Is the plasma ACTH concentration a reliable parameter in the insulin tolerance test?

OBJECTIVE: The insulin tolerance test (ITT) is an established standardized test for the evaluation of the hypothalamic-pituitary-adrenal axis. While a peak cortisol value of >18 microg/dl is usually interpreted as a sufficient response to the ITT, the plasma ACTH response has not yet been standardized. METHODS: We evaluated retrospectively the peak plasma ACTH concentrations during 140 ITTs in 125 patients with suspected pituitary insufficiency and prospectively in 15 healthy subjects. RESULTS: All healthy subjects had a peak cortisol concentration >/=18 microg/dl; 32 of 125 tests in the patients showed an insufficient cortisol response (peak cortisol concentration <18 microg/dl). The peak stimulated ACTH concentration in patients with secondary adrenal insufficiency (SAI) was 49.2+/-37.2 pg/ml (mean+/-s.d.) vs 130.9+/-89.3 pg/ml in patients without SAI, and 110.9+/-55.4 pg/ml in normal subjects (P<0.001). There was a weak, but significantly positive correlation between the peak ACTH and peak cortisol concentrations (rho=0.446, P<0.001), but there was also a very wide spread of the values. Defining a cut-off value for the peak plasma ACTH concentration with a sufficient sensitivity and specificity to identify patients with an impaired hypothalamic-pituitary-adrenal (HPA) axis was not possible. A peak plasma ACTH <20 pg/ml as a cut-off value had a sensitivity of 25% and a specificity of 98% for SAI. A cut-off value of a peak plasma ACTH <140 pg/ml had a sensitivity of 97% but a low specificity of 39%. CONCLUSIONS: Although there is a significant positive correlation between the peak ACTH and the peak cortisol concentrations, we conclude that there is no additional benefit in determining the ACTH concentrations during an ITT. Because of the strong variations of the values, the peak ACTH concentration is a poor parameter for the evaluation of the HPA axis.     

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 (GABA)-ergic receptors, exerts a clear inhibitory effect on the activity of the hypothalamo-pituitary-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 benzodiazepines on the HPA response to CRH or AVP is contradictory. It has been shown that benzodiazepines 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 microg/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 microg 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 microg/l) were similar to those recorded after AVP (31.7+/-6.5 pg/ml and 164.8+/-18.0 microg/l); the cortisol response to 0.06 microg ACTH (190.4+/-11.8 microg/l) was similar to that recorded after hCRH and AVP but lower (p<0.01) than that after 250 microg ACTH (260.6+/-17.4 microg/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 microg/l) and AVP (119.4+/-14.5 microg/l), which, on the other hand, showed a trend toward decrease. The cortisol peaks after 0.06 microg ACTH were significantly reduced (p<0.02) by AL pre-treatment (115.0+/-7.7 microg/l) which, in turn, did not modify the cortisol response to the subsequent ACTH bolus (214.7+/-16.6 microg/l). The DHEA and aldosterone 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.     

The relationship of saline-induced changes in vasopressin secretion to basal and corticotropin-releasing hormone-stimulated adrenocorticotropin and cortisol secretion in man

To investigate the effect of endogenous arginine vasopressin (AVP) on ACTH secretion, normal subjects were given infusions of either hypertonic saline (HS) or isotonic saline (NS) combined with human corticotropin-releasing hormone (CRH) or placebo. Basal plasma AVP was 2.3 +/- 0.3 (+/- SE) pg/ml, did not change with NS treatment, and rose to 5.4 +/- 0.6 pg/ml during HS infusion (P less than 0.01). Both basal and CRH-stimulated plasma ACTH and cortisol concentrations increased during HS infusion. Peak plasma ACTH and cortisol levels were 11.4 +/- 1.5 pg/ml and 8.6 +/- 0.8 micrograms/dl, respectively, during the HS (plus placebo) infusion. During the NS (plus placebo) infusion, plasma ACTH and cortisol gradually declined to 6.8 +/- 0.5 pg/ml and 2.6 +/- 0.4 micrograms/dl. The timing of the rise in ACTH during the HS infusion paralleled the rise in AVP. When an iv dose of 1 microgram/kg CRH was administered during the saline infusions, peak plasma ACTH and cortisol levels were 27.7 +/- 6.3 pg/ml and 17.5 +/- 1.0 micrograms/dl, respectively, during the HS infusion and 15.6 +/- 1.7 pg/ml and 13.4 +/- 1.2 micrograms/dl during the NS infusion. When the areas under the hormone response curves were compared, CRH stimulated ACTH and cortisol secretion to a greater extent than did HS (P less than 0.05). The hormonal stimulation due to combined CRH and hypertonic saline was greater than that attributable to either factor alone (P less than 0.025), but was not different than the sum of the effects of the individual factors. These results indicate that increases in endogenous AVP produced by HS are associated with increases in both basal and CRH-stimulated ACTH and cortisol release. The effect of HS appears to be additive to but not consistently synergistic with the effect of CRH.     

Agouti-related protein stimulates the hypothalamic-pituitary-adrenal (HPA) axis and enhances the HPA response to interleukin-1 in the primate

alpha-MSH antagonizes many of the immune and neuroendocrine effects induced by inflammatory cytokines. Studies have shown that alpha-MSH attenuates the stimulatory effect of IL-1 on the hypothalamic-pituitary-adrenal (HPA) axis and plays a physiological role in limiting the HPA response to IL-1. Recently an alpha-MSH antagonist, agouti-related protein (AGRP), has been identified in the hypothalamus, which stimulates food intake by antagonizing the effects of alpha-MSH at specific melanocortin receptors. It is unknown whether AGRP can also modulate neuroendocrine responses to inflammatory cytokines. We have therefore examined the effects of AGRP on the HPA axis and on prolactin (PRL) at baseline and in response to stimulation by IL-1 beta in nine ovariectomized rhesus monkeys. In the first study, the effects of intracerebroventricular (i.c.v) infusion of 20 microg (n = 6) and 50 micro g (n = 4) of human AGRP (83-132)-NH(2) were compared with icv saline infusion. There was a significant stimulatory effect of 20 microg AGRP on cortisol release over time (P < 0.001). The area under the hormone response curve (AUC) for cortisol increased by 29% after 20 microg AGRP vs. saline; the AUC for ACTH increased by 166% (P = 0.028); the AUC for PRL increased by 108% (P = 0.046). There was a significant stimulatory effect of 50 microg AGRP on ACTH (P < 0.001), cortisol (P < 0.001), and PRL (P < 0.001) release over time. The AUC for ACTH after 50 microg AGRP increased by 98%; the AUC for cortisol increased by 37%; the AUC for PRL increased by 161%. The effects of AGRP on ACTH, cortisol, and PRL release were prevented by alpha-MSH infusion. In the second study, animals received icv either 50 ng of human IL-1 beta or 20 microg of AGRP followed by 50 ng IL-1 beta. AGRP significantly enhanced the ACTH (P < 0.05) response to IL-1 beta. The peak ACTH response to IL-1 beta alone was 124 +/- 55 pg/ml vs. 430 +/- 198 pg/ml after IL-1 beta plus AGRP; the peak cortisol response was 70 +/- 8.2 microg/dl vs. 77 +/- 6.2 microg/dl, but this was not significantly different. In conclusion, AGRP stimulated ACTH, cortisol, and PRL release in the monkey and enhanced the ACTH response to IL-1 beta. These studies suggest that, in addition to its known orexigenic effects, AGRP may play a role in neuroendocrine regulation and specifically that AGRP may interact with alpha-MSH to modulate neuroendocrine responses to inflammation.     

Effect of recombinant human growth hormone (GH) replacement on the hypothalamic-pituitary-adrenal axis in adult GH-deficient patients

The aim of the study was to evaluate the hypothalamus-pituitary-adrenal (HPA) axis in patients (nine males, three females; mean age +/- sem 51 +/- 2 yr) with adult-onset GH deficiency (GHD) due to surgically treated pituitary tumors with preserved HPA function and without evidence of tumor recurrence before and during recombinant human (rh) GH replacement therapy (duration 31 +/- 6 months). HPA function was assessed by urinary free cortisol and morning serum cortisol levels as well as cortisol responses to 1 mug ACTH test (n = 7 patients) or insulin tolerance test (n = 5 patients) before and during rhGH therapy, the cut-off for the diagnosis of hypoadrenalism being a cortisol peak less than 18 microg/dl (<500 nmol/liter) after stimulatory tests. Serum cortisol and urinary free cortisol levels were significantly lower on therapy than before [7.6 +/- 0.8 vs. 11.5 +/- 0.9 microg/dl (208 +/- 22 vs. 317 +/- 24 nmol/liter), P < 0.01, and 19.6 +/- 2.5 vs. 32.2 +/- 3.2 microg per 24 h (54 +/- 7 vs. 89 +/- 9 nmol per 24 h), P < 0.05, respectively], whereas no change in cortisol-binding globulin levels was observed. Cortisol peak after either ACTH test or insulin tolerance test was lower on rhGH therapy than before [15.9 +/- 1.5 vs. 20.2 +/- 1.1 microg/dl (437 +/- 43 vs. 557 +/- 31), P = 0.01, and 13.1 +/- 2.6 vs. 20.4 +/- 1.4 microg/dl (362 +/- 71 vs. 564 +/- 37 nmol/liter), P = 0.03, respectively]. Accordingly, central hypoadrenalism was detected in nine of 11 patients. In conclusion, low GH and IGF-I levels, likely enhancing the conversion of cortisone to cortisol, may mask a condition of central hypoadrenalism. Therefore, the reassessment of HPA function in GHD patients during rhGH therapy is mandatory.     

Estrogen modulates the hypothalamic-pituitary-adrenal and inflammatory cytokine responses to endotoxin in women

Endotoxin stimulates the release of the inflammatory cytokines interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF)-alpha, which are potent activators of the hypothalamic-pituitary-adrenal (HPA) axis. Recent studies in the rodent and in the primate have shown that the HPA responses to endotoxin and IL-1 were enhanced by gonadectomy and attenuated by estradiol (E2) replacement. In addition, there is some evidence, in the rodent, that estrogen modulates inflammatory cytokine responses to endotoxin. To determine whether estrogen has similar effects in humans, we studied the cytokine and HPA responses to a low dose of endotoxin (2--3 ng/kg) in six postmenopausal women with and without transdermal E2 (0.1 mg) replacement. Mean E2 levels were 7.3 +/- 0.8 pg/mL in the unreplaced subjects and increased to 102 +/- 13 pg/mL after estrogen replacement. Blood was sampled every 20 min for 1--2 h before, and for 7 h after, iv endotoxin administration. Endotoxin stimulated ACTH, cortisol, and cytokine release in women with and without E2 replacement. E2 significantly attenuated the release of ACTH (P < 0.0001) and of cortisol (P = 0.02). Mean ACTH levels peaked at 190 +/- 91 pg/mL in the E2-replaced group vs. 411 +/- 144 pg/mL in the unreplaced women, whereas the corresponding mean cortisol levels peaked at 27 +/- 2.9 microg/dL with E2 vs. 31 +/- 3.2 microg/dL without E2. Estrogen also attenuated the endotoxin-induced release of IL-6 (P = 0.02), IL-1 receptor antagonist (P = 0.003), and TNF-alpha (P = 0.04). Mean cytokine levels with and without E2 replacement peaked at 341 +/- 94 pg/mL vs. 936 +/- 620 pg/mL for IL-6, 82 +/- 14 ng/mL vs. 133 +/- 24 ng/mL for IL-1 receptor antagonist, and 77 +/- 46 pg/mL vs. 214 +/- 87 pg/mL for TNF-alpha, respectively. We conclude that inflammatory cytokine and HPA responses to a low dose of endotoxin are attenuated in postmenopausal women receiving E2 replacement. These data show, for the first time in the human, that a physiological dose of estrogen can restrain cytokine and neuroendocrine responses to an inflammatory challenge.     

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 microg/kg s.c. at -180 min) or placebo on the ACTH and cortisol responses to hCRH (human CRH; 2.0 microg/kg i.v. at 0 min) or hexarelin (HEX; 2.0 microg/kg i.v. 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 s.c. 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 microg/l and 149.4+/-12.3 vs 119.8+/-16.4 microg/l, respectively, p<0.04). RhIGF-I pretreatment did not modify the ACTH and cortisol responses to hCRH (46.0+/-13.8 pg/ml and 181.1+/-16.9 microg/l, respectively) as well as those to HEX (28.8+/-5.0 pg/ml and 144.1+/-16.2 microg/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 microg/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.     

Investigation of the hypothalamo-pituitary-adrenal axis and changes in the size of adrenal glands in acute brucellosis

The aim of the study was to investigate the hypothalamo-pituitary-adrenal (HPA) axis by ACTH stimulation test and the changes in adrenal size in acute brucellosis before and after therapy in a prospective study. Sixteen patients with acute brucellosis and 15 healthy subjects were included in the study during the last two years. Cortisol levels were assessed before, 30 and 60 minutes after ACTH (250 microg i.v.) injection and the size of the adrenals was measured in both groups. Mean basal cortisol levels in the patients before the therapy and after the therapy were 22.1 +/- 6.9 microg/dL and 11.3 +/- 6.0 microg/dL, respectively. The difference was statistically significant (p<0.001). There was also statistically significant difference for basal cortisol levels between the healthy subjects (12.2 +/- 4.6 microg/dL) and the patients before the therapy (p<0.001). Peak cortisol responses to ACTH were higher before the therapy in the patients with acute brucellosis (39.3 +/- 10.7 microg/dL) than in the healthy subjects (30.4 +/- 4.8 microg/dL, p = 0.014). However, there was no significant difference for peak cortisol levels in the patients before and after the therapy (32.7 +/- 8.0 microg/dL). Mean basal cortisol levels and peak cortisol responses to ACTH between the patients after the therapy and the healthy controls were similar. Both the maximum width of the adrenal glands and the width of the adrenal limbs were significantly greater before the therapy compared to healthy subjects and post-treatment period. We concluded that the HPA axis is activated and the adrenal glands are enlarged in acute brucellosis, which is reduced after appropriate therapy.     

The responses of plasma adrenocorticotropin and cortisol to corticotropin-releasing hormone (CRH) and cerebrospinal fluid immunoreactive CRH in anorexia nervosa patients

Pituitary-adrenocortical responses to the iv injection of 100 micrograms synthetic ovine corticotropin-releasing hormone (CRH) were studied in 13 patients with anorexia nervosa, and the concentrations of immunoreactive CRH in cerebrospinal fluid were measured in 7 of them. Mean basal levels of plasma ACTH and cortisol were 32 +/- 5 pg/ml (+/- SEM) and 21.1 +/- 1.5 micrograms/dl, respectively. The latter value was significantly higher than that in age-matched normal women (P less than 0.005). The mean increments of plasma ACTH and cortisol in response to CRH injection in those 13 patients were 21 +/- 5 pg/ml and 5.3 +/- 1.7 micrograms/dl, respectively, significantly lower than those in normal women (58 +/- 6 pg/ml and 15.3 +/- 7.7 micrograms/dl, respectively; P less than 0.005). When 4 patients were reexamined after weight gains of between 3 and 22 kg, their responses to the CRH injection increased. The mean concentration of immunoreactive CRH in the cerebrospinal fluid of seven patients was 30.8 +/- 3.9 pg/ml (+/- SEM), which was higher than the value of 18.4 +/- 1.1 pg/ml (P less than 0.005) in control subjects with cervical spondylosis. These findings suggest the possibility that hypersecretion of CRH may occur in patients with anorexia nervosa.     

Twenty-four hour 17-hydroxyprogesterone response to adrenocorticotropine in adrenal incidentalomas: augmented response after adrenalectomy in two patients

The current study aimed to investigate the midterm (24 hour) response of 17-hydroxyprogesterone (17-OHP) and dehydroepiandrosterone sulphate (DHEA-S) to synthetic high-dose adrenocorticotropin (ACTH) in adrenal incidentalomas (Al). Seventeen patients with Al and 40 age- and sex-matched controls received synthetic ACTH (tetracosactide, 1000 microg, IM). Plasma, 17-OHP and DHEA-S were collected in basal conditions and after 1, 4, 6, 8 and 24 hours. (HPA) axis was also evaluated using circadian serum cortisol, urinary free cortisol and over-night 2 mg dexamethasone suppression. Basal plasma 17-OHP levels did not differ among the groups. However, the increment in plasma 17-OHP in patients both in terms of peak [13.76 +/- 2.52, 4.77 +/- 0.30ng/ml, mean +/- S.E.M, p < 0.001] and area under the curve [190 +/- 46, 96.75 +/- 32 ng/ml/h, p < 0.001] were significantly higher than that of the controls. Stimulated 17OH-P levels never reached 9.1 ng/ml in controls. Sixty-five (11/17) % of the patients were found to have exaggerated response. Three of the patients were found to have subclinical Cushing's syndrome and interestingly, two augmented their 17-OHP response to ACTH after unilateral adrenalectomy and normalisation of their HPA axis. Basal DHEA-S levels of the patients were significantly lower [99.21 +/- 45, 230.18 +/- 34 microg/dl, p < 0.01] and stayed persistently lower than that of the controls. Evidence of a heterozygous 21 hydroxylase deficiency, as indicated by the exaggerated 17-OHP response to ACTH, has been widely reported in Al patients. However, to our knowledge to date there is no report on augmented 17-OHP response to ACTH after adrenalectomy. Possible reasons for the augmentation were discussed.     

Effects of the opiate agonist loperamide on pituitary-adrenal function in patients with suspected hypercortisolism

In the present work the possible use of loperamide, an opiate agonist, in the dynamic evaluation of patients with suspected hypercortisolism was investigated. The effects of loperamide on plasma ACTH and cortisol levels were evaluated in normal subjects and in 58 patients with suspected Cushing's syndrome. The results were compared to those obtained after the overnight dexamethasone suppression test. In normal subjects plasma ACTH and cortisol levels were significantly (p less than 0.005) suppressed by both loperamide (16 mg po) and dexamethasone (1 mg po). In 17 patients, in whom the diagnosis of Cushing's syndrome was confirmed by subsequent investigations, neither loperamide or dexamethasone inhibited cortisol (from a baseline of 606 +/- 55 nmol/L) to a nadir of 502 +/- 43 nmol/L and 539 +/- 50 nmol/L, respectively) and ACTH concentration (from a basal level of 70.1 +/- 11.8 pg/ml to a nadir of 46.0 +/- 8.6 pg/ml and 54.3 +/- 7.5 pg/ml, respectively). In 34 patients, in whom the suspect of hypercortisolism was ruled out, either loperamide or dexamethasone suppressed the pituitary-adrenal axis: cortisol and ACTH levels significantly fell from 417 +/- 24 nmol/L and 28.3 +/- 3.5 pg/ml to 60 +/- 6 nmol/L and 14.4 +/- 1.4 pg/ml after loperamide and to 26 +/- 4 nmol and 16.4 +/- 1.7 pg/ml after dexamethasone. In 7 patients discordant responses were observed. In 3 patients treated with antiepileptic drugs ACTH and cortisol levels were inhibited by loperamide, but not by dexamethasone.(ABSTRACT TRUNCATED AT 250 WORDS)     

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 secretagogue (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 microg/kg i.v.) and/or hCRH (2.0 microg/kg i.v.) 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 microg/l, respectively; p<0.02). In CS, the ACTH and F responses to HEX, evaluated as deltaAUC (mean+/-SE: 128.7+/-39.2 pg x min/ml and 328.5+/-93.2 microg x min/l, respectively) were lower, though not significantly, than those after hCRH (375.8+/-128.4 pg x min/ml and 1714.2+/-598.0 microg x 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 x min/ml) and F secretion (3452.9+/-648.6 microg x 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 x min/ml and 10955.9+/-6184.6 microg x 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 x min/ml and 4832.7+/-2146.5 microg x 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 x min/ml) but not on F (10985.4+/-3900.8 microg x 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.     

A case of congenital hypopituitarism: difficulty in the diagnosis of ACTH deficiency due to high serum cortisol levels from a hypothyroid state.

A three-month-old boy presented congenital hypopituitarism in which the hypothyroid state masked ACTH deficiency. Multiple anterior pituitary hormone deficiencies, including ACTH, were finally confirmed. High basal serum cortisol levels (up to 45.1 microg/dl) were observed during a stressful episode before L-thyroxine replacement therapy was started. Decreased morning serum cortisol levels (5.0 microg/dl or below) were observed on the sixth day of L-thyroxine replacement therapy despite mild hypoglycemia (lowest serum glucose level of 50 mg/dl). ACTH deficiency was then confirmed by insulin-induced hypoglycemia test (peak serum cortisol level of 4.9 microg/dl). The present findings showed that serum cortisol levels can be high during a stressful episode in an infant with ACTH deficiency and a coexisting hypothyroid state. Thus, the diagnostic evaluation of adrenal function soon after L-thyroxine replacement therapy is important in order to verify a possible subclinical ACTH deficiency, even in the presence of high serum cortisol levels before L-thyroxine replacement therapy.     

Ovine corticotropin-releasing hormone stimulation test in normal children

We administered ovine corticotropin-releasing hormone (CRH) as a bolus iv injection (1 microgram/kg) to 21 normal boys and girls, aged 6-15 yr. CRH stimulated release of immunoreactive ACTH and cortisol in all children. The peak plasma ACTH and cortisol levels after CRH were 15.7 +/- 9.4 (SD) pg/ml and 14.3 +/- 3.6 micrograms/dl, respectively, in the girls, and 20.7 +/- 9.7 pg/ml and 16.6 +/- 3.3 micrograms/dl, respectively, in the boys. Plasma ACTH and cortisol responsiveness to CRH did not differ between girls or boys, or between children and adults. Cortisol-binding globulin concentrations in plasma did not change with age. We conclude that CRH provides a safe means of stimulating the pituitary-adrenal axis in children.     

Stimulation of the Hypothalamic-Pituitary-Adrenal Axis with the Opioid Antagonist Nalmefene

Nalmefene Stimulation of the HPA Axis. Background: The Hypothalamic-pituitary-adrenal (HPA) axis plays a vital role in the body's response to stress. The traditional gold standard for evaluating the HPA axis, the insulin hypoglycemia test (IHT), has several known limitations, and a second test, the standard ACTH stimulation test, can detect severe deficiencies of cortisol, but often misses mild or early cases. Therefore, a better test for the evaluation of the HPA axis is needed. This study evaluated the opiate antagonist nalmefene as a stimulation test of the HPA axis. Methods: 25 healthy subjects were studied, 9 women and 16 men, mean age 30.4 yr. (range 21–55), and mean BMI 24.1 kg/m² (range 18.6–34.2). Subjects received one of 3 doses of intravenously administered nalmefene: 2 mg (n = 6), 6 mg (n = 12), or 10 mg (n = 7). Serum cortisol and plasma ACTH were measured before and serially over two hours after the administration of nalmefene. Results: ACTH and cortisol levels rose significantly and similarly after the 10 mg dose and the 6 mg dose. After the 10 mg dose, mean peak ACTH was 82.4 ± 22.6 pg/ml and mean peak cortisol was 25.2 ± 1.8 μg/dl. After the 6 mg dose, mean peak ACTH was 70.3 ± 7.7 pg/ml and mean peak cortisol was 24.7 ± 1.7 μg/dl. Cortisol levels rose above 18 μg/dl in all subjects receiving 10 mg of nalmefene, and in all but two of the subjects receiving 6 mg of nalmefene. Side effects to nalmefene were of greater duration and intensity in the subjects receiving 10 mg of nalmefene vs. those receiving 6 or 2 mg. These included most notably fatigue, lightheadedness, nausea and vomiting. Conclusions: Of the nalmefene doses we studied, 6 mg achieved the best combination of stimulation of ACTH and cortisol and fewest side effects. If further studies show a concordance between nalmefene and IHT, nalmefene testing could be used to assess the HPA axis in patients at risk for dysfunction of this axis.     

The pituitary-adrenocortical system of neonatal rats is responsive to stress throughout development in a time-dependent and stressor-specific fashion.

The responsiveness of the neonatal hypothalamus-pituitary-adrenal (HPA) axis to stress has been thought to be impaired or diminished during the first 2 weeks of life. Although we previously found full responsiveness of the hypothalamus-pituitary unit to adrenalectomy in young rats [days (d) 5-10], we failed to measure a significant increase in ACTH 10 min after ether administration until d14 of age. These studies were, therefore, designed to test the functional activation of the HPA axis after a single or repeated exposures to stress. Both qualitative (time-course, stressor-specific, circadian) and quantitative changes in the ACTH and corticosterone (B) responses to various stressors were tested during the first 10 days of life. Exposure to 3 min of ether vapor increased ACTH and B secretion (P less than 0.05-0.01) in 1-, 5-, and 10-d-old rats, with an increasing amplitude of both ACTH and B responses as a function of age. Peak secretion of ACTH occurred 5 min after the onset of stress (122 +/- 3.8 to 359 +/- 54 pg/ml on d1-10), while the time of maximal B increased as a function of age. Other stressors, such as maternal separation (12 h), cold (4 C; 60 min), or histamine injection (4 mg/kg BW, ip), provoked significant and stressor-specific ACTH and B responses in 10-d old rats. Histamine administration increased ACTH secretion above that of vehicle-injected rats, with a peak of secretion 15 min after drug injection (272 +/- 29 vs. 127 +/- 8 pg/ml; P less than 0.01). Histamine-induced B secretion peaked at 60 min (3.7 +/- 0.5 micrograms/dl). In contrast to early responses observed after ether, separation, or histamine stress, cold stress in 10-d-old pups caused a large ACTH and B release 4 h after the onset of cold compared to that in maternally deprived pups [ACTH: cold, 457 +/- 61 pg/ml; separated, 150 +/- 14 (P less than 0.01); B: cold, 3.3 +/- 0.4 micrograms/dl; separated, 1.8 +/- 0.2 (P less than 0.05)]. We did not detect morning-evening (AM-PM) differences in either the pattern or the magnitude of the ACTH or B response to maternal separation or cold stress. Suppression of cold-induced ACTH release by B injection (1 mg/kg BW) 2 h before stress was observed until 4 h after stress in the AM and PM, whereas when given after cold, B was less effective in the PM than in the AM at preventing the rise in ACTH levels observed at 4 h.(ABSTRACT TRUNCATED AT 400 WORDS)     

Differential effects of estradiol on the adrenocorticotropin responses to interleukin-6 and interleukin-1 in the monkey.

Endotoxin and the inflammatory cytokines interleukin (IL)-1 and IL-6 are potent activators of the hypothalamic-pituitary-adrenal (HPA) axis. Although estradiol (E(2)) has been shown to enhance the HPA response to certain types of stress, previous studies in the rodent have shown that HPA responses to endotoxin and to IL-1 were enhanced by ovariectomy and attenuated by E(2). The mechanisms underlying these observations are unclear, but there is evidence that E(2) may have direct inhibitory effects on IL-6 synthesis and release. Because endotoxin and IL-1 both stimulate IL-6, it is possible that the E(2)-induced suppression of the HPA response to endotoxin and IL-1 results from decreased IL-6 release. We have therefore examined the ACTH response to IL-6 and IL-1beta in six ovariectomized rhesus monkeys with and without 3 weeks of E(2) replacement. In the first study, plasma ACTH levels peaked at 60 min after iv injection of 6 microg recombinant human IL-6. Both the ACTH response, over time, and the area under the ACTH response curve were significantly higher in the E(2)-treated animals (P < 0.05). The peak ACTH level was 66 +/- 16 pg/ml without E(2) vs. 161 +/- 69 pg/ml with E(2). In the second study, iv infusion of recombinant human IL-1beta (400 ng) produced plasma IL-6 levels comparable with those seen after IL-6 injection in the first study. In the IL-1 study, however, there was a significant attenuation of the ACTH response, over time, in the E(2)-treated animals (P < 0.001); the peak ACTH level was 83 +/- 34 pg/ml vs. 13 +/- 4.4 pg/ml after E(2). The IL-6 response was similarly attenuated (P < 0.001); the peak IL-6 level was 614 +/- 168 pg/ml vs. 277 +/- 53 pg/ml after E(2) treatment. Our results demonstrate that physiological levels of E(2) enhance the ACTH response to IL-6 but attenuate the ACTH response to IL-1. The attenuated ACTH response to IL-1 was accompanied by a blunted IL-6 response. Our results suggest that the blunted HPA response to IL-1 can be explained, at least in part, by E(2)-induced alterations in IL-6 release. It remains to be determined whether E(2) affects other inflammatory mediators that also participate in this process.     

Plasma adrenocorticotropin, cortisol, and aldosterone responses to corticotropin-releasing factor: modulatory effect of basal cortisol levels

Two hundred micrograms of corticotropin-releasing factor (CRF) were administered as an iv bolus injection to 10 normal subjects (5 men and 5 women). Mean plasma ACTH levels rose significantly (P less than 0.0005, by Friedman's nonparametric analysis of variance) from a basal value of 27 +/- 5 pg/ml (mean +/- SEM) to a peak value of 63 +/- 8 pg/ml 30 min after CRF administration. This ACTH response was followed by a rise in plasma mean cortisol levels (P less than 0.0005, by Friedman's test) from a baseline value of 12.3 +/- 1.4 micrograms/100 ml to a peak value of 21.0 +/- 0.7 micrograms/100 ml 60 min after CRF and a rise in mean plasma aldosterone levels from a basal value of 13 +/- 2 ng/100 ml to a peak value of 23 +/- 2 ng/100 ml. There was no significant difference between men and women in the responsiveness of ACTH, cortisol, and aldosterone to CRF administration. The individual basal cortisol levels were highly significantly and negatively correlated with the areas under the individual ACTH curves (r = -0.76; P less than 0.005, by Pearson's correlation test) and cortisol curves (r = -0.91; P less than 0.001, by Pearson's test). These data suggest a modulatory effect of physiological cortisol levels on the response of the pituitary-adrenal axis to CRF.     

Normal opioid tone and hypothalamic-pituitary-adrenal axis function in chronic fatigue syndrome despite marked functional impairment

OBJECTIVE: To determine whether the functional impairment seen in chronic fatigue syndrome (CFS) is associated with reduced levels of central opioids and/or deficiency of the hypothalamic-pituitary-adrenal (HPA) axis. DESIGN: Single-blinded case-control study measuring functional and psychological status, basal hormonal parameters and ACTH/cortisol response to naloxone and ovine corticotrophin-releasing hormone (oCRH) vs. placebo in people with CFS and healthy controls. PATIENTS: Twelve people with CFS and 11 age-matched controls. MEASUREMENTS: Hormonal parameters: basal levels of 09:00 h plasma cortisol, dehydroepiandrosterone sulfate (DHEAS) and IGF-1. 24-h urinary free cortisol. Plasma ACTH and cortisol response to naloxone 125 microg/kg, oCRH 1 microg/kg and placebo (normal saline). Psychological parameters: SF-36, Hamilton Depression Score, Hospital Anxiety and Depression Scale and Fatigue Scale. RESULTS: There were highly significant differences between the CFS subjects and the controls with respect to the measures of fatigue and physical functioning. However, there were no differences in basal levels of 09:00 h cortisol (367 +/- 37 vs. 331 +/- 39 nmol/l, P = 0.51), DHEAS (4.2 +/- 0.6 vs. 4.0 +/- 0.5 micromol/l, P = 0.81), 24-h urinary free cortisol (182 +/- 27 vs. 178 +/- 21 nmol/24 h, P = 0.91) or IGF-1 (145 +/- 19 vs. 130 +/- 11 microg/l, P = 0.52) between the CFS group and controls, respectively. There was also no difference between the groups with respect to the ACTH and cortisol response to either oCRH or naloxone. CONCLUSIONS: Our data do not support an aetiological role for deficiency in central opioids or the HPA axis in the symptoms of CFS.     

Sodium salicylate augments the plasma adrenocorticotropin and cortisol responses to insulin hypoglycemia in man

To test the hypothesis that prostaglandins attenuate neuroendocrine responses to changes in circulating glucose levels in man, we studied the effects of sodium salicylate (SS), a prostaglandin synthesis inhibitor, on the plasma ACTH and cortisol responses to insulin hypoglycemia. Six normal men were given insulin (0.05 U/kg, iv) on 2 different days during the infusion of either SS (40 mg/min) or saline. Compared to the saline control, SS had no significant effect on either the rate of fall of plasma glucose after insulin or the glucose nadir (mean +/- SEM, 33 +/- 3 vs. 36 +/- 3 mg/dl; P = NS). Peak ACTH levels after insulin were higher during SS compared to those during saline in all six subjects (316 +/- 95 vs. 102 +/- 26 pg/ml; P less than 0.05), and SS had a clear effect to increase both the overall ACTH response (F = 21.3; P less than 0.01, by analysis of variance) and the plasma cortisol response (F = 6.72; P less than 0.05, by analysis of variance). The most striking example of this effect of SS occurred in one subject whose peak plasma ACTH was only 44 pg/ml during saline but reached 750 pg/ml during SS despite an identical fall of plasma glucose to 42 mg/dl. Augmentation of the ACTH and cortisol responses to insulin hypoglycemia may be the result of an alteration by SS of recognition of glucose levels by glucose-sensitive cells of the brain, and effect which could be due to the inhibition of prostaglandin synthesis.