GH-releasing peptide (GHRP-6)-induced ACTH release in patients with addison's disease: effect of glucocorticoid withdrawal

GH releasing peptide (GHRP-6) is a synthetic hexapeptide with potent GH releasing activity both in man and in animals. This peptide is also able to stimulate ACTH and cortisol (F) release. It has been suggested that the ACTH responsiveness to GHRP-6 is modulated by circulating glucocorticoid levels. To further clarify this hypothesis, we studied the effect of GHRP-6 (1 ug/kg, iv) on ACTH and F release in patients with Addison's disease (no.=6) during replacement therapy and after 72 h of glucocorticoid withdrawal. Seven controls were also submitted to a single GHRP-6 test. In control subjects, ACTH values (pmol/l; mean +/- SE) increased from 2.9 +/- 0.8 to 4.7 +/- 1.4 (peak). AUC (pmol.min/l) values were 170.3 +/- 48.8. F (nmol/l) values increased from 257.0 +/- 42.9 to 367.0 +/- 50.8. In patients with Addison's disease there was an increase in ACTH levels from 38.1 +/- 17.1 to 174.9 +/- 79.4 after GHRP-6 administration. AUC values were 5490.4 +/- 2269.1. After 72 h withdrawal of glucocorticoid, there was an increase in basal ACTH values (191.2 +/- 97.3), and a trend toward an increase in ACTH levels after GHRP-6 (p=0.053). Patients with Addison's disease on therapy showed a significantly higher ACTH response to GHRP-6 when compared to controls. Our results show that in patients with Addison's disease on replacement there is an increased ACTH release after GHRP-6 administration, compared to controls. After 72 h glucocorticoid withdrawal, this enhanced responsiveness is not maintained. Our data suggest that circulating glucocorticoids modulate GHRP-6-induced ACTH release and that multiple mechanisms may be involved in this process.     

Usefulness of the desmopressin test in the postoperative evaluation of patients with Cushing's disease

OBJECTIVE: To evaluate the plasma ACTH and serum cortisol responses to desmopressin in patients with Cushing's disease either before or after pituitary adenomectomy during long-term follow-up, and to compare the results with those obtained after corticotrophin-releasing hormone (CRH) testing. DESIGN: Plasma ACTH and serum cortisol concentrations were evaluated after the administration of desmopressin (10 microg i.v.) or CRH (1 microg/kg i. v.) in 34 patients with Cushing's disease. Twenty-four patients with active Cushing's disease were evaluated both before and after transsphenoidal pituitary surgery (TSS); these patients were followed up for 1-36 months. Ten patients were studied only after a long-term period (1-19 years, median 4 years) after TSS (six patients), TSS plus external pituitary irradiation (three patients) and TSS plus radiosurgery (one patient). RESULTS: In 24 patients with active Cushing's disease a significant ACTH/cortisol response (P<0.001) was induced by either desmopressin (ACTH from a baseline of 15.3+/-2.7 pmol/l to a peak of 40.9+/-7.3 pmol/l; cortisol from 673+/-59 nmol/l to 1171+/-90 nmol/l) or CRH (ACTH from a basal of 14. 2+/-2.5 pmol/l to a peak of 47.2+/-7.7 pmol/l; cortisol from 672+/-50 nmol/l to 1192+/- 80 nmol/l). In all patients a positive cortisol response to desmopressin was found. After pituitary adenomectomy the 14 'cured' patients were followed up for 1-36 months; desmopressin administration never induced ACTH or cortisol responsiveness in any patient. In contrast, a progressive recovery of ACTH and cortisol responses after CRH was observed at different intervals of time in all patients but one. Five patients, in whom the cortisol concentration only normalized after surgery, showed a persistent responsiveness to desmopressin, and two of them relapsed 12 and 24 months later. In five patients who were not cured, the hormonal responsiveness to either CRH or desmopressin was similar before and after operation. Of 10 patients studied only after long-term follow-up, six were cured and a normal response to CRH was present, whereas no changes in ACTH/cortisol concentrations were induced by desmopressin. The other four unsuccessfully operated patients underwent pituitary irradiation and showed different and equivocal hormonal responses to desmopressin and to CRH. CONCLUSIONS: During the postoperative follow-up of patients with Cushing's disease, the maintenance or the disappearance of the hormonal response may be related to the persistence or the complete removal of adenomatous corticotrophs, respectively. It is suggested that desmopressin test should be performed in the preoperative evaluation and follow-up of patients with ACTH-dependent Cushing's syndrome.     

Failure of somatostatin and octreotide to acutely affect the hypothalamic-pituitary-adrenal function in patients with corticotropin hypersecretion

Although somatostatin inhibits a variety of pituitary and non-pituitary hormones, not univocal data on its effects on ACTH release have been reported so far. In this study we investigated the effects of somatostatin or octreotide on ACTH levels of patients with corticotropin hypersecretion: 7 patients with Addison's disease, 2 patients previously adrenalectomized for Cushing's disease, 4 patients with Cushing's disease and 3 patients with ectopic ACTH syndrome. Plasma ACTH and cortisol levels were determined after somatostatin (500 micrograms over 60 min) infusion or octreotide (100 micrograms sc) injection. In 5 other patients with Cushing's disease ACTH and cortisol responses to CRH (1 microgram/kg iv) were evaluated in basal conditions and after octreotide acute administration. In no patients with Addison's disease any inhibitory influence of somatostatin (delta % = -21, -25) or octreotide (delta % = -38 +/- 12 vs -39 +/- 12 after saline) on plasma ACTH was found. Somatostatin did not significantly inhibit plasma ACTH in the two patients previously adrenalectomized for Cushing's disease and in 3 patients with Cushing's syndrome; in other 4 patients with Cushing's syndrome octreotide did not affect plasma ACTH levels. In 5 patients with Cushing's disease the plasma ACTH and cortisol responses to CRH were similar both before (ACTH from 9.9 +/- 1.7 pmol/L to 19.4 +/- 6.1 pmol/L; cortisol from 496 +/- 43.9 nmol/L to 923 +/- 355 nmol/L) and after octreotide injection (ACTH from 8.8 +/- 2.4 pmol/L to 19.1 +/- 8.2 pmol/L; cortisol from 510 +/- 54.6 nmol/L to 735 +/- 220 nmol/L). In conclusion, the acute administration of somatostatin or octreotide is not able to modify ACTH levels in patients with corticotropin hypersecretion either due to hypocortisolemic state or consequent to ACTH-secreting pituitary or ectopic tumors; moreover, octreotide does not affect the pituitary-adrenal responsiveness to CRH in patients with Cushing's disease.     

Pituitary-adrenal responses to CRH and insulin hypoglycemia in patients with idiopathic GH deficiency

It is well known that the activation of the hypothalamus-pituitary-adrenal axis (HPA) by insulin-induced hypoglycemia (IIH) is more potent and multifactorial than that caused by CRH administration. In this study we compared the clinical value of both tests in assessing the integrity of the HPA system. Plasma ACTH and cortisol responses to oCRH (1 microgram/kg iv) and IIH (insulin 0.1 U/kg iv, glycemia less than 40 mg/dl) were compared in 15 patients with idiopathic GH deficiency. The CRH-induced mean ACTH response was lower, but not significantly, in patients than in controls (peak: 8.8 +/- 1.7 vs 13.4 +/- 2.2 pmol/l), while the mean cortisol response was significantly lower than in normals (peak: 585.7 +/- 49.5 vs 764.5 +/- 52.2 nmol/l, p less than 0.005). Plasma ACTH and cortisol responses to IIH were significantly lower than in normal subjects (peak: 22.3 +/- 5.3 vs 35.8 +/- 5.2 pmol/l, p less than 0.05 and peak: 566.5 +/- 55 vs 803 +/- 38.5 nmol/l, p less than 0.02, respectively). Both in controls and in patients the CRH-induced mean ACTH response was significantly lower (p less than 0.02) than that after insulin, while cortisol peaks were not different. In conclusion, in patients with GH deficiency the impairment of ACTH secretion is not evident in basal condition, but it is disclosed after appropriate dynamic tests. It is confirmed that insulin hypoglycemia is a more potent stimulus than CRH for ACTH release.     

Hexarelin as a test of pituitary reserve in patients with pituitary disease

BACKGROUND: The insulin tolerance test (ITT) is the reference standard for the diagnosis of cortisol and growth hormone (GH) deficiency, but problems have occurred in small children in inexperienced hands and it is contraindicated in patients with cardiac disease and epilepsy. Hexarelin is a growth hormone-releasing peptide with GH-, ACTH/cortisol- and prolactin-releasing effects which involve both hypothalamic and direct pituitary mechanisms. We therefore investigated whether it could be used to test GH and ACTH/cortisol reserve in patients with pituitary disease. METHODS AND SUBJECTS: The changes in GH and cortisol in response to insulin-induced hypoglycaemia (intravenous human Actrapid 0.15 IU/kg) and hexarelin (2 microg/kg) in 19 patients with possible pituitary disease (5 males, mean age 39 years, range 21-70) were compared. The patients' responses during the hexarelin test were also compared to normal ranges of GH and cortisol responses established in healthy volunteers following hexarelin administration. RESULTS AND DISCUSSION: GH peak levels were significantly higher after hexarelin than after hypoglycaemia (mean +/- SEM; 67.1 +/- 16 vs. 26.9 +/- 6.8 mU/l respectively; P < 0. 001), while cortisol levels were significantly lower (420 +/- 34 vs. 605 +/- 50 nmol/l; P < 0.001). The peak responses of both hormones correlated significantly between the hexarelin and insulin-induced hypoglycaemia tests (r = 0.80, P < 0.001 for cortisol). Peak GH levels after hexarelin and ITT showed a significant positive correlation with IGF-I levels (r = 0.84 and r = 0.77, P < 0.001 for both). All patients with a subnormal GH response to hexarelin (<41.4 mU/l) had a peak GH response to ITT of <9 mU/l, and only one patient had a normal (although borderline) response to hexarelin with a subnormal GH response to the ITT. Although 17 of the 19 patients had corresponding cortisol responses to hexarelin and the ITT test (either failing or passing both), two patients had normal cortisol responses to hexarelin but subnormal responses to the ITT. A peak serum cortisol level following hypoglycaemia of >580 nmol/l is indicative of normal cortisol reserve, as established in patients undergoing surgery; only five of the normal volunteers and one of the thirteen patients with a normal ACTH/cortisol reserve on ITT had a peak cortisol >580 nmol/l in response to hexarelin. CONCLUSION: Adult patients who have a subnormal peak GH response to hexarelin are likely to be GH deficient on an insulin tolerance test. However, our data suggest that the hexarelin test is not a useful test of ACTH/cortisol reserve. The hexarelin test could be a useful first/screening test to diagnose adult GH deficiency, particularly in patients in whom an insulin tolerance test is contraindicated or who are already ACTH deficient and in whom the GH reserve alone is of interest.     

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.     

Interaction between glucagon and hexarelin, a peptidyl GH secretagogue, on somatotroph and corticotroph secretion in humans

OBJECTIVE: Glucagon administration stimulates both somatotroph and corticotroph secretion in humans, although this happens only if glucagon is administered by the intramuscular route and not by the intravenous route. On the other hand, GH secretagogues (GHS) strongly stimulate GH and also possess ACTH-releasing activity. DESIGN AND METHODS: To clarify the mechanisms underlying the stimulatory effects of both glucagon and GHS on somatotroph and corticotroph secretion, we studied the GH, ACTH and cortisol responses to glucagon (GLU, 0.017 mg/kg i.m.) and Hexarelin, a peptidyl GHS (HEX, 2.0 microg/kg i.v.) given alone or in combination in 6 normal young volunteers (females, aged 26-32 years, body mass index 19.7-22.5 kg/m). RESULTS: GLU administration elicited a clear increase in GH (peak vs baseline, mean+/-S.E.M.: 11.6+/-3.4 vs 3. 3+/-0.7 microg/l, P<0.02), ACTH (11.6+/-3.3 vs 4.1+/-0.3 pmol/l, P<0. 02) and cortisol (613.5+/-65.6 vs 436.9+/-19.3 nmol/l, P<0.05) levels. HEX induced a marked increase in GH levels (55.7+/-19.8 vs 3. 7+/-1.9 microg/l, P<0.005) and also significant ACTH (5.7+/-1.1 vs 3. 4+/-0.6 pmol/l, P<0.01) and cortisol (400.2+/-31.4 vs 363.4+/-32.2 nmol/l, P<0.05) responses. The GH area under the curve (AUC) after HEX was clearly higher than after GLU (1637.3+/-494.0 vs 479.1+/-115. 7 microg/l/120 min, P<0.04) while HEX and GLU coadministration had a true synergistic effect on GH release (3243.8+/-687.5 microg/l/120 min, P<0.02). The ACTH and cortisol AUCs after HEX were lower (P<0. 02) than those after GLU (208.3+/-41.3 vs 426.3+/-80.9 pmol/l/120 min and 18 874.5+/-1626.1 vs 28 338.5+/-2430.7 nmol/l/120 min respectively). The combined administration of HEX and GLU had an effect which was less than additive on both ACTH (564.02+/-76.5 pmol/l/120 min) and cortisol (35 424.6+/-5548.1 nmol/l/120 min) secretion. CONCLUSIONS: These results show that the intramuscular administration of glucagon releases less GH but more ACTH and cortisol than Hexarelin. The combined administration of glucagon and Hexarelin has a true synergistic effect on somatotroph secretion but a less than additive effect on corticotroph secretion; these findings suggest that these stimuli act via different mechanisms to stimulate somatotrophs while they could have a common action on the hypothalamo-pituitary-adrenal axis.     

Vasoactive intestinal polypeptide enhances ACTH levels in some patients with adrenocorticotropin-secreting pituitary adenomas

Vasoactive intestinal polypeptide (VIP) was administered (75 micrograms iv over 12 min) to 14 patients with Cushing's disease, 1 patient with Nelson's syndrome, and 8 normal subjects. VIP induced a significant rise of plasma ACTH levels in 6 patients with Cushing's disease, from a baseline of 13.2 pmol/l (9.9-18.5 pmol/l) to a peak of 24.5 pmol/l (7.7-18.9 pmol/l), median and range (P less than 0.05), and in the patient with Nelson's syndrome, from a baseline of 260.9 to 461.3 pmol/l. A significant elevation of cortisol levels was also observed, from a baseline of 567 nmol/l (185-842 nmol/l) to a peak of 727 nmol/l (364-1029 nmol/l); P less than 0.05. No modifications in plasma ACTH and cortisol levels were noticed in the other 8 patients with Cushing's disease, or in the normal subjects. In the responsive patients, the median plasma ACTH level reached after VIP was found to be less than that induced by CRH administration. In 2 of the responsive patients, VIP was injected again after successful microadenomectomy and did not then cause changes in ACTH and cortisol concentration. These data demonstrate that VIP specifically stimulates ACTH release in some patients with corticotropinomas but not in normal subjects; the disappearance of such abnormal ACTH responses after successful adenomectomy suggests the presence of specific VIP receptors only on the adenomatous corticotropes.     

The corticotropin-releasing hormone test in normal short children: comparison of plasma adrenocorticotropin and cortisol responses to human corticotropin-releasing hormone and insulin-induced hypoglycemia

The human corticotropin-releasing hormone (hCRH) tests were performed in twelve normal short children, and the responses of plasma ACTH and cortisol to iv administration of 1 micrograms/kg hCRH were compared with those to insulin-induced hypoglycemia. After administration of hCRH, the mean plasma ACTH level rose from a basal value of 3.3 +/- 0.4 pmol/l (mean +/- SEM) to a peak value of 9.2 +/- 0.8 pmol/l at 30 min, and the mean plasma cortisol level rose from a basal value of 231 +/- 25 nmol/l to a peak value of 546 +/- 30 nmol/l at 30 min. The ACTH response after insulin-induced hypoglycemia was greater than that after hCRH administration; the mean peak level (P less than 0.01), the percent maximum increment (P less than 0.01), and the area under the ACTH response curve (P less than 0.01) were all significantly greater after insulin-induced hypoglycemia than those after hCRH administration. Although the mean peak cortisol level after insulin-induced hypoglycemia was about 1.3-fold higher than that after hCRH administration (P less than 0.01), neither the percent maximum increment in plasma cortisol nor the area under the cortisol response curve after insulin-induced hypoglycemia was significantly different from that after hCRH administration. Consequently, the acute increases in plasma ACTH after the administration of 1 microgram/kg hCRH stimulated the adrenal gland to almost the same cortisol response as that obtained with a much greater increase in plasma ACTH after insulin-induced hypoglycemia. These results suggest that a plasma ACTH peak of 9-11 pmol/l produces near maximum acute stimulation of adrenal steroidogenesis.     

Effect of metyrapone pretreatment on adrenocorticotropin secretion induced by corticotropin-releasing hormone in normal subjects and patients with Cushing's disease

To examine the influence of endogenous cortisol on the ACTH response to CRH, we compared ACTH secretion during CRH tests before and after metyrapone administration in 9 normal subjects and 12 patients with Cushing's disease. The administration of 4.5 g metyrapone (750 mg, orally, every 4 h) resulted in a decrease in basal (pre-CRH) plasma cortisol levels and an increase in basal plasma ACTH levels in both normal subjects and Cushing's patients. The pretreatment with metyrapone significantly blunted the increase in plasma cortisol levels and markedly enhanced ACTH secretion after iv injection of 100 micrograms human CRH. The peak ACTH levels during CRH test before and after metyrapone administration were 8 +/- 1 and 58 +/- 8 pmol/L, respectively, in normal subjects (P less than 0.01) and 26 +/- 5 and 50 +/- 11 pmol/L, respectively, in Cushing's patients (P less than 0.05). Although the basal and peak ACTH levels as well as delta ACTH (peak ACTH - basal ACTH) during the CRH test before metyrapone administration were significantly higher in Cushing's disease patients than in normal subjects (P less than 0.01), no such difference was observed between the 2 groups after metyrapone administration. The results clearly indicate that the endogenous cortisol levels greatly influence the ACTH response to CRH, and that the CRH test as commonly performed does not allow a correct evaluation of potential responsiveness of normal pituitaries and Cushing's adenomas to CRH.     

Assessment of cortisol and ACTH responses to the desmopressin test in patients with Cushing's syndrome and simple obesity

OBJECTIVE: The desmopressin test has recently been introduced in clinical practice as an adjunctive tool in the differential diagnosis of ACTH-dependent Cushing's syndrome (CS). It has been reported that the majority of patients with pituitary-dependent CS (Cushing's disease, CD) respond to desmopressin, while no such response is usually observed in other forms of this syndrome. In the present study, the responsiveness of the HPA axis to desmopressin was studied in a group of obese subjects. In addition, the ability of desmopressin administration to differentiate between patients with obesity and the various forms of Cushing's syndrome was investigated. DESIGN AND SUBJECTS: Cortisol and ACTH responses to the administration of desmopressin (10 microg bolus i.v.) were examined in 20 consecutive patients with obesity (14 women and six men; BMI range: 34.5-66.7 kg/m2). Obese subjects had no clinical stigmata of CS. In all obese patients, either an overnight (dex 1 mg at 2300 h) (n = 8) or a formal low-dose (dex 0.5 mg 6-hourly for 2 days) (n = 12) dexamethasone suppression test was performed for the exclusion of Cushing's syndrome. Three of eight subjects showed failure of cortisol suppression (i.e. F > 28 nmol/l) to the overnight dexamethasone suppression test, but they had undetectable cortisol levels (< 28 nmol/l) on further testing with the formal 2-day test. All but two of the remaining subjects had undetectable cortisol levels (< 28 nmol/l) following the formal 2-day, low-dose, dexamethasone suppression test. For comparison, desmopressin responses were also tested in 33 patients with CS of varied aetiologies (25 patients with pituitary-dependent CS, three patients with occult ectopic ACTH secretion and five patients with primary adrenal CS). A positive response was considered to be an increment greater than 20% and 50% from baseline levels of cortisol and ACTH, respectively. RESULTS: Mean cortisol (F) and ACTH levels did not differ from the baseline at any time point following desmopressin administration in the obese group (basal F: 417 +/- 41, peak F: 389 +/- 32 nmol/l, P > 0.05; basal ACTH: 33.5 +/- 4.3, peak ACTH: 50.6 +/- 16.6 ng/l, P > 0.05), or in patients with occult ectopic or primary adrenal CS. In contrast, in the group of patients with CD, there was a significant rise in the mean ACTH and F levels from baseline (basal F: 725 +/- 50, peak F: 1010 +/- 64 nmol/l, P < 0.01; basal ACTH: 88.6 +/- 11.8, peak ACTH: 351 +/- 64 ng/l, P < 0.01). Cortisol responses greater than 20% from baseline were observed in 21/25 (84%) patients with CD, but in only 3/20 (15%) of the obese patients. With regard to ACTH, increments greater than 50% over baseline were observed in 23/25 (92%) of patients with CD, and in only 3/20 (15%) of the obese patients. As previously reported, none of the patients with occult ectopic ACTH secretion or primary adrenal CS had a positive response. CONCLUSIONS: The prevalence of subjects who met the criteria adopted to define positive cortisol and ACTH responses to the desmopressin test was significantly higher in the group of patients with Cushing's disease than in the group of patients with obesity. It is therefore suggested that this test may be occasionally useful in the differentiation between simple obesity and the pituitary-dependent form (but not other forms) of Cushing's syndrome.     

Effect of one month ketoconazole treatment on GH, cortisol and ACTH release after ghrelin, GHRP-6 and GHRH administration in patients with Cushing's disease

GH responses to ghrelin, GHRP-6, and GHRH in Cushing's disease (CD) are markedly blunted. There is no data about the effect of reduction of cortisol levels with steroidogenesis inhibitors, like ketoconazole, on GH secretion in CD. ACTH levels during ketoconazole treatment are controversial. The aims of this study were to compare the GH response to ghrelin, GHRP-6, and GHRH, and the ACTH and cortisol responses to ghrelin and GHRP-6 before and after one month of ketoconazole treatment in 6 untreated patients with CD. Before treatment peak GH (microg/L; mean +/- SEM) after ghrelin, GHRP-6, and GHRH administration was 10.0 +/- 4.5; 3.8 +/- 1.6, and 0.6 +/- 0.2, respectively. After one month of ketoconazole there was a significant decrease in urinary cortisol values (mean reduction: 75%), but GH responses did not change (7.0 +/- 2.0; 3.1 +/- 0.8; 0.9 +/- 0.2, respectively). After treatment, there was a significant reduction in cortisol (microg/dL) responses to ghrelin (before: 30.6 +/- 5.2; after: 24.2 +/- 5.1). No significant changes in ACTH (pg/mL) responses before (ghrelin: 210.9 +/- 69.9; GHRP-6: 199.8 +/- 88.8) and after treatment (ghrelin: 159.7 +/- 40.3; GHRP-6: 227 +/- 127.2) were observed. In conclusion, after short-term ketoconazole treatment there are no changes in GH or ACTH responses, despite a major decrease of cortisol levels. A longer period of treatment might be necessary for the recovery of pituitary function.     

Effects of chronic administration of PPAR-gamma ligand rosiglitazone in Cushing's disease

OBJECTIVE: Rosiglitazone, a thiazolidinedione compound with peroxisome proliferator-activated receptor-gamma (PPAR-gamma)-binding affinity, is able to suppress adrenocorticotropic hormone (ACTH) secretion in treated mice and in AtT20 pituitary tumor cells. These observations suggested that thiazolidinediones may be effective as therapy for Cushing's disease (CD). PATIENTS AND METHODS: Rosiglitazone (8 mg/day) was administered to 14 patients with active CD (13 women, one man, 18-68 years). Plasma ACTH, serum cortisol (F) and urinary free cortisol (UFC) levels were measured before and then monthly during rosiglitazone administration. RESULTS: In six patients a reduction of ACTH and F levels and a normalization of UFC were observed 30-60 days after the beginning of rosiglitazone administration: there was a significant difference between basal and post-treatment values for UFC (1238+/-211 vs 154+/-40 nmol/24 h, P<0.03), but not for ACTH (15.9+/-3.7 vs 7.9+/-0.9 pmol/l) and F levels (531+/-73 vs 344+/-58 nmol/l). Two of six cases, followed up for 7 months, showed a mild clinical improvement. Eight patients were nonresponders after 30-60 days of rosiglitazone treatment: their ACTH, F and UFC levels did not differ before and during drug administration. Immunohistochemical analysis of pituitary tumors removed from two responder and two nonresponder patients showed a similar intense immunoreactivity for PPAR-gamma in about 50% of cells. CONCLUSIONS: The administration of rosiglitazone seems able to normalize cortisol secretion in some patients with CD, at least for short periods. Whether the activation of PPAR-gamma by rosiglitazone might be effective as chronic pharmacologic treatment of CD needs a more extensive investigation through a randomized and controlled study.     

Hypothalamus-pituitary-adrenal axis in central diabetes insipidus: ACTH and cortisol responsiveness to CRH administration

A strong relationship has been found between arginine-vasopressin (AVP) and hypothalamus-pituitary-adrenal axis in humans. The aim of the current study was to evaluate baseline and CRH-stimulated ACTH and F levels in patients with central diabetes insipidus (CDI), before and after replacement therapy with desamino-D-AVP (DDAVP). Twenty-five patients with CDI, and 25 sex- and age- and BMI-matched healthy subjects entered the study. A standard CRH test (measurement of plasma ACTH and serum F before and every 15 min for 2 h after the administration of 100 microg of human CRH) was performed in all subjects. In patients with CDI, CRH test were repeated after 1 week of DDAVP at standard doses. At study entry, ACTH and F levels were significantly higher in patients with CDI than in controls either at baseline (ACTH: 45.5+/-4.8 vs 18.5+/-3.3 ng/l, p<0.05; F: 375.1+/-55.7 vs 146.6+/-19.4 microg/l, p<0.05) or after CRH test considered as a peak (ACTH: 90.8+/-14.4 vs 42.5+/-7.4 ng/l, p<0.05; F: 501.6+/-65.7 vs 226.3+/- 25.6 microg/l, p<0.05) and AUC (ACTH: 3997.0+/-571.7 vs 2136.0+/-365.8 ng/l/120 min, p<0.05; F: 31,489.0+/-4299.4 vs 14,854.5+/-1541.5 microg/l/120 min, p<0.05). In patients with CDI, 1 week of replacement with DDAVP brought down ACTH (peak: 56.9+/-9.3 ng/l; AUC: 2390.7+/-480.7 ng/l/120 min) and F (peak: 310.3+/-39.5 microg/l; AUC: 17,555.5+/-2008.7 microg/l/120 min) responses to CRH to normal but did not significantly modify baseline hormone levels (ACTH: 29.6+/-3.6 ng/l; F: 239.0+/-32.3 microg/l). In conclusion, CDI is associated to increased baseline ACTH and F levels and increased responsiveness of ACTH and F to CRH administration. In addition, replacement treatment with DDAVP normalized CRH-induced but not baseline ACTH and F secretion.     

ACUTE DEXAMETHASONE SUPPRESSION OF ACTH SECRETION STIMULATED BY HUMAN CORTICOTROPHIN RELEASING HORMONE, AVP AND HYPOGLYCAEMIA

In order to obtain more insight into the mechanisms regulating endogenous ACTH secretion in humans we studied the inhibitory effect of acute i.v. dexamethasone administration on ACTH release under various conditions. Six male volunteers were subjected to six different protocols. After combined i.v. injection of 100 micrograms corticotrophin releasing hormone (CRH) and 100 micrograms growth hormone releasing hormone (GRH) there was the expected rise in ACTH (area under the curve, 1053 +/- 204 (SE) (pmol/l) min) and cortisol (59788 +/- 10098 (nmol/l) min) rise which was suppressed by prior i.v. injection of 2 mg dexamethasone (ACTH: 444 +/- 63 (pmol/l) min; cortisol: 28528 +/- 2152 (nmol/l) min). Insulin hypoglycaemia (IH) led to a more pronounced ACTH and cortisol rise compared with CRH (6307 +/- 817 (pmol/l) min and 82080 +/- 21934 (nmol/l) min, respectively) which was not completely suppressed by prior pretreatment with dexamethasone (ACTH, 580 +/- 103 (pmol/l) min; cortisol: 55649 +/- 5821 (nmol/l) min). Combined AVP/CRH injection (10 IU/100 micrograms) after pretreatment with dexamethasone (344 +/- 41 (pmol/l) min for ACTH; 32832 +/- 3173 (nmol/l) min for cortisol) could not reproduce the ACTH secretion following IH after pretreatment with dexamethasone (579 +/- 103 (pmol/l) min for ACTH and 55649 +/- 5821 (nmol/l) min for cortisol). In all subjects a saline control with 2 mg dexamethasone was performed. These findings confirm the acute inhibitory effect of glucocorticoids on CRH-stimulated ACTH secretion. Since CRH-induced ACTH secretion is almost completely abolished by administration of dexamethasone the ACTH rise following IH after dexamethasone can not be mediated by endogenous CRH alone. Moreover, since the addition of AVP to CRH (after dexamethasone suppression) could not reproduce the ACTH rise during IH after dexamethasone pretreatment, an additional, yet unknown factor stimulating ACTH secretion may be involved. In the same protocols, no significant difference could be observed comparing IH and GRH induced GH secretion (4948 +/- 1172 (mU/l) min vs 3596 +/- 820 (mU/l) min, NS); furthermore, in contrast to results obtained by chronic steroid administration, acute i.v. dexamethasone pretreatment did not affect IH or GRH-induced GH secretion (4110 +/- 666 (mU/l) min vs 2916 +/- 462 (mU/l) min, NS). The GRH-stimulated GH secretion (3596 +/- 820 (mU/l) min) was not suppressed by prior intravenous treatment with dexamethasone (2916 +/- 504 (mU/l) min, NS).     

A patient with recurrent hypercortisolism after removal of an ACTH-secreting pituitary adenoma due to an adrenal macronodule

A 41-yr-old female was referred for signs and symptoms of Cushing's syndrome. Cortisol was not suppressed by 1 mg dexamethasone (0.41 micromol/l). Midnight cortisol and ACTH were 0.44 micromol/l and 18 pmol/l, respectively. Urinary cortisol excretion was 250 nmol/24 h (normal between 30 and 150 nmol/24 h). A magnetic resonance imaging (MRI) revealed a pituitary lesion of 7 mm. ACTH and cortisol levels were unaltered by administration of human CRH and high-dose dexamethasone. Inferior sinus petrosus sampling showed CRH-stimulated ACTH levels of 128.4 (left sinus) vs a peripheral level of 19.2 pmol/l, indicating Cushing's disease. After 4 months of pre-treatment with metyrapone and dexamethasone, endoscopic transsphenoidal resection of an ACTH-positive pituitary adenoma was performed. ACTH levels decreased to 2.6 pmol/l and fasting cortisol was 0.35 micromol/l. Despite clinical regression of Cushing's syndrome and normalization of urinary cortisol, cortisol was not suppressed by 1 mg dexamethasone (0.30 micromol/l). Ten months post-operatively, signs and symptoms of Cushing's syndrome reoccurred. A high dose dexamethasone test according to Liddle resulted in undetectable ACTH, but no suppression of cortisol levels, pointing towards adrenal-dependent Cushing's syndrome. Computed tomography (CT)-scanning showed a left-sided adrenal macronodule. Laparoscopic left adrenalectomy revealed a cortical macronodule (3.5 cm) surrounded by micronodular hyperplasia. Fasting cortisol had decreased to 0.02 micromol/l. Glucocorticoid suppletion was started and tapered over 12 months. Symptoms and signs of hypercortisolism gradually disappeared. This case illustrates, that longstanding ACTH stimulation by a pituitary adenoma can induce unilateral macronodular adrenal hyperplasia with autonomous cortisol production.     

Alprazolam (a benzodiazepine activating GABA receptor) reduces the neuroendocrine responses to insulin-induced hypoglycaemia in humans

OBJECTIVE: Alprazolam (ALP), a benzodiazepine-activating GABAergic receptor, possesses clear centrally mediated inhibitory effects on ACTH and cortisol secretion that could reflect an inhibitory influence on CRH- and/or AVP-secreting neurones. An inhibitory effect of ALP on catecholamine release has also been shown while its effect on GH secretion is unclear. To further clarify the neuroendocrine actions of ALP, we studied the ALP effects on the neurohormonal responses to hypoglycaemia in a group of normal subjects. DESIGN: In eight normal subjects [four women and four men, 22-34 years old, body mass index (BMI) 20-25 kg/m2] the ACTH, cortisol, GH, adrenaline (A) and noradrenaline (NA) responses to insulin-induced hypoglycaemia [ITT, 0.1 UI/kg regular insulin intravenously (i.v.) at 0 min] preceded by placebo or ALP (0.02 mg/kg orally at -90 min) were studied in two sessions at least 10 days apart. MEASUREMENTS: Blood samples were taken basely at -90 and 0 min and every 15 min up to +120 min. ACTH, cortisol, GH, A and NA level were assayed at each time point in both sessions. RESULTS: All subjects experienced hypoglycaemia (plasma glucose levels below 2.2 mmol/l). After placebo ITT induced clear-cut increases in ACTH (peak vs. baseline, mean +/- SEM: 27.9 +/- 3.9 vs. 7.1 +/- 1.5 pmol/l), cortisol (438.1 +/- 32.0 vs. 237.7 +/- 19.3 nmol/l) and GH (38.1 +/- 9.7 vs. 5.7 +/- 2.0 micro g/l) levels (P < 0.05). Marked increase in A (6627.2 +/- 116.7 vs. 263.7 +/- 71.4 pmol/l) and NA (3.8 +/- 1.5 vs. 1.6 +/- 1.0 nmol/l) levels were also recorded (P < 0.05). Pretreatment with ALP significantly inhibited the ACTH peak response to ITT (17.8 +/- 5.0 pmol/l, P < 0.05), while the cortisol response showed a non significant reduction (342.1 +/- 38.7 nmol/l). ALP also significantly reduced the GH (21.7 +/- 4.7 micro g/l, P < 0.02) and A (3828.0 +/- 1400.7 pmol/l, P < 0.02) responses to ITT. On the contrary, ALP lowered basal NA levels (P < 0.05) but did not significantly affect its response to ITT (2.2 +/- 1.2 nmol/l). Glucose changes induced by ITT were not modified by ALP. CONCLUSIONS: This study shows that GABAergic activation by alprazolam significantly inhibits the neuroendocrine and adrenomedullary responses to hypoglycaemia.     

Baseline and CRH-stimulated ACTH and cortisol levels after administration of the peroxisome proliferator-activated receptor-gamma ligand, rosiglitazone, in Cushing's disease

The ability of acute rosiglitazone administration in influencing ACTH/cortisol secretion in basal conditions and after CRH stimulation was studied in patients with Cushing's disease. Ten patients (8 women and 2 men, aged 18-65 yr) with Cushing's disease were enrolled in the study: 6 of them had previously undergone unsuccessful surgery and 4 were untreated. Plasma ACTH and serum cortisol levels were evaluated at serial time points for 3 h during saline infusion and after the administration of rosiglitazone (8 mg, po) and for 1 h after the injection of CRH (1 microg/kg iv) given alone or 30 min following rosiglitazone administration. The 4 tests were performed in all subjects in randomized order on different days. No significant difference was observed between the pattern of hormone secretion during saline alone and after rosiglitazone, as evaluated by two-way analysis of variance (ANOVA). The integrated areas under the curves (AUCs) were also not significantly different (ACTH: 5683 +/- 1038 vs 6111 +/- 1007 pg/ml/180 min; cortisol: 2333 +/- 267 vs 2902 +/- 486 microg/dl/180 min). In addition, there was no difference for ACTH and cortisol responses to CRH given either alone or after rosiglitazone, when evaluated as peak, increment or AUC; the pattern of the responses analyzed by two-way ANOVA was also similar. In conclusion: 1) the administration of a single dose of rosiglitazone did not decrease ACTH/cortisol levels or blunt their response after CRH injection; 2) the activation of PPAR-gamma receptors by rosiglitazone seems unable to affect ACTH and cortisol secretion, at least in acute conditions, in patients with ACTH-secreting pituitary adenomas.     

COMPARISON OF THE ACTH AND CORTISOL RESPONSES TO PROVOCATIVE TESTING WITH GLUCAGON AND INSULIN HYPOGLYCAEMIA IN NORMAL SUBJECTS

The glucagon stimulation test (GST) is often used to assess pituitary ACTH reserve, particularly when other tests are contra-indicated. In a preliminary investigation, in patients with pituitary disease, we failed to demonstrate the ACTH dependence of the cortisol response. We have therefore compared the ACTH, cortisol and glucose responses to glucagon (1 mg s.c.), insulin (0.2 U/kg i.v., ITT) and placebo in six healthy male volunteers, sampling every 10 min for 6 h. During the GST, mean +/- SD serum cortisol rose from 256 +/- 80 nmol/l to a peak of 481 +/- 164 nmol/l (range 289-717 nmol/l, P less than 0.01) in comparison with 280 +/- 81 nmol/l to 602 +/- 110 nmol/l (range 493-742 nmol/l) during the ITT (P less than 0.002). The mean peak cortisol levels achieved in the two tests did not differ significantly. In the GST, plasma ACTH rose from a mean basal value of 10.9 +/- 16.6 ng/l to a mean peak level of 123 +/- 76 ng/l (P less than 0.02) (ACTH ng/l x 0.225 = pmol/l). The corresponding values in the ITT were 7.1 +/- 16.2 ng/l and 263 +/- 91 ng/l (P less than 0.001). The mean peak ACTH level was significantly greater during the ITT (P less than 0.05). Thus the cortisol response was ACTH dependent in both the GST and the ITT in normal subjects. Furthermore, the ACTH response was of sufficient duration to be detected by the usual procedure of sampling every 30 min.(ABSTRACT TRUNCATED AT 250 WORDS)