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Aim of our study was to investigate the effect of clonidine and galanin (alone or in combination) on growth hormone (GH) secretion in normal subjects and in adult patients with increased somatostatin tone due to chronic daily immunosuppressive glucocorticoid treatment. We studied 7 adult patients undergoing long-term (no less than 6 months) immunosuppressive glucocorticoid treatment for non endocrine diseases (4F, 3M; age 49.7 +/- 6.3 years). Six normal adult nonobese subjects (3F, 3M; age 34 +/- 2.7 years) served as controls. All subjects underwent the following three tests in random order: 1) iv infusion of clonidine, 150 micrograms in 10 mL of saline, from time 0 to 10 min; 2) iv infusion of synthetic porcine galanin, 500 micrograms in 100 mL of saline from -15 to 30 min; 3) iv infusion of clonidine from 0 to 10 min combined with synthetic porcine galanin iv infusion from -15 to 30 min. Blood samples for GH assay were taken at -15, 0, 15, 30, 45, 60, 90, 120 min. No significant differences in GH absolute values were observed at any time between the three different tests within each group of subjects. Normal subjects showed significantly (p0.05) higher GH peaks and GH absolute values from 15 to 90 min after galanin alone, clonidine alone and clonidine+galanin with respect to the glucocorticoid-treated patients. The absence of any either synergistic or at least additive effect on GH secretion of galanin and clonidine in conditions of both normal and increased somatostatin tone suggests that also in man, as well as in the rat, the action of galanin on the GH axis may be mediated through alpha-adrenergic pathways.

The aim of our study was to investigate the effects of exercise on albuminuria and blood pressure in patients with essential hypertension, and the short-term effect of the calcium channel blocker isradipine on exercise-induced albuminuria (UAE) and blood pressure in the same patients. Ten patients (7 males, 3 females) with essential hypertension were admitted to the study. The mean age was 54 +/- 2.7 years and the mean body mass index was 27 +/- 1 kg/m2. Patients performed two physical exercise tests on a cycloergometer. Workload was increased by 30 watts every 2 min until 90% of the theoretical maximal heart rate was achieved. This workload was maintained for 5 min. Samples for albuminuria assay were collected at the end of exercise and 1 h after exercise. The first physical exercise test was performed after 15 days of placebo washout; the second exercise was performed after 10 days of therapy with isradipine 5 mg once daily p.o. After 10 days of therapy with isradipine, UAE immediately after (31 +/- 8.3 micrograms/min) and 1 h after exercise (31.5 +/- 7.3 micrograms/min) were significantly (p0.05) lower as compared to the values found after placebo (37.1 +/- 9.3 micrograms/min; 43.5 +/- 9.9 micrograms/min). Our data show that short-term administration of the calcium channel blocker isradipine is able to cause a concomitant significant decrease in exercise-induced pressor and albuminuric response in patients with essential hypertension. The finding that short-term calcium channel blockade can reduce exercise-induced albuminuria in essential hypertensive patients suggests that progression of nephropathy in this early phase could be slowed by isradipine in these patients.

Recent studies have demonstrated that short-term angiotensin converting enzyme (ACE) inhibition with captopril can reduce urinary albumin excretion rate (UAER) after exercise in normotensive diabetic patients with early-stage nephropathy. The aim of this study was to investigate whether this effect of ACE inhibition was due to a systemic hypotensive action or a specific action at the intrarenal level. Thus, we compared the acute effects of captopril and the Ca2+-channel blocker nifedipine on exercise-induced UAER in normotensive (blood pressure

Some studies have demonstrated that the function of the growth hormone (GH)-insulin-like growth factor (IGF)-1 axis is significantly impaired in patients with oral corticosteroid (CS)-induced osteoporosis. The aim of study was to investigate the effects of long-term therapy with inhaled CSs (ICSs) on the hypothalamic-pituitary-GH axis by the GH response to GH-releasing hormone (GHRH), as well as bone turnover, in adult asthmatic patients.Cross-sectional study.Twenty-seven adult subjects with mild-to-moderate persistent asthma (long-term ICS therapy [ie,1 year], 20 patients; naive to ICS treatment, 7 patients) and 10 control subjects.Each subject underwent testing with an IV bolus (1 mug/kg) injection of human GHRH, and samples of GH were taken 15 min before the GHRH injection, at 0 min (ie, at the time of GHRH injection), and at 15, 30, 45, 60, and 90 min after injection to obtain values for peak GH and DeltaGH. At baseline, samples of serum IGF-1 and blood-urine were collected for bone turnover markers.The GH response to GHRH was significantly reduced in asthmatic patients receiving ICSs (peak GH, p0.05; and DeltaGH, p0.01) in comparison with control subjects and asthmatic patients who were naive to ICS therapy (peak GH and DeltaGH, p0.01). Baseline IGF-1 levels were similar in the three groups. Serum osteocalcin, a marker of bone formation, was significantly reduced (p0.01) and correlated with GH peak (r(2) = 0.34; p = 0.007) in asthmatic patients who were treated with ICSs.We conclude that GH secretion in response to GHRH is significantly reduced in adult asthmatic patients receiving therapy with ICS and that such inhibition could play a negative role in bone metabolism.

Recent clinical studies have demonstrated an increase of urinary albumin excretion (UAE) at rest in acromegalic patients and, on the other hand, a reduced UAE in patients with growth hormone (GH) deficiency. Physical exercise is known to induce abnormal UAE in patients with diabetes, probably unmasking early glomerular alterations. The effect of exercise on UAE in acromegaly is not known. Moreover, the effect of acute but sustained GH inhibition in acromegaly on UAE at rest and after exercise has never been studied. The aim of our study was to evaluate the acute short-term effects of slow-release lanreotide (SR-L), a long-acting somatostatin analog, on UAE and alpha1-microglobulinuria (A-1-M), a marker of renal tubular damage, at rest and after exercise in 7 normotensive patients with active acromegaly and normal renal function (4 males and 3 females; mean age, 53 +/- 3.1 years; body mass index [BMI], 27.3 +/- 1.1 kg/m2) at baseline and 7 and 14 days after SR-L injection (30 mg). Two of the acromegalic patients were microalbuminuric at rest, and in other 3 cases, UAE was in the borderline range (10 to 20 microg/min). At baseline in the acromegalic subjects, we found a significant increase in UAE at rest with respect to 7 normal subjects considered as a control group. GH and insulin-like growth factor-1 (IGF-1) were also reduced compared with baseline 7 and 14 days after SR-L injection (GH, 13.4 +/- 7.3 and 13.61 +/- 7 v 18.5 +/- 9.3 microg/L, P.05; IGF-1, 230 +/- 53 and 255 +/- 54 v 275 +/- 64 microg/L). Concomitantly, we observed a significant decrease of UAE at rest and after exercise and 7 and 14 days after SR-L injection as compared with baseline values (27.3 +/- 20.5 and 18.2 +/- 13.7 v 35.3 +/- 12.8 microg/min, P.05; exercise, 48.5 +/- 24.1 and 18.6 +/- 6.8 v68.3 +/- 39.7 microg/min, P.05). A-1-M always remained in the normal range (12 mg/L) both at rest and after exercise. We can thus conclude that in acromegaly, submaximal exercise induces abnormal increases in microalbuminuria. We hypothesize that this phenomenon may be due to the functional glomeruler involvement. SR-L can significantly reduce UAE at rest and after exercise in the short-term in acromegaly, probably via a decrease in circulating GH levels.

Spontaneous and stimulated GH secretion is blunted in hypercortisolemic states due to increased hypothalamic somatostatinergic tone. However, no data are available on the characteristics of GH secretion in patients with incidentally discovered adrenal adenomas. They represent an interesting model for studying GH secretion, as a slight degree of cortisol excess may frequently be observed in such patients who do not present with any clear Cushingoid sign. In the present study, 10 patients (3 men and 7 women, aged 48-63 yr) with an adrenal mass discovered serendipitously underwent, on separate occasions, a GHRH injection alone or combined with an infusion of the functional somatostatin antagonist, arginine. Thirteen age-matched healthy volunteers served as controls. Briefly, arginine (30 g) was infused from -30 to 0 min, and GHRH (100 microg) was injected as a bolus at 0 min, with measurement of serum GH [immunoradiometric assay (IRMA)] every 15 min for 150 min. Plasma IGF-I (RIA after acid-ethanol extraction) was measured in a morning sample. The diagnosis of cortical adenoma was based on computed tomography features and pattern of uptake on adrenal scintigraphy. Patients with obesity and/or diabetes were excluded. The study design included also an endocrine work-up aimed to study the hypothalamic-pituitary-adrenal axis [urinary free cortisol (UFC) excretion, serum cortisol at 0800 h, plasma ACTH at 0800 h, morning cortisol after overnight 1 mg dexamethasone]. Five of 10 patients showed abnormalities of the hypothalamic-pituitary-adrenal axis, including borderline or increased UFC excretion in 4 of them accompanied by blunted ACTH in 2 cases and failure of cortisol to suppress after dexamethasone in 1; the fifth patient displayed low ACTH and resistance to dexamethasone suppression. However, all patients had a unilateral uptake of the tracer on the side of the mass with suppression of the contralateral normal adrenal gland. As a group, the patients displayed greater UFC excretion and lower ACTH concentrations than the controls. GH release after GHRH treatment was blunted in patients bearing adrenal incidentaloma compared with controls (GH peak, 5.7 +/- 5.2 vs. 18.0 +/- 7.0 microg/L; P0.0001), whereas GHRH plus arginine was able to elicit a comparable response in the 2 groups (GH peak, 33.5 +/- 20.3 vs. 33.7 +/- 17.5 microg/L; P = NS). The ratio between GH peaks after GHRH plus arginine and after GHRH plus saline was significantly greater in patients than in controls (751 +/- 531% vs. 81 +/- 45%; P = 0.0001). Similar data were obtained when comparing GH area under the curve after GHRH plus saline or GHRH plus arginine between the 2 groups. In summary, the present data suggest that in patients with incidental adrenal adenomas the GH response to GHRH is blunted due to increased somatostatinergic tone, as it can be restored to normal by pretreatment with the functional somatostatin antagonist arginine. The blunted GH release to GHRH may be an early and long lasting sign of autonomous cortisol secretion by the adrenal adenoma.

The regulation of GH secretion in the aged human is still not clearly understood. Results from a large number of studies suggest that aging decreases both spontaneous pulsatile GH secretory activity, and baseline serum GH concentrations. In addition, the GH response to physiological and pharmacological stimuli, including the administration of exogenous GH-releasing hormone (GHRH) have also been reported to be decreased in aged subjects. Recent studies have suggested that the inhibitory effect of aging on GH secretion may be due to an enhancement of hypothalamic somatostatin release both in the rat and in man. Shortly after the documentation of decreases in GH secretion in humans, other studies showed that the amplitude of spontaneous GH pulses decreased with age in rodents and that these changes were associated with a decline in plasma IGF-I. These studies immediately progressed to an investigation of the mechanisms responsible for the decline in GH secretion. Research efforts were eventually directed to the level of hypothalamic releasing (GHRH) and inhibiting (somatostatin) hormones. Results of these studies provided evidence that increased somatostatin tone and decreased GHRH tone at the hypothalamic level may both be a contributing factor in the decline in GH secretion with age. These conclusions were supported by research in humans, where administration of cho

The aim of our study was to elucidate the relationship between the level of circulating cortisol and the GH responsiveness to GHRH in six hypoadrenal patients (one male and five females; age range, 35-67 yr; body mass index range, 18-31 kg/m2). Twenty-four hours after taking the last dose of replacement therapy, each patient underwent the following experimental trials on nonconsecutive days: 1) saline, and 2) 12.5 mg, or 3) 25 mg, or 4) 250 mg hydrocortisone hemisuccinate in 250 mL saline constant iv infusion from 0-180 min. On each occasion, 1 micrograms/kg human GHRH-(1-29)NH2 was injected as an iv bolus at 60 min. During GHRH and saline infusion, serum cortisol levels were always less than the detection limit of the assay (55 nmol/L). During 12.5-, 25-, and 250-mg hydrocortisone infusions (from 15-180 min), serum cortisol averaged 413.8 +/- 19.3, 772.5 +/- 46.9, and 1520.2 +/- 110.4 nmol/L, respectively. The GH peaks after GHRH treatment during the various infusions of hydrocortisone were compared to the GH peaks observed after saline, which were normalized to 100% in each subject. GH peaks after GHRH and 25 mg hydrocortisone (70 +/- 11%) and GHRH and 250 mg hydrocortisone (69 +/- 7%) were significantly (P < 0.05) lower than the GH peaks after GHRH and saline or GHRH and 12.5 mg hydrocortisone (83 +/- 15%). No significant differences were observed between the GH peaks after GHRH and 12.5 mg hydrocortisone or GHRH and saline. Our data demonstrate that in hypoadrenal patients, the acute absence of circulating cortisol does not impair the GH secretory response to GHRH with respect to the eucortisolemic state. Moreover, our data suggest that 700 nmol/L is the approximate threshold serum cortisol concentration above which a decrease in the GH responsiveness to GHRH is observed in humans. Further increases in serum cortisol levels above this threshold value do not cause a proportional decrease in the GH responsiveness to GHRH.

Galanin is able to enhance growth hormone (GH)-releasing hormone stimulated GH secretion in normal man. In acromegaly circulating GH levels are elevated and the GH response to GHRH may be exaggerated. Galanin has been recently shown to decrease circulating GH levels in acromegaly. Dopaminergic drugs were the only previously known agents able to cause a paradoxical GH fall in acromegaly. Aim of our study was to investigate the effects of a potent central dopaminergic receptor blocker, metoclopramide (MCP), on the galanin-induced paradoxical GH secretion in acromegalic subjects. Two male and three female patients with active acromegaly (age range 44-66 years, body mass index range 24.6-28 Kg/m2) were studied after 45 min i.v. infusion of porcine galanin (0.5 mg in 100 ml of saline) from 0 to 45 min combined with a 60 min i.v. infusion of a) saline (100 ml) or b) MCP (10 mg in 100 ml of saline) from -15 to 45 min. After galanin, GH values fell from baseline (27.5 +/- 10 micrograms/L) to a mean nadir of 16.4 +/- 6.1 micrograms/L; after galanin + MCP, circulating GH levels were also decreased (mean nadir 17.3 +/- 8.1 micrograms/L) in all the patients with respect to baseline (23.6 +/- 9.7 micrograms/L). No significant differences were found in absolute or percent of baseline GH levels after galanin+saline vs galanin + MCP. Our results suggest that the paradoxical GH fall after galanin in acromegalic patients is not mediated through dopaminergic receptor. It can be hypothesized that galanin may interact at the pituitary level with its own receptors expressed by GH-secreting adenomatous cells.

Attenuated plasma GH secretion during sleep and blunted GH responses to provocative stimuli have been observed in patients with Cushing's disease. Synthetic porcine galanin elicits GH secretion when given alone, and enhances the GH response to GHRH in normal human subjects. The aim of our study was to investigate the effects of galanin on the GH response to GHRH in patients with Cushing's disease. We studied 5 female subjects with untreated active Cushing's disease caused by micro-pituitary adenomas (age 43 +/- 6.7 years; BMI 30 +/- 0.7 kg/m2). Four normal adult females, matched for age and body weight with the patients with Cushing's disease, were studied as controls. Subjects underwent in random order: (1) infusion of synthetic porcine galanin IV, 500 micrograms in 100 mL; (2) infusion of saline, IV, 100 mL. A bolus of human GHRH(1-29)NH2 (Geref, Serono, Italy), 100 micrograms in 1 mL saline, was injected IV at 0 minutes. Patients with Cushing's disease showed blunted GH peaks after GHRH (1.2 +/- 0.4 micrograms/L) during saline infusion, as compared to normal controls (24.6 +/- 4.6 micrograms/L; p0.05). During galanin infusion a significantly enhanced GH response to GHRH, as compared with saline infusion, was observed in control subjects (GH peak: 51.4 +/- 9.8 micrograms/L; p0.05), but not in patients with Cushing's disease (GH peak: 2.3 +/- 0.6 micrograms/L). GH levels were significantly lower both after saline and after galanin in patients with Cushing's disease as compared to normal controls. Our data demonstrate that galanin is not able to enhance the GH response to GHRH in patients with Cushing's disease. That galanin cannot reverse this effect suggests that the mechanism of action of galanin is not via a decrease in somatostatin release by the hypothalamus.

In patients with acromegaly, circulating growht hormone (GH) levels and GH responses to GH-releasing hormone (GHRH) are decreased by long-term administration of pharmacological doses of glucocorticoids. The aim of our study was to investigate the acute effects of intravenous (IV) infusion of hydrocortisone combined either with saline or arginine infusion on circulating GH levels in acromegaly. We studied five adult patients with acromegaly, two men and three women aged 54.6 ± 4 years having a body mass index of 25.9 ± 1.2 kg/m 2 . On two randomized occasions, patients underwent a bolus IV injection of 100 mg hydrocortisone succinate at time 0 followed by a 120-minute IV infusion of 250 mg hydrocortisone in 250 mL saline, combined with a 90-minute (from −15 to 75 minutes) IV infusion of (1) 60 g arginine hydrochloride in 200 mL saline, or (2) 200 mL saline. In all of the acromegalic patients during the infusion of hydrocortisone alone, serum GH levels clearly decreased (nadir range, 26.4% to 68.1%) with respect to GH levels before hydrocortisone administration (mean of time −15 and 0, basal level), with a nadir between 90 and 180 minutes after the beginning of the infusion. After arginine pretreatment, GH levels were significantly enhanced compared with levels attained with hydrocortisone saline, and they were also significantly increased (peak, 167.5% ± 27.7%) with respect to basal levels. Our data show that arginine blocks the inhibitory effect of acute and sustained hypercortisolism on circulating GH levels in acromegaly. It also seems likely that in both acromegalic patients and normal subjects, acute increases in serum cortisol levels may cause an enhancement of hypothalamic somatostatin secretion, which in turn may be responsible for the glucocorticoid-mediated GH inhibition.

In man the GH response to GHRH is variable within and between subjects. Pyridostigmine (PD), an acetylcholinesterase inhibitor, has been shown to reduce the variability of the GH response to GHRH in normal subjects. The aim of this study was to assess the existence of either inter- or intraindividual variability in the GH response to GHRH in type 1 diabetic patients. Moreover, we investigated the effect of PD on such variability in the same patients. Seven (4 females-3 males) nonobese type 1 diabetic patients underwent two experiments performed in consecutive days according to a single-blind protocol: 1) 120 mg oral PD 60 min before iv injection of human (h) GHRH-(1-29) NH2, 100 μg in 2 ml of sterile water; 2) oral placebo 60 min before iv injection of 100 μg hGHRH. The two experiments were then repeated, following the same procedure, one and two weeks after the start of the study. The GH peaks after GHRH were variable within different subjects but also in the same subject on different occasions. However, the mean GH peak levels after GHRH in the three tests were not significantly different (14.2±3.5, 15.3±3, 16.5±6.4 μg/L, respectively), the coefficient of variation for each test was 65%, 51.8%, 102.4%, respectively (mean 73.1±15.1%). The GH response to GHRH was always significantly enhanced by PD administration: the mean GH peak levels in the three tests were 31.9±7.1, 44.8±10.4, 49.9±13.1 μg/L, respectively, without significant differences between tests. After PD+GHRH the interindividual variability in the GH response was still present but significantly lower than after GHRH alone. The coefficient of variation for each test was 58.7%, 61.3%, 69.3%, respectively (mean 63.1±3.2%). It can be hypothesized that PD may reduce the interindividual variability of the GH response to GHRH in the diabetic population by decreasing somatostatin tone only in diabetic patients with normal-high hypothalamic somatostatin.

We investigated the short-term effect of the TXB inhibitor picotamide on albuminuria induced by exercise in 15 microalbuminuric (i.e., with UAE at rest between 20 and 200 μg/min) type II diabetic patients (12 men and 3 women, age 56 ± 2, BMI 28 ± 1 kg/m2) and in six normal age-matched control subjects. The diabetic subjects performed five submaximal exercise tests (90% of theoretical heart rate) on a cycle ergometer: the first two under basal conditions; the third and fifth after subjects had received picotamide (900 mg/day) or placebo (3 tablets/day) for 10 days; the fourth exercise always was performed after 10 days of wash-out. Control subjects performed two exercises: the first in baseline conditions and the second after 10 days of picotamide administration (900 mg/day). When diabetic patients were untreated, a significant (P < 0.05) increase in UAE with respect to baseline levels was observed immediately after and 1 h after the exercise test. After picotamide administration, UAE significantly decreased (P < 0.05) immediately after and 1 h after exercise, as compared with diabetic patients given a placebo. In normal subjects, exercise was followed by a slight increase in UAE, which was not significantly affected by picotamide administration. Our results show that short-term administration of picotamide is associated with a reduction in UAE after exercise in type II diabetes patients with microalbuminuria while at rest. Picotamide, a TXB synthetase and receptor inhibitor, may decrease exercise-induced albuminuria in diabetic patients through a reduction in circulating TXB levels andinhibition of TXB action, which in turn may act by lowering glomerular capillary hydraulic pressure.

Glucocorticoids are thought to inhibit GH secretion through an enhancement of endogenous somatostatin tone. The aim of our study was to evaluate the effect of arginine, a secretagogue that increases GH secretion acting at the hypothalamic level, probably by decreasing somatostatin tone, on GH-releasing hormone (GHRH)-induced GH secretion in three male and five female adult patients with nonendocrine disease who were receiving daily immunosuppressive glucocorticoid therapy. Six normal subjects (four males and two females) served as controls. GHRH-induced GH secretion was evaluated after 30-min iv infusion of saline (100 mL) or arginine (30 g) in 100 mL saline. After saline administration, steroid-treated patients showed a blunted GH response to GHRH (GH peak, 8.7 +/- 2.4 micrograms/L) compared to that of normal subjects (GH peak, 23.8 +/- 3.9 micrograms/L). The GH responses to GHRH increased (P less than 0.05) after pretreatment with arginine compared to saline pretreatment in both normal subjects (GH peak, 36.6 +/- 4.0 micrograms/L) and steroid-treated patients (GH peak, 28.4 +/- 5.5 micrograms/L). The GH responses to GHRH plus arginine were not significantly different in steroid-treated and normal subjects. Thus, arginine is able to normalize the GH response to GHRH in patients receiving chronic glucocorticoid treatment. Our data are evidence that the stimulatory action of arginine and the inhibitory action of glucocorticoids on GH secretion are mediated by opposite effects on hypothalamic somatostatin tone.

Growth hormone-releasing hormone (GHRH) increases serum GH levels in a dose-dependent manner. Pyridostigmine (PD), an acetylcholinesterase inhibitor, is able to elicit GH secretion when administered alone and to enhance the GH response to GHRH in normal subjects, probably via a decrease in the hypothalamic release of somatostatin. The aim of the present study was to investigate if an enhancement of the cholinergic tone was able to influence the dose-response relationship between GHRH and GH in normal adult subjects. Six healthy adult volunteers underwent 10 experimental protocols. They were: human GHRH (1-29)NH2, 1 micrograms/kg injected as an intravenous (IV) bolus 60 minutes after (a) PD, 120 mg administered orally, or (b) placebo, two tablets administered orally; GHRH, 0.3 micrograms/kg injected as an IV bolus 60 minutes after (c) PD or (d) placebo; GHRH, 0.1 micrograms/kg injected as an IV bolus 60 minutes after (e) PD or (f) placebo; GHRH, 0.01 micrograms/kg injected as an IV bolus 60 minutes after (g) PD or (h) placebo; saline, 1 mL injected as an IV bolus 60 minutes after (i) PD or (l) placebo. The GH response in placebo-treated subjects was similar after 1 microgram/kg and 0.3 microgram/kg GHRH, while the 0.1 microgram/kg dose elicited a lower response. The 0.01 microgram/kg dose of GHRH did not significantly increase GH levels as compared with saline. After PD, the GH responses to GHRH were greatly enhanced at all doses tested: 1.0, 0.3, and 0.1 microgram/kg GHRH all elicited similar GH responses; the GH response to 0.01 microgram/kg GHRH was lower, but was still higher than that observed after saline.(ABSTRACT TRUNCATED AT 250 WORDS)

Subjects with Cushing's disease have diminished growth hormone (GH) response to growth hormone-releasing hormone (GHRH). The aim of our study was to investigate the underlying mechanism of this diminished GH response in these patients using pyridostigmine (PD), an acetylcholinesterase inhibitor, which is reported to increase GH secretion by reducing somatostatin tone. Eight subjects with untreated Cushing's disease (caused by a pituitary adenoma) and 6 control subjects received GHRH 100 micrograms in 1 ml of saline, as intravenous bolus injection 60 min after (1) placebo (2 tablets, p.o.) or (2) PD (120 mg, p.o.). After GHRH plus placebo, the GH peak (mean +/- SEM) was significantly lower in subjects with Cushing's disease (2.4 +/- 0.5 micrograms/l) compared to control subjects (25.1 +/- 1.8 micrograms/l, p less than 0.05). After GHRH plus PD, the GH peak was significantly enhanced both in subjects with Cushing's disease (7.1 +/- 2.3 micrograms/l, p less than 0.05) and in control subjects (42.3 +/- 4.3 micrograms/l, p less than 0.05). In patients with Cushing's disease, the GH response to GHRH plus PD was lower with respect to the GH response to GHRH alone in normal subjects. We conclude that hypercortisolism may cause a decrease in central cholinergic tone which is in turn hypothesized to be responsible of an enhanced somatostatin release from the hypothalamus. However, other metabolic or central nervous system alterations may act synergistically with hypercortisolism in causing GH inhibition in patients with Cushing's disease.

OBJECTIVES: We aimed to investigate both nocturnal spontaneous and morning growth hormone (GH)-releasing hormone (GHRH)-induced GH secretion in children on daily glucocorticoid treatment after liver transplantation and to evaluate the effect of pyridostigmine (an acetylcholinesterase inhibitor thought to reduce hypothalamic somatostatin tone) on GH secretion in these patients. DESIGN: We performed a randomized, single-blind, cross-over study. PATIENTS: We studied three male and three female juvenile patients, within a year of orthotopic liver transplantation and under immunosuppressive glucocorticoid therapy (mean dose +/- SEM, 5.92 +/- 0.63 mg/day) and five normal children (four males, one female). MEASUREMENTS: Both nocturnal spontaneous and morning GHRH-induced GH secretion were evaluated after administration of placebo, 1 tablet p.o., or pyridostigmine, 2 mg/kg p.o. RESULTS: Spontaneous GH. Placebo: in liver transplanted children nocturnal GH secretion (mean GH level 10.8 +/- 2.0 mU/l) was not significantly different with respect to normal children (mean GH level 12.8 +/- 1.2 mU/l); pyridostigmine: nocturnal GH secretion was significantly increased as compared to placebo in subjects with liver transplantation but not in normal children. GHRH test. Placebo: liver transplanted patients showed a blunted GH response to GHRH with respect to normal children; pyridostigmine: the GH responses to GHRH (P less than 0.05) increased as compared to placebo and did not differ significantly in the two groups. CONCLUSIONS: Our data suggest a steroid-mediated increase in hypothalamic somatostatin tone in liver transplanted children

In the present study we investigated the effects of the acetylcholinesterase inhibitor pyridostigmine (PD), which is hypothesized to decrease hypothalamic somatostatin tone, alone and in association with GH-releasing hormone (GHRH) on GH secretion in 18 type 1 diabetic patients and 12 normal subjects using a randomized double blind placebo-controlled protocol. All subjects received either 120 mg oral PD or placebo 60 min before iv injection of either human GHRH-(1-29) NH2 (100 micrograms) or sterile water (2 mL). In normal subjects both PD alone and GHRH alone caused a significant increase in GH. PD and GHRH acted in a synergistic fashion when combined. In diabetic patients the GH response to GHRH was variable. To segregate the responses, the ratio between the GH increase after GHRH plus PD and after GHRH alone was calculated for each subject. In 10 diabetic patients (group A) the ratio was lower than 2 SD (P less than 0.05) from the mean response of normal subjects. These patients showed an exaggerated GH increase after GHRH and a lower GH increase after PD with respect to normal subjects. Eight diabetic patients (group B) showed a ratio similar to that in normal subjects and similar GH responses to the stimuli. No significant differences were found between groups A and B with respect to age, body mass index, and blood glucose levels. Duration of diabetes was longer and basal GH levels were higher in group A. Hemoglobin-A1c was higher in group A, but of only borderline statistical significance (P = 0.052). Our data demonstrate that in diabetic patients with exaggerated GH responses to GHRH an increase in cholinergic tone does not affect GH secretion. These data suggest that in some type 1 diabetic patients an altered somatostatinergic control of GH secretion may contribute to their abnormal GH response to GHRH.

Glucocorticoids have been shown to inhibit GH secretion in normal man when administered in large amounts for several days. The aim of our study was 1. to investigate the acute effects of a single dose of glucocorticoids on GH secretion in normal man; 2. to look at the relationship between the increase in serum cortisol concentration and GH response to the stimuli. Six healthy volunteers received on three occasions in random order an iv injection of GHRH (1–29) NH2, 100 μg, alone or 60 min after oral administration of either 25 or 50 mg of cortisone acetate. Mean stimulated GH levels, GH peak and integrated GH concentration were significantly lower after GHRH plus cortisone 25 mg than after GHRH alone. Mean GH levels at 15 and 30 min after GHRH injection and the peak GH level showed a further decrease after GHRH plus cortisone 50 mg. We conclude that acute administration of pharmacological doses of glucocorticoids is able to inhibit GH response to GHRH, probably through enhancement of endogenous somatostatin release. Moreover, this pharmacological effect of glucocorticoids seems to be dose-dependent and thus directly related to serum cortisol concentrations.

Glucocorticoids have been shown to inhibit GH secretion in normal man when acutely and chronically administered in pharmacological amounts. Pyridostigmine (PD), an acetylcholinesterase inhibitor, is able to elicit GH secretion when administered alone and to enhance the GH response to GHRH in normal subjects probably via a decrease in the hypothalamic release of somatostatin. The aim of the present study was to investigate the influence of glucocorticoids on the GH response to PD administered either alone or in combination with GHRH in normal adult subjects. Six healthy adult volunteers underwent six experimental protocols. They received 1) human (h) GHRH(1-29)NH2, 100 micrograms injected as an iv bolus; 2) cortisone acetate, 50 mg administered orally (po) 60 min before an hGHRH iv bolus injection; 3) PD, 120 mg administered po, 60 min before an hGHRH iv bolus injection; 4) PD and cortisone acetate, administered po 60 min before an hGHRH iv bolus injection; 5) PD, administered po 60 min before a saline iv bolus injection; 6) PD and cortisone acetate administered po 60 min before a saline iv bolus injection. Mean GH levels, peak GH levels, and GH area under the curves (AUCs) were significantly lower after GHRH + cortisone as compared to GHRH alone. However, these parameters were not significantly different after PD + GHRH + cortisone when compared to PD + GHRH and after PD + cortisone when compared to PD alone. We conclude that acute administration of pharmacological amounts of glucocorticoids cannot inhibit the GH response to PD alone or in combination with GHRH. Thus, we hypothesize that the inhibitory action of glucocorticoids on the GH response to GHRH in man may be mediated by an enhancement of either somatostatin release by the hypothalamus or somatostatin action on the pituitary.

We have compared the effects of aztreonam and placebo in the prevention of urinary tract infections (UTI) in elderly hospitalized patients who needed urethral catheterization. 162 patients (96 males, 66 females; age range 60-91 years) were randomly allocated to receive double-blind a single dose of aztreonam (2 g i.m. 80 patients) or placebo (4 ml lidocaine 2%, 82 patients) three hours before catheterization. All patients were followed-up for 7 days. Urine culture was performed before, at the first, third and seventh day of catheterization. At the end of follow-up 71/80 patients (88.7%) who received a single preventing dose of aztreonam had negative urine culture without clinical signs of UTI. On the contrary, in the group treated with placebo at the end of follow-up only 38/82 patients (46.3%) had negative urine without clinical signs of UTI. In conclusion, our data suggest that a single 2g i.m. dose of aztreonam is effective in preventing UTI in elderly patients needing indwelling urethral catheterization.

SUMMARY Studies in man demonstrated that salmon calcitonin (sCT) administration blunts the pituitary GH response to GH-releasing hormone (GHRH). However, the mechanisms underlying this inhibitory action of CT in man are unclear. Pyridostigmine (PD), an acetylcholinesterase inhibitor, is hypothesized to enhance the GH response to GHRH in normal subjects probably via a decrease in the somatostatinergic tone. The aim of the present study was to investigate the mechanism of the inhibitory action of sCT on the GH response to human GHRH (1–29) NH2 by concomitant PD administration in normal humans. The GH response to GHRH was significantly suppressed by prior administration of sCT. Pretreatment of subjects with PD significantly enhanced the GH response to GHRH but did not alter the inhibitory actions of sCT. We conclude that sCT is able to inhibit GHRH-stimulated GH secretion in man without influencing the hypothalamic somatostatinergic tone.

Physical exercise can induce micro-albuminuria, a urinary albumin excretion rate of 20-200 micrograms/min, in diabetics without micro-albuminuria at rest (stage II of diabetic nephropathy). The aim of the present study was to evaluate the acute effects of captopril, an angiotensin converting enzyme (ACE) inhibitor, and nifedipine, a calcium channel blocker, on exercise-induced micro-albuminuria in hypertensive diabetics with stage II nephropathy. Eleven hypertensive World Health Organisation (WHO) stages I-II non-obese diabetics (five insulin-dependent diabetics, six non-insulin dependent diabetics) underwent five submaximal cycloergometric tests, the first two in basal conditions, the other three after 24-h administration of captopril (25 mg twice a day), placebo (1 tablet twice a day) or nifedipine AR (20 mg twice a day) according to a randomized double-blind design. Our results demonstrate that despite a lower reduction in exercise blood pressure, captopril is more effective than nifedipine in blunting diabetic exercise-induced micro-albuminuria.