Prevalence and characteristics of metabolic syndrome in primary hyperparathyroidism.

AIMS: Primary hyperparathyroidism (pHPT) is characterized by an increased frequency of glucose tolerance abnormalities associated with insulin resistance. Few studies evaluated the prevalence of metabolic syndrome (MetS) in pHPT and whether there are differences between asymptomatic pHPT patients and symptomatic ones. Thus, we sought to investigate the prevalence of MetS in pHPT patients in comparison to the prevalence of MetS in Italian population. SUBJECTS AND METHODS: We conducted a retrospective chart review of 294 pHPT patients, of these 154 [age (mean ± SD) 58.7 ± 13.3 yr, body mass index 25.6 ± 4.8 kg/m(2); serum calcium (11.3 ± 1.2 mg/dl) 2.8 ± 0.3 mmol/l; PTH 234.8 ± 224.3 ng/l] met the inclusion criteria. A modified National Cholesterol Educational Program (NCEP)/Adult Treatment Panel III (ATP III) definition of the MetS was used. Prevalence of MetS was compared with that reported for the Italian population (Progetto Cuore Study). RESULTS: The prevalence of the MetS (34/154, 22.1%) was similar to that reported in the general Italian population. Asymptomatic pHPT patients were older (62.1 ± 12.7 vs 56.4 ± 13.2 yr, p<0.008) and showed higher prevalence of MetS than symptomatic ones (30.2% vs 16.5%, p<0.045). Moreover the prevalence of nephrolitiasis or overt bone disease was not different between patients MetS+pHPT compared to MetS-pHPT, whereas femoral bone mineral density (BMD) was higher in MetS+pHPT (p<0.003). In the logistic regression model age and femoral BMD were independent predictors of MetS. CONCLUSIONS: The prevalence of MetS in pHPT is not increased in comparison to the general population, thus, its diagnosis is not an appropriate tool to identify the additional cardiovascular risk related to pHPT. Difference in age affects the increased prevalence of MetS in asymptomatic pHPT patients.

Interplay between serum osteocalcin and insulin sensitivity in primary hyperparathyroidism.

Osteocalcin (OC) has been proposed as a regulator of insulin sensitivity in both humans and other animals. Primary hyperparathyroidism (PHPT) is characterized by high OC levels and insulin resistance. The aim of this study was to evaluate whether in PHPT the link between OC levels and blood markers of insulin resistance was maintained. In a consecutive series of 219 adult PHPT patients, serum OC as well as fasting insulin and glucose levels were measured. Insulin sensitivity was estimated by homeostatic model assessment (HOMA2-S%). The same parameters were evaluated in a subgroup of 45 patients after parathyroidectomy (PTX). PHPT patients were characterized by markedly high OC levels. After subdividing them according to glucose tolerance, it was found that OC was similar in subjects with normal glucose tolerance (NGT) and impaired glucose tolerance (IGT), while diabetic subjects had lower serum OC than those with NGT (P < 0.02) or IGT (P < 0.04). OC was negatively associated with fasting glucose and positively associated with HOMA2-S%. OC independently predicted HOMA2-S% in a multivariate analysis. In the subgroup of surgically cured PHPT patients, OC levels significantly decreased after PTX, while HOMA2-S% did not change. Our findings indicate that in PHPT there is a positive relationship between OC and glucose metabolism, OC being one of the predictors of insulin sensitivity. However, data in surgically cured patients, showing OC normalization in spite of unchanged HOMA2-S%, suggest that OC does not likely play a major role in affecting insulin sensitivity in PHPT.

Hypopituitaric patients with corticotropin insufficiency show marked impairment of the cortisol response to ACTH (1-24) independently of the duration of the disease.

It is widely accepted that the classical dose of 250.0 microg ACTH (1-24) (tetracosactin) is clearly supra-maximal while 1.0 and 0.03 microg have been shown as the maximal and the lowest stimulatory ACTH doses for cortisol (F) secretion in normal young subjects. Testing with low ACTH dose would better evaluate adrenal sensitivity to corticotropin. The aims of the present study were: a) to clarify the adrenal sensitivity to ACTH in patients with different duration of corticotroph insufficiency by testing with low and very low tetracosactin doses; and b) to evaluate diagnostic implication regarding the ability of ACTH tests to distinguish patients with corticotroph insufficiency from normal subjects. In 24 hypopituitaric patients (HYPOPIT, 15 male and 9 female, age 22-50 yr, BMI: 22-26 kg/m2) with corticotrophin deficiency we studied the F, DHEA and aldosterone (A) responses to challenges with low ACTH doses (0.06 or 0.5 microg iv at 0 min) followed by 250 microg iv (at +60 min). The results in HYPOPIT were compared with those recorded in 12 normal controls (NS, 6 male and 6 female, age 22-34 yr, BMI: 20-25 kg/m2). Basal F and DHEA levels in HYPOPIT were lower than in NS, while A levels were similar in both groups. The F responses to ACTH in HYPOPIT were dose-independent and markedly lower (p < 0.0001) than in NS. After the 0.06 and 0.5 microg ACTH dose, 16% of HYPOPIT patients showed AF peak within the range of normal response. No HYPOPIT showed AF peak within the normal range after 250 microg ACTH. The DHEA responses to ACTH in HYPOPIT were dose-independent and markedly lower than in NS (p < 0.0001). Overlap between individual DHEA responses in HYPOPIT and NS was present after 0.06 microg and 0.5 microg but not after 250 microg tetracosactin. The A responses in HYPOPIT were dose-dependent and overlapped with those in NS. The adrenal responses to ACTH in HYPOPIT were not associated with the duration of the disease. In conclusion, the present study shows that the mean F and DHEA but not the A responses to ACTH (1-24) are markedly impaired in hypopituitaric patients with corticotroph insufficiency independently of the duration of the disease. The impaired F and DHEA response to ACTH is also independent of the dose, suggesting the existence of relatively enhanced sensitivity of the fasciculata and reticularis adrenal zone to ACTH but meantime remarkable impairment of the adrenal function due to corticotrophin deficiency. In the present study, testing with submaximal ACTH doses did not distinguish patients with secondary adrenal insufficiency from normal subjects.

Short children with familial short stature show enhancement of somatotroph secretion but normal IGF-I levels.

The aim of the present study was to evaluate the GH status in children with familial, idiopathic short stature (FSS). To this goal we evaluated the GH response to GHRH (1 microg/kg iv) + arginine (ARG) (0.5 g/kg iv) test which is one of the most potent and reproducible provocative tests of somatotroph secretion, in 67 children with FSS [50 boys and 17 girls, age 10.8+/-0.4 yr, pubertal stages I-III, height between -3.6 and -1.6 standard deviation score (SDS), target height <10 degrees centile, normality of both spontaneous and stimulated GH secretion as well as of IGF-I levels]. The results in FSS were compared with those in groups of children of normal height (NHC) (42 NHC, 35 boys and 7 girls, age 12.0+/-0.5 yr, pubertal stages I-III, height between -1.3 and 1.4 SDS, height velocity standard deviation score (HVSDS)>25 degrees centile, GH peak >20 microg/l after GHRH+ARG test, mean GH concentration [mGHc]>3 microg/l) and children with organic GH deficiency (GHD) (38 GHD, 29 boys and 9 girls, age 11.2+/-3.7 yr, pubertal stages I-III, height between -5.7 and -1.3 SDS, GH peak <20 microg/l after GHRH +ARG test, mGHc <3 mg/l). Basal IGF-I levels and mGHc were also evaluated in each group over 8 nocturnal hours. IGF-I levels in FSS (209.2+/-15.6 microg/l) were similar to those in NHC (237.2+/-17.2 microg/l) and both were higher (p<0.0001) than those in GHD (72.0+/-4.0 microg/l). The GH response to GHRH +ARG test in FSS (peak: 66.4+/-5.6 microg/l) was very marked and higher (p<0.01) than that in NHC (53.3+/-4.5 microg/l) which, in turn, was higher (p<0.01) than in GHD (8.2+/-0.8 microg/l). Similarly, the mGHc in FSS was higher than in NHC (6.7+/-0.5 microg/l vs 5.1+/-0.7 microg/l, p<0.05) which, in turn, was higher than in GHD (1.5+/-0.2 microg/l, p<0.0001). In conclusion, our present study demonstrates that short children with FSS show enhancement of both basal and stimulated GH secretion but normal IGF-I levels. These findings suggest that increased somatotroph function would be devoted to maintain normal IGF-I levels thus reflecting a slight impairment of peripheral GH sensitivity in FSS.

Impairment of GH secretion in adults with primary empty sella.

Primary empty sella (PES) is generally not associated with overt endocrine abnormalities, although mild hyperprolactinemia and, in children, deficient GH secretion have been reported. The aim of this multi-center collaborative study was to evaluate basal and stimulated GH secretion in a large series of adult PES patients. The study group consisted of 51 patients [41 women and 10 men, age range: 20-78 yr; (mean+/-SD) 47+/-11 yr]; results were compared with those in normal subjects (Ns) (Ns: no.=110, 55 women, age: 20-50 yr, 37+/-14 yr), and in hypopituitaric patients (HYP) with GH deficiency (HYP: no.=44,17 women, age: 20-72, 49+/-16 yr). Baseline IGF-I levels and GH responses to insulin-induced hypoglycemia (insulin tolerance test, ITT) and/or GHRH+arginine (ARG) stimulation tests were evaluated. PES patients were also subdivided according to BMI in lean (BMI <28 kg/M2 no.=22) or obese (BMI >28 kg/m2 no.=29). PES patients had serum total IGF-I concentrations (mean+/-SE: 142.2+/-9.6 ng/ml) higher than HYP patients (77.4+/-6.4 ng/ml, p<0.001), but lower than Ns (213.3+/-17.2 ng/ml, p<0.005), with no differences between lean and obese PES subjects. The increase in serum GH concentrations following ITT and/or GHRH+ARG stimulation tests, although higher than that observed in HYP patients, was markedly reduced with respect to Ns. No difference was observed in the GH response to provocative tests between lean and obese PES patients. When individual GH responses to ITT or GHRH+ARG were taken into account, a large proportion of PES patients (52% after ITT, 61% after GHRH+ARG) showed a GH peak increase below the 1st centile of normal limits. Serum IGF-I levels in PES patients with blunted GH responses to provocative tests were significantly (p<0.001) lower in PES patients with normal GH responses, and a positive correlation was observed between IGF-I levels and serum GH peak concentrations after GHRH+ARG. In conclusion, the results of the present study provide evidence that adult PES patients often have an impairment of GH secretion, as indicated by the blunted GH response to ITT and GHRH+ARG provocative tests, and by the reduction in serum IGF-I levels. These changes are independent of body mass.

Growth hormone deficiency in the transition adolescent: should treatment be continued in adult life?

Adults with growth hormone (GH) deficiency (GHD) have impaired health, which improves with GH replacement. GHD in adulthood leads to impairment in body composition and structure functions as well as to deranged lipoprotein and carbohydrate metabolism leading to increased cardiovascular morbidity. Therefore the transition adolescent in whom severe GHD is confirmed has to continue GH replacement with an appropriate age-related dosage. All short children who have been treated with rhGH for classical and non-classical GHD should be suspected as potentially GHD in adulthood though only in classical organic and idiopathic forms is severe GHD likely to be confirmed. GHD must be shown biochemically by single provocative testing. Insulin-induced hypoglycemia (ITT) and GHRH + arginine are the tests of choice provided that appropriate cutoff limits are assumed; these tests show good specificity and sensitivity. Testing with GHRH + GH secretagogues is another reliable alternative. Low IGF-I levels can be definitive evidence of persistent severe GHD in patients with genetic GHD or panhypopituitarism, but normal IGF-I levels do not rule out severe GHD. Individual titration of the rhGH dose is recommended and measurement of IGF-I levels is needed for monitoring the adequacy of replacement. The mean GH dose for replacement in the transition adolescent, however, is still higher than in adulthood; after puberty the rhGH dose should be progressively decreased in the following years (probably up to 25 years old) in order to obtain optimal peak bone mass.

Short procedure of GHRH plus arginine test in clinical practice.

Either in children or in adults, arginine (ARG) alone and combined with GHRH (GHRH+ARG) are reliable tests for the diagnosis of GH deficiency. The procedures of these tests generally include GH measurement every 15 min from baseline up to 90-120 min. Aim of our study was to verify if the procedure of these tests could be usefully shortened in clinical practice. To this goal we have studied 173 normally growing children and adolescents (C, 117 M and 56 F, age: 11.3 +/- 0.4 yr.) and 125 young and middle aged normal adults (A, 68 M and 57 F, age: 30.0 +/- 0.6 yr.). ARG alone test was performed by 81 C and 33 A (0.5 g/kg arginine, i.v., from 0 to +30 min, up to a maximum of 30 g) while GHRH (1 microg/kg i.v. bolus at 0 min) + ARG test was performed by 92 C and 92 A. After ARG alone, taking into account data from +15 to +105 min, GH values above the 3rd centile limit of arbitrary cut-off (7 or 10 microg/l in C and 5 microg/l in A) occurred in 85% or 64% and 94% subjects, respectively. After GHRH+ARG test, taking into account only data at +30, +45, +60 min GH values above the 3rd centile limit (20 microg/l in C and 16.5 microg/l in A) occurred in 99% of subjects in both groups. Taking into account only these 3 timing points, the percentage of GH peak above the third centile limits after ARG alone was never higher than 60% in C and 85% in A. In conclusion, this study shows that single GHRH+arginine test can be reliably performed in a shortened procedure which makes easier the clinical practice and further reduces costs.

Retesting young adults with childhood-onset growth hormone (GH) deficiency with GH-releasing-hormone-plus-arginine test.

Within an appropriate clinical context, severe GH deficiency (GHD) in adults has to be defined biochemically by provocative testing of GH secretion. Patients with childhood-onset GHD need retesting in late adolescence or young adulthood to verify whether they have to continue recombinant human GH treatment. GHRH + arginine (GHRH+ARG) is the most reliable alternative to the insulin-induced hypoglycemia test (ITT) as a provocative test for the diagnosis of GHD in adulthood, provided that appropriate cut-off limits are assumed (normal limits, 16.5 microg/L as 3rd and 9.0 microg/L as 1st centile). We studied the GH response to a single GHRH (1 microg/kg iv) + ARG (0.5 g/kg iv) test in 62 young patients who had undergone GH replacement in childhood, based on the following diagnosis: 1) organic hypopituitarism with GHD (oGHD) In = 18: 15 male (M), 3 female (F); age, 26.8+/-2.2 yr; GH peak < 10 microg/L after two classical tests]; 2) idiopathic isolated GHD (iGHD) [n = 23 (15 M, 8 F); age, 23.0+/-1.5 yr; GH peak < 10 microg/L after two classical tests]; and 3) GH neurosecretory dysfunction (GHNSD) [n = 21 (10 M, 11 F); age, 25.1+/-1.6 yr; GH peak > 10 microg/L after classical test but mGHc < 3 microg/L]. The GH responses to GHRH+ARG in these groups were also compared with that recorded in a group of age-matched normal subjects (NS) [n = 48 (20 M, 28 F); age, 27.7+/-0.8 yr]. Insulin-like growth factor I levels in oGHD subjects (61.5+/-13.7 microg/L) were lower (P < 0.001) than those in iGHD subjects (117.2+/-13.1 microg/L); the latter were lower than those in GHNSD subjects (210.2+/-12.9 microg/L), which, in turn, were similar to those in NS (220.9+/-7.1 microg/L). The mean GH peak after GHRH+ARG in oGHD (2.8+/-0.8 microg/L) was lower (P < 0.001) than that in iGHD (18.6+/-4.7 microg/L), which, in turn, was clearly lower (P < 0.001) than that in GHNSD (31.3+/-1.6 microg/L). The GH response in GHNSD was lower than that in NS (65.9+/-5.5 microg/L), but this difference did not attain statistical significance. With respect to the 3rd centile limit of GH response in young adults (i.e. 16.5 microg/L), retesting confirmed GHD in all oGHD, in 65.2% of iGHD, and in none of the GHNSD subjects. With respect to the 1st centile limit of GH response (i.e. 9.0 microg/L), retesting demonstrated severe GHD in 94% oGHD and in 52.1% of iGHD. All oGHD and iGHD with GH peak after GHRH+ARG lower than 9 microg/L had also GH peak lower than 3 microg/L after ITT. In the patients in whom GHD was confirmed by retesting, the mean GH peak after GHRH+ARG was higher than that after ITT (3.4+/-0.5 vs. 1.9+/-0.4). In conclusion, given appropriate cut-off limits, GHRH+ARG is as reliable as ITT for retesting patients who had undergone GH treatment in childhood. Among these patients, severe GHD in adulthood is generally confirmed in oGHD, is frequent in iGHD, but never occurs in GHNSD.

Stimulatory effect of adrenocorticotropin on cortisol, aldosterone, and dehydroepiandrosterone secretion in normal humans: dose-response study.

The short ACTH test is widely used in clinical practice for the diagnosis of adrenal insufficiency. It is classically performed administering 250.0 microg ACTH(1-24) although 1.0 microg ACTH dose has been reported having maximal stimulatory effect on cortisol levels in normal subjects. We aimed to define the maximal and the minimal stimulatory ACTH dose on cortisol, aldosterone, and dehydroepiandrosterone (DHEA) in humans. To this goal, in 12 normal volunteers (6 males and 6 females; age, 22-34 yr; body mass index 20-25 kg/m2; body surface 1.6-1.9 m2), we studied the dose-response effect of eight ACTH doses (0.01, 0.03, 0.06, 0.125, 0.5, 1.0, 25.0, and 250.0 microg) on cortisol, aldosterone, and DHEA levels. Each ACTH dose administered at 0 min was followed by a second ACTH dose of 250.0 microg at +60 min. The cortisol delta areas under response curve (deltaAUCs) after all ACTH doses, apart from 0.01 microg, were significantly higher (P < 0.02) than that after placebo, showing a clear dose-response relationship (P < 0.001). The doses of 0.03 and 1.0 microg ACTH were the minimal and maximal effective doses, respectively. The cortisol response to 250.0 microg ACTH was not modified by pretreatment with 0.01, 0.03, and 0.06 microg ACTH doses, whereas it was progressively reduced by increasing the dose of ACTH pretreatment (P < 0.001). The aldosterone deltaAUCs to all but 0.01 microg ACTH doses were significantly higher (P < 0.02) than that after placebo, showing a clear dose-response relationship (P < 0.001). The dose of 0.03 microg was the minimal effective stimulating dose, whereas 25.0 microg showed the same aldosterone-releasing effect of 250.0 microg. The aldosterone response to 250.0 microg ACTH, preceeded by placebo, was not modified by pretreatment with 0.01 and 0.03 microg ACTH doses, whereas it was reduced by increasing the dose of ACTH pretreatment (P < 0.05-0.02). The DHEA deltaAUCs to all ACTH doses were significantly higher (P < 0.01) than that after placebo, showing a clear dose-response relationship (P < 0.001). The doses of 0.01 and 1.0 microg ACTH were the minimal and maximal effective dose, respectively. The DHEA response to 250.0 microg ACTH was not modified by pretreatment with 0.01, 0.03, 0.06, and 0.125 microg ACTH doses, whereas it was progressively reduced by pretreatment with 0.5, 1.0, and 25.0 microg ACTH doses (P < 0.01). In conclusion, these results show that an extremely low ACTH dose is needed to stimulate adrenal steroids and, among them, DHEA seems the most sensitive to corticotropin stimulation.

The negative GH auto-feedback in childhood: effects of rhGH and/or GHRH on the somatotroph response to GHRH or hexarelin, a peptidyl GH secretagogue, in children.

Aim of the present study was to further clarify the negative GH auto-feedback mechanisms in childhood. To this goal we studied the effects of rhGH and/or GHRH administration on the GH response to GHRH or hexarelin (HEX), a peptidyl GH secretagogue, in normal short children. In 34 prepubertal children (12 girls and 22 boys, age 8.2- 14.2 yr) with normal short stature (normal height velocity and IGF-I levels) the following tests were performed: group A (no.=11): GHRH (GHRH 1 - 29, Geref, Serono; 1 microg/kg iv at 150 min) preceded by saline or GHRH at 0 min; group B (no.=6): GHRH preceded by saline or rhGH (0.005 IU/kg iv at 0 min); group C (no.=6): GHRH preceded by rhGH alone or combined with GHRH; group D (no.=6): HEX (2 microg/kg iv at 150 min) alone or preceded by rhGH. In group A, the GH response to GHRH was not modified by pre-treatment with GHRH (GH peak, mean+/-SEM: 16.7+/-2.9 vs 15.1+/-2.3 microg/l, respectively). In group B, the GH response to GHRH was clearly inhibited by rhGH (8.7+/-2.3 vs 38.8+/-4.5 microg/l, p<0.001); the GH rise after rhGH in group B overlapped with that after GHRH in group A. In group C, the GH response to GHRH after pre-treatment with rhGH (13.2+/-4.0 microg/l) was similar to that in group B and was not significantly modified by pre-treatment with rhGH+ GHRH (6.9+/-2.7 microg/l); the GH rise after rhGH+GHRH was higher (p<0.05) than that after rhGH alone. In group D, the GH response to HEX was significantly blunted by pre-treatment with rhGH (34.1+/-11.7 vs 51.2+/-17.9 microg/l, p<0.05). Our results demonstrate that in childhood the somatotroph response to GHRH is preserved after GHRH while it is inhibited after rhGH administration, which is also able to blunt the GH response to HEX. Thus, the somatostatin-mediated negative GH auto-feedback is already operative in childhood; the reason why the GHRH- induced GH rise is not inhibited by GHRH pre-treatment is unexplained.

Sequential administration of arginine and arginine plus GHRH to test somatotroph function in short children.

The hormonal diagnosis of GH deficiency in childhood is conventionally based on the GH response to at least two provocative stimuli. Among these, arginine (ARG) has long been considered a classical, centrally mediated stimulus of GH secretion. ARG is also able to potentiate the GH response to GHRH, likely inhibiting hypothalamic somatostatin; this combined test is one of the most potent to explore the maximal secretory capacity of somatotroph cells. Based on these premises, we verified whether the sequential administration of ARG and ARG+GHRH could be feasible as single step provocative test to evaluate the GH releasable pool in short children. To this goal, 48 normal short children (35 M and 13 F, 12.0+/-0.4 yr, PS 1: 255 II-IV: 23) underwent a test with ARG (0.5 g/kg i.v. from 0 to +30 min) followed by a coadministration of ARG (from +120 to 150 min) plus GHRH (1 microg/kg i.v. at +120 min). ARG alone elicited a clear GH response (mean peak vs baseline: 12.1+/-1.7 vs 2.0+/-0.4 microg/l, p<0.001, Cmax range 12-51.0 microg/l). Following this GH rise, the hormonal levels at +120 min approached to baseline levels (4.2+/-0.8 microg/l) but then showed marked response to the coadministration of ARG+GHRH. The GH peak following ARG+GHRH (mean peak: 47.8+/-3.3 microg/l, p<0.001; Cmax 22.4-150.0 microg/l) was clearly higher (p<0.001) than that recorded after ARG alone. The GH responses to both ARG and ARG+GHRH were independent of gender, puberty, height velocity, body mass index (BMI) and IGF-I levels. Nine normal short children (16%) had GH peaks lower than 7 microg/l after ARG alone, while none showed GH peak below 20 microg/l after ARG+GHRH. Thus, ARG alone is a good stimulus of GH secretion but false positive responses frequently occur in normal short children. ARG+GHRH is a more potent stimulus giving no false positive responses even after previous challenge with ARG alone. Testing with sequential administration of ARG and ARG+GHRH may allow the single step evaluation of the somatotroph response to central and pituitary stimuli in short children.

Comparisons among old and new provocative tests of GH secretion in 178 normal adults.

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.

DHEA-S levels in hypopituitaric patients with severe GH deficiency are strongly reduced across lifespan. Comparison with IGF-I levels before and during rhGH replacement.

Both IGF-I and DHEA-S undergo an age-related decrease and their decrease could be involved in age-related changes in body composition, structure functions and metabolism. On the other hand, it is well known that mean IGF-I levels are clearly reduced in hypopituitaric patients with GH deficiency (GHD) while data about dehydroepiandrosterone sulfate (DHEA-S) levels in hypopituitarism are scanty. We evaluated DHEA-S and IGF-I levels and their relationship in 90 patients with panhypopituitarism (HYPOPIT) with severe GHD [49 women and 41 men; age, mean+/-SE: 47.9+/-1.49 yr, range: 20-80 yr, BMI: 26.4+/-0.6 kg/m2; 21 with childhood-onset (CO) and 69 with adult-onset (AO) HYPOPIT]. DHEA-S and IGF-I levels were also evaluated in 24 HYPOPIT with GHD after 3-month recombinant human GH (rhGH) replacement. Data in HYPOPIT were compared with those in a large group of healthy controls (NS, 233 women and 103 men, aged 20-80 yr; all subjects were within +/-15% of their ideal body weight). In NS both DHEA-S levels and IGF-I were gender-independent while showed a strong, inverse correlation with age (r=-0.6; p<0.001 and r=-0.56; p<0.0001, respectively). Nevertheless, no relationship was found between DHEA-S and IGF-I levels in NS. In HYPOPIT, age-adjusted mean DHEA-S and IGF-I levels were clearly lower than those in NS (2.3+/-0.4 vs 16.0+/-0.7 microg/l, p<0.005; 71.1 +/- 4.5 vs 170+/-4.7 microg/l, p<0.005). IGF-I levels in CO-HYPOPIT were lower (p<0.01) than those in AO-HYPOPIT (49.6+/-4.8 vs 77.0+/-5.4 microg/l), while DHEA-S levels were similar in both subgroups (2.6+/-0.7 vs 2.3+/-0.4 microg/l). In HYPOPIT both DHEA-S and IGF-I were independent of age and gender while there was a trend toward a positive association between each other (r=0.45; p<0.003). Analyzing individual levels in HYPOPIT with respect to age-adjusted normal ranges, IGF-I levels were below normal in 84, 62 and 0% between 20-40, 40-60 and 60-80 yr, respectively. On the other hand, DHEA-S levels were below normal in 84, 86 and 67% between 20-40, 40-60 and 60-80, respectively. In HYPOPIT rhGH treatment strikingly increased IGF-I levels (150+/-3.2 vs 85.3+/-4.1 microg/l, p<0.005) while did not modify DHEA-S levels (1.7+/-0.2 vs 1.6+/-0.2 microg/l). In conclusion, our results demonstrate that DHEA-S and IGF-I are negatively and independently associated to age in physiological conditions but not in hypopituitaric patients in whom both are strikingly reduced. Both DHEA-S and IGF-I levels in HYPOPIT show some overlap with those in normal subjects; thus the assay of these parameters is not diagnostic for hypopituitarism. DHEA-S reduction in HYPOPIT does not depend on IGF-I as indicated also by evidence that GH replacement restores IGF-I but does not modify DHEA-S levels.

Reduction of the pituitary GH releasable pool in short children with GH neurosecretory dysfunction.

OBJECTIVES: The classical 'GH neurosecretory dysfunction' (GHNSD) refers to slowly growing children with normal GH responses to classical provocative tests but impaired spontaneous GH secretion over 24 h frequently leading to low IGF-I levels. Thus it has been assumed that these subjects have insufficiency of spontaneous GH secretion due to neuroendocrine abnormalities in spite of a normal releasable pool of GH. However, classical provocative tests do not reliably assess the maximal somatotroph capacity; thus it is still unclear if the GH pool is really preserved or not. GHRH + arginine test is more potent than the classical tests and evaluates the maximal secretory capacity of somatotroph cells. The GH response to this stimulus is reproducible and also independent of age and puberty. DESIGN AND PATIENTS: We studied the GH response to GHRH (1 microgram/kg iv) + arginine (ARG, 0.5 g/kg iv) in 19 short children with GHNSD (14 boys and 5 girls, age: 12.1 +/- 0.7 years, pubertal stages I-III, HV-SDS between -1.6 and -4.9; GH peak > 10 micrograms/l after classical stimuli but mean GH concentration (mGHc) < 3 micrograms/l). The results in GHNSD were compared with those in 38 short children with idiopathic or organic severe GHD (GHD, 29 boys and 9 girls, age: 11.2 +/- 0.6 years, pubertal stages I-III, HV-SDS between -1.8 and -4.4; GH peak < 10 micrograms/l after 2 classical provocative tests) and in 83 children with normal or familial short stature (NC, 59 boys and 24 girls, age: 11.5 +/- 0.3 years., pubertal stages I-III; HV-SDS > 25th centile, normal IGF-I levels). RESULTS: Mean IGF-I levels in GHNSD (121.9 +/- 20.3 micrograms/l) were lower (P < 0.001) than those in NC (270.3 +/- 13.8 micrograms/l) but higher (P < 0.001) than those in GHD (72.0 +/- 4.0 micrograms/l). The mean GH concentration (mGHc) in GHNSD (2.1 +/- 0.1 micrograms/l) was lower (P < 0.01) than that in NC (4.9 +/- 0.5 micrograms/l) but higher (P < 0.01) than that in GHD (1.5 +/- 0.2 micrograms/l). On the other hand, the mean peak GH response to GHRH + ARG in GHNSD (43.7 +/- 3.7 micrograms/l) was markedly higher (P < 0.001) than that in GHD (8.2 +/- 0.9 micrograms/l) but significantly lower (P < 0.01) than that in NC (60. 4 +/- 2.7 micrograms/l). All GHD patients had peak GH responses to GHRH + ARG below the 3rd centile limit of normality (20 micrograms/l), while all GHNSD patients had peak GH responses within the normal range. No significant correlation was found between GH peak after GHRH + ARG, mGHc and IGF-I levels in each group. CONCLUSION: Our study demonstrates that short children with 'GH neurosecretory dysfunction' show reduction in the GH releasable pool evaluated by the provocative and potent GHRH + arginine test. However, the peak GH response to a single GHRH + arginine test in GH neurosecretory dysfunction is always within the normal range indicating that this test as well as classical stimuli does not distinguish normal subjects from GH neurosecretory dysfunction.

GH response to GHRH combined with pyridostigmine or arginine in different conditions of low somatotrope secretion in adulthood: obesity and Cushing's syndrome in comparison with hypopituitarism.

BACKGROUND: Diagnosing GH deficiency in adults is difficult due to the age-related variations of GH/IGF-I axis and the influence of nutrition. Nowadays, GH replacement is allowed for patients with GH peak to provocative stimuli < 3 micrograms/L. Somatotrope insufficiency is present in hypopituitarism but also in obesity and hypercortisolism. However, to evaluate GH insufficiency in adults is difficult due to variations of GH and IGF-I levels as function of age and nutrition status. METHODS: We aimed to verify the GH response to GHRH (1 mg/kg i.v.) combined with pyridostigmine (PD, 120 mg p.o.) or arginine (ARG, 0.5 g/kg i.v.), in 26 hypopituitaric patients (GHD), in 11 obese women (OB), in 8 women with Cushing's syndrome (CS), and in 72 control subjects (NS). RESULTS: IGF-I levels in GHD were lower than those in OB (p < 0.01) and in CS (p < 0.01) which, in turn, were lower to those in NS (p < 0.02). In NS, the GH peak responses to GHRH + PD and GHRH + ARG were similar and the minimum normal GH peak was 16.5 mg/L. GHD had GH responses similar, lower than those in NS (p < 0.01) and always below the normal limit. However, only 12/20 and 8/14 had peaks < 3 micrograms/L; conventionally, below this limit severe GH deficiency is shown and rhGH replacement is allowed. In OB, the GH responses to GHRH + PD and GHRH + ARG were similar, lower (p < 0.01) and higher (p < 0.01) than those in NS and GHD, respectively. Six out of 11 OB had GH peaks below the normal limits but nobody < 3 micrograms/L. In CS, the GH response to GHRH + PD was lower than that to GHRH + ARG (p < 0.01); both these responses were lower than those in NS (p < 0.01) and even in OB (p < 0.01) but higher than those in GHD (p < 0.01). All and 7/8 CS had GH peaks lower than normal limits after PD + GHRH and ARG + GHRH, respectively while 6/8 showed GH peak < 3 micrograms/L after PD + GHRH but only 1 after ARG + GHRH. CONCLUSIONS: Present data demonstrate that the maximal somatotrope secretory capacity is reduced in OB and even more in CS. From a diagnostic point of view, PD + GHRH and ARG + GHRH tests distinguish OB from severe GHD. As hypercortisolism impairs the activity of cholinesterase inhibitors, only ARG + GHRH, but not PD + GHRH is a reliable test to explore the maximal somatotrope secretory capacity in CS. Notably, even with the ARG + GHRH test, in CS the maximal somatotrope secretory capacity is sometimes so reduced as to overlap with that of severe GHD.

IGF-I levels in prepubertal and pubertal children with Down syndrome.

BACKGROUND: Growth retardation is a main feature of Down syndrome but it is still unclear whether an alteration of the GH/IGF-I axis is present in this condition. Concerning IGF-I levels, they have been found reduced by some authors but normal by others. METHODS: On these bases, IGF-I levels have been assessed from prepubertal to late pubertal stages of gonadal maturation in a large group of children and adolescents with Down syndrome (DS, 68 M, 45 F, 12.5 +/- 0.6 yr; prepubertal n = 39, pubertal n = 74) with those in a group of normal children and adolescents (NS, 75 M, 87 F; 11.1 +/- 0.4 yr; prepubertal n = 94, pubertal n = 68). RESULTS: Within each group, IGF-I levels were gender-independent while showed age-related variations with positive association with pubertal stage--peaking up in pubertal stage IV--(DS: r = 0.6, NS: r = 0.4, both p < 0.0001) and testosterone (DS: r = 0.6, NS: r = 0.5, p < 0.001) or estradiol (DS: r = 0.6, NS: r = 0.5, p < 0.001) levels. Considering whole groups, mean IGF-I levels in DS were slightly but significantly lower than those in NS (257.9 +/- 12.5 vs 310.8 +/- 12.6 micrograms/l, p < 0.02). Analyzing individual IGF-I levels in DS with respect to normal ranges per pubertal stage, more than 85% of IGF-I levels resulted within the normal limits. These results demonstrate that IGF-I levels in DS patients are generally within the normal range--though a slight reduction of mean IGF-I levels is present--and follow normal age-related variations with clear cut increase at puberty and positive association with gonadal steroid levels. CONCLUSIONS: This evidence points toward the need to clarify the GH/IGF-I axis function and activity in DS patients.