Body fat mass is a strong and negative predictor of peak stimulated growth hormone and bone mineral density in healthy adolescents during transition period

The adipose tissue has detrimental effects on growth hormone secretion, even in the absence of obesity. The majority of previous studies have shown an inverse relationship between fat mass and the growth hormone response to several stimulation tests in adults and in children. The contribution of body fat mass on growth hormone response to provocative tests during the transition age is not known. We analyzed the GH-IGF1 axis by GHRH-arginine test in 30 healthy adolescents with normal stature during the transition period from 14 to 18 years. All subjects underwent body composition analysis by dual-energy X-ray absorptiometry (DXA). We found that total body fat mass was inversely correlated with peak GH to provocative test (r=-0.6, p=0.004). GH deficiency was shown in 2 of our healthy patients if diagnosis was based on GH peak below 19 μg/l. Both children who failed the GHRH-arginine were overweight (BMI for age above 85th percentile). However, their GH status was normal when assessed by insulin tolerance test. Multivariate analysis demonstrated strong correlation between peak stimulated GH and measures of body adiposity, including body mass index and fat mass index, with the latter showing the most important effect on GH secretion. Fat mass index alone explained 34.5% of the variability in peak GH. This study has shown for the first time that during the transition period, GH response to GHRH-arginine test is strongly influenced by body composition, and cutoff values appropriate for overweight and obese adolescents are needed.

Disruption of Friend of GATA 2 gene (FOG-2) by a de novo t(8;10) chromosomal translocation is associated with heart defects and gonadal dysgenesis

FOG-2 (Friend of GATA 2) is a transcriptional cofactor able to differentially regulate the expression of GATA-target genes in different promoter contexts. Mouse models evidenced that FOG-2 plays a role in congenital heart disease and normal testis development. In human, while FOG-2 mutations have been identified in sporadic cases of tetralogy of Fallot, no mutations are described to be associated with impaired gonadal function. We here describe a young boy with a balanced t(8;10)(q23.1;q21.1) translocation who was born with congenital secundum-type atrial septal defect and gonadal dysgenesis. Fluorescence in situ hybridization mapped the chromosome 8 translocation breakpoint (bkp) to within the IVS4 of the FOG-2 gene, whereas the chromosome 10 bkp was found to lie in a desert gene region. Quantitative analysis of FOG-2 expression revealed the presence of a truncated transcript but there was no detectable change in the expression of the genes flanking the 10q bkp, thus making it possible to assign the observed clinical phenotype to altered FOG-2 expression. Genetic and clinical analyses provide insights into the signaling pathways by which FOG-2 affects not only cardiac development but also gonadal function and its preservation.

Increased lipid peroxidation in adult GH-deficient patients: effects of short-term GH administration

OBJECTIVE

Adult GH deficiency (GHD) syndrome is characterized by increased risk of atherosclerosis and hence of cardio- and cerebrovascular mortality. Oxidative stress appears to play an important role in early atherogenesis. Oxidized LDL represents an important predictor of cardiovascular risk and is mainly responsible for oxidative damage of the endothelium. Its concentrations are increased in GHD, but the association between this abnormality and oxidative stress is still unclear, due to the discordant results yielded by the few available studies.

DESIGN AND METHODS

In 13 GHD patients, plasma lipid peroxide concentrations were measured before and after a 4-month treatment with recombinant human GH (rhGH) and compared with those of 13 age- and sex-matched controls. In the same subjects, the so-called "lag-time", an index of anti-oxidant activity and thus of plasma oxidative balance, was also measured using a fluorescence kinetics method.

RESULTS

Before treatment, peroxide levels were significantly higher in patients than in controls (374.0+/-31.52 vs 268.0+/-8.51 U.C., p<0.01), whereas the lag-time was significantly lower (113.0+/-10.70 vs 168.0+/-7.80 min, p<0.01). RhGH administration to patients resulted both in a significant decrease in lipid peroxide levels (from 374.0+/-31.52 to 336.0+/-33.17 U.C., p<0.01) and a significant prolongation of lag-time (from 113.0+/-10.70 to 144.0+/-15.00 min, p<0.01). After treatment, both parameters were no longer significantly different in patients and controls. Lag-time and peroxide levels at baseline did not show any correlation with IGF-I concentrations in GHD patients. After replacement therapy, however, lag-time was positively (r2= 0.62, p<0.01), and peroxide levels negatively (r2=0.41, p<0.05), correlated with IGF-I levels.

CONCLUSIONS

These data support the view that adult GHD syndrome is characterized by an unbalance between pro- and anti-oxidant factors with marked preponderance of the former. This abnormality, likely contributing to the increased atherogenic risk of GHD patients, is corrected by short-term GH administration at a dose able to increase, although not to fully normalize, IGF-I levels.

Three weekly injections (TWI) of low-dose growth hormone (GH) restore low normal circulating IGF-I concentrations and reverse cardiac abnormalities associated with adult onset GH deficiency (GHD)

GH replacement therapy given 3 times weekly (TWI) and adjusted to allow serum IGF-I concentrations in the mid-normal range for sex and age has been shown to be as effective as the daily regimen in improving lipid profile, body composition, bone mass and turnover in adult GH deficient (GHD) patients. Only one study has investigated so far the short-term (6 months) effect of a fixed weight-based TWI dosing schedule on heart structure and function in childhood onset (CO) GHD patients, whereas such a schedule in adult onset (AO) GHD patients has not been studied as yet. Aim of this study was to investigate whether a 1-yr low-dose titrated TWI GH-replacement regimen aimed at achieving and maintaining IGF-I levels within the low normal limits for age and sex is able to affect cardiovascular and heart parameters in a group of AO GHD patients. Eight adult patients (4 women and 4 men, age 35.8 +/- 3.37 yr, body mass index, BMI, 28.7 +/- 2.62 kg/m2) with AO GHD were included in the study, along with 10 healthy subjects, matched for age, sex, BMI and physical activity (6 women and 4 men, age 35.2 +/- 4.05 yr, BMI 28.4 +/- 2.34 kg/m2). M- and B- mode ecocardiography and pulsed doppler examination of transmitral flow were performed in GHD patients at baseline and after 3 and 12 months of GH therapy (mean GH dose 6.7 +/- 0.8 microg/kg/day given thrice a week), while normal subjects were studied once. Treatment with GH for 1 yr induced a significant increase in left ventricular (LV) diastolic and systolic volumes (+11.1 and +16.5%, respectively). Systolic LV posterior wall thickness and LV mass were increased (+10.2 and +7.7%, respectively) by GH administration. Systemic vascular resistance was significantly decreased by 1-yr GH therapy (-13.8% after 1 yr), while stroke volume, cardiac output and cardiac index were increased (+9.4, +11.6 and + 11.9%, respectively). LV end-systolic stress was decreased at the end of GH therapy (-11.2%). E and A wave, significantly reduced at baseline, were increased by 1 yr of GH therapy (+23.3% and +28.1%, respectively); likewise, the abnormally high E peak deceleration time was partially reversed by GH administration (-10.7%). Our study, though conducted in a small sample size, demonstrates that a TWI GH treatment schedule is able to reverse the cardiovascular abnormalities in AO GHD patients and to improve body composition and lipid profile. The maintenance of circulating IGF-I concentrations within the low normal range allows to avoid most of the side-effects reported with higher GH doses while being cost-effective and improving the patient's compliance.

Plasma ghrelin concentrations in elderly subjects: comparison with anorexic and obese patients

Ghrelin, a novel endogenous ligand for the GH secretagogue receptor, has been reported to stimulate GH secretion and food intake in both humans and other animals. Interestingly, recent data indicate that ghrelin is up- and down-regulated in anorexia nervosa (AN) and obesity, which are also known to be accompanied by increased and reduced GH levels respectively. Ageing is associated with a gradual but progressive reduction in GH secretion, and by alterations in appetite and food intake. The role of ghrelin in the decline of somatotroph function and the anorexia of ageing is unknown. To investigate the influence of age on circulating levels of ghrelin, a total of 19 young and old normal weight subjects (Y-NW, n=12; O-NW, n=7), six patients with active AN (A-AN), and seven patients with morbid obesity (OB) were studied. In addition to fasting plasma ghrelin concentrations, baseline serum TSH, IGF-I and insulin levels were measured. Mean plasma ghrelin concentrations in A-AN or OB were higher and lower respectively than those present in Y-NW. Interestingly, mean plasma ghrelin concentrations in O-NW were significantly lower than those present in Y-NW and superimposable on those of OB. The mean fasting plasma ghrelin concentrations in all groups of subjects were negatively correlated with body mass index and serum insulin levels, but not with TSH and IGF-I levels. This study provides evidence of an age-related decline of plasma ghrelin concentrations, which might explain, at least partially, the somatotroph dysregulation and the anorexia of the elderly subject.

The serum concentration of tumor necrosis factor alpha is not an index of growth-hormone- or obesity-induced insulin resistance

BACKGROUND

The tumor necrosis factor alpha (TNF-alpha) might play a central role in insulin resistance, a frequent correlate of obesity likely contributing to some obesity-associated complications. Adult growth hormone (GH) deficiency syndrome (GHDA) shares with obesity excessive fat mass, hyperlipidemia, increased cardiovascular risk, and insulin resistance. On the other hand, GH has been shown to induce transient deterioration of glucose metabolism and insulin resistance when administered in normal humans and in GHDA patients. No information is presently available on the relationship between serum TNF-alpha levels and insulin sensitivity in GHDA.

METHODS

We compared the serum TNF-alpha levels found in 10 GHDA patients before and after a 6-month recombinant human GH therapy (Genotropin), in an insulin resistance prone population of 16 obese (OB) patients and in 38 normal-weight healthy blood donors (controls). The insulin sensitivity was assessed by a euglycemic-hyperinsulinemic glucose clamp in all the GHDA patients and in 10 OB and in 6 control subjects.

RESULTS

The serum TNF-alpha levels were not significantly different in OB patients (42.2 +/- 12.81 pg/ml), in GHDA patients at baseline (71.3 +/- 23.97 pg/ml), and in controls (55.3 +/- 14.28 pg/ml). A slight decrease of TNF-alpha values was noted in GHDA patients after 6 months of recombinant human GH treatment (44.5 +/- 20.19 pg/ml; NS vs. baseline). The insulin sensitivity (M) was significantly reduced in OB patients (2.4 +/- 0.30 mg/kg/min) as compared with control subjects (7.5 +/- 0.39 mg/kg/min) and in GHDA patients both at baseline (6.6 +/- 0.6 mg/kg/min) and after recombinant human GH therapy (5.6 +/- 0.7 mg/kg/min). The insulin sensitivity in the GHDA patients, similar to that of controls at baseline, worsened after recombinant human GH treatment (p < 0.05 vs. baseline; p = 0.05 vs. controls). Linear regression analysis showed no correlation between TNF-alpha and M values (see text) in all patient groups.

CONCLUSIONS

These data indicate that circulating concentrations of TNF-alpha do not reflect the degree of insulin resistance in obesity and GHDA. They, however, do not exclude that TNF-alpha may induce insulin resistance at tissue level.

Prevalence and pathogenesis of sleep apnea and lung disease in acromegaly

Respiratory disorders are common and important complications in acromegaly. Patients suffering from acromegaly display a 1.6-3.3 fold increase in mortality rate, which is due to respiratory disorders in 25% of cases. In these patients, mortality for lung disease is 2-3 fold higher than in the general population. Every portion of the respiratory system may be involved. Deformities of facial bones, edema and hypertrophy of the mucosae and pharyngeal and laryngeal cartilages, enlargement of the tongue and inspiratory collapse of the hypopharinx, all may contribute to respiratory alterations. Nasal polyps, "hormonal rhinitis", changes of the voice and snoring are common occurrences. Though rarely, a laryngocele may ensue. Pneumomegaly is frequently observed and, as suggested by functional studies, might be due to an increased number rather than volume of the alveoli. An obstructive respiratory syndrome caused by mucosal thickening of the upper airways and bronchi is observed in 25% of female and 70% of male patients. The sleep apnea syndrome (SAS) affects 60-70% of acromegalic patients. SAS may be of obstructive, central or mixed type. Obstructive SAS is the prevailing form in acromegaly. It is due to intermittent obstruction of upper airways with preserved activity of the respiratory center, as testified by the remarkable thoracic and abdominal respiratory efforts. The pathogenesis of the central type of SAS is more complex. Narrowing of the upper airways may induce reflex inhibition of the respiratory center. Moreover, increased GH levels and, possibly, defects in the somatostatinergic pathways, may increase the ventilatory response of the respiratory center to carbon dioxide, thereby leading to respiratory arrest. In the mixed type of SAS, the phenomena underlying the other two forms coexist. Oxygen desaturation concomitant with the apneic episodes accounts for the frequent nocturnal wakening and diurnal drowsiness. Among the clinical correlates of SAS, arterial hypertension is of particular interest due to the close correlation existing between the two disorders. Sleep deprivation related to SAS seems per se to favor the appearance of hypertension. Moreover, short lasting hypoxemia may induce prolonged elevations of blood pressure, mediated by decreased endothelial generation of nitric oxide. Thus, since cardiovascular events are the main cause of mortality in patients with acromegaly, it is reasonable to hypothesize that SAS is involved in the reduced life span of these patients.

Hyperinsulinemia in the physiologic range is not superior to short-term fasting in suppressing insulin secretion in obese men

The negative-feedback control exerted by plasma insulin on beta-cell insulin release in normal-weight and obese subjects is still a matter of debate. Subjects submitted to a euglycemic insulin clamp undergo a suppression of insulin secretion that is due to both the infused insulin and the 2- to 3-hour fast during the procedure. We elected to elucidate the role of physiologic hyperinsulinemia per se in the insulin negative autofeedback in obese men. Ten men with massive uncomplicated obesity (age, 18 to 37 years; body mass index [BMI], 41 +/- 1.15 kg/m2) and 6 normal-weight healthy men (age, 22 to 30 years; BMI, 22 +/- 0.28 kg/m2) underwent 2 studies in random order: (1) a euglycemic-hyperinsulinemic glucose clamp with an insulin infusion rate of 1 mU/kg/min and (2) a control study with saline infusion. Serum C-peptide concentrations were significantly higher in obese versus control subjects at baseline (2.54 +/- 0.178 v 1.63 +/- 0.256 ng/mL, P < .05). Exogenous insulin infusion significantly suppressed serum C-peptide at steady state ([SS] last 30 minutes of insulin or saline infusion) in controls (mean of the last 4 measurements from 120 minutes to 150 minutes, 0.86 +/- 0.306 ng/mL, P < .05 vbaseline) but not in obese patients (2.03 +/- 0.26 ng/mL, nonsignificant [NS] v baseline). During the saline infusion studies, C-peptide levels slightly and similarly declined over time in both groups (2.71 +/- 0.350 at baseline v 2.31 +/- 0.300 ng/mL at SS in obese patients, NS, and 1.96 +/- 0.189 v 1.62 +/- 0.150 ng/mL in controls, NS). This study shows that in obese men hyperinsulinemia within the postprandial range is not superior to a 2.5-hour fast for the suppression of beta-cell activity, suggesting an impairment of the insulin negative autofeedback in this clinical condition.

Effects of recombinant human insulin-like growth factor I administration on spontaneous and growth hormone (GH)-releasing hormone-stimulated GH secretion in anorexia nervosa

Exaggerated GH and reduced insulin-like growth factor I (IGF-I) levels are common features in anorexia nervosa (AN). A reduction of the negative IGF-I feedback could account, in part, for GH hypersecretion. To ascertain this, we studied the effects of recombinant human (rh)IGF-I on spontaneous and GH-releasing hormone (GHRH)-stimulated GH secretion in nine women with AN [body mass index, 14.1 +/- 0.6 kg/m2] and in weight matched controls (normal weight). Mean basal GH concentrations (mGHc) and GHRH (2.0 microg/kg, iv) stimulation were significantly higher in AN. rhIGF-I administration (20 microg/kg, sc) significantly reduced mGHc in AN (P < 0.01), but not normal weight, and inhibited peak GH response to GHRH in both groups; mGHc and peak GH, however, persisted at a significantly higher level in AN. Insulin, glucose, and IGFBP-1 basal levels were similar in both groups. rhIGF-I inhibited insulin in AN, whereas glucose remained unaffected in both groups. IGFBP-1 increased in both groups (P < 0.05), with significantly higher levels in AN. IGFBP-3 was under basal conditions at a lower level in AN (P < 0.05) and remained unaffected by rhIGF-I. This study demonstrates that a low rhIGF-I dose inhibits, but does not normalize, spontaneous and GHRH-stimulated GH secretion in AN, pointing also to the existence of a defective hypothalamic control of GH release. Moreover, the increased IGFBP-1 levels might curtail the negative IGF-I feedback in AN.

Growth hormone in obesity

Growth hormone (GH) secretion, either spontaneous or evoked by provocative stimuli, is markedly blunted in obesity. In fact obese patients display, compared to normal weight subjects, a reduced half-life, frequency of secretory episodes and daily production rate of the hormone. Furthermore, in these patients GH secretion is impaired in response to all traditional pharmacological stimuli acting at the hypothalamus (insulin-induced hypoglycaemia, arginine, galanin, L-dopa, clonidine, acute glucocorticoid administration) and to direct somatotrope stimulation by exogenous growth hormone releasing hormone (GHRH). Compounds thought to inhibit hypothalamic somatostatin (SRIH) release (pyridostigmine, arginine, galanin, atenolol) consistently improve, though do not normalize, the somatotropin response to GHRH in obesity. The synthetic growth hormone releasing peptides (GHRPs) GHRP-6 and hexarelin elicit in obese patients GH responses greater than those evoked by GHRH, but still lower than those observed in lean subjects. The combined administration of GHRH and GHRP-6 represents the most powerful GH releasing stimulus known in obesity, but once again it is less effective in these patients than in lean subjects. As for the peripheral limb of the GH-insulin-like growth factor I (IGF-I) axis, high free IGF-I, low IGF-binding proteins 1 (IGFBP-1) and 2 (IGFBP-2), normal or high IGFBP-3 and increased GH binding protein (GHBP) circulating levels have been described in obesity. Recent evidence suggests that leptin, the product of adipocyte specific ob gene, exerts a stimulating effect on GH release in rodents; should the same hold true in man, the coexistence of high leptin and low GH serum levels in human obesity would fit in well with the concept of a leptin resistance in this condition. Concerning the influence of metabolic and nutritional factors, an impaired somatotropin response to hypoglycaemia and a failure of glucose load to inhibit spontaneous and stimulated GH release are well documented in obese patients; furthermore, drugs able to block lipolysis and thus to lower serum free fatty acids (NEFA) significantly improve somatotropin secretion in obesity. Caloric restriction and weight loss are followed by the restoration of a normal spontaneous and stimulated GH release. On the whole, hypothalamic, pituitary and peripheral factors appear to be involved in the GH hyposecretion of obesity. A SRIH hypertone, a GHRH deficiency or a functional failure of the somatotrope have been proposed as contributing factors. A lack of the putative endogenous ligand for GHRP receptors is another challenging hypothesis. On the peripheral side, the elevated plasma levels of NEFA and free IGF-I may play a major role. Whatever the cause, the defect of GH secretion in obesity appears to be of secondary, probably adaptive, nature since it is completely reversed by the normalization of body weight. In spite of this, treatment with biosynthetic GH has been shown to improve the body composition and the metabolic efficacy of lean body mass in obese patients undergoing therapeutic severe caloric restriction. GH and conceivably GHRPs might therefore have a place in the therapy of obesity.

Metabolic effects of biosynthetic growth hormone treatment in severely energy-restricted obese women

OBJECTIVE

Severe energy restriction in the treatment of obesity is limited by catabolism of body protein stores and, consequently, loss of lean as well as fat tissue. Growth hormone (GH), whose secretion is markedly impaired in obesity, is endowed with both lipolytic and protein anabolic properties. The aim of this study was to verify the effects of GH administration on body composition, plasma leptin levels and energy metabolism in obese patients undergoing severe dietary restriction.

DESIGN

Single-blind placebo-controlled study. Twenty obese women were fed a diet of 41.86 kJ/kg ideal body weight (IBW) daily for 4 weeks: 10 of them were randomly assigned to a 4 week treatment with biosynthetic GH (rhGH, Saizen, Serono, Rome, Italy), 1 U/kg IBW/week in daily subcutaneous injections; the other 10 patients, matched for age and BMI, received vehicle only.

SUBJECTS

Twenty women with simple obesity (age: 25.4+/-1.07 y, BMI: 35.9+/-0.35 kg/m2).

MEASUREMENTS

Plasma IGF-I and leptin, serum markers of bone turnover (serum bone isoenzyme of alkaline phosphatase, osteocalcin and urinary hydroxyproline), nitrogen balance, body composition (by DEXA), and resting energy expenditure (REE, by indirect calorimetry) were evaluated at baseline and after 4 weeks.

RESULTS

Mean IGF-I plasma levels, not influenced by energy restriction in patients receiving placebo, displayed a significant increase in the group treated with rhGH. The mean weight reduction and fat mass loss were not significantly different in the two groups (6.0+/-0.51 vs 7.2+/-0.30 kg, NS, and 5.36+/-0.460 vs 4.28+/-0.572 kg, NS, with rhGH and placebo, respectively). Likewise, plasma leptin levels decreased significantly in weight-reduced subjects receiving either rhGH (from 16.2+/-2.37 to 6.4+/-0.39 ng/ml, P < 0.05) or placebo (from 14.3+/-2.55 to 7.7+/-3.77 ng/ml, P < 0.05). On the contrary, the mean decrease of lean body mass (LBM) was significantly lower in the GH-treated patients than in those receiving vehicle (1.52+/-0.60 vs 3.79+/-0.45 kg, P < 0.05). In keeping with these findings, the mean daily nitrogen balance was significantly less negative in the GH-treated subjects than in the vehicle-injected patients (mean of the 4 week daily urine collections -185.7+/-40.33 vs -363.9+/-55.47 mmol/d, P < 0.05, respectively). Further, a significant reduction of mean REE was recorded in the energy-restricted placebo-treated patients (from 8807+/-498 to 7580+/-321 kJ/24 h, P < 0.05), but not in the patients receiving rhGH (from 8367+/-580 to 8903+/-478 kJ/24 h, NS). Actually, when corrected for LBM, REE was even increased by GH administration (from 197.9+/-11.76 to 219.3+/-9.87 kJ/kg LBM/24 h, P < 0.05), whereas it was unchanged in the placebo group (from 201.7+/-13.85 to 190.0+/-9.87 kJ/kg LBM/24 h, NS). A tendency of serum markers of bone turnover to increase was observed in the patients treated with rhGH, however with no changes in bone mineral content and density.

CONCLUSION

rhGH treatment, though unable to enhance diet-induced weight and fat mass reduction, was effective in stimulating IGF-I production and conserving LBM and increasing its energy metabolism even in the presence of severe energy restriction.

Spontaneous nocturnal growth hormone secretion in anorexia nervosa

In anorexia nervosa, serum GH levels are increased under basal conditions and respond abnormally to provocative stimuli. We report here, for the first time, an analysis of pulsatile GH secretion in these patients performed by Cluster algorithm. Seven anorectic and six normal weight, healthy women underwent serial blood sampling at 20-min intervals form 2030-0830 h for GH estimation. The total area under the curve (AUC; micrograms per L/min) was elevated 4-fold in anorectic patients compared to controls (4743.0 +/- 1520.09 vs. 1148.6 +/- 519.27; P < 0.01), largely due to an increase in the non-pulsatile fraction (3212.5 +/- 990.45 vs. 378.7 +/- 123.27; P < 0.01). Accordingly, the valley mean value was higher in anorectic than in control subjects (5.9 +/- 2.25 vs. 1.0 +/- 1.30 micrograms/L; P < 0.01). Furthermore, pulsatile AUC was also greater in anorectic patients (1530.4 +/- 654.72 vs. 769.8 +/- 404.02; P < 0.01) due to a significant increase in GH peak frequency (5.0 +/- 0.81 vs. 3.0 +/- 0.89; P < 0.01). No correlations were observed in these patients between body mass index and any of the parameters of spontaneous GH release, whereas a positive correlation was found between insulin-like growth factor I levels and pulsatile AUC (r2 = 0.583; P < 0.05), peak height (r2 = 0.743; P = 0.01), peak increment (r2 = 0.801; P < 0.01), and GH valley mean (r2 = 0.576; P < 0.05). In conclusion, it appears that the enhanced GH secretion in anorexia nervosa is the result of an increased frequency of secretory pulses superimposed on enhanced tonic GH secretion. Although this latter is consistent with a reduction of hypothalamic SRIH tone, the former may be accounted for by an increased number of GHRH discharges. Considering that in normal weight and obese subjects parameters of GH release are negatively correlated with adiposity indexes, the lack of such a negative correlation in our patients suggests that the enhancement of spontaneous GH release in anorectic patients is not merely the consequence of malnutrition-dependent impairment of insulin-like growth factor I production, but reflects a more complex hypothalamic dysregulation of GH release.

Effect of chronic treatment with biosynthetic growth hormone (GH) on the GH response to double GH-releasing hormone administration in children with short stature

Growth hormone (GH) exerts a negative feedback on its own secretion through direct and indirect mechanisms. Normal children, unlike adults, display consecutive GH responses after repeated GH-releasing hormone (GHRH) administration. In this study, we investigated the effects of long-term GH administration on this peculiar secretory pattern. Eight children with severe short stature and impaired GH responses to suprapituitary provocative stimuli associated with normal GH responsiveness to GHRH, underwent, while on chronic treatment with biosynthetic GH and on the 10th day following drug withdrawal, a double bolus GHRH test (two GHRH injections of 1 microg/kg b.w. given as i.v. boluses two hours apart). During GH therapy the GH response to the first GHRH bolus appeared to be reduced, though not significantly so, compared to that observed at diagnosis; after treatment withdrawal, this response returned quite similar to pretreatment. Both during and after treatment, the GH response to the second GHRH bolus was comparable for magnitude to that evoked by the first application. In conclusion, even prolonged treatments with rhGH do not induce persisting alterations of the physiological mechanisms subserving GH regulation.

Influence of insulin on beta-endorphin plasma levels in obese and normal weight subjects

OBJECTIVE

To establish the possible role of hyperinsulinemia in the elevation of plasma beta-endorphin (beta-EP) levels observed in obese patients after an oral glucose load.

DESIGN

Oral glucose tolerance test (OGTT) and euglycemic-hyperinsulinemic clamp.

SUBJECTS

Two groups of six (age: 22-39 y, BMI: 30-48 kg/m2) and eight obese men (age: 18-37 y, BMI: 35-45 kg/m2), respectively, and five normal weight healthy men (age: 22-30 y, BMI 22-23 kg/m2).

MEASUREMENTS

Glucose, insulin and beta-EP levels at baseline and every 30 min until 180 min during the OGTT; glucose, insulin, C-peptide and beta-EP concentrations at baseline and in steady state condition (i.e. during the last 30 min of insulin infusion) in the euglycemic-hyperinsulinemic clamp studies.

RESULTS

In the six obese patients undergoing the OGTT a significant elevation of beta-EP plasma levels was observed between 60 and 90 min after glucose ingestion. In the clamp studies no significant differences in beta-EP plasma levels, blood glucose and serum insulin were observed between obese and normal weight subjects both at baseline and at steady state. A markedly diminished insulin sensitivity along with a lower inhibition of C-peptide during insulin infusion was observed in obese patients compared to control subjects.

CONCLUSION

A rise in serum insulin levels unaccompanied by a concomitant increase in blood glucose concentration is unable to elicit a beta-EP response in obese patients.

Lack of growth hormone response to acute administration of dexamethasone in anorexia nervosa

High plasma growth hormone (GH) levels, associated with abnormal hormone responses to provocative stimuli, point to an altered GH secretion in anorexia nervosa. The GH-releasing effect of acutely administered glucocorticoids, firmly established in normal subjects, has not been reported in these patients. In this study, acute iv administration of 4 mg of dexamethasone, compared with saline, increased plasma GH in nine normal-weight women (AUC 848.2 +/- 127.95 vs 242.8 +/- 55.35 micrograms.l-1.min-1, p < 0.05, respectively) but was ineffective in 11 anorectic patients (AUC 3271.8 +/- 1407.11 vs 2780.0 +/- 1162.04 micrograms.l-1.min-1, NS). After dexamethasone, a significant lowering of plasma cortisol was observed in normal women (AUC 25367.0 +/- 3128.43 vs 47347.1 +/- 4456.61 nmol.l-1.min-1, after dexamethasone and saline, respectively, p < 0.05), but not in anorectic patients (AUC 77809.3 +/- 8499.92 vs 78454.9 +/- 7603.62 nmol.l-1.min-1, NS). In both groups, plasma adrenocorticotrophin (ACTH) displayed a significant decrease after dexamethasone (AUC 523.6 +/- 92.08 vs 874.2 +/- 115.03 pmol.l-1.min-1, p < 0.05, after dexamethasone and saline, respectively, in anorectic patients and 377.5 +/- 38.41 vs 1004.9 +/- 200.51 pmol.l-1.min-1, p < 0.05, in controls). However, when considering the hormonal decremental areas, a significant dexamethasone-induced ACTH inhibition, compared to saline, was evidenced in normal (delta AUC -414.4 +/- 65.75 vs 222.9 +/- 42.40 pmol.l-1.min-1, p < 0.05) but not in anorectic women (delta AUC -254.2 +/- 96.92 vs 2.9 +/- 132.32 pmol.l-1.min-1, NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of follicle maturation and ovulation by gonadotropin administration in women with beta-thalassemia

The objective of this paper was to assess the ability of gonadotropin administration to induce ovarian steroidogenesis, follicle maturation and ovulation in hypogonadal women affected by beta-thalassemia. Thirteen hypogonadal thalassemic women underwent a test with gonadotropin-releasing hormone (GnRH), with estimation of serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels. They were then administered human menopausal gonadotropin (hMG) for a period ranging from 11 to 15 days with a total dose variable from 3,300 to 4,200 IU. In each patient, the initial dosage of 300 IU daily, adopted for the first 9 days, was modified subsequently according to the ovarian morphology, as shown by serial echographic examinations and by serum estradiol levels. In those patients in whom a dominant follicle was evidenced and the occurrence of pregnancy could be excluded, induction of ovulation was attempted by administration of 10,000 IU of human chorionic gonadotropin (hCG). All patients displayed a reduced LH and FSH rise in response to GnRH. Upon hMG administration, they exhibited echographic evidence of follicular growth with a clear-cut increase of serum estradiol, which peaked between the 9th and the 16th day from the start of treatment. In two out of three patients in whom a dominant follicle developed, ovulation was induced successfully by hCG injection, as shown by the increase of serum progesterone and by the ultrasonographic demonstration of a corpus luteum. This study has shown that, by proper pharmacological stimulation, the steroidogenic function of the gonads and even ovulation can be reinstated in hypogonadal thalassemic women.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of meal ingestion on insulin profiles following intraperitoneal delivery

This study evaluated the effect of meal ingestion on intraperitoneal insulin absorption in type I diabetic patients with an implanted pump for long-term intraperitoneal insulin delivery. On four separate occasions, patients (n = 7) were administered 15 IU insulin as a 20-minute square-wave infusion using their implanted device; hypoglycemia was prevented by intravenous infusion of 10% dextrose at a variable rate. Two studies were performed during fasting conditions (n = 2 fasting tests) and two studies after the administration of an 800-kcal standard meal (n = 2 postprandial tests). An insulin peak of 630 +/- 545.4 pmol/L (mean +/- SD) in fasting tests and 696 +/- 420.5 pmol/L in postprandial tests was reached in the peripheral circulation after 45 +/- 11.7 and 45 +/- 14.7 minutes, respectively, with no significant difference between the two experimental conditions. Areas under the insulin curves were not significantly different in fasting and postprandial tests (51,500 +/- 34,278 v 50,916 +/- 20,558 pmol/L.min-1, respectively; NS). In type I diabetic patients receiving long-term intraperitoneal insulin therapy, the increase in splanchnic blood flow following ingestion of a standard meal does not accelerate the appearance of insulin in the peripheral circulation.