B. Maccagno

Effects of GHRP-2 and hexarelin, two synthetic GH-releasing peptides, on GH, prolactin, ACTH and cortisol levels in man. Comparison with the effects of GHRH, TRH and hCRH.

GHRP-2 (D-Ala-D-beta Nal-Trp-D-Phe-Lys-NH2) and Hexarelin (HEX) (His-D-2-methylTrp-Ala-Trp-DPhe-Lys-NH2) are synthetic, non-natural super-analogs of GHRP-6 endowed with potent stimulatory effect on GH secretion and slight stimulatory effect on PRL, ACTH and cortisol levels. Their GH-releasing activity ahs never been compared each other and their effects on PRL, ACTH and cortisol have never been compared with that of other stimuli. To clarify these points, in 6 normal young adults (22-27 yr) we studied the GH, PRL, ACTH and cortisol responses to 1 and 2 micrograms/kg i.v. GHRP-2 and HEX comparing them with that after 1 micrograms/kg i.v. GHRH and 400 micrograms i.v. TRH + 2 micrograms/kg i.v. hCRH. The Gh responses to 2 micrograms/kg i.v. GHRP-2 or HEX, compared with those to 1 microgram/kg GHRH, were also studied in 6 normal elderly subjects (66-73 yr). In young adults 1 microgram/kg i.v. GHRP-2 and HEX induced a similar, strong GH response, which was higher (p < 0.05) than that to GHRH. The administration of 2.0 micrograms/kg i.v. GHRP-2 and HEX again elicited a similar GH response, which was higher (p < 0.05) than that after the 1.0 microgram/kg dose. In elderly subjects, the GH those in young subjects. In young adults, the PRL responses to all doses of GHRP-2 or HEX were similar and lower (p < 0.01) responses were similar to those to hCRH. In conclusion, our results demonstrate that, in man, GHRP-2 and HEX have similar, 2 and HEX is not fully specific, as they induce similar increases in PRL, ACTH and cortisol levels. The PRL-releasing activity of GHRPs is lower than that of TRH while their ACTH/cortisol-releasing activity is similar to that of hCRH.

Effects of Dexamethasone and Alprazolam, a Benzodiazepine, on the Stimulatory Effect of Hexarelin, a Synthetic GHRP, on ACTH, Cortisol and GH Secretion in Humans

Hexarelin (HEX) is a synthetic GHRP which acts on specific receptors at both the pituitary and the hypothalamic level to stimulate GH release both in animals and in humans. Like other GHRPs, HEX possesses also acute ACTH and cortisol-releasing activity similar to that of hCRH. The mechanisms underlying the stimulatory effect of GHRPs on hypothalamo-pituitary-adrenal (HPA) axis are still unclear, although a CNS-mediated action has been demonstrated. In 6 normal healthy young women (26–34 years) we studied the effects on ACTH and cortisol secretion of HEX (2.0 µg/kg i.v. at 0 min) alone and preceded by dexamethasone (DEXA, 1 mg p.o. at 23.00 h on the previous night) or alprazolam (ALP, 0.02 mg/kg p.o. at –90 min), a benzodiazepine which binds to GABA receptors and possesses CRH-mediated inhibitory activity on HPA axis. ACTH and cortisol secretion after saline administration as well as the GH response to HEX alone and preceded by DEXA or ALP were also studied. HEX administration elicited an increase in ACTH (peak vs. baseline, mean ± SEM: 28.0 ± 6.7 vs. 11.7 ± 2.2 pg/ml, p < 0.05) and cortisol secretion (162.6 ± 15.0 vs. 137.7 ± 12.6 µg/l, p < 0.05). DEXA pretreatment strongly inhibited basal ACTH (3.2 ± 0.7 pg/ml, p < 0.01) and cortisol levels (11.3 ± 2.5 µg/l, p < 0.001) and abolished the ACTH and cortisol responses to HEX (3.6 ± 0.9 pg/ml, p < 0.01 and 10.7 ± 2.0 µg/l, p < 0.001), respectively. On the other hand, ALP pretreatment did not significantly modify basal ACTH (7.9 ± 2.0 pg/ml) and cortisol levels (127.6 ± 14.5 µg/l) but abolished the HEX-induced ACTH and cortisol secretions (8.6 ± 2.4 pg/ml, p < 0.05 and 111.0 ± 6.0 µg/l, p < 0.05), respectively. ACTH and cortisol levels after HEX when preceded by ALP overlapped with those recorded during saline. HEX induced a clear GH response (peak at 15 min vs. baseline: 65.5 ± 20.5 vs. 2.2 ± 0.7 µg/l, p < 0.03) which was blunted by ALP (peak at 15 min: 21.5 ± 5.5 µg/l, p < 0.05) while it was not modified by DEXA pretreatment (78.7 ± 7.6 µg/l). In conclusion, our present data demonstrate that the ACTH- and cortisol-releasing effect of HEX is abolished by either dexamethasone or alprazolam, a benzodiazepine, which is even able to blunt the GH-releasing activity of the hexapeptide. These findings suggest that, in physiological conditions, the stimulatory effect of GHRPs on HPA axis is sensitive to the negative glucocorticoid feedback and could be mediated by GABAergic mechanisms; the latter seem also involved in the GH-releasing activity of GHRPs.

Hexarelin, a Synthetic Growth-Hormone Releasing Peptide, Shows No Interaction with Corticotropin-Releasing Hormone and Vasopressin on Adrenocorticotropin and Cortisol Secretion in Humans

Hexarelin (HEX) is a synthetic growth-hormone-releasing peptide (GHRP) which acts via specific receptors at both the pituitary and the hypothalamic level to stimulate GH release both in animals and in man. Like other GHRPs, HEX possesses also significant prolactin- and adrenocorticotropin (ACTH) cortisol-releasing activity, but the mechanisms underlying these effects are even less clear. To clarify the mechanisms by which HEX stimulates the pituitary-adrenal axis in man, in 7 healthy young volunteers we studied the effects of HEX (2.0 microg/kg i.v.) and/or human corticotropin-releasing hormone (hCRH; 2.0 microg/kg i.v.) and/or arginine vasopressin (AVP; 0.17 U/kg i.m.) on ACTH and cortisol secretion. The GH responses to HEX alone and combined with hCRH and/or AVP were also studied. HEX increased ACTH and cortisol secretion (peak, mean +/- SEM: 26.3 +/- 5.1 vs. 15.8 +/- 3.1 pg/ml and 145.0 +/- 11.4 vs. 131.7 +/- 11.7 microg/l, p < 0.01, respectively) to levels overlapping with those induced by AVP (27.9 +/- 6.1 vs. 13.1 +/- 3.5 pg/ml and 167.6 +/- 16.2 vs. 113.3 +/- 9.4 microg/l, p < 0.01, respectively) and similar to those elicited by hCRH (28.1 +/- 4.6 vs. 17.4 +/- 3.1 pg/ml and 182.7 +/- 22.8 vs. 114.8 +/- 12.3 microg/l, p < 0.02, respectively). The ACTH but not the cortisol response to hCRH was higher (p < 0.02) than those to HEX when evaluated as area under the curve. The co-administration of HEX and AVP had no significant interaction on ACTH and cortisol peak levels (40.7 micro 5.3 pg/ml and 168.8 +/- 13.5 microg/l, respectively). On the other hand, the co-administration of HEX and hCRH had a less than additive effect on ACTH and cortisol secretion (53.3 +/- 11.2 pg/ml and 204.0 +/- 13.7 microg/l, respectively). CRH and AVP had a true synergistic effect on ACTH (104.9 +/- 14.2 pg/ml, p < 0.01) and an additive effect on cortisol secretion (281.3 +/- 10.8 microg/l, p < 0.02). HEX did not modify the effect of CRH + AVP on both ACTH (135.5 +/- 22.0 pg/ml) and cortisol secretion (261.1 +/- 13.2 microg/l). The GH response to HEX (55.7 +/- 19.8 vs. 2.7 +/- 1.9 microg/l, p < 0.005) was unaffected by the administration of CRH alone (53.5 +/- 21.0 microg/l) and/or AVP co-administration (60.2 +/- 21.2 and 45.9 +/- 10.6 microg/l, respectively). In conclusion, the results of this study demonstrate that GHRPs, beside their well-known GH-releasing activity, possess a remarkable ACTH-releasing activity, overlapping with that of AVP and similar to that of hCRH, two neurohormones which are known to play the major role in the control of the pituitary-adrenal axis. It is noteworthy that HEX shows no synergistic effect with either AVP or hCRH which, on the other hand, truly synergize. This evidence suggests the hypothesis that the ACTH-releasing activity of GHRPs could be, at least partially, independent of both CRH- and AVP-mediated actions in humans.

ALPRAZOLAM, A BENZODIAZEPINE, DOES NOT MODIFY THE ACTH AND CORTISOL RESPONSE TO HCRH AND AVP, BUT BLUNTS THE CORTISOL RESPONSE TO ACTH IN HUMANS

Alprazolam (AL), a benzodiazepine which activates gamma-amino butyrric acid (GA-BA)-ergic receptors, exerts a clear inhibitory effect on the activity of the hypothalamo-pitu-itary-adrenal (HPA) axis and is able to markedly reduce the ACTH response to metyrapone-induced inhibition of glucocorticoid feedback. It has been suggested that its inhibitory action could be regulated by CRH or AVP mediated mechanisms. However, the effect of benzodi-azepines on the HPA response to CRH or AVP is contradictory. It has been shown that benzodi-azepines have specific receptors on the adrenal gland but it is unclear if they mediate biological effects in humans. In order to further clarify the mechanisms underlying the inhibitory effect of benzodiazepine on HPA axis in humans, we studied the effect of AL (0.02 mg/kg po at −90 min) or placebo in 7 healthy young volunteers (7 female, age: 26–34 yr; wt: 50–58 kg, BMI 20–22 kg/m2) on: 1) the ACTH and cortisol responses to hCRH (2.0 μg/kg iv at 0 min) or AVP (0.17 U/kg im at 0 min); 2) the cortisol, aldosterone and DHEA responses to ACTH 1–24 (0.06 and 250 μg iv at 0 and 60 min, respectively). After placebo, the ACTH and cortisol responses to hCRH (peaks, mean±SE: 29.8± 4.4 pg/ml and 199.3±19.6 μg/l) were similar to those recorded after AVP (31.7±6.5 pg/ml and 164.8±18.0 μg/l); the cortisol response to 0.06 μg ACTH (190.4±11.8 μg/l) was similar to that recorded after hCRH and AVP but lower (p<0.01) than that after 250 μg ACTH (260.6±17.4 μg/l). AL did not modify the ACTH response to both hCRH (42.5±7.1 pg/ml) and AVP (33.3±2.7 pg/ml), which even showed a trend toward increase. AL also failed to significantly modify the cortisol response to both hCRH (156.3±12.7 μg/l) and AVP (119.4±14.5 μg/l), which, on the other hand, showed a trend toward decrease. The cortisol peaks after 0.06 μg ACTH were significantly reduced (p<0.02) by AL pre-treatment (115.0±7.7 μg/l) which, in turn, did not modify the cortisol response to the subsequent ACTH bolus (214.7±16.6 μg/l). The DHEA and aldos-terone responses to all the ACTH doses were not significantly modified by AL. In conclusion, these data show that the HPA response to AVP as well as to hCRH is refractory to the inhibitory effect of AL which, in turn, blunts the cortisol response to low ACTH dose. These findings suggest that both CRH- and AVP-mediated mechanisms could underlie the CNS-mediated inhibitory effect of AL on HPA axis; in the meantime, these results suggest that benzodiazepines could also act on adrenal gland by blunting the sensitivity of the fasciculata zone to ACTH.

Effects of the combined administration of hexarelin, a synthetic peptidyl GH secretagogue, and hCRH on ACTH, cortisol and GH secretion in patients with Cushing’s disease

Hexarelin (HEX) is a peptidyl GH sec-retagogue (GHS) which markedly stimulates GH release but, like other GHS, possesses also CNS-mediated ACTH- and cortisol-releasing activity. Interestingly, the stimulatory effect of HEX on ACTH and cortisol release is exaggerated and higher than that of hCRH in patients with Cushing’s disease (CD). To further clarify the mechanisms by which HEX stimulates the activity of hypothalamo-pituitary-adrenal (HPA) axis in man, in 6 patients with CD (6 women, 38–68 yr old) and in 7 control subjects (CS, 7 women, 22–29 yr old) we studied the effects of HEX (2.0 ώg/kg iv) and/or hCRH (2.0 ώg/kg iv) on ACTH and cortisol (F) secretion. The GH responses to HEX alone and combined with hCRH were also studied in all subjects. Basal ACTH and F levels in CD were higher than in CS (66.3±5.1 vs 16.5±0.6 pg/ml and 217.8±18.5 vs 134.4±4.6 ώg/l, respectively; p<0.02). In CS, the ACTH and F responses to HEX, evaluated as △AUC (mean±SE: 128.7±39.2 pg*min/ml and 328.5±93.2 ώg*min/l, respectively) were lower, though not significantly, than those after hCRH (375.8±128.4 pg*min/ml and 1714.2±598.0 ώg*min/l, respectively), though the peak ACTH and F responses to both stimuli were similar. The co-administration of HEX and hCRH had an additive effect on both ACTH (1189.6±237.2 pg*min/ml) and F secretion (3452.9±648.6 ώg*min/l). In fact, the ACTH and F responses to HEX+hCRH were significantly higher (p<0.01) than those elicited by single stimuli. In CD, HEX induced ACTH and F responses (3603.8±970.7 pg*min/ml and 10955.9±6184.6 ώg*min/l, respectively) clearly higher (p<0.002) than those in CS. The HEX-induced ACTH and F responses in CD were higher, though not significantly, than those recorded after hCRH (1432.7 ±793.5 pg*min/ml and 4832.7±2146.5 ώg*min/l, respectively). On the other hand, the hCRH-induced ACTH and F responses in CD were similar to those in CS. In CD, the coadministration of HEX and hCRH had an additive effect on ACTH (8035.7±1191.1 pg*min/ml) but not on F (10985.4 ±3900.8 ώg*min/l) secretion. In fact, the ACTH, but not the F response to HEX+hCRH was significantly higher (p<0.02) than that elicited by single stimuli. In conclusion, the present study demonstrates that in patients with Cushing’s disease as well as in subjects control Hexarelin and hCRH have an additive effect on ACTH secretion. Considering that, at least in humans, differently from hCRH, GHS have no interaction with AVP, our present findings further agree with the hypothesis that the ACTH-releasing activity of GHS is, at least partially, independent of CRH-mediated mechanisms.

Effects of beta-adrenergic agonists and antagonists on the growth hormone response to growth hormone-releasing hormone in anorexia nervosa

BACKGROUND In anorexia nervosa (AN), growth hormone (GH) hypersecretion and low insulin-like growth factor I (IGF-I) levels are present. It is unclear whether this is due to a peripheral GH resistance and a reduced IGF-I negative feedback on GH secretion or to a primary hypothalamic dysfunction. In AN, in contrast to normal subjects, cholinergic antagonists and agonists, whose action is somatostatin (SS)-mediated, have reduced and absent effects on the GH response to growth hormone-releasing hormone (GHRH). Since arginine, another substance acting via inhibition of SS, maintains its potentiating effect on GH secretion in AN, it has been hypothesized that somewhat specific alteration of the SS-mediated cholinergic influence may be present in this condition. To further clarify the neural control of AH secretion in AN, we evaluated the effects of beta-adrenergic agonists and antagonists, which are known to inhibit and increase, respectively, the GHRH-induced GH secretion in normal subjects. METHODS We studied the effect of atenolol (ATE), a beta 1-adrenergic antagonist, and salbutamol (SALB), a beta 2-adrenergic agonist, on the GHRH-induced GH release in 10 patients with AN and in 10 normal age-matched women (NW). RESULTS Basal GH levels were higher, whereas IGF-I were lower in AN than in NW. The GHRH-induced GH rise in AN was higher than that in NW. ATE significantly enhanced the GH response to GHRH in NW, but not in AN. The GH responses to GHRH after ATE pretreatment were similar in NW and in AN. The GH response to GHRH was inhibited by SALB in both NW and AN. The GH responses to GHRH after SALB pretreatment were similar in NW and AN. CONCLUSIONS These data reveal an exaggerated somatotrope responsiveness to GHRH in AN that is not further increased by beta-adrenergic blockade, while is abolished by beta-adrenergic activation. This suggests that an impairment of beta-adrenergic influence on GH secretion is present in anorexia nervosa.

Glucagon Is an ACTH Secretagogue as Effective as hCRH after Intramuscolar Administration while It Is Ineffective When Given Intravenously in Normal Subjects

It is widely accepted that glucagon stimulates GH, ACTH and cortisol release in humans, though the mechanisms underlying these effects are unclear. Aim of the present study was to evaluate the stimulatory effect of intramuscolar (im) and intravenous (iv) glucagon (GLU) administration on ACTH, cortisol (F) and GH release in normal adult subjects and to compare its effect on hypothalamo-pituitary adrenal (HPA) axis with that of hCRH. To this goal, in 6 normal young women (26–32 yrs, 50–58 kg) we studied the ACTH and F responses to either im or iv GLU (1 mg, approximately 0.017 mg/kg in subjects of 54.1 ± 1.6 kg) administration as well as to iv hCRH (2.0 μg/kg) or placebo administration. The GH and glucose variations after GLU administration were also studied. Iv GLU did not modify the spontaneous decrease of ACTH and cortisol levels observed after placebo. Conversely, im GLU elicited clear-cut ACTH and F responses (peak vs baseline, mean ± SEM: 53.0 ± 15.2 vs 19.0 ± 1.5 pg/ml, p < 0.05 and 222.3 ± 23.8 vs 158.3 ± 7.0 μg/l, p < 0.05) which were higher than those recorded after hCRH (28.1 ± 4.6 vs 17.4 ± 3.1 pg/ml, p < 0.02 and 182.7 ± 22.8 vs 114.8 ± 12.3 μg/l p < 0.02), though this difference did not attain statistical significance. Also GH rise was recorded after im but not after iv GLU administration (11.6 ± 3.4 vs 3.3 ± 0.7 μg/l, p < 0.05). Thirty min after both iv and im GLU administration glucose levels showed a similar increase followed by similar decrease. The intramuscular administration of GLU induced negligible side-effects in some subject (mild and transient nausea) which, on the contrary, were clear in all subjects after its intravenous administration (nausea, vomiting, tachicardia). In conclusion, glucagon “per se” is not an ACTH, cortisol and GH secretagogue. After intramuscular administration glucagon is a stimulus of HPA axis at least as effective as hCRH. The mechanisms underlying the ACTH, cortisol and GH responses to im glucagon unlikely include glucose variations or stress.

Effects of histaminergic antagonists on the GH-releasing activity of GHRH or hexarelin, a synthetic hexapeptide, in man.

The role of histamine in the neural control of GH secretion in man is still unclear, although a stimulatory influence has been hypothesized in man. To clarify this point, in 7 normal young women (23–28 yr) in their early follicular phase, we studied the effect of the histaminergic blockade by diphenhydramine (DPH, 80 mg os at −60 min) on the GH response to GHRH (2 μg/Hg iv) or Hexarelin (HEX, 2 μg/kg iv), a synthetic hexapeptide with strong GH-releasing effect. In 6 of the 7 women the effect of terfenadine (TRF, 120 mg os at −60 min), another H1-receptor antagonist, on the GH response to GHRH or HEX was also studied. As HEX has also PRL- and ACTH-releasing activity and histamine has been shown to have a stimulatory role in the neural control of these hormones, the effects of DPH or TRF on the HEX-induced PRL, ACTH and Cortisol release were also studied. GHRH induced a GH rise (peak, mean±SEM: 35.4±6.5 vs 2.5±1.1 μ/l, p<0.02, n=7; 34.7±7.9 vs 3.9±5 μg/l, p<0.02, n=6) lower (p<0.05) than that elicited by HEX (49.1±8.5 vs 3.9±1.0 μg/l, p<0.01, n=7; 48.7±8.9 vs 3.2±0.8 μg/l, p<0.01, n=6). DPH inhibited the GH response to both GHRH (AUG: 453.9±104.7 vs 1223.7±202.6 μg*min/l, p<0.05) and HEX (922.0±215.4 vs 1636.4±267.5 μg*min/l, p<0.05), although the HEX-induced GH rise persisted higher than that induced by GHRH (p<0.05). TRF did not modify the GHRH-induced GH rise (950.5±369.2 mg*min/l vs 1115.3±255.6 μg*min/l) as well as the somatotrope responsiveness to HEX (1163.2±188.7 vs 1427.3±323.3 mg*min/l). HEX also significantly increased PRL (13.9±3.1 vs 6.5±0.8 μg/l, p<0.03), ACTH (31.1 ±6.6 vs 16.6±2.9 µg/ml, p<0.02) and Cortisol (96.6±6.3 vs 822<62 μg/L, p<0.05)’levels. PRL, ACTH and Cortisol responses to HEX were unaffected by DPH (536.5±85.6 vs 599.5±129.2 μg*min/l, 1068.5±306.0 vs 1282.8±222.0 µg*min/ml and 4277.4±588.4 vs 4738.3±355.3 μg*min/l, respectively) as well as by TRF (621.3±110.4 vs 530.3±131.4 μg*min/L, 972.4±189.6 vs 1060.2±224.7 µg*min/ml and 6203.8±1329.5 vs 5141.2±295.5 μg*min/l, respectively). In conclusion, our findings are against the hypothesis of a major role of H1-receptor-mediated histaminergic influence on GH secretion in humans. In fact, the H1-histaminergic blockade by TRF does not affect the GH response to GHRH or HEX; the inhibitory effect of DPH may probably be due to its intrinsic anticholinergic activity. Our data also confirm that Hexarelin releases more GH than GHRH and demonstrate that its effect on GH, PRL and ACTH release is not mediated by H1-receptors.

Recombinant human IGF-I does not modify the ACTH and cortisol responses to hCRH and hexarelin, a peptidyl GH secretagogue, in humans

An inhibitory influence of insulin-like growth factor-I (IGF-I) on hypothalamus-pituitary-adrenal (HPA) axis has been hypothesized. In fact, it has been reported that the rhGH (recombinant human GH)-induced IGF-I increase inhibits both cortisol and GH response to MK-0677, a non-peptidyl GH secretagogue in animals. The aim of this study was to further clarify the inhibitory role, if any, of IGF-I on corticotroph function. We studied the effect of rhIGF-I (recombinant human IGF-I; 20 μg/kg sc at −180 min) or placebo on the ACTH and cortisol responses to hCRH (human CRH; 2.0 μg/kg iv at 0 min) or hexarelin (HEX; 2.0 μg/kg iv at 0 min), a peptidyl GHS, in normal young women. The effect of rhIGF-I on the GH response to HEX was also studied. The subjects were six normal young women [age: 26–35 yr; body mass index (BMI): 19–23 kg/m2] in their early follicular phase. The results showed that after sc rhIGF-I administration, circulating IGF-I levels increased approximately 77%, peaking at −60 min and persisting similar up to +120 min. The mean ACTH, cortisol and GH concentrations did not change from −180 to 0 min when evaluated after both placebo or rhIGF-I. CRH and HEX induced similar ACTH (peak vs baseline, mean±SE: 47.5±10.9 vs 21.3±3.0 pg/ml and 30.3±6.9 vs 19.2±3.8 pg/ml, respectively; p<0.04) and cortisol responses (177.5±5.4 vs 109.3±10.3 μg/l and 149.4±12.3 vs 119.8±16.4 μg/l, respectively, p<0.04). RhIGF-I pre-treatment did not modify the ACTH and cortisol responses to hCRH (46.0±13.8 pg/ml and 181.1±16.9 μg/l, respectively) as well as those to HEX (28.8±5.0 pg/ml and 144.1±16.2 μg/l, respectively). On the other hand, the GH response to HEX was clearly reduced by rhIGF-I (23.9±4.7 vs 64.7±14.8 μg/l, p<0.05). Our findings show that rhIGF-I-induced increase of circulating IGF-I levels exerts negative feedback action on somatotroph secretion, while it does not modify the corticotroph and the adrenal responsiveness to CRH or hexarelin.

Effects of alprazolam, a benzodiazepine, on the ACTH-, GH- and PRL-releasing activity of hexarelin, a synthetic peptidyl GH secretagogue (GHS), in patients with simple obesity and in patients with Cushing's disease.

GH secretagogues (GHS) possess potent GH-releasing activity but also stimulate PRL, ACTH and cortisol (F) secretion. To further clarify the endocrine activities of GHS, in 9 obese patients, 9 patients with Cushings Disease and 14 controls we studied the ACTH, F, GH and PRL responses to hexarelin (HEX, 2.0 µg/kg i.v.), a peptidyl GHS, alone and preceeded by alprazolam (ALP, 0.02 mg/kg p.o.), a benzodiazepine. The HEX-induced ACTH response in controls was similar to that in obese patients (Δpeak: 9.9 ± 1.9 and 24.7 ± 7.6 ng/L, respectively) and both were lower (p < 0.002) than that in Cushings patients (peak: 210.7 ± 58.4 ng/L). The GH response to HEX in controls (peak: 58.1 ± 10.3 □g/L) was higher (p < 0.001) than those in obese and Cushings patients (18.2 ± 3.8 and 12.6 ± 5.4 □/L, respectively) which, in turn, were similar. The PRL responses to HEX in controls, obese and Cushings patients (peak: 11.9 ± 1.6, 18.0 ± 4.5 and 12.4 ± 1.4 □/L, respectively) were similar. In controls the HEX-induced ACTH response was abolished by ALP (peak: 8.6 ± 2.4 vs 28.0 ± 6.7 ng/L, p < 0.03) which, on the other hand, only blunted that in obese (peak: 12.7 ± 2.1 vs 42.4 ± 8.4 ng/L, p < 0.02) and did not modify that in Cushings patients (205.6 ± 55.4 vs 175.9 ± 47.6 ng/L). ALP blunted the GH response to HEX in controls (peak: 31.0 ± 7.1 □/L, p < 0.03) while did not modify those in obese and in Cushings patients (14.5 ± 5.3 and 13.3 ± 11.1 □/L, respectively). ALP did not modify the HEX-induced PRL response in controls, obese and Cushings patients (peak: 13.8 ± 0.9, 16.3 ± 2.4 and 19.2 ± 1.1 □/L, respectively). In conclusion, alprazolam inhibits the ACTH response to hexarelin in normal and obese subjects while fails to modify the exaggerated ACTH response in Cushings Disease suggesting that GHS activate the HPA axis via the hypothalamus in normal and obese subjects but not in patients with Cushings disease. Alprazolam is also able to blunt the GH-releasing activity of hexarelin in normal subjects but not the low GH response to the hexapeptide in obese and Cushings patients. The PRL-releasing activity of hexarelin in controls, obese and hypercortisolemic patients is similar and is not modified by alprazolam pretreatment.