/l, range 0.1–6.1 μg/l) compared with the 39 controls (18.5±15.5 μg/l, range 6.1–84.0 μg/l; P < 0.0001). One subject with septo-optic dysplasia had a peak GH response of 6.1 μg/l that overlapped the lowest peak GH response obtained in normal subjects. There was an overlap for IGF-I SDS between subjects with IGHD and MPHD, as well as with normal controls. The diagnostic accuracy of a peak GH response of 6.1 μg/l showed a 96% sensitivity with 100% specificity. The maximum diagnostic accuracy with IGF-I SDS was obtained with a cut-off of −1.7 SDS (sensitivity 77%, specificity 100%) while an IGF-I ≤ − 2.0 SDS showed a sensitivity of 62%.

Conclusion: Our data show that the cut-off value of the peak GH response to ITT of less than 3 μg/l or 5 μg/l and of IGF-I of less than −2.0 SDS are too restrictive for the diagnosis of permanent GH deficiency in the transition period. We suggest that permanent GHD could be investigated more accurately by means of an integrated analysis of clinical history, the presence of MPHD, IGF-I concentration and the MR imaging findings of structural hypothalamic–pituitary abnormalities.

Free access

Ginevra Corneli, Carolina Di Somma, Flavia Prodam, Jaele Bellone, Simonetta Bellone, Valentina Gasco, Roberto Baldelli, Silvia Rovere, Harald Jörn Schneider, Luigi Gargantini, Roberto Gastaldi, Lucia Ghizzoni, Domenico Valle, Mariacarolina Salerno, Annamaria Colao, Gianni Bona, Ezio Ghigo, Mohamad Maghnie and Gianluca Aimaretti

Objective

To define the appropriate diagnostic cut-off limits for the GH response to GHRH+arginine (ARG) test and IGF-I levels, using receiver operating characteristics (ROC) curve analysis, in late adolescents and young adults.

Design and methods

We studied 152 patients with childhood-onset organic hypothalamic–pituitary disease (85 males, age (mean±s.e.m.): 19.2±0.2 years) and 201 normal adolescents as controls (96 males, age: 20.7±0.2 years). Patients were divided into three subgroups on the basis of the number of the other pituitary hormone deficits, excluding GH deficiency (GHD): subgroup A consisted of 35 panhypopituitary patients (17 males, age: 21.2±0.4 years), subgroup B consisted of 18 patients with only one or with no more than two pituitary hormone deficits (7 males, age: 20.2±0.9 years); and subgroup C consisted of 99 patients without any known hormonal pituitary deficits (60 males, age: 18.2±0.2 years). Both patients and controls were lean (body mass index, BMI<25 kg/m2). Patients in subgroup A were assumed to be GHD, whereas in patients belonging to subgroups B and C the presence of GHD had to be verified.

Results

For the GHRH+ARG test, the best pair of highest sensitivity (Se; 100%) and specificity (Sp; 97%) was found choosing a peak GH of 19.0 μg/l. For IGF-I levels, the best pair of highest Se (96.6%) and Sp (74.6%) was found using a cut-off point of 160 μg/l (SDS: −1.3). Assuming 19.0 μg/l to be the cut-off point established for GHRH+ARG test, 72.2% of patients in subgroup B and 39.4% in subgroup C were defined as GHD. In patients belonging to group B and C and with a peak GH response <19 μg/l to the test, IGF-I levels were lower than 160 μg/l (or less than 1.3 SDS) in 68.7 and 41.6% of patients respectively predicting severe GHD in 85.7% of panhypopituitary patients (subgroup A).

Conclusions

In late adolescent and early adulthood patients, a GH cut-off limit using the GHRH+ARG test lower than 19.0 μg/l is able to discriminate patients with a suspicion of GHD and does not vary from infancy to early adulthood.

Restricted access

Roberta Ricotti, Arianna Solito, Elena Mariotti Zani, Marina Caputo, Giulia Genoni, Francesco Barone-Adesi, Valentina Mancioppi, Emanuela Agosti, Gianluca Aimaretti, Simonetta Bellone and Flavia Prodam

Background/objective

Data on metabolic impairments in Cushing’s syndrome and GH deficiency all suggest that the relationship between cortisol and GH/IGF-I axis in obesity may have a role in the related diseases. However, studies focusing only on one of these hormones are often controversial in paediatrics. We aimed to explore the simultaneous relationship between cortisol and IGF-I with the metabolic alterations in paediatric obesity.

Subjects/methods

Retrospective cross-sectional study in a tertiary care center. We recruited 876 (441 males and 435 females) overweight and obese children and adolescents. A complete clinical and biochemical evaluation including OGTT was performed. Cortisol and IGF-I SDS were divided in quartiles and then crossed to explore the reciprocal influence of high/high, low/low, and high/low levels of each one on the metabolic alterations of obesity.

Results

Subjects in the higher quartiles of IGF-I-SDS and cortisol had an increased risk of hypertension, hypercholesterolemia, high levels of triglycerides, and reduced HDL cholesterol. Diversely, lower IGF-I-SDS quartiles were associated with higher blood glucose, insulin, insulin resistance, and reduced insulin sensitivity levels with the rise of cortisol quartiles.

Conclusions

We observed that apart from glucose metabolism that is associated with low IGF-I and high cortisol levels, the other parameters known to be associated with increased cardiovascular risk were related to high levels of both IGF-I and cortisol, even if within normal range. Cortisol and IGF-I play a complex role in the comorbidities of obesity, and the evaluation of both variables could clarify some of the discordant results.