Inhibitory effect of dexamethasone on arginine-vasopressin release induced by physical exercise in man

To establish whether glucocorticoids inhibit the arginine-vasopressin (AVP) response to physical exercise, 10 healthy men underwent bicycle ergometer tests until exhaustion (exercise control test, exercise plus dexamethasone [2 or 4 mg in an intravenous bolus]). Physiological and biochemical variables were similar in all tests. Pretreatment with dexamethasone (2 or 4 mg) partially but significantly decreased the AVP response induced by physical exercise. Our results demonstrate a partial inhibition induced by glucocorticoids of AVP neurosecretion during cycle ergometer tests.

[Sulphur mineral water and SPA therapy in osteoarthritis]

OBJECTIVE

Osteoarthritis (OA), the most common degenerative osteoarticular disease, is cause of pain and limitations in physical function with high disability that can conduct to a state of psycological stress, not always considered adequately, with negative impact on the quality of life. The mud and bath therapy can improve this aspect. However, these studies are insufficient. The objective of our research was to evaluate the impact of SPA therapy cycle on safety, efficacy and psychosocial disability in osteoarthritis.

MATERIALS AND METHODS

The study was carried out on 99 subjects suffering from OA. The patients has treated for 12 days with applications of sulphurous mud-bath therapy from "Terme di Telese" (Benevento, Italy). At the beginning and at the end of the SPA therapy considered has assessed: 1) the adverse reactions; 2) the efficacy on the pain and functional limitations; c) the impact on the psychosocial function using the VAS scale, the SF-36 questionnaire, the WOMAC index and the SDS-Zung test. Statistical analysis of the data was performed by determining the mean ± SD. The results were compared with the Student "t" test or Wilcoxon test. A p value < 0.05 was considered significant.

RESULTS

In comparison to the basal values, this investigation has demonstrated that sulphurous mud and bath therapy has induced a significant (p < 0.01) improvement of overall quality of life with reduction of pain at rest (2.1 ± 1.5 → 1.2 ± 1.3) and during daily activities (2.3 ± 1.3 → 1.4 ± 1.3). This has facilitated the physical function and psychosocial disability as shown by the questionnaires SF-36, WOMAC and SDS Zung.

CONCLUSIONS

In conclusion our data suggest that mud-bath therapy with sulphurous mineral water can be considered as an important phase of the therapeutic strategy in OA.

Effect of physiological exercise on osteocalcin levels in subjects with adrenal incidentaloma

AIM

In the present study, we have evaluated whether physical exercise affect low osteocalcin concentrations observed in patients with subclinical hypercortisolism.

SUBJECTS AND METHODS

Sixteen patients (10 men and 6 women, age 38-55 yr) with adrenal incidentaloma were studied. Fifteen healthy volunteers matched for age (range 35-47 yr) were used as controls. Subjects were submitted to a 8-week exercise-training program with cycle-ergometer for 1 h/day 3-4 days/week at 60% of their individual VO2 max. Before and after this period, resting venous serum osteocalcin and GH concentrations were measured in the same batch. The blood sampling after 8 weeks of the training program were performed after resting for one day. All patients and controls underwent also the following endocrine evaluation: serum cortisol, plasma ACTH.

RESULTS

Our results demonstrate a significant increase of osteocalcin after physical exercise and a positive correlation between osteocalcin and GH. This later might suggest a role of GH in the increased osteocalcin secretion.

CONCLUSIONS

The data of the present study suggest a positive effect of physical exercise on bone metabolism in patients with adrenal incidentaloma.

Naloxone decreases the inhibitory effect of alprazolam on the release of adrenocorticotropin/cortisol induced by physical exercise in man

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• Alprazolam (ALP), a benzodiazepine activating GABAergic receptors, is involved in ACTH secretion.

WHAT THIS STUDY ADDS

• This study demonstrates a partial opioid influence in the inhibitory effect of ALP on the release of ACTH/cortisol during physical exercise.

AIMS

To establish the possible involvement of alprazolam (ALP) and/or opiates in the mechanism underlying the ACTH/cortisol response to physical exercise.

METHODS

Tests were carried out under basal conditions (exercise control test), exercise plus ALP (50 µg at time -90 min), naloxone (10 mg at time 0) or ALP plus naloxone. Plasma ACTH and serum cortisol concentrations were evaluated in blood samples taken before, during and after the bicycle ergometer tests.

RESULTS

ACTH and cortisol concentrations rose significantly after physical exercise. Maximum peak at time 15 min (P ≤ 0.01 vs. baseline) for ACTH and at time 30 min (P ≤ 0.01 vs. baseline) for cortisol. In the presence of naloxone, the ACTH and cortisol responses were significantly increased (maximum peak at time 20 min, P ≤ 0.02 vs. control test for ACTH, and at time 30 min (P ≤ 0.01 vs. baseline) for cortisol) whereas they were abolished by ALP. When ALP and naloxone were given together, the inhibitory effect of ALP was partial.

CONCLUSIONS

These data demonstrate an inhibitory effect of ALP in the regulation of the ACTH/cortisol response to physical exercise in man and suggest that GABAergic receptor activating benzodiazepines and opioids interact in the neuroendocrine secretion of ACTH/cortisol.

Somatostatin reduces neuropeptide Y rise induced by physical exercise

The effect of an i. v. infusion of somatostatin (SRIH) 4.1 μg/min×90 min on the basal secretion of NPY and on the NPY response to physical exercise was studied in normal men. Basal NPY secretion was not modified by SRIH infusion, whereas the NPY response to physical exercise was significantly lower in the presence of SRIH. These data suggest the involvement of a somatostatinergic mechanism in the regulation of NPY response to physical exercise.

Increased arginine-vasopressin response to hypertonic stimulation and upright posture in idiopathic hyperprolactinemia

To evaluate the possible influence of idiopathic hyperprolactinemia on the arginine-vasopressin (AVP) response to osmotic and pressure-volumetric stimuli, 14 idiopathic hyperprolactinemic women and 13 normoprolactinemic women were studied during a hypertonic saline infusion test (0.51M NaCl infusion for 2h) and an orthostatic test (standing upright and maintaining an orthostatic position for 20min). In both experimental conditions, the AVP response was significantly higher in women with idiopathic hyperprolactinemia than in normal normoprolactinemic women. These results indicate that in women hyperprolactinemia influences the AVP response to hyperosmotic and hypovolemic stimuli.

Oxytocin does not modify GH, ACTH, cortisol and prolactin responses to Ghrelin in normal men

BACKGROUND

In order to test the possible effect of Oxytocin (OT) on Ghrelin-stimulated GH, PRL, ACTH and cortisol, ten healthy normal men were studied.

TESTS

Ghrelin (0.2 μg/kg body weight (BW)) as an iv bolus; Ghrelin plus OT (2 IU as bolus plus 0.07 IU/min administered for 90 min).

RESULTS

The administration of OT did not change GH, PRL, ACTH and cortisol release induced by Ghrelin.

CONCLUSIONS

The data suggests that in humans OT did not modulate the GH, PRL, ACTH and cortisol response to Ghrelin.

Naloxone decreases the inhibitory effect of somatostatin on GH release induced by cigarette smoking in man

To establish whether somatostatin (SRIH) exerts its inhibitory effect on the nicotine-induced release of GH by interacting with an opioid pathway, normal volunteers were treated with naloxone during (2 no-filter) cigarettes smoking and with SRIH. Nicotine significantly increased serum GH levels about 3.5 fold. Naloxone alone did not change GH rise induced by cigarette smoking. The stimulatory effect of GH by nicotine was completely blocked by SRIH. In the presence of both SRIH and naloxone, GH levels rose 1.5 fold in response to nicotine. Since naloxone only partially reversed the inhibiting action of SRIH, only a partial involvement of opioid peptides in SRIH action might be supposed. Alternatively, SRIH and naloxone-sensitive opiates might produce this inhibiting effect on GH rise in response to cigarette smoking through independent pathways.

Systemic oxytocin administration modulates NPY response to insulin-induced hypoglycemia in man

The present study was undertaken to establish whether oxytocin (OT) is able to modify the NPY response to insulin-induced hypoglycemia in man. At 8:00 AM of 2 different days at least 1 week apart, 10 normal men were tested with insulin (0.15 IU/kg) and with the administration of OT (infused from time -15-60 min, at a constant rate of 2 mIU/ml) or placebo. Plasma NPY concentrations rose significantly during insulin tolerance test (ITT). Oxytocin treatment significantly reduced the NPY response to hypoglycemia. The finding demonstrates for the first time in humans that the systemic administration of OT exerts an inhibitory effect on the NPY rise caused by insulin-induced hypoglycemia.

Effect of physical training on age-related reduction of GH secretion during exercise in normally cycling women

OBJECTIVE

To evaluate whether prolonged physical activity (25 km/week running for 8 years) modifies GH decline.

DESIGN

The GH response to maximal exercise on bicycle-ergometer was tested in younger (26-30 years) and older (42-46 years) healthy women. Each age group included 2 subgroups of 10 sedentary and 10 runners, which were compared. The workload was increased at 3 min intervals from time 0 until exhaustion. Subjects with a low maximal capacity (as established in a preliminary test) pedalled for 3-4 min against no workload at the beginning of the test, so that exercises lasted about 15 min in all individuals.

RESULTS

At exhaustion, heart rate and systolic pressure were significantly higher in sedentary than in trained subjects, whereas V(O(2)max), blood glucose and plasma lactate levels were similar in all groups. Exercise induced similar GH responses in younger sedentary and exercise-trained subjects and in older exercise-trained subjects, with mean peak levels 7.5 times higher than baseline. In contrast, in older sedentary women peak GH level was only 4.4 times higher than baseline and was significantly lower than in the other groups.

CONCLUSION

These data suggest that in women prolonged physical training exerts protective effects against age-dependent decline in GH secretion.

Effect of serotonergic system on AVP secretion induced by physical exercise

The present study was undertaken in order to establish the possible involvement of serotonergic receptors in the control of physical exercise-stimulated vasopressin secretion. Twenty-one healthy men (divided in three groups of seven) underwent bicycle-ergometer tests until exhaustion: exercise control test (n=21), exercise plus ondansetron, selective 5-HT3 antagonist (n=7), exercise plus buspirone, selective 5-HT1A receptor agonist (n=7), exercise plus sumatriptan, selective 5-HT1D receptor agonist (n=7). AVP levels, physiological and biochemical variables were measured and compared during tests. Results showed that exercise-induced AVP rise did not change after the administration of buspirone and sumatriptan. In contrast, the administration of ondansetron significantly reduced physical exercise-induced AVP rise. Mean peak levels during physical exercise were 4.9 times higher than basal values in the control test and 2.6 times higher than basal values in the ondansetron plus exercise test. These data demonstrate that 5-HT3 serotonergic receptors at least partially mediate the AVP response to physical exercise. On the other hand, 5-HT1A and 5-HT1D serotonergic receptors do not appear to be involved in the control of AVP secretion during exercise.

Naloxone decreases the inhibitory effect of ethanol on the release of arginine-vasopressin induced by physical exercise in man

To establish whether ethanol and/or endogenous opioids play a role in the control of arginine-vasopressin (AVP) response to physical exercise, six healthy men underwent six bicycle-ergometer tests until exhaustion [exercise control test; exercise plus ethanol (50 of 110 ml proof whiskey orally), exercise plus naloxone (2 mg injected plus 5 mg infused or 4 mg injected plus 10 mg infused intravenously] or exercise plus ethanol plus naloxone). Plasma AVP levels, physiological and biochemical variables were measured during tests. Physiological and biochemical variables were similar in all tests. During the control test, exercise significantly increased plasma AVP levels, with a peak value five times higher than baseline. The AVP response to exercise was similar in the presence of naloxone, whereas it was abolished by ethanol. When ethanol tests were repeated in the presence of naloxone, at both lower and higher dose, ethanol inhibition on AVP secretion was only partial, with mean peak responses 2.5 times higher than basal values. Results indicate an ethanol involvement in regulation of the AVP response to physical exercise. Furthermore, naloxone-sensitive endogenous opioids appear to play a role in the mechanism underlying ethanol inhibitory action, but not in mediation of the AVP response to physical exercise.

Effect of Potentiation of Cholinergic Tone by Pyridostigmine on the GH Response to GHRH in Elderly Men

The plasma GH response to GHRH (100 micrograms i.v.) was evaluated either alone or after pretreatment with pyridostigmine (120 mg orally 1 h prior to GHRH) in 9 younger men (age range: 22-39 years) and in 9 healthy elderly men (age range: 63-77 years). On a different occasion, subjects were tested with pyridostigmine alone. Basal concentrations of glucose, cortisol, androgens, estrogens, thyroid hormones and GH were similar in all subjects, whereas insulin-like growth factor was lower in elderly men. The GH response to GHRH was significantly lower in the older (mean peak was 6 times higher than baseline) than in the younger group (mean peak was 11.3 times higher than baseline). The pretreatment with pyridostigmine induced a striking increase in the GH response to GHRH in the younger subjects (mean peak was 26 times higher than baseline), whereas it produced only a slight increase in the GHRH-induced GH response in elderly men (mean peak was 8.7 times higher than baseline). When pyridostigmine was given alone, plasma GH levels rose significantly in both groups; however, the pyridostigmine-stimulated GH response was significantly higher in younger (mean peak was 6 times higher than baseline) than in older subjects (mean peak was 2.5 times higher than baseline). These data indicate that the cholinergic stimulatory regulation of GH release is reduced in elderly subjects. Since acetylcholine inhibits hypothalamic somatostatin release, the reduced cholinergic tone in elderly subjects may result in an increased somatostatinergic tone.

Oxytocin inhibits the stimulatory effect of ghrelin on circulating neuropeptide Y levels in humans

Oxytocin (OT) effect on ghrelin-stimulated neuropeptide Y (NPY) secretion was evaluated in 12 normal men.

TESTS

ghrelin (1 microg/kg B.W. as an intravenous bolus); OT (2 mIU/min infusion); ghrelin plus OT; normal saline. Plasma NPY did not change during saline or OT infusions, whereas it showed a significant 29% increase vs baseline at 15 min after ghrelin injection. When OT was present, ghrelin-induced NPY increment was completely abolished. Results show that oxytocin modulates the NPY response to ghrelin, whereas it is unable to produce direct inhibitions of basal circulating NPY levels.

High-calcium mineral water as a calcium supplementing measure for post-thyroidectomy hypocalcemia

AIM

The aim of this study was to test the possibility of enhancing blood calcium levels in totally thyroidectomized patients by supplementation with 1 L/d carbonate-bicarbonate-high-calcium mineral water.

METHODS

This study enrolled 95 outpatients, totally thyroidectomized four months earlier, and hence treated with oral calcium and vitamin-D. At recruitment, ionized blood calcium was either below (Group A; N. 55) or above (Group B; N. 40, randomly divided in Group B1 [N. 20] and Group B2 [N.20]) the lower limit of the normal range (1.12 mmol/L). For one month, Group A was treated with 1 L/d high-calcium (483 mg/L) mineral water and continued the usual therapy with Ca and vitamin-D. In contrast, Group B1 and Group B2 substituted their Ca and vitamin-D therapy with 1 L/d high-calcium mineral water (Group B1) or 1 L/d of placebo mineral water (Ca:80 mg/L) (Group B2).

RESULTS

After one month, a significant 7.5% increase in blood ionized-calcium levels was observed in Group A, no change in Group B1 and a significant drop below normality in Group B2 (Group B2 vs Group B1, P<0.001). Thereafter, 1 L/d of the high-calcium mineral water, given to Group B2 instead of placebo for an additional month, significantly enhanced ionized-calcium levels above the lower limit of normality (Group B2 vs Group B1, NS).

CONCLUSION

These experiments show that calcium supplementation as 1 L/d of a high-calcium mineral water may efficaciously enhance blood calcium levels in thyroidectomized patients. This complementary treatment might at least in part contribute to the prevention and/or treatment of hypocalcemia and substitute vitamin-D and calcium therapies after thyroidectomy.

Effect of naloxone on somatostatin inhibition of arginine vasopressin response to physical exercise in normal men

To establish whether somatostatin (SRIH) and/or endogenous opioids play a role in the control of arginine-vasopressin (AVP) response to physical exercise, eight healthy men underwent four bicycle-ergometer tests until exhaustion: exercise control test; exercise plus SRIH, naloxone or SRIH plus naloxone. Serum AVP levels, physiological and biochemical variables were measured during tests. Physiological and biochemical variables were similar in all tests. During control test exercise significantly increased serum AVP levels, with a peak value 4.1 times higher than baseline. The AVP response to exercise was similar in the presence of naloxone, whereas it was significantly reduced by SRIH (AVP peak was only 2.8 times higher than baseline). When SRIH and naloxone were given together, the exercise-induced AVP rise was comparable to that observed in the control test. Results indicate a somatostatinergic involvement in the regulation of the AVP response to physical exercise. Furthermore, naloxone-sensitive endogenous opioids appear to play a role in the mechanism underlying SRIH inhibitory action, but not in mediation of the AVP response to physical exercise.

Free fatty acids inhibit adrenocorticotropin and cortisol secretion stimulated by physical exercise in normal men

BACKGROUND

The basal circulating levels of ACTH and cortisol, but not the ACTH/cortisol response to hCRH, are significantly reduced by free fatty acid (FFA) infusion.

OBJECTIVE

To verify whether FFA infusion modifies the ACTH/cortisol response to physical exercise, a well-known activator of the HPA axis at suprapituitary level.

DESIGN

Exercise tests on a bicycle ergometer during infusion of a lipid-heparin emulsion (LHE) (experimental test) or normal saline (NaCl 0.9%) (control test).

SETTING

Department of Cardiology at the University-Hospital.

SUBJECTS

Seven healthy male subjects aged 25-33 years.

INTERVENTIONS

On two mornings, at weekly intervals, LHE or saline were infused for 60 min; infusion started 10 min before exercise test on a bicycle ergometer, which lasted about 15 min.

MAIN OUTCOME MEASURES

Circulating ACTH/cortisol levels and physiological variables during physical exercise.

RESULTS

FFA levels (0.4 +/- 0.1 mEq/l) remained constant during control test, whereas they progressively rose (peak at 60 min, 2.7 +/- 1.0 mEq/l) during LHE infusion. Neither basal nor exercise-induced changes in physiological variables were modified by LHE infusion. Both ACTH and cortisol increased during exercise, with peak levels at 20 min and 30 min (control test: 103% and 42%, P < 0.001; experimental test: 28.5% and 18.6%, P < 0.05 higher than baseline, respectively). Both ACTH and cortisol responses were significantly lower in the experimental than in the control test (at 20 min P < 0.002 and at 30 min P < 0.05 for ACTH; at 20 min P < 0.05 and at 30 min, 40 min and 50 min P < 0.001 for cortisol).

CONCLUSIONS

These data represent the first demonstration of an inhibitory action of increased circulating FFA levels on the HPA axis under stimulatory conditions (i.e. physical exercise, a challenge acting at suprapituitary level). In contrast, previous studies did not show FFA effects on the CRH-induced ACTH/cortisol response. Therefore, our data suggest negative effects of FFAs on the HPA axis at hypothalamic or higher centres in the central nervous system.

Adrenocorticotropic Hormone/Cortisol Response to Physical Exercise in Abstinent Alcoholic Patients

BACKGROUND

Alterations in the hypothalamic-pituitary-adrenal (HPA) axis in alcoholic patients have been reported in various experimental conditions.

METHODS

To establish whether alcoholism affects the HPA axis activation during physical exercise, 10 recent abstinent alcoholic patients (age range: 33-45 years; duration of alcohol dependence: range 4-6 years) were tested by exercising on a bicycle ergometer. Ten age-matched healthy nonalcoholic men participated as controls. The workload was gradually increased at 3-minute intervals until exhaustion and lasted about 15 minutes for all subjects. Alcoholic patients were tested at 3 time points, at 4, 6, and 8 weeks after alcohol withdrawal, whereas controls were tested only once. Main outcome measurements were circulating levels of adrenocorticotropic hormone (ACTH) and cortisol and physiological variables during physical exercise [heart rate, blood pressure, ventilation, frequency of breathing, tidal volume, oxygen consumption (VO2), carbon oxide production (VCO2), and respiratory exchange ratio (R)].

RESULTS

Similar basal and exercise-induced changes in physiological variables were observed in controls and alcoholic patients in all tests. Basal levels of ACTH and cortisol were similar in all tests performed on alcoholic patients and on normal controls. In normal subjects, exercise induced a significant increase in plasma ACTH and serum cortisol levels, with peak levels at 20 minutes for ACTH (84% higher than baseline) and at 30 minutes for cortisol (70% higher than baseline). After 4 weeks of abstinence, slight but not significant ACTH/cortisol responses to physical exercise were observed in alcoholic patients (mean peaks were 10 and 18% higher than baseline, respectively, for ACTH and cortisol). By contrast, when the exercise test was repeated after 6 weeks abstinence, ACTH/cortisol levels rose significantly versus baseline (mean peak levels of ACTH and cortisol were 48 and 38% higher than baseline, respectively, for ACTH and cortisol). However, the hormonal responses were significantly lower than in the normal controls. At 8 weeks of abstinence, ACTH/cortisol responses were significantly higher than 2 weeks previously, and were not distinguishable from the increments observed in the normal controls (76 and 68% higher than baseline, respectively, for ACTH and cortisol).

CONCLUSIONS

In concurrence with previous reports showing alterations of the HPA axis in the central nervous system in alcohol-dependent subjects, these data show a defect of the neuroendocrine mechanism(s) underlying the ACTH/cortisol response to physical exercise for at least a month after alcohol withdrawal, with reconstitution of a normal hormonal response at 8 weeks.

Effects of moderate ethanol drinking on the GH and cortisol responses to physical exercise

OBJECTIVE

To evaluate the effects of moderate amounts of ethanol on the GH and cortisol responses to physical exercise.

METHODS

Ten normal men underwent three bicycle ergometer tests. Test were carried out in basal conditions (control test) or after drinking 0.5 or 0.75 g/kg BW ethanol. Tests lasted 15 min in all subjects; the workload was increased at 3 min intervals from time 0 until exhaustion. Non-endocrine physiological parameters (NEPP), such as heart rate, blood pressure, ventilation, frequency of breathing, tidal volume, oxygen consumption, carbon oxide production and respiratory exchange ratio were measured from time 0 until exhaustion. Serum GH and cortisol levels were evaluated in blood samples taken at 5-10 min intervals over a 50 min period from time 0.

RESULTS

Neither basal values, nor exercise-induced changes in NEPP were altered by ethanol drinking. Both GH and cortisol levels significantly rose during the exercise control test. The hormonal responses did not change after 0.5 g/kg BW ethanol, whereas they significantly decreased after 0.75 g/kg BW ethanol.

CONCLUSIONS

Modification of the GH and cortisol responses to exercise represents an "endocrine window" of the effects that even moderate ethanol drinking produces in the CNS. The data show that 0.75 g/kg BW ethanol is the minimal amount producing significant inhibitory effects on the GH and cortisol responses to physical exercise. In view of the important roles played by GH and cortisol during physical activity, even moderate ethanol drinking must be avoided before sport.

Effects of ghrelin on circulating neuropeptide Y levels in humans

OBJECTIVE

Ghrelin is a 28 amino-acid peptide with a strong GH-releasing activity and a complex role in regulation of appetite, fuel utilization, body weight and composition. Neuropeptide Y (NPY) is a well-known stimulator of pathways favouring food intake and energy storage. Recently, studies in rodents suggested a possible mediation of ghrelin action by NPY. In contrast, until now no evidence of ghrelin-NPY interaction in humans has been provided. In the present study, we examined whether ghrelin influences NPY secretion in normal men.

SUBJECTS AND DESIGN

Twelve healthy normal men (aged 24-35 years; body mass index (BMI) 22.3+/-0.93 kg/m2) were tested twice at 08.00 AM on two different days, in random order at weekly intervals, after an overnight fast and rest in bed. An intravenous bolus of 1 microg/kg body weight ghrelin (esperimental test) or an equal amount of normal saline (control test) was injected at time 0. Blood was taken before and over 90 minutes after injections, and was used for the measurement of plasma NPY levels.

RESULTS

Plasma levels of NPY slightly, but significantly rose in response to ghrelin, with a mean peak level at 15 min after injection, whereas no significant change was observed after saline administration.

MAIN FINDING

Our results show a significant enhancement of plasma NPY levels under ghrelin stimulation.

CONCLUSIONS

To our knowledge, this is the first demonstration of a ghrelin-NPY interaction in humans, which may suggest a possible mediation of ghrelin action by NPY in humans.

Different plasma neuropeptide Y concentrations in women athletes with and without menstrual cyclicity

The circulating levels of leptin and neuropeptide Y, which are both involved in the control of feeding and reproduction, were measured in amenorrheic and normal cycling highly trained women athletes, and in normal cycling sedentary controls. Leptin showed similar low values in all athletes, whereas neuropeptide Y levels were significantly higher in normal cycling athletes than in the other groups, suggesting the possibility of a protective role of neuropeptide Y in the maintenance of the menstrual cycle in highly trained athletes.

Graves' disease in interferon-alpha-treated and untreated patients with chronic hepatitis C virus infection

An association between Graves' disease (GD) and chronic hepatitis C (C-HC) has been observed both in the presence and the absence of recombinant interferon-alpha (rIFN-alpha) treatment. rIFN-alpha-induced GD is characterized by suppressed thyroid-stimulating hormone levels; normal or elevated free triiodothyronine (FT3) and free thyroxine (FT4) values; the presence of thyroid peroxidase antibodies, antithyroglobulin antibodies, and thyroid receptor antibodies; and high iodine thyroid uptake. In contrast, GD developed during C-HC without rIFN-alpha is less clearly defined. In this study, we examined two groups of patients: group A, 28 patients with C-HC treated with rIFN-alpha who developed GD after 1 to 9 months, and group B, 10 patients with C-HC who developed GD without a previous rIFN-alpha treatment. At the time of GD, both groups started methimazole therapy; thyroid function was reevaluated after 3, 6, 9, and 12 months. Group A patients continued IFN. After 12 months, all patients of group A were euthyroid, and 21 of them (75%) had already stopped methimazole treatment, whereas all patients of group B were euthyroid and only 2 (20%) had stopped methimazole. In conclusion, the data show a better course of GD, with a more precocious and significantly higher number of recoveries in patients with rIFN-alpha-induced GD than in rIFN-alpha-unrelated disease. Further studies are needed to establish whether the two types of GD differ not only from a clinical point of view but also because of different underlying pathogenetic mechanisms.

Is steroid therapy needed in the treatment of destructive thyrotoxicosis induced by alpha-interferon in chronic hepatitis C?

OBJECTIVE

Treatment with interferon (IFN) of patients affected by chronic hepatitis C (CH-C) may produce alterations in thyroid function, such as hypothyroidism, Graves'-like hyperthyroidism and destructive thyrotoxicosis (DT). IFN-induced DT is characterized by suppressed serum TSH levels, normal or elevated FT4 and FT3 concentrations, with the presence or absence of thyroid peroxidase antibodies and antithyroglobulin antibodies, the absence of thyroid receptor antibodies and radioactive iodine uptake suppressed or <5%.

DESIGN

IFN-induced DT is a mild clinical disease, because thyroid-destructive processes last for a short time and involve a small portion of the gland. At present, the therapeutic approach in DT suggests IFN withdrawal and 1-2 months of methylprednisolone treatment.

METHODS

In consideration of possible untoward side effects of steroid treatment in patients with CH-C, we studied two groups of patients with CH-C who developed DT after treatments with various preparations of recombinant IFN (with or without ribavirin). Patients sequentially entered the study during a 4-year period, at the time of DT diagnosis, when IFN therapy was discontinued. The first 12 subjects (group A) were treated with 8-16 mg/day methylprednisolone for 30-40 days after IFN withdrawal; in the following 15 patients (group B), IFN withdrawal was not followed by any additional treatment. All patients underwent clinical and laboratory controls of thyroid function at 1, 2, 3 and 6 months after DT diagnosis.

RESULTS

The results showed restoration of euthyroidism in both group A and group B patients at 6 months after DT diagnosis, regardless of steroid treatment.

CONCLUSIONS

The simple withdrawal of IFN therapy in patients with CH-C, who had developed DT, appears to be effective in the treatment of the thyroid disease. This therapeutic approach should be preferred in order to avoid possible undesired side effects of steroid therapy in patients with CH-C.

Extraprostatic complications of testosterone replacement therapy

Testosterone therapy has been reported to be useful in the treatment of hypogonadism and partial androgen deficiency of the aging male (PADAM) syndrome. Testosterone administration is needed in order to maintain secondary sexual characteristics, muscle mass, bone mineral density, cognitive function and sexual drive. Newer testosterone-containing compounds, particularly gel preparations, are known to produce more stable circulating testosterone levels than im-administered drugs, with scarce side-effects and good patient compliance. All patients treated with testosterone must undergo a careful follow-up to prevent the development of the major side effects, such as sleep-apnea, erythrocytosis, cardiovascular diseases and the alterations of hepatic function and plasma lipid concentrations.

Adrenocorticotropin/cortisol and arginine-vasopressin secretory patterns in response to ghrelin in normal men

This study was performed in order to establish the secretory patterns and the possible relationships between the adrenocorticotropin (ACTH)/cortisol and arginine vasopressin (AVP) responses in normal men to the systemic administration of ghrelin, an endogenous ligand for the growth hormone secretagogue receptor. For this purpose, a bolus of 1 microg/kg ghrelin was injected intravenously in 9 normal men. AVP, ACTH and cortisol significantly rose in response to ghrelin injection; however, in all subjects the AVP rise preceded the ACTH/cortisol responses. In fact, the mean peak levels of AVP, ACTH and cortisol after ghrelin injection were observed at 15, 30 and 45 min, respectively. When peak AVP responses to ghrelin were considered together with ACTH and cortisol peak levels, highly significant positive correlations were observed (AVP and ACTH, r = 0.94, p < 0.001; AVP and cortisol, r = 0.92, p < 0.001). In conclusion, this study shows that the AVP response to ghrelin precedes the concomitant ACTH/cortisol rise and that these hormonal responses are highly positively correlated. These observations support the hypothesis that AVP mediates ghrelin-induced ACTH secretion in normal men.

Difference between diabetic and nondiabetic smokers in the pituitary response to physical exercise

The growth hormone (GH), cortisol, and arginine vasopressin (AVP) responses to bicycle ergometry (with increasing workload until exhaustion) were measured in 20 patients affected by insulin-dependent diabetes mellitus (IDDM) (10 habitual smokers and 10 nonsmokers) and 20 nondiabetic subjects (normal controls) (10 habitual smokers and 10 nonsmokers). Cardiorespiratory parameters such as heart rate, blood pressure, ventilation, frequency of breathing, tidal volume, oxygen consumption (Vo(2)), carbondioxide production (Vco(2)), and respiratory exchange ratio (R) were monitored before and during exercise tests. No significant differences between groups were observed; furthermore, there were no differences in circulating somatomedin-C (SM-C) and free fatty acids (FFA) levels between groups. Blood glucose levels were similar before exercise and followed a similar pattern during tests in diabetic smokers and nonsmokers. Basal GH, cortisol, and AVP levels were similar in diabetic smokers, diabetic nonsmokers, normal smokers, and normal nonsmokers. In all groups, exercise induced a significant increase in the serum concentrations of all examined hormones. Increments were significantly higher in diabetic than in nondiabetic groups. No significant differences were observed between diabetic smokers and nonsmokers for all examined hormones. AVP responses during tests were similar in normal smokers and nonsmokers. In contrast, exercise-induced GH and cortisol increments were significantly lower in normal smokers than in normal nonsmokers. These data support the hypothesis that in normal subjects habitual nicotine consumption may attenuate both GH and cortisol responses to a releasing stimulation, such as physical exercise. This phenomenon may represent an expression of adaptation of nicotinic neurotransmission to chronic stimulation. Furthermore, the data show that the effect induced by habitual smoking is absent in diabetics, probably because of diabetes-induced neuroendocrine alterations in the central nervous system.

Inhibition of growth hormone secretion in mild primary hyperparathyroidism

INTRODUCTION

Impairment in growth hormone (GH) secretion has been reported to occur in primary hyperparathyroidism (PHP) with strikingly elevated (>150 pg/ml) plasma PTH and free Ca levels. Patients with these characteristics are relatively few, whereas the great majority of patients with biochemically diagnosed PHP are asymptomatic and show borderline or slightly elevated plasma PTH and Ca levels. We wondered whether also patients in these latter conditions show a defective GH secretory pattern.

METHODS

In order to answer this question, 8 female subjects (mean age +/- SE: 44 +/- 1.3 years) were selected at the time of a checkup examination from a larger population of persons in fairly good clinical condition. Inclusion criteria were plasma PTH values slightly above the normal range (up to 50% higher than the maximum limit) with free Ca levels in the upper normal range or slightly higher (experimental group). Normal values in our laboratory are ionized calcium: 1.22-1.42 mmol/ml and plasma PTH: 12-72 pg/ml. A group of 15 age-matched healthy women with plasma PTH and Ca levels in the middle normal range and significantly lower than values found in the experimental group was also selected and used as control. Experimental and control groups were tested with arginine [0.5 mg/kg body weight (BW)] infused intravenously over 30 min and arginine plus GH-releasing hormone (GHRH; 1 microg/kg BW in an intravenous bolus injection). The GH responses to these challenging stimulations were compared between groups.

RESULTS

Basal serum GH values were similar in all subjects. Both arginine and arginine plus GHRH induced a significant GH rise in both groups; however, the GH responses were significantly lower in the experimental than in the control group. Mean GH peak was 27.7 and 14.6 times higher than baseline after arginine and 57.5 and 26.6 times higher than baseline after arginine plus GHRH in the control and experimental group, respectively. No significant correlation was observed between PTH or Ca levels and the GH responses to challenging stimuli in any group.

CONCLUSION

These data show that impairment in GH secretion is associated with slightly elevated levels of PTH in the presence of serum Ca values in the upper normal range. GH responses to stimulations were reduced by about 50% in our hyperparathyroid subjects. A long-time duration of this relatively small decline of GH secretory activity may be supposed to contribute to age-related catabolic processes in a large number of patients with mild primary hyperparathyroidism.

Glucoreceptors Located Inside the Blood-Brain Barrier Mediate Hypoglycemia-Induced LH Inhibition in Man

OBJECTIVE

To establish the role of hyperinsulinemia and hypoglycemia during the insulin tolerance test (ITT) in the regulation of luteinizing hormone (LH) secretion and the location with respect to the blood-brain barrier (BBB) of the glucosensitive areas controlling LH release.

METHODS

The LH-secretory pattern during an ITT (0.15 IU/kg body weight) was evaluated in 8 normal men during infusion with normal saline (control test), glucose or fructose.

RESULTS

lnsulin-induced hypoglycemia produced a significant decrement in serum LH levels in the control test, but not when the concomitant infusion of glucose prevented hypoglycemia. Fructose infusion did not change LH decrease during ITT.

CONCLUSIONS

These data exclude a direct role of hyperinsulinemia in the mechanism underlying the inhibition of LH secretion during ITT. Furthermore, since glucose but not fructose crosses the BBB, the LH decrease during ITT appears to be generated by hypoglycemia at the level of glucosensitive areas located inside the BBB.

Serum Total Prostate-Specific Antigen Assay in Women with Cushing’s Disease or Alcohol-Dependent Pseudo-Cushing’s State

BACKGROUND

The distinction between Cushing's disease (Cushing's syndrome dependent on adrenocorticotropic hormone (ACTH)-secreting tumors of pituitary origin) and pseudo-Cushing's states (Cushingoid features and hypercortisolism sometimes present in alcoholic, depressed or obese subjects) can present a diagnostic challenge in clinical endocrinology. Recently, the availability of a highly sensitive immunofluorometric assay for the measurement of total prostate-specific antigen (PSA) provided the possibility to measure serum PSA levels in women. Interestingly, PSA gene expression and protein production has been found to be upregulated by steroid hormones, such as androgens, glucocorticoids, mineral corticoids and progestins. In fact, serum total PSA concentrations appear to be higher in female patients with Cushing's disease than in normal women. We wondered whether a similar phenomenon also occurs in pseudo-Cushing's state.

METHODS

In order to answer this question, we compared the serum total PSA levels measured in 10 female subjects with alcohol-dependent pseudo-Cushing's state with those observed in 8 female patients with Cushing's disease and in 15 age-matched healthy women. Serum testosterone, ACTH and cortisol, and 24-hour urinary cortisol levels were measured; cortisol suppression after dexamethasone was also tested in all subjects.

RESULTS

The basal serum levels of ACTH and cortisol were significantly lower in normal subjects than in patients with Cushing's disease or pseudo-Cushing's state; these latter groups showed similar basal hormonal values. Dexamethasone administration was unable to suppress serum cortisol levels in 5 subjects with Cushing's disease and 6 subjects with pseudo-Cushing's state. Serum testosterone values in the group with Cushing's disease were higher than in the other groups. No differences were observed between pseudo-Cushing's and normal subjects. Serum total PSA levels were significantly higher in women with Cushing's disease than in subjects with pseudo-Cushing's state and normal controls; these latter groups showed similar PSA values. When serum total PSA and testosterone levels were considered together, a significant positive correlation was observed in the group with Cushing's disease, but not in the other groups.

CONCLUSIONS

These data indicate that the steroid milieu responsible for the elevation in serum PSA in women with Cushing's disease is not present in subjects with alcohol-dependent pseudo-Cushing's state, suggesting the possible use of PSA as a marker of differentiation between these pathological conditions in women.

Effect of oxytocin on nitric oxide activity controlling gonadotropin secretion in humans

BACKGROUND

Previously described inhibitory effects of the nitric oxide synthase (NOS) inhibitor L-NAME on luteinizing hormone-releasing hormone (LH-RH)-induced LH and follicle stimulating hormone (FSH) secretion in humans suggested modulation by nitric oxide (NO) of the gonadotropin-releasing action of LH-RH.

DESIGN

In order to establish whether oxytocin (OT) participates in this regulatory mechanism, 10 normal men were treated with LH-RH (100 micro g as an i.v. bolus) given alone or in the presence of L-NAME (40 micro g kg-1 injected plus 50 micro g kg-1 infused i.v. for 60 min), OT (2 IU injected plus 4 IU infused i.v. for 60 min) or a combination of both drugs.

RESULTS

The administration of OT was unable to change the gonadotropin responses to LH-RH. In contrast, L-NAME significantly reduced both FSH and LH increments induced by LH-RH. When L-NAME was given in the presence of OT, the LH and FSH responses to LH-RH were similar to those observed after the administration of LH-RH alone.

CONCLUSION

These data suggest antagonistic actions of OT and L-NAME in the control of NOS activity in regulation of gonadotropin secretion induced by LH-RH.

The nocturnal serum thyrotropin surge is inhibited in patients with adrenal incidentaloma

BACKGROUND

Alterations in hypothalamic-pituitary function have been described in patients with incidentally discovered adrenal adenomas and have been attributed to their subtle hypercortisolemic status.

METHODS

To establish whether the central control of the hypothalamic-pituitary-thyroid axis is altered in these endocrine conditions, the nocturnal (10:30 PM-2:00 AM) serum thyroid-stimulating hormone (TSH) surge (measured by dividing the difference between nighttime and morning TSH values by the morning TSH value and then multiplying by 100), the TSH response to thyrotropin-releasing hormone (200 microg as an intravenous bolus) and serum free thyroid hormone levels were evaluated in patients with adrenal incidentaloma (experimental group) and in normal controls (control group). Urinary free cortisol concentrations were also measured.

RESULTS

The nocturnal TSH surge was observed in the normal controls, whereas it was inhibited in the patients of the experimental group. Serum free triiodothyronine levels were similar in the two groups, whereas the TSH response to thyrotropin-releasing hormone was significantly lower in the experimental than in the control group. Urinary free cortisol levels were significantly higher in the experimental group.

CONCLUSION

These data indicate that even conditions of slight glucocorticoid excess may exert inhibitory effects on TSH secretion, which suggests the presence of a slight central hypothyroidism in patients with adrenal incidentaloma.

Effect of dexamethasone on TSH secretion induced by TRH in human obesity

BACKGROUND

The presence of an abnormally high thyroid-stimulating hormone (TSH) response to thyrotropin-releasing hormone (TRH) makes it difficult to distinguish some euthyroid obese subjects from subelinically hypothyroid obese patients. Here, we examine whether such distinction may be achieved after treatment with glucocorticoids, which inhibit TSH secretion at the hypothalamic-pituitary level.

METHODS

TRH tests (200 microg as an intravenous bolus injection) were performed in 30 age- and weight-matched, obese, but otherwise healthy, men. All subjects were tested again with TRH after treatment with dexamethasone (dex) (2 mg/d in four divided doses orally for 3 days).

RESULTS

In all subjects, total thyroxine and triiodothyronine concentrations were in the normal range. According to basal and TRH-stimulated serum thyrotropin (TSH) levels, subjects were divided into the following three groups: group I (n=10), euthyroid subjects; group II (n=10), euthyroid subjects with normal basal but abnormally elevated TSH responses to TRH; group III (n=10), subjects with elevated basal and TRH-induced TSH levels (subclinical hypothyroidism). Basal TSH levels were 1.8+/-0.4 mU/L in group I, 1.7+/-0.3 in group II, and 6.0+/-0.7 in group III. In both groups II and III, TRH-induced TSH increments were above the normal range (maximal increment> 15 mU/L) and were significantly higher than in group I. After the second treatment with TRH, pretreatment with dex significantly decreased both basal TSH levels and peak TSH responses to TRH in all groups. However, a striking percentage decrease (>50%) in TRH-induced peak TSH responses was observed in euthyroid obese subjects of groups I and II, whereas hypothyroid subjects of group III showed only a slight decrement (<25%).

CONCLUSIONS

The sensitivity of the TSH secretory system to glucocorticoid inhibitory action is preserved in obese subjects with abnormally elevated TSH response to TRH, but not in subclinically hypothyroid obese patients. The TRH plus dex test might be useful in future studies to understand the mechanisms underlying alterations in TSH secretion in obesity.

Different control of GH secretion by gamma-amino- and gamma-hydroxy-butyric acid in 4-year abstinent alcoholics

The present study attempted to establish whether long term abstinence from alcohol restores the stimulatory effects on GH secretion of gamma-aminobutyric acid (GABA) and gamma-hydroxybutyric acid (GHB) that are absent during the first month of alcohol withdrawal. Six 4-year abstinent alcoholic subjects--already tested with GHB 4 years earlier, and seven age- and weight-matched normal controls, were tested p.o. with 800 mg sodium valproate (a drug that enhances endogenous GABA activity), 10 mg baclofen (a GABA(B) receptor agonist), 25 mg/kg body-weight GHB, or a placebo. The blood samples for growth hormone (GH) assay were taken every 30 min for the next 150 min. Placebo administration did not modify GH secretion in any subject. All drugs induced a significant increase in serum GH levels in normal controls. GH secretion in abstinent alcoholics did not change after baclofen or sodium valproate administration, whereas the GH response to GHB was similar to that observed in normal controls. The data confirm previous observations which suggest that different neuroendocrine mechanisms underlie GABA and GHB control of GH secretion. The data also indicates that the GHB--but not the GABA--stimulated pathway returns to normal in alcoholics after 4 years abstinence.

Effect of systemic oxytocin administration on dexamethasone-induced leptin secretion in normal and obese men

To establish whether the regulatory mechanism of leptin secretion is sensitive to oxytocin (OT), seven healthy nonobese men were tested with dexamethasone (dex; 4 mg, iv, at 0730 h) in feeding (2000 Cal given at 3 meals over 7 h) conditions either in the absence (iv normal saline infusion) or in the presence of a constant iv infusion of OT (1, 2, or 4 mIU/min from 0730 h for 10 h). In six additional subjects under similar experimental conditions, normal saline or OT (1, 2, or 4 mIU/min from 0730 h for 10 h) were infused iv without the previous treatment with dexamethasone. Serum leptin concentrations were measured in samples taken at 60-min intervals during infusion. Leptin levels remained constant during the infusion of normal saline or OT (1, 2, or 4 mIU/min) alone. In contrast, serum leptin concentrations rose significantly from the baseline after dex administration. The leptin response to dex was not modified by the concomitant infusion of 1 mIU/min OT, whereas it was completely abolished by the administration of 2 or 4 mIU/min OT. These findings led us to evaluate the secretory pattern of leptin in 12 obese patients in similar experimental conditions. In all patients basal leptin levels were significantly higher than those in normal weight subjects. In 6 obese subjects, the infusion of OT alone (1, 2, or 4 mIU/min) was unable to change serum leptin levels. In the remaining 6 obese subjects, dex administration significantly increased serum leptin levels; however, the leptin response to dex was not modified by the concomitant infusion of 1, 2, or 4 mIU/min OT. These data show inhibition by elevated circulating OT levels of glucocorticoid-induced, but not basal, leptin secretion in normal weight subjects, suggesting a possible role for OT in the regulatory control of leptin. Furthermore, the results obtained in obese subjects indicate that this regulation is disrupted in obesity.

Desmopressin and hexarelin tests in alcohol-induced pseudo-Cushing's syndrome

BACKGROUND

A challenge in clinical endocrinology is the distinction between Cushing's disease (Cushing's syndrome dependent by adrenocorticotrophic hormone (ACTH)-secreting tumours of pituitary origin) and alcohol-dependent pseudo-Cushing's syndrome. Patients with Cushing's disease are known to have high ACTH/cortisol responses to desmopressin (DDAVP, a vasopressin analogue) and to hexarelin (HEX, a synthetic GH-releasing peptide).

OBJECTIVE

To compare the ACTH/cortisol responses to desmopressin and to hexarelin of subjects with alcohol pseudo-Cushing's syndrome with those obtained in patients with Cushing's disease and in normal controls.

DESIGN

Randomized, single-blind study.

SETTING

University medical centre.

SUBJECTS

Eight alcoholics with pseudo-Cushing's syndrome, six patients with Cushing's disease and nine age-matched normal controls.

INTERVENTION

Three tests at weekly intervals. The dexamethasone (1 mg) suppression test (DST) was carried out first. The desmopressin (10 microg intravenously at 09:00 h) test and hexarelin (2 microgram kg-1 intravenously at 09:00 h) test were carried out in random order.

MEASUREMENTS

Plasma ACTH and cortisol levels.

RESULTS

The basal plasma levels of ACTH and cortisol were significantly lower in normal subjects than in patients with Cushing's disease and in alcoholic subjects; these latter groups showed similar basal hormonal values. All normal controls, two patients with Cushing's disease and two alcoholics showed suppression of plasma cortisol levels (<5 microgram dL-1) after dexamethasone administration. Both desmopressin and hexarelin induced striking ACTH/cortisol responses in patients with Cushing's disease, whereas hexarelin, but not desmopressin, slightly increased ACTH/cortisol secretion in the normal controls. Neither desmopressin nor hexarelin administration induced any significant change in ACTH/cortisol secretion in alcoholics.

CONCLUSIONS

These data suggest that either the hexarelin or desmopressin test can be used to differentiate patients with Cushing's disease from subjects with alcohol-dependent pseudo-Cushing's syndrome.

Effect of aging on the arginine-vasopressin response to physostigmine and angiotensin II in normal men

The effect of age on the stimulatory control exerted by cholinergic- and angiotensin II (ANG II)-mediated neurotransmission on arginine vasopressin (AVP) secretion was evaluated by measuring and comparing the AVP responses to the administration of either the cholinesterase inhibitor physostigmine (13.5 micrograms/kg in 50 mL normal saline infused in 10 minutes) or ANG II (increasing doses of 4, 8, and 16 micrograms/kg/min, each dose for 20 min) in 8 younger (23-37 years), 8 middle age (42-60 years), and 8 older (63-79 years) healthy male subjects. Both drugs induced significant increments in plasma AVP levels in the youngest group, with mean peak levels 4.8 times higher than baseline at 20 minutes after the beginning of physostigmine infusion and 1.5 times higher than baseline at 60 minutes after the beginning of ANG II infusion. Similar responses were observed in the middle age group. Basal AVP levels in older subjects were similar to those observed in the other groups. However, the AVP increases induced by physostigmine (mean peak was 9 times higher than baseline) and ANG II (mean peak was 2.2 times higher than baseline) were significantly higher in the oldest group than in the other groups. These data suggest age-related enhancement of the stimulatory regulation exerted by cholinergic- and ANG II-mediated neurotransmission on AVP secretion.

Dopaminergic and cholinergic involvement in the inhibitory effect of dexamethasone on the TSH response to TRH

BACKGROUND

Glucocorticoid administration is associated with reduced basal thyroid-stimulating hormone (TSH) levels and a blunted TSH response to thyrotropin-releasing hormone (TRH), despite thyroid hormone levels within the normal range. In light of the inhibitory effect of somatostatin and dopamine on TSH secretion, we examined whether this condition is caused by glucocorticoids through an increased hypothalamic somatostatinergic and/or dopaminergic inhibitory control of TSH. We measured the TSH response to TRH and serum-free T4 and T3 levels. The study group comprised 18 normal men (age 24-35) within 10% of the ideal body weight, randomly divided into 3 groups of six.

METHODS

We used the antidopaminergic agent metoclopramide (MCP) and the acetylcholinesterase inhibitor pyridostigmine, which enhances acetylcholine and thus inhibits hypothalamic somatostatin release. Subjects from group 1 were tested with TRH (20 micrograms in an intravenous bolus) after placebo, dexamethasone (dex) (2 mg/day in 4 divided doses for 3 days before the experimental day), or dex plus pyridostigmine (120 mg p.o.). Subjects from group 2 were tested with TRH after placebo, dex, or dex plus MCP (2.5 mg in an i.v. bolus injection). Subjects from group 3 were tested with TRH after placebo, dex, or dex plus pyridostigmine plus MCP.

RESULTS

In all subjects from groups 1, 2, and 3, TRH-induced TSH rise was significantly lower after dex than after placebo treatment. Neither pyridostigmine nor MCP, given alone, changed the TSH response to TRH after dex treatment. In contrast, the concomitant administration of MCP and pyridostigmine significantly enhanced the TRH-induced TSH rise in dex-treated subjects and made the TSH response to TRH similar to that observed in the TRH plus placebo test.

CONCLUSIONS

These data indicate that enhanced-hypothalamic somatostatinergic and dopaminergic inhibitory activities are involved in the mechanism underlying the reduced TSH response to TRH induced by glucocorticoid treatment.

Muscarinic cholinergic mediation of the GH response to gamma-hydroxybutyric acid: neuroendocrine evidence in normal and parkinsonian subjects

We have recently reported that parkinsonian patients show a significant GH response to gamma-hydroxybutyric acid (GHB), but not to gamma-aminobutyric acid (GABA)-ergic drug administration. In order to establish whether muscarinic cholinergic receptors mediate the GH secretion induced by GHB, normal men and parkinsonian patients were tested with GHB both in the absence and in the presence of the anticholinergic agent, pirenzepine. Both normal controls and parkinsonian patients showed a significant serum GH rise in response to GHB (25 mg/kg body weight p.o.) even though a slightly, but significantly lower response was observed in parkinsonian patients. Pretreatment with pirenzepine (100 mg p.o. 2 h before GHB) completely suppressed the GHB-induced GH release in both normal controls and parkinsonian patients. These data indicate that a cholinergic mechanism mediates the GH response to GHB in normal men. In addition the data indicate that this pathway is preserved in the parkinsonian brain.

Enhancement of the GH responsiveness to GH releasing stimuli by lysine vasopressin in type 1 diabetic subjects

OBJECTIVE

We tested the possibility that lysine vasopressin (LVP) changes the GH responsiveness to exogenously administered GH-RH (at its minimal and maximal doses), clonidine (which is thought to stimulate endogenous GH-RH release) and arginine (which is thought to inhibit somatostatin) in patients with type 1 diabetes mellitus and normal subjects.

DESIGN AND PATIENTS

Normal male subjects (NC) and age- and weight-matched insulin-dependent diabetic men (DM) with good metabolic control were studied. An iv bolus of LVP at a dose (15 microg/kg body weight (BW)) lower than the minimal GH releasing effective dose was injected just before the I.V. injection of the minimal effective dose of GH-RH (0.035 microg/kg BW) in 10 NC and 10 DM, the I.V. injection of the maximal effective dose of GH-RH (100 microg) in 7 NC and 7 DM, the I.V. infusion of arginine (30 g over 30 min) in 7 NC and 8 DM or the oral administration of clonidine (150 microg) in 7 NC and 8 DM. On different occasions, GH stimuli, LVP or normal saline were given alone to the same normal and diabetic subjects.

MEASUREMENTS

GH responses in the presence and absence of LVP were measured and compared within each group and between normal and diabetic groups.

RESULTS

LVP or normal saline administration did not modify the basal concentrations of GH in any subject. The administration of GH-RH (at the minimal dose), arginine or clonidine alone induced significantly higher GH responses in the diabetic subjects than in the normal controls. At the maximal dose GH-RH induced similar GH responses in normal and diabetic subjects. The simultaneous administration of LVP did not change the GH response to any challenging stimulation in the normal controls; in contrast, GH-RH- (at both minimal and maximal dose), arginine- and clonidine-induced GH increments were significantly enhanced by LVP in the diabetic subjects.

CONCLUSIONS

These data show that in diabetic, but not in normal subjects LVP enhances the GH responsiveness to secretagogues, such as GH-RH, clonidine and arginine, which act through three different mechanisms. These findings suggest that in diabetes mellitus, vasopressin functions as a primer for various GH responses.

Effect of cigarette smoking on ACTH/cortisol secretion in alcoholic after short- and medium-term abstinence

BACKGROUND

To gain a better insight into the alterations of the hypothalamic-pituitary-adrenal axis in alcoholism, we evaluated the ACTH response to nicotine inhaled from cigarette smoking (two nonfilter cigarettes in succession within 10 min) in nine nonalcoholic men and nine age- and weight-matched alcoholic men who had been addicted to alcohol for at least 8 years. All subjects were regular cigarette smokers.

METHODS

Alcoholic men were tested after 2 weeks of abstinence, when the possible interferences because of alcohol assumption or the acute withdrawal period had completely ceased, and again after 12 weeks of abstinence.

RESULTS

At both 2 and 12 weeks of abstinence, basal plasma ACTH and cortisol levels were not significantly different in the alcoholic men from those observed in the control group. In the control group subjects, cigarette smoking induced a striking increase in the circulating concentrations of ACTH and cortisol, with peak responses 1.4 and 1.5 times higher than baseline at 20 and 30 min, respectively. In contrast, no significant ACTH/cortisol increase was observed in alcoholic subjects at any time after cigarette smoking in any test.

CONCLUSION

These data suggest that alterations of nicotinic cholinergic transmission occur in the control of ACTH secretion in the alcoholic men, providing further evidence of modification of the hypothalamic-pituitary-adrenal axis in alcoholism.