Feedback control of vasopressin and corticotrophin secretion in conscious dogs: effect of hypertonic saline

Glucocorticoids are known to inhibit the ACTH response to a variety of stimuli. It has been suggested that vasopressin secretion is also inhibited by glucocorticoid negative feedback. The purpose of this study was to (1) determine the ACTH response to hypertonic saline and its sensitivity to glucocorticoid negative feedback and (2) to determine whether physiological elevations of plasma cortisol inhibit subsequent vasopressin responses to hypertonic saline. Five mongrel dogs (15-18 kg) were prepared with chronic arterial and venous catheters and studied while conscious. Ten experiments were performed on each dog in a randomized design separated by at least 5 days. Each experiment consisted of a pretreatment period (from -60 to -30 min except for dexamethasone administration) during which a glucocorticoid feedback signal was applied and a stimulus period (from 0 to 30 min) during which hypertonic saline was infused. The pretreatment and stimulus periods were separated by 30 min. Pretreatments were as follows: isotonic saline (control), half-maximal and maximal cortisol infusion (5.5 or 11 nmol/kg per min), ACTH(1-24) infusion (6.8 pmol/kg per min) which produces increases in endogenous cortisol, and dexamethasone (1.5 mg i.m.) given at 17.00 h the day before experimentation. Stimuli were as follows: hypertonic saline was infused at 0.2 or 0.4 mmol/kg per min which increased plasma sodium by about 6 or 12 mmol/l respectively. NaCl infusion at 0.2 mmol/kg per min had no effect on plasma ACTH or cortisol except when subsequent to ACTH(1-24) pretreatment when plasma ACTH actually increased to 41.4 +/- 2.9 pmol/l in response to hypertonic saline.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increased adrenocorticotropin, cortisol, and arginine vasopressin secretion in primates after the antiglucocorticoid steroid RU 486: dose response relationships

The antiglucocorticoid steroid, RU 486, elevated plasma ACTH concentrations when administered im at 0700 h in a dose of 1.0 mg/kg in nonhuman primates (Macaca fascicularis; P less than 0.05). The duration, but not the magnitude, of this response increased after 5.0 mg/kg RU 486 im; release of ACTH did not rise further after 10 mg/kg. Peak ACTH elevations occurred 1-2 h after RU 486 administration. Plasma cortisol concentrations peaked 4 h after RU 486 administration and the response was significant only after 5.0 mg/kg RU 486. Plasma arginine vasopressin (AVP) concentrations also increased after RU 486 but the increase occurred only after the 10.0 mg/kg dose (P less than 0.05). The AVP elevation was greatest 4 h after 10 mg/kg RU 486 and was abolished by dexamethasone pretreatment. We conclude that: 1) RU 486 elevates plasma ACTH, cortisol, and AVP concentrations in a manner which is both dose and time dependent, 2) ACTH release occurred at an order of magnitude lower dose than did AVP release, and 3) plasma AVP changes after RU 486 are glucocorticoid dependent.     

Propranolol enhances the effect of ACTH on plasma cortisol, but not on aldosterone in man

An accidental observation led to the suspicion that propranolol (P) enhances the effect of exogenous ACTH on plasma cortisol. To examine this matter further, large-dose ACTH tests (25 IU im) were performed in 10 normal young males: i) without treatment (n =10); ii) after 11/2 days of P treatment (n = 10); iii) after 11/2 days of metoprolol treatment (n = 6). Six other subjects received infusions of 0.2 IU of ACTH/hour for 12 h: i) without pretreatment; ii) after 11/2 days of P treatment. P pretreatment (80 mg t.i.d.) led to a small but significant decrease in plasma cortisol (9.4 +/- 0.8 micrograms/100 mg; mean +/- SE, vs. 11.3 +/- 0.7 micrograms/100 ml in controls). The maximum percentage increase of plasma cortisol after ACTH injection was 383% +/- 35% (mean +/- SE) after P and 253% +/- 22% in controls (p less than 0.05). The enhancement of the absolute and relative increase of plasma cortisol after ACTH injection seems to be mainly due to lowering of basal cortisol levels, since the effect of ACTH on plasma cortisol in normal subjects in inversely related to basal cortisol. The effect of metoprolol on basal cortisol and the cortisol response to ACTH was less pronounced than that of P. In the long-term-infusion study the effect of P was less apparent than in the acute study. P had no significant effect on basal plasma aldosterone or on the aldosterone response to ACTH.(ABSTRACT TRUNCATED AT 250 WORDS)     

Failure of glucocorticoid feedback in males of a population of small marsupials (Antechinus swainsonii) during the period of mating

In an investigation of the factors leading to the increase in the concentration of plasma free glucocorticoid, which results in immunosuppression and death after mating of all males in natural populations of a small shrew-like marsupial, the dusky antechinus (Antechinus swainsonii), the integrity of the glucocorticoid feedback control of the concentration of plasma cortisol was examined by use of dexamethasone-suppression tests. Injection of 0.2 mg dexamethasone/kg i.m. caused a marked fall in the concentration of plasma cortisol 17 h later, approximately 2 months and 2 weeks before the annual mating period in mid-July. However, the same dose had no significant effect on the increased concentration of plasma cortisol characteristic of the mid- to late July mating period. Injection of 100 i.u. ACTH/kg i.m. caused a significant increase in the concentration of plasma cortisol 6-7 h later on all occasions, indicating that the responsiveness of the adrenal cortex to ACTH did not change. Pretreatment with dexamethasone had no effect on the ACTH-stimulated cortisol concentration, ruling out a possible direct effect of dexamethasone on adrenocortical secretion in this species. Dexamethasone also reduced the concentration of plasma testosterone when the level was low, before the mating period, but not when the level was high, at the beginning of the mating period. It is concluded that, in association with a rapid increase in the concentration of plasma testosterone, an increase in aggression and intense mating activity, glucocorticoid feedback control of ACTH secretion is impaired.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pulsatile ACTH and cortisol in goats: effects of insulin-induced hypoglycemia and dexamethasone.

Insulin-induced hypoglycemia is a metabolic stress that stimulates secretion of adrenocorticotropic hormone (ACTH) and cortisol in a number of animal species. Dexamethasone is a potent synthetic glucocorticoid that suppresses the secretion of ACTH and cortisol. Both ACTH and cortisol exhibit complex secretory patterns demonstrating ultradian and circadian rhythms. This work investigated the pattern of ACTH and cortisol response to hypoglycemia in goats and the effect of dexamethasone on this response. Five goats were pretreated with dexamethasone (0.1 mg/kg) and 5 with saline. Blood samples were taken every 2 min for 60 min before and 60 min after administration of insulin (2.5 IU/kg, i.v.). Immunoreactive ACTH and cortisol were measured in all samples and glucose in selected samples. Data sets were analyzed for significant pulses with the Cluster Analysis program. Complete data sets were compared as well as those for each 30-min interval. Plasma glucose was lower than preinsulin levels at 10 min, declined rapidly between 10 and 30 min, and remained low 30-60 min after insulin injection in both treatment groups. Controls showed a rapid rise in ACTH and cortisol beginning 30 +/- 10 min postinsulin. The increase in mean plasma hormone levels during hypoglycemia was predominantly due to an increase in amplitude of secretory pulses for ACTH and cortisol compared with the 30 min before insulin. Dexamethasone significantly lowered mean ACTH and cortisol levels and prevented alteration in plasma ACTH and cortisol secretion during hypoglycemia but did not totally ablate pulsatile activity of either hormone. The amplitude of ACTH and cortisol pulses was significantly decreased by dexamethasone treatment. The frequency of cortisol but not ACTH pulses was also significantly decreased.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of therapeutic glucocorticoids on the adrenal response in a randomized controlled trial in patients with rheumatoid arthritis

OBJECTIVE: To measure the effect of low-dose systemic glucocorticoid treatment on the adrenal response to adrenocorticotropic hormone (ACTH) in patients with rheumatoid arthritis (RA). METHODS: Patients with RA who took part in a randomized double-blind placebo-controlled trial of budesonide (3 mg/day and 9 mg/day) and prednisolone (7.5 mg/day) underwent a short (60-minute) test with injection of ACTH (tetracosactide hexaacetate) at baseline and the day after completing the 3-month treatment program. Plasma cortisol measurements at baseline and 3 months were compared within and between the treatment groups. Individual patients were classified as normal responders to ACTH or as abnormal responders if changes were >2 SD below the pretreatment value in the entire group of study patients. RESULTS: Short tests with ACTH injection were performed on 139 patients before beginning the study medication and on 134 patients after cessation of the medication. There were no changes in the placebo group. Mean plasma cortisol levels following treatment were reduced in all active treatment groups. In addition, mean values were significantly reduced for the 30-minute and 60-minute responses to ACTH. The maximum reduction (35%) occurred in the prednisolone group at 60 minutes. Following treatment, 34% of patients taking budesonide 9 mg and 46% of those taking prednisolone 7.5 mg failed to reach the normal maximum cortisol response to ACTH. Four patients failed to achieve the normal percentage increase in cortisol levels, but only 1 patient failed to meet both criteria. CONCLUSION: Low doses of a glucocorticoid resulted in depression of baseline and ACTH-stimulated cortisol levels after 12 weeks of therapy. Although the responsiveness of the hypothalamic-pituitary-adrenal axis in individual patients generally remained within the normal range, these changes should be investigated further.     

ESCAPE FROM DEXAMETHASONE-INDUCED ACTH AND CORTISOL SUPPRESSION BY CORTICOTROPHIN-RELEASING HORMONE: MODULATORY EFFECT OF BASAL DEXAMETHASONE LEVELS

The response of ACTH and cortisol to corticotrophin-releasing hormone (CRH) after pretreatment with various doses of dexamethasone was investigated in five healthy subjects. The five subjects participated in six experiments. In each experiment 200 micrograms ovine CRH was administered as an i.v. bolus injection at 0900 h after pretreatment with respectively: (A) 1 mg dexamethasone orally at 2300 h in the evening before CRH injection, (B) 2 mg dexamethasone orally at 2300 h in the evening before CRH injection, (C) 4 mg dexamethasone orally at 2300 h in the evening before CRH injection, (D) 2 mg dexamethasone orally at 2300 h in the evening before CRH injection, followed by 2 mg dexamethasone orally 1 h before CRH, (E) no dexamethasone and (F) 1 mg dexamethasone orally 1 h before CRH injection. In spite of overnight suppression with a single dose of dexamethasone CRH elicited cortisol rises in all individuals (experiments A-C). Dexamethasone pretreatment in experiment D abolished the CRH-induced stimulation of the pituitary-adrenal axis. There was a significant and negative correlation between the basal dexamethasone levels (i.e. the dexamethasone levels immediately before CRH administration) in the experiments A-D and the areas under the individual ACTH (R = -0.62; P less than 0.01 by Spearman's rank correlation test) and cortisol (R = -0.81; P less than 0.001 by Spearman's test) curves, i.e. the lower the basal dexamethasone levels, the greater the rise in ACTH and cortisol levels after CRH administration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Enhancement of adrenal cortisol secretion after intravenous high dose dexamethasone

To assess the possible existence of a short loop feedback mechanism of direct glucocorticoid suppression on the adrenal glands, we performed a series of tests employing insulin hypoglycemia or ACTH infusions to obtain adrenal stimulation by ACTH levels that remained within the physiological range. Although the rapidity of glucocorticoid suppression of the pituitary thwarted efforts to use endogenous ACTH as a stimulus, we were able to mimic the stressed state by very low dose ACTH infusions (0.05 microgram/kg BW). No inhibition of cortisol secretion in response to ACTH infusions was detected in tests done after administration of dexamethasone compared to placebo [mean integrated response, 29.37 +/- 1.91 (+/- SE) vs. 29.12 +/- 1.12 microgram . h/dl, respectively]. Furthermore, when high doses of dexamethasone were administered iv, a small paradoxical increase in cortisol secretion was found (33.82 +/- 1.44 microgram . h/dl) without a difference in ACTH levels. These data do not support the concept of significant direct glucocorticoid inhibition of adrenal secretion. Non-ACTH factors that may enhance cortisol secretion in the presence of ACTH may exist.     

Activity of the hypothalamic-pituitary-adrenal axis is altered by aging and exposure to social stress in female rhesus monkeys

Age-related changes in glucocorticoid negative feedback inhibition of hypothalamic CRF and pituitary ACTH are observed in rodents. Attempts to study similar effects in humans have produced mixed results due in part to the difficulty in matching older subjects on social and lifestyle variables. The present study used female rhesus monkeys as a model for women by comparing young adult (n = 20) to old (n = 20) females to test the hypotheses that the hypothalamic-pituitary-adrenal axis is altered in older animals and that this difference is exacerbated by exposure to social stress. The effects of age on the response to two doses of dexamethasone and two doses of CRF were assessed in females living in a stable social environment (control) and in socially stressed females removed from their group and housed temporarily in a remote, nonsocial environment (separated). The suppression of serum cortisol was not different between the two doses of dexamethasone. Before dexamethasone administration (2100 h), serum cortisol was significantly higher in old control females than in either young or old separated females, who were not different from one another. The young control females had baseline cortisol concentrations significantly lower than all other groups. Serum cortisol was suppressed approximately 75% below baseline values in all groups by 10 h after dexamethasone administration. Age significantly affected serum cortisol after dexamethasone, as the old control group showed a release from suppression 19 h posttreatment compared to the young control group and compared to the separated groups. Social condition had a significant effect on the responses of serum cortisol and plasma ACTH to CRF administration. At baseline (0930 h), serum cortisol was significantly higher in young controls compared with older controls, with both separated groups having intermediate values. Similarly, plasma ACTH at baseline was significantly higher in young controls compared to all other groups. Social separation significantly diminished the elevation of both serum cortisol and ACTH after stimulation with either dose of CRF. Control females showed a prolonged increase in plasma ACTH through 60 min and an increase in serum cortisol through 120 min after CRF. In contrast, these hormones either declined by 60 min or did not increase in socially separated females after CRF administration. These data suggest that the circadian rhythm in serum cortisol may be affected by aging, as levels were higher in the evening and lower in the morning in old control compared to young control females. The effect of age on the response to dexamethasone treatment among the control groups lends support to the hypothesis that the sensitivity of glucocorticoid negative feedback diminishes with aging. Although age did not affect the response to CRF, social separation diminished the elevation in both serum cortisol and plasma ACTH. Whether this effect was due to stress-induced down-regulation of pituitary CRF receptors remains to be determined.     

Stress-mediated effect of metoclopramide on cortisol secretion in man

Five healthy adult men were given metoclopramide (10 and 20 mg) iv, and in repeated tests almost always developed transient restlessness lasting from 10-30 min. The effects of L-dopa and dexamethasone on metoclopramide-induced increases in cortisol concentration were determined. These response values were compared with those of a control. After an injection of 10 mg metoclopramide, the cortisol level increased significantly only at 40 min; the ACTH level did not change. The cortisol rise was suppressed by dexamethasone pretreatment. Pretreatment with 0.5 g L-dopa resulted in a decrease in the PRL level from -20 min to 20 min, and the increase in cortisol seen at 40 min was cancelled. The ACTH level did not change. After injecting 20 mg metoclopramide, the ACTH level increased significantly from 20 min to 60 min and the cortisol level showed a significant increase from 20 min to 120 min. Pretreatment with dexamethasone resulted in a decrease in these hormones. The L-dopa pretreatment did not reduce even the rise in the PRL level which resulted from the administration of 20 mg metoclopramide. These findings suggest that the ACTH and cortisol response to metoclopramide is a stress-mediated effect. Plasma cortisol responses to 20 mg metoclopramide and insulin-induced hypoglycemia were studied and compared in seven volunteers and found to be similar.     

Effects of ovine corticotropin-releasing hormone on adrenocorticotropin secretion in the absence of glucocorticoid feedback inhibition in man

We studied 1) the nature of the plasma ACTH response to ovine CRH (oCRH) in the absence of normal glucocorticoid negative feedback inhibition and 2) the cause of the diminished circadian peak in plasma ACTH in normal men the morning after 3-30 micrograms/kg BW doses of oCRH. Placebo or oCRH (3 micrograms/kg BW, iv) was administered as iv injections to five normal men given metyrapone to produce acute glucocorticoid deficiency. Four studies were performed: 1) placebo oCRH plus placebo hydrocortisone (HC), 2) oCRH plus placebo HC, 3) placebo oCRH plus HC, and 4) oCRH plus HC. HC was given as a variable rate iv infusion to mimic the plasma cortisol response to the same dose of oCRH in normal men. Plasma cortisol levels rose only slightly after oCRH, indicating nearly complete blockade of cortisol biosynthesis. Plasma cortisol levels during the HC infusion were similar to those in normal men given 3 micrograms/kg oCRH. There was an exaggerated rise in both the first and second peaks of the plasma ACTH response to oCRH in the metyrapone-treated men. HC infusion did not alter the plasma ACTH response during the first 60 min after oCRH, but markedly attenuated the response thereafter; however, it did not affect the timing of the second peak. This inhibitory effect continued for up to 11 h, which was 2-3 h longer than the period that plasma cortisol levels were increased. Thus, cortisol secreted in response to ACTH released by oCRH modulates, after about a 60-min delay, the continuing release of ACTH. Despite the greater oCRH-induced release of pituitary ACTH in the metyrapone-treated men, the magnitude of their next morning's circadian plasma ACTH peak was similar to that after they received placebo oCRH. Thus, depletion of pituitary ACTH did not appear to explain the diminished circadian peak. Its magnitude was reduced by the combination of oCRH and HC, but not by HC alone. Administration of oCRH, alone or in combination with HC, delayed the onset of the circadian rise, while oCRH, HC, or the combination thereof delayed the time of the circadian peak. Thus, it appears that both the glucocorticoid response to oCRH and direct or indirect effect(s) of oCRH are required to produce these two phenomena.     

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).     

Effects of high-dose ketoconazole and dexamethasone on ACTH-stimulated adrenal steroidogenesis in orchiectomized prostatic cancer patients

The effects of high-dose ketoconazole (i.e. 400 mg every 8 h) therapy on adrenal steroidogenesis were investigated in 7 patients with advanced prostatic cancer who no longer responded to orchiectomy. An ACTH challenge was performed before and on days 14 and 28 of high-dose ketoconazole treatment. During the last 14 days, dexamethasone (0.5 mg twice daily) was administered together with ketoconazole. High-dose ketoconazole alone lowered the basal levels of the androgens by 49-66%. It almost completely inhibited their stimulation by ACTH, whereas plasma progesterone was doubled. Basal cortisol was only slightly lowered, but the response to ACTH stimulation was markedly blunted. Basal and stimulated plasma aldosterone remained unaffected. Both basal and stimulated 11-deoxycortisol, 11-deoxycorticosterone, and, to a lesser extent, corticosterone rose more markedly after ketoconazole than after placebo. The basal and stimulated plasma adrenal androgen levels were further reduced after combined ketoconazole-dexamethasone treatment, whereas plasma corticosterone, 11-deoxycortisol, and 11-deoxycorticosterone were lowered in the same way as cortisol. Aldosterone and progesterone profiles were similar to those observed under high-dose ketoconazole, but plasma 17 alpha-hydroxyprogesterone increased more markedly than after high-dose ketoconazole alone. These results demonstrate that high-dose ketoconazole lowers plasma androgen levels in orchiectomized patients and partly inhibits the gluco- and mineralocorticoid syntheses, especially after ACTH-stimulation. The addition of dexamethasone does not only correct the possible consequence of the impairment of the cortisol production by high-dose ketoconazole, but it further reduces the androgen levels and lowers the plasma concentrations of most precursors, for instance 11-deoxycorticosterone, which has some physiological mineralocorticoid activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

THE EFFECT OF PERIPHERAL CATECHOLAMINE CONCENTRATIONS ON THE PITUITARY-ADRENAL RESPONSE TO CORTICOTROPHIN RELEASING FACTOR IN MAN

To evaluate the effect of changes in plasma catecholamines on the pituitary-adrenal response to ovine corticotrophin releasing factor (CRF) in normal man, the response to CRF alone (10 subjects) was compared responses after infusions of adrenaline (6 subjects), noradrenaline (6 subjects) and after oral administration of the alpha 2 agonist clonidine (10 subjects). Compared to control levels, plasma adrenaline and noradrenaline concentrations were increased three- and four-fold respectively by exogenous infusions, whereas plasma noradrenaline was significantly lowered by clonidine. Despite these changes in plasma catecholamine levels, the responses of plasma ACTH, cortisol and aldosterone to CRF did not differ significantly from control (CRF alone) in any of the three studies. Neither clonidine pretreatment nor catecholamine infusions altered basal levels of plasma ACTH, cortisol or aldosterone and no effect of CRF or catecholamine manipulations on plasma arginine vasopressin concentration was observed. These results show that modulation of peripheral plasma catecholamine levels within physiological limits does not affect CRF-stimulated release of ACTH or the adrenal response in normal man.     

The role of corticosterone in human hypothalamic-pituitary-adrenal axis feedback

OBJECTIVE: In humans, the glucocorticoid corticosterone circulates in blood at 10-20-fold lower levels than cortisol, but is found in higher relative amounts in postmortem brain samples. Access of cortisol and corticosterone to the central nervous system may not be equal. Additionally, the relative affinities for the glucocorticoid and mineralocorticoid receptors differ, such that corticosterone may play a significant role in human brain function. DESIGN: We measured cortisol and corticosterone levels in paired plasma and cerebrospinal fluid (CSF) samples. To test the relative potency of cortisol vs. corticosterone on hypothalamic-pituitary-adrenal (HPA) feedback, subjects underwent a three-phase, single-blind, randomized study assessing the postmetyrapone ACTH response over 3 h to an intravenous bolus of vehicle, cortisol or corticosterone (0.15 mg/kg and 0.04 mg/kg). PARTICIPANTS: Outpatients undergoing diagnostic lumbar puncture who were subsequently deemed to be free of disease. Feedback was tested in healthy male volunteers. MEASUREMENTS: Plasma and CSF corticosterone to cortisol ratio was calculated and the ACTH response over time after the bolus glucocorticoid measured. RESULTS: Plasma corticosterone : cortisol was 0.069 +/- 0.007; CSF corticosterone : cortisol was 0.387 +/- 0.050 (P < 0.001). Cortisol and corticosterone (0.15 mg/kg) suppressed ACTH vs. vehicle (P = 0.002); there was no difference between corticosterone and cortisol. The 0.04 mg/kg dose had no effect on ACTH despite supraphysiological plasma corticosterone levels. CONCLUSIONS: Corticosterone contributes almost 40% of total active glucocorticoids (cortisol and corticosterone) in the CSF. Significant effects on HPA axis suppression were only seen with supraphysiological levels of corticosterone, suggesting that corticosterone is not important in this model of nonstress-induced ACTH hypersecretion, in which the effect of cortisol predominates.     

Corticotropin-releasing effect of hexarelin, a peptidyl GH secretagogue, in normal subjects pretreated with metyrapone or RU-486, a glucocorticoid receptor antagonist, and in patients with Addison's disease.

GH secretagogues (GHS) are peptidyl and nonpeptidyl molecules which possess strong GH-releasing activity but also stimulatory effect on hypothalamo-pituitary-adrenal axis. The ACTH and cortisol responses to Hexarelin (HEX), a peptidyl GHS, are abolished by low-dose dexamethasone pretreatment in normal subjects but are exaggerated and higher than those after hCRH in patients with pituitary ACTH-dependent Cushing's disease, in spite of their hypercortisolism. Based on the foregoing, we studied the ACTH, cortisol and GH responses to HEX (2.0 microgram/kg i.v. at 0 min) alone and after metyrapone (2 g p.o. at 23:00 h the night before) or RU-486 (400 mg p.o. at 02:00 h), a glucocorticoid receptor antagonist, in 6 normal women (NS, age 26-34 years). The endocrine responses (mean +/- SEM) to HEX alone were also studied in 8 patients with Addison's disease (AD, 6 males, 2 females, age 30-77 years; last hydrocortisone administration the day before testing). In NS, HEX stimulated basal ACTH (peak, mean +/- SEM: 26.0 +/- 7.8 vs. 10.7 +/- 2.0 pg/ml, p < 0. 05), cortisol (163.2 +/- 18.3 vs. 137.4 +/- 15.4 microgram/l, p < 0.05) and GH (72.6 +/- 23.5 vs. 3.7 +/- 1.3 microgram/l, p < 0.01) levels. Metyrapone markedly increased basal ACTH (294.4 +/- 61.6 pg/ml, p < 0.05), reduced basal cortisol (19.6 +/- 7.2 microgram/l, p < 0.05), while it did not modify GH levels. After metyrapone pretreatment the ACTH response to HEX was clearly increased (DeltaAUC: 2,857.4 +/- 901.9 vs. 367.3 +/- 274.0 pg/ml/h, p < 0.05), while the GH response was not modified. HEX did not stimulate the low cortisol levels after metyrapone pretreatment. RU-486 significantly increased basal ACTH (76.6 +/- 12.5 pg/ml, p < 0.05) and cortisol (312.7 +/- 22.2 microgram/l, p < 0.05), while it did not modify basal GH levels. RU-486 pretreatment did not modify the ACTH, cortisol and GH responses to HEX. In AD, HEX elicited a marked ACTH response (6,619.4 +/- 3,365.8 pg/ml/h; p < 0.01), which was clearly higher (p < 0.01) than that in NS after HEX alone but not significantly different from that after HEX+MET. The GH response to HEX in AD (1,325.6 +/- 284.1 microgram/l/h) was similar to that in NS (1,519.7 +/- 483.8 microgram/l/h). In conclusion, our present data demonstrate that the ACTH-releasing activity of HEX is increased in primary hypoadrenalism as well as in normal subjects after metyrapone but not after RU-486 pretreatment. These findings indicate that in normal subjects as well as in hypocortisolemic patients the ACTH-releasing activity of GHS is enhanced by the lack of negative glucocorticoid feedback.     

Effect of androgen on adrenal steroidogenesis in normal women

Ovarian hyperandrogenism may induce adrenal enzymatic defects that mimic true inherited disorders of adrenal hormone biosynthesis. To assess the effect of hyperandrogenism on adrenal steroidogenesis, seven normal ovulatory women were studied on 2 days during the early follicular phase of their cycles. Plasma 17-hydroxyprogesterone (17-Prog), 17-hydroxypregnenolone, dehydroepiandrosterone (DHEA), DHEA sulfate, androstenedione (Adione), testosterone (T), 11-deoxycortisol, and cortisol concentrations were measured every 15 min for 3 h after iv injection of 0.25 mg ACTH (day 1) and pretreatment with dexamethasone on each day. On the second study day, T (80 micrograms/h) was infused iv for 5 h, and ACTH was given after 2 h of T infusion. The T infusion raised mean serum T levels from 1.2 +/- 0.3 (+/- SE) to 8.6 +/- 0.6 nmol/L. The maximum incremental (delta max) plasma Adione response to ACTH was significantly higher (2.6 +/- 0.3 to 3.2 +/- 0.4 nmol/L; P less than 0.009) during the T infusion, while the delta max responses of the other steroids did not change. There was an increase in the delta max 17-Prog to cortisol ratio (4.9 +/- 0.7 to 7.0 +/- 1.0; P less than 0.05), but no change in the delta max 17-Prog to Adione or 17-hydroxypregnenolone to DHEA ratios and no changes in the delta max delta 5- to delta 4-steroid ratios. These data suggest that acute T elevations result in subtle inhibition of 21-and/or 11 beta-hydroxylase activities, but not in 17-20-desmolase or 3 beta-ol activities.     

Suppression of pituitary-adrenal axis by triamcinolone acetonide in asthmatics]

To assess the inhibitory effect of triamcinolone acetonide on pituitary-adrenal axis, we measured plasma cortisol, plasma ACTH and performed short ACTH stimulation test before and after injection of 40 mg of triamcinolone acetonide intramuscularly in 34 asthmatic patients. At the same time salivary cortisol levels had been followed up for four weeks in ten of the 34 patients. Maximum adrenal suppression was found in two to three days after the administration. The suppression rates of salivary cortisol, plasma cortisol, plasma ACTH and ACTH stimulation test were 81.5%, 53.2%, 70% and 45.6% respectively. Such suppression lasted for two weeks. Afterwards the secretion of pituitary and adrenal glands recovered gradually. The secretion of plasma ACTH and salivary cortisol returned to normal in four weeks and that of plasma cortisol in five weeks. Triamcinolone acetonide, 40 mg monthly, is comparable with prednisone 10 mg daily, or oral dexamethasone 0.75 mg daily. The inhibitory effect of the steroids on pituitary-adrenal axis was in the order of dexamethasone, triamcinolone acetonide and prednisone.     

The new steroid analog RU 486 inhibits glucocorticoid action in man

RU 486 [17 beta-hydroxy-11 beta-(4- dimethylaminophenyl )-17 alpha-(prop-1- ynyl )-estra-4,9-dien-3-one] is a new steroid analog which antagonizes glucocorticoid action at the receptor level in animals. To assess its potential antiglucocorticoid activity in man we studied the pituitary-adrenal response to RU 486 in normal men. The compound was administered at 0200 h and plasma cortisol and lipotropins (LPH) were measured hourly for 10 h. After 400 mg RU 486 significant and sustained elevation of both hormones occurred during the 0700-1200 h period: mean (+/- SE) plasma levels after placebo or RU 486 during this interval were, respectively, for cortisol (ng/ml), 63.4 +/- 8.2 and 112.7 +/- 2.9 (P less than 0.02); and for LPH (pg/ml), 34.8 +/- 11.3 and 71.6 +/- 15.4 (P less than 0.01). The 200- and 100-mg doses induced only transient cortisol and LPH increases. Administration of RU 486 (400 mg) at 1400 h induced no increase in plasma cortisol compared to placebo in the corresponding 2000 to 2400 h period. When RU 486 was administered concomitantly with dexamethasone (1 mg) at 2400 h, dose-dependent blockade of the dexamethasone-induced cortisol suppression at 0900 h was found (r = 0.62, P less than 0.01); this blockade was partial after the 100-mg dose, but complete after the 400-mg dose. Plasma LPH and ACTH showed parallel variations. We conclude that RU 486 antagonizes the negative pituitary feedback of both the nocturnal endogenous cortisol rise and exogenously administered dexamethasone. These actions are consistent with an antiglucocorticoid activity of this compound in man.     

PATTERNS OF PLASMA CORTISOL AND ACTH CONCENTRATIONS IN PATIENTS WITH ADDISON''S DISEASE TREATED WITH CONVENTIONAL CORTICOSTEROID REPLACEMENT

Plasma cortisol and adrenocorticotrophin hormone (ACTH) profiles were estimated in twelve patients with Addison's disease following randomized oral administration of either cortisone acetate (25 mg) or hydrocortisone (20 mg) alternately, at 0900 h on consecutive days. Normal corticosteroid replacement therapy was discontinued from 1200 h on the day prior to the study period. In four patients elevated basal plasma ACTH concentrations were not suppressed to the limit of detection following the administration of either drug, and in three of these no suppression was found following the prolonged administration of pharmacological doses of dexamethasone. Diminished sensitivity of pituitary ACTH secretion to cortisol inhibition may result from chronic loss of negative feedback before and/or after diagnosis and treatment. In three patients elevated basal plasma ACTH concentrations were suppressed adequately during the administration of either drug, but in five, low basal ACTH concentrations following corticosteroid withdrawal suggested chronic inhibition of anterior pituitary corticotrophs by over-replacement with glucocorticoid. However, further study is necessary to determine whether the estimation of ACTH profiles is a more accurate reflection of the adequacy of corticosteroid replacement than the estimation of cortisol profiles alone, and whether this estimation leads to an improvement in patient management. Hydrocortisone (20 mg) achieved higher mean cortisol levels and lower mean ACTH levels than cortisone acetate (25 mg), but either drug may be suitable for glucocorticoid replacement provided the dose is tailored to the individual needs.