Hypothalamus-pituitary-adrenal hyperactivity in human aging is partially refractory to stimulation by mineralocorticoid receptor blockade

CONTEXT: The hypothalamus-pituitary-adrenal (HPA) axis is mainly regulated by CRH, arginine vasopressin, and glucocorticoid feedback. Hippocampal mineralocorticoid receptors mediate proactive glucocorticoid feedback and mineralocorticoid antagonists, accordingly, stimulate HPA axis. Age-related HPA hyperactivity reflects impaired glucocorticoid feedback at the suprapituitary level. DESIGN: ACTH, cortisol, and dehydroepiandrosterone (DHEA) secretion were studied in eight healthy elderly (75.1 +/- 3.2 yr) and eight young (25.0 +/- 4.6 yr) subjects during placebo or canrenoate (CAN) administration (200 mg i.v. bolus followed by 200 mg infused over 4 h). RESULTS: During placebo administration, ACTH and cortisol areas under the curve (AUCs) in elderly subjects were higher than in young subjects (P < or = 0.01); conversely, DHEA AUCs in elderly subjects were lower than in young subjects (P = 0.002). CAN increased ACTH, cortisol, and DHEA levels in both groups. In young subjects, ACTH, cortisol, and DHEA levels at the end of CAN infusion were higher (P < or = 0.05) than after placebo. In elderly subjects, at the end of CAN infusion, ACTH, cortisol, and DHEA levels were higher (P = 0.01) than after placebo. Under CAN, ACTH and cortisol AUCs were persistently higher (P < or = 0.01) and DHEA AUCs lower (P = 0.006) in elderly than in young subjects. Cortisol AUCs after CAN in young subjects did not become significantly different from those in elderly subjects after placebo. CONCLUSIONS: 1) Evening-time ACTH and cortisol secretion in elderly subjects is higher than in young subjects; 2) ACTH and cortisol secretion in elderly subjects is enhanced by CAN but less than that in young subjects; and 3) DHEA hyposecretion in elderly subjects is partially restored by mineralocorticoid antagonism. Age-related variations of HPA activity may be determined by some derangement in mineralocorticoid receptors function at the hippocampal level.     

Disrupted cortisol-ACTH relationships in elderly women given corticotrophin-releasing hormone two weeks after proximal femur fracture

OBJECTIVE: In elderly women with hip fractures plasma cortisol is persistently higher than in healthy elderly women, possibly causing undesirable catabolic effects. A lack of corresponding changes in plasma ACTH or in the cortisol response to exogenous ACTH has prompted us to study cortisol-ACTH relationships after giving corticotrophin-releasing hormone (CRH) to such subjects. SUBJECTS: Seventeen women aged 70-90 years who had sustained a hip fracture about two weeks previously were compared with 19 healthy women aged 68-85 years. MEASUREMENTS: 100 microg CRH was injected into each subject and ACTH and cortisol concentrations were measured at intervals for 90 minutes beforehand and 180 minutes afterwards. The concentrations of vasopressin and various cytokines and related peptides were also measured during the baseline period. RESULTS: Under baseline conditions plasma cortisol was higher and plasma ACTH lower in the injured patients than in the healthy subjects. The patients showed smaller incremental ACTH and cortisol responses to CRF but because of the higher baseline value the peak cortisol concentration was enhanced. A strong correlation between the cortisol and ACTH responses in the healthy subjects was completely lost in the patients and the slope of the ACTH-cortisol dose-response relationship varied greatly between individuals, with no overall increase. The concentrations of vasopressin, interleukin-1 receptor antagonist and soluble tumour necrosis factor receptors were higher in the patients but did not correlate with the responses to CRH. CONCLUSIONS: The results are not consistent with increased sensitivity to ACTH and suggest an independent stimulus to the adrenals of hip-fracture patients. Its identity is unknown as the non-ACTH stimuli proposed hitherto are reported to enhance sensitivity to ACTH.     

Stress and dementia: the role of the hypothalamicpituitary-adrenal axis

Hippocampus plays a crucial role in learning and memory and, in spite of its remarkable plasticity, it is also particularly sensitive to stress hormones due to its high concentration of corticosteroid receptors. Indeed, adrenal steroids modulate hippocampal plasticity, acting on excitability and long term potentiation or depression. By a chronobiological approach, we studied the cortisol and DHEAS secretion in clinically healthy old subjects and in age-matched demented patients, including both the degenerative and the vascular type. When compared to young controls, both clinically healthy elderly subjects and demented patients, particularly those with AD, had significantly higher cortisol levels at night time, i.e. at the moment of the maximal sensitivity of HPA axis to stimulatory or inhibitory inputs. At the same time, a clear age- and disease-dependent reduction of DHEAS secretion was found. Thus the cortisol to DHEAS molar ratio was significantly higher in healthy old subjects, and even more in demented patients, when compared to young controls, and significantly linked to both age and cognitive impairment. Finally, the quantitative and qualitative changes of the adrenal secretory pattern were significantly correlated with the decline of hippocampal volumes, measured by MRI. In conclusion, several lines of evidence deal with a pathogenetic role of stress hormones in the occurrence and progression of cognitive disorders in elderly subjects. The consequent hippocampal neuronal impairment may in turn be responsible for the continuous activation of HPA axis and the increased hypothalamic expression of vasopressin and corticotropin releasing hormone.     

Pineal and pituitary-adrenocortical function in physiological aging and in senile dementia

The simultaneous evaluation of the circadian rhythm of plasma melatonin and ACTH and of serum cortisol and DHEAS represents a clinically reliable tool to appreciate the neuroendocrine changes occurring in physiological and pathological brain aging.

A selective impairment of the nocturnal melatonin secretion has been observed in elderly subjects, being significantly related either to the age or to the severity of dementia. A significant increase of serum cortisol levels during evening- and night-times was found in elderly subjects, particularly if demented, when compared to young controls. Besides, both the circadian amplitude of cortisol rhythm and the nocturnal cortisol increase were significantly reduced in relation either to age or to cognitive impairment. By comparison to vascular dementia, patients with Alzheimer's disease exhibited the highest cortisol concentrations throughout the 24 h. The sensitivity of the hypothalamic-pituitary-adrenal axis to the steroid feedback was significantly impaired in old subjects and particularly in the demented ones. The serum DHEAS levels were significantly lower in elderly subjects and even more in demented patients than in young controls. Consequently, a significant increase of the cortisol/DHEAS molar ratio was evident when going from young controls to healthy elderly subjects and to demented patients.

In conclusion, the aging process affects many neuroendocrine functions resulting in subtle but clinically relevant consequences; the occurrence of senile dementia seems to play an additive role.     

Isolated adrenocorticotropic hormone deficiency secondary to hypothalamic deficit of corticotropin releasing hormone.

A 42-year-old man and a 51-year-old woman with a positive history of weakness and gastrointestinal complaints were shown to have low basal plasma cortisol and ACTH levels, and low daily urinary excretion of free cortisol. An empty sella was found in patient no. 1, while patient no. 2 was hypothyroid. Both patients showed a normal plasma cortisol response to ACTH and an increment in plasma ACTH and lipotropin levels after ovine CRH (oCRH), lysine vasopressin (LVP) and oCRH-LVP stimulation tests. These studies clearly report an isolated idiopathic ACTH deficiency due to a deficit in CRH in two adult subjects.     

A visual recognition memory test for the assessment of cognitive function in aging and dementia

Young, non-demented elderly, and elderly demented subjects were administered a computerized visual recognition memory task. In the task, subjects were instructed to point out the new object from a group of objects whose number was progressively incremented. The test was subject-paced and made use of face-valid stimulus materials; it is closely comparable to tests developed for memory assessment in non-human primates that are sensitive to the effects of hippocampal ablation. The present task was found to elicit significant differences in performance between young and non-demented aged subjects, between the non-demented and demented elderly, and between demented subjects in the early and more advanced stages of senile dementia of the Alzheimer type (SDAT). In a discriminant analysis, the visual recognition memory test scores correctly classified 72.6% of the aged subjects and early SDAT patients. No significant difference in task performance was found between SDAT patients and demented patients with a significant cerebrovascular etiological component. Thus, although the task does not appear to be suitable for diagnostic purposes it would be useful for the assessment of treatment effects upon age-related cognitive dysfunction.     

Mineralocorticoid receptor blockade by canrenoate increases both spontaneous and stimulated adrenal function in humans.

Animal studies indicate that mineralocorticoid receptors (MR) in the hippocampus play a major role in the glucocorticoid feedback control of the hypothalamo-pituitary-adrenal (HPA) axis. Specifically, MR mediate the proactive feedback of glucocorticoids in the maintenance of basal HPA activity. The stimulatory effect of intracerebroventricular and intrahippocampal MR blockade on the HPA axis in animals has been clearly shown, whereas the effect of systemic administration of mineralocorticoid antagonists in humans is still contradictory. To clarify this point, in seven normal young women (aged 25-32 yr; body mass index, 19.0-23.0 kg/m(2)) we studied the effects of canrenoate (CAN; 200 mg as iv bolus at 2000 h, followed by 200 mg infused in 500 mL saline over 4 h up to 2400 h) or placebo (saline, 1.0 mL as iv bolus at 2000 h, followed by 500 mL over 4 h up to 2400 h) on the spontaneous ACTH, cortisol, dehydroepiandrosterone (DHEA) and aldosterone secretion as well as on the ACTH, cortisol, and DHEA responses to human CRH (2.0 microg/kg as iv bolus at 2200 h) or arginine vasopressin (AVP; 0.17 U/kg as im bolus at 2200 h). Blood samples were taken every 15 min from 2000-2400 h. During placebo, spontaneous ACTH and cortisol levels showed progressive decreases (P < 0.05) from 2000-2400 h (baseline vs. nadir, mean +/- SEM, 2.0 +/- 0.3 vs. 1.4 +/- 0.2 pmol/L and 115.1 +/- 23.7 vs. 63.5 +/- 24.3 nmol/L), whereas DHEA and aldosterone levels did not change. CRH induced clear increases in ACTH, cortisol, and DHEA levels (peaks, mean +/- SEM, 7.1 +/- 1.1 vs. 1.6 +/- 0.2 pmol/L, 322.9 +/- 19.5 vs. 92.8 +/- 24.5 nmol/L, and 44.2 +/- 2.7 vs. 20.0 +/- 3.0 nmol/L; P < 0.05). Similarly, AVP elicited significant increases in ACTH, cortisol, and DHEA levels (3.8 +/- 0.3 vs. 1.5 +/- 0.1 pmol/L, 211.9 +/- 27.2 vs. 67.7 +/- 9.7 nmol/L, and 51.6 +/- 4.0 vs. 16.3 +/- 2.0 nmol/L; P < 0.05). During CAN treatment, ACTH, cortisol, and DHEA levels showed progressive rises, which begun at approximately 60 min and peaked between 2300 and 2400 h (ACTH, 3.4 +/- 0.4 vs. 1.1 +/- 0.3 pmol/L; cortisol, 314.5 +/- 49.6 vs. 123.3 +/- 13.2 nmol/L; DHEA, 52.0 +/- 8.8 vs. 21.0 +/- 2.3 nmol/L; P < 0.05 vs. baseline as well as vs. the same time points during placebo). Aldosterone secretion was not modified by CAN. The ACTH, cortisol, and DHEA responses to human CRH were enhanced by CAN (10.0 +/- 1.7 pmol/L, 462.2 +/- 36.9 nmol/L, and 66.3 +/- 8.8 nmol/L), although statistical significance (P < 0.05) was obtained for cortisol and DHEA only. Also the ACTH, cortisol and DHEA responses to AVP were amplified by CAN (8.0 +/- 2.6 pmol/L, 324.0 +/- 34.8 nmol/L, and 77.8 +/- 4.0 nmol/L); again, statistical significance (P < 0.05) was obtained for cortisol and DHEA only. In conclusion, our study shows that the blockade of MR by CAN significantly enhances the activity of the HPA axis in humans, indicating a physiological role for MR in its control. These results also suggest that the stimulatory effect of CAN on HPA axis is mediated by concomitant modulation of CRH and AVP release.     

Interactions of CRH, AVP and cortisol in the secretion of ACTH from perifused equine anterior pituitary cells: "permissive" roles for cortisol and CRH

To further elucidate the interaction of CRH, AVP and cortisol in the control of ACTH secretion, we used an in vitro perifusion model with dispersed equine anterior pituitary cells. To approximate the in vivo milieu in the horse, CRH was perifused continuously (at 0, 2 and 20 pmol/L) and 5-min pulses of AVP (0, 1, 3 and 10 nmol/L) were given every 30 min in the presence of 0 or 100 nmol/L cortisol. Total (baseline + incremental) ACTH secretion increased as both the CRH (p<0.001) and the AVP (p<0.001) concentration increased and interaction between CRH and AVP was significant (p=0.042). Cortisol reduced total ACTH secretion in the presence of 2 pmol CRH/L (p=0.001) but not 0 or 20 pmol CRH/L. For incremental ACTH there was interaction between CRH and AVP (p<0.0001), with increased secretion at higher concentrations, and no significant main effect of cortisol. There was significant (p=0.001) interaction between cortisol and CRH, with cortisol attenuating ACTH release at 0 pmol CRH/L (p=0.008), having no effect at 2 pmol CRH/L and potentiating it at 20 pmol CRH/L (p=0.026). We conclude that (1) CRH at high physiological levels has a "permissive" role in preventing the cortisol inhibition of the ACTH response to AVP, and (2) basal cortisol levels have a "permissive" action in priming the HPA axis for maximal responsiveness to stimulated levels of CRH and AVP.     

Effect of deltorphin on pituitary-adrenal response to insulin-induced hypoglycemia and ovine corticotropin-releasing hormone in healthy man.

To determine the role of delta-opioid receptors in the modulation of hypothalamic-pituitary-adrenal activity, we studied in normal subjects the effect of the highly selective delta-opioid receptor agonist deltorphin (DT) on the secretion of ACTH, cortisol, and arginine vasopressin in response to insulin-induced hypoglycemia. In an attempt to clarify the site of opiate modulation of ACTH secretion, we also studied in normal subjects the effect of DT on the ACTH response to ovine CRH-41. DT blunted the ACTH, cortisol, and arginine vasopressin responses to insulin-induced hypoglycemia, whereas it had no effect on the ACTH and cortisol responses to CRH. We conclude that DT-induced activation of delta-opioid receptors exerts an inhibitory influence on hypoglycemia-stimulated ACTH secretion. Based on the lack of an effect of DT on the ACTH response to CRH, we postulate that DT may modulate the secretion of ACTH through suprapituitary mechanisms.     

Free fatty acids exert an inhibitory effect on adrenocorticotropin and cortisol secretion in humans

Free fatty acid (FFA) administration stimulates the hypothalamic-pituitary-adrenal (HPA) axis in rats, suggesting that the HPA axis and lipolysis may be linked by a positive-feedback loop. To clarify the influence of FFA on the HPA axis in humans, we studied the effect of lipid load on both basal and stimulated ACTH and cortisol secretion in normal subjects. In six young female volunteers [(mean +/- SEM) age, 24.4 +/- 2.1 yr; body mass index, 23.1 +/- 1.2 kg/m(2)), ACTH, cortisol, FFA, glucose, and insulin levels were measured every 30 min for 330 min during the following procedures: 1) i.v. saline infusion (from 0 to 330 min); 2) i.v. FFA infusion (Intralipid 10%, from 0 to 210 min) followed by saline infusion (from 210 to 330 min); 3) human CRH (hCRH) administration (2 microg/kg i.v. at 90 min) during saline infusion (from 0 to 330 min); and 4) hCRH administration during FFA infusion (Intralipid 10%, from 0 to 210 min, followed by saline infusion from 210 to 330 min). During saline infusion, ACTH and cortisol levels progressively declined. Lipid-heparin emulsion (LHE) infusion strikingly increased circulating FFA levels and, simultaneously, amplified the ACTH and cortisol decrease (P < 0.05). After LHE withdrawal, FFA decrease was associated with an increase (P < 0.05) in ACTH and cortisol levels (restored to baseline values within 60 min). The ACTH and cortisol responses to hCRH, however, were unaffected by LHE that, concomitantly, induced an increase (P < 0.05) in glucose but not in insulin levels. This study shows that an LHE-induced increase in FFA levels has an inhibitory effect on spontaneous ACTH and cortisol secretion in humans. Lipid load, however, does not affect the ACTH and cortisol responses to hCRH; this evidence would indicate that the negative influence of FFA on the HPA axis in humans takes place at the suprapituitary level.     

Fetal programming of the hypothalamic-pituitary-adrenal (HPA) axis: low birth weight and central HPA regulation

Fetal programming of the hypothalamic-pituitary-adrenal (HPA) axis has been proposed as an intermediary in the association between reduced fetal growth and adult cardiovascular and metabolic diseases. Previous studies have shown that small size at birth is associated with increased fasting plasma cortisol and adrenal responsiveness to ACTH stimulation. We have extended these studies by evaluating the salivary cortisol response to awakening and plasma ACTH and cortisol responses to CRH stimulation and a dexamethasone-suppressed CRH (DEX/CRH) test in a group of low birth weight [LBW; <3.18 kg (7 lb), n = 58] and high birth weight [>3.86 kg (8.5 lb), n = 65] men aged 60-69 yr. Despite no difference in basal pituitary-adrenal activity or in their ACTH and cortisol responses to CRH, LBW men had significantly lower pituitary-adrenal responses in the DEX/CRH test. Although these findings do not explain the HPA abnormalities associated with LBW in previous studies, they provide further evidence of dysregulation of the HPA axis in people who were small at birth.     

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.     

The combined dexamethasone-suppression/CRH-stimulation test in alcoholics during and after acute withdrawal

BACKGROUND: Chronic alcoholism is often accompanied by disturbances of the hypothalamic-pituitary-adrenal (HPA) system. Patients with alcoholism frequently show nonsuppression in the dexamethasone (Dex) suppression test and also a blunted increase of adrenocorticotropin (ACTH) after injection of corticotropin-releasing hormone (hCRH). However, the underlying mechanisms have not been fully elucidated. The combined Dex/CRH test (pretreatment with 1.5 mg dexamethasone at 2300 hr, injection of 100 microg hCRH at 1500 hr the next day) has been established as a more sensitive tool to investigate HPA system regulation in depressed patients. METHODS: We studied the effect of the combined Dex/CRH test in 19 alcoholic inpatients (9 male, 10 female) during and after withdrawal along with 19 healthy controls. RESULTS: Compared to normal controls, patients showed a severely dysregulated HPA system during withdrawal, with significantly elevated cortisol and ACTH response to hCRH after pretreatment with dexamethasone. After completed withdrawal, cortisol levels after injection of hCRH were almost normalized while ACTH values were partially lower in patients, compared to controls. CONCLUSIONS: We conclude that the HPA system is severely disturbed during alcohol withdrawal, possibly reflecting an exaggerated release of hypothalamic corticotropin and vasopressin.     

Serum alpha 1-antichymotrypsin in senile dementia]

To evaluate the clinical significance of serum alpha 1-Antichymotrypsin (ACT) as an early diagnostic marker of senile dementia of Alzheimer type (SDAT), we measured 333 healthy and not demented elderly subjects, 27 cases SDAT and 25 cases of vascular dementia (VD). For the measurement, a new high-sensitivity method, double antibody radioimmunoassay method was developed. In healthy elderly subjects, the mean value of serum ACT was 0.229 mg/ml. A tendency towards increase of ACT with aging was noted but was not significant. The serum level of ACT in the SDAT patients was significantly higher (0.309 mg/ml) compared with the healthy elderly subjects and the VD patients (0.226 mg/ml) (p < 0.01). We concluded that in the patients with SDAT, there was an overproduction of ACT and the serum value of ACT was markedly elevated. The measurement of serum ACT is very useful (sensitivity = 88.9%, specificity = 68.7%; cut-off value = 0.250 mg/ml) for the early differential diagnosis of senile dementia.     

Adrenergic modulation of adrenocorticotropin responses to insulin-induced hypoglycemia and corticotropin-releasing hormone

To study possible adrenergic modulation of pituitary-adrenal responses to insulin-induced hypoglycemia and CRH we examined the effect of nonselective alpha-blockade (phentolamine) and nonselective beta-blockade (propranolol) on plasma ACTH, cortisol, and vasopressin (AVP) responses to hypoglycemia and CRH in five normal men. Infusion of propranolol or phentolamine did not alter basal plasma ACTH or cortisol levels. The propranolol infusion enhanced the stimulatory effect of hypoglycemia on ACTH, cortisol, and AVP secretion and also enhanced the stimulatory effect of CRH on ACTH and cortisol secretion. Infusion of phentolamine inhibited hypoglycemia-induced ACTH and AVP secretion, but had no effect on the stimulatory effect of CRH on ACTH and cortisol secretion. The increments of plasma ACTH and cortisol induced by an almost maximal dose of CRH (1 microgram/kg) were smaller than those induced by hypoglycemia. The propranolol-induced enhancement of the ACTH response to hypoglycemia was almost the same as the ACTH response to CRH alone. From these results we conclude that propranolol may act at the pituitary level to enhance CRH action, rather than AVP action, and that the ACTH response to hypoglycemia may be mediated by hypothalamic alpha-adrenergic activation.     

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.     

Preclinical Cushing's syndrome in adrenal "incidentalomas": comparison with adrenal Cushing's syndrome.

Adrenal tumors are usually diagnosed by clinical symptoms of hormone excess. The increasing use of ultrasound and computed tomography results in the detection of a substantial number of incidentally discovered adrenal tumors. Most of these tumors are nonfunctional adrenocortical adenomas, but a few cases of subclinical cortisol production in "incidentalomas" have been reported. We investigated prospectively the prevalence of autonomous cortisol production in 68 patients (44 females and 24 males, aged 25-90 yr) with adrenal incidentalomas at our institution. As a screening procedure all patients with incidentalomas underwent an overnight dexamethasone suppression test (1 mg). Patients who failed to suppress serum cortisol below 140 nmol/L (5 micrograms/dL) underwent more comprehensive studies (prolonged dexamethasone suppression test, determination of the diurnal rhythm of cortisol secretion in saliva, and CRH stimulation test). Eight patients (12% of all patients with incidentalomas; 5 females and 3 males, aged 25-71 yr) were finally identified as having cortisol-producing tumors, and the findings in these patients were compared with those of overt Cushing's syndrome in 8 patients (8 females, aged 26-50 yr) suffering from cortisol-producing adrenal adenomas. The tumor size of patients with cortisol-producing incidentalomas ranged from 2-5 cm. No specific signs and symptoms of hypercortisolism were present, but arterial hypertension (seven of eight subjects), diffuse obesity (four of eight subjects), and noninsulin-dependent diabetes mellitus (NIDDM; two of eight subjects) were frequently observed. Baseline cortisol levels were in the normal to upper normal range, whereas baseline ACTH levels were suppressed in five of the eight patients. In none of the patients was serum cortisol suppressible by low dose or high dose dexamethasone. The ACTH and cortisol responses to CRH were normal in two, blunted in one, and suppressed in four patients. Unilateral adrenalectomy was performed in seven patients and resulted in temporary adrenal insufficiency in four of them. After surgery, improvement of arterial hypertension, a permanent weight loss in obese subjects, and a better metabolic control of NIDDM were noted in the majority of patients. The following conclusions were reached. Incidentally diagnosed adrenal tumors with pathological cortisol secretion in otherwise clinically asymptomatic patients are more frequently observed than previously assumed. Adrenocortical insufficiency is a major risk in these patients after adrenalectomy. After surgery, hypertension, obesity, and NIDDM may improve. Patients with asymptomatic adrenal incidentalomas, therefore, should be screened for cortisol production by means of an overnight dexamethasone suppression test.     

Potentiation of the classic ovine corticotrophin releasing hormone stimulation test by the combined administration of small doses of lysine vasopressin

OBJECTIVE To assess the corticotrophic response to ovine corticotrophin releasing hormone (CRH) with the lowest dose of lysine vasopressin able to induce both the greatest stimulation and the lowest degree of side-effects. SUBJECTS Fourteen healthy young adult males. DESIGN Increasing intravenous doses (either 0, 0.03, 0.1, 0.3, or 1 IU) of lysine vasopressin, infused over 20 minutes, combined with a bolus of 100 μg ovine CRH. MEASUREMENT Radioimmunoassay of plasma ACTH, lipotrophin hormones and Cortisol levels. RESULTS (1) Responses to stimulation tests were evaluated as the area under the curves of plasma levels versus sample times, from 0 to 120 minutes after injection or start of perfusion (six subjects). The lowest dose of lysine vasopressin that induced an additional stimulation in the CRH-stimulated ACTH response was 0 3 IU. The combination of 1 IU lysine vasopressin with CRH doubled values of the area under the curve for the ACTH. Lysine vasopressin alone (0 3 and 1 IU) failed to stimulate ACTH responses. (2) The combined test (100 μg CRH and 1 IU lysine vasopressin) was carried out on eight additional control subjects. From a mean basal level of 23 ± 5.6 (SEM), plasma ACTH peaked to 104.5±8 ng/l (23.0 ± 1.8 pmol/l) as early as 20–30 minutes after the start of injection. When repeated after a two-week interval, the combined test induced identical stimulation in a given subject. Results of lipotrophin hormone determinations roughly paralleled those of ACTH. However the effects on Cortisol levels were less clear. Subjects injected with CRH experienced slight facial flush. Following the 1 IU lysine vasopressin dosage, side-effects were reduced to skin pallor. No changes in heart-rate or blood-pressure were observed. CONCLUSIONS Under these conditions, the combination of 100 μg CRH with 1 lU lysine vasopressin constitutes a powerful test for direct assessment of the pituitary reserve and therefore can be employed as a routine investigational tool.     

Responsiveness of hypophyseal-adrenocortical axis to repetitive administration of synthetic ovine corticotropin-releasing hormone in patients with isolated adrenocorticotropin deficiency

The primary lesion site in isolated ACTH deficiency was studied in three patients by examining the responses of immunoreactive ACTH to insulin-induced hypoglycemia, lysine vasopressin, and synthetic ovine corticotropin-releasing hormone (CRH). In all patients, no significant changes in immunoreactive ACTH followed insulin-induced hypoglycemia or lysine vasopressin. Fifty micrograms (greater than or equal to 1 microgram/kg BW) of CRH administered as an iv bolus dose daily for 6 consecutive days elicited no significant increase in plasma immunoreactive ACTH, beta-lipotropin, or cortisol levels in all patients. Eight iv bolus injections of 0.63 microgram/kg BW CRH at 4-h intervals also failed to induce a significant response of immunoreactive ACTH to an iv bolus dose of 1 microgram/kg CRH at 36 h in one patient. In contrast, a single bolus dose of 50 micrograms CRH induced a response of plasma immunoreactive ACTH in a patient with Cushing's disease and a patient with Addison's disease. The present results suggest that the primary lesion of isolated ACTH deficiency is not the hypothalamus, but, rather, is located in pituitary ACTH-secreting cells.     

The corticotropin-releasing hormone test in the diagnosis of ACTH-dependent Cushing's syndrome: a reappraisal

OBJECTIVE: Stimulation with corticotropin-releasing hormone (CRH) is one of principal tools for the differential diagnosis of ACTH-dependent Cushing's syndrome. However, different dosages and species of CRH may be employed; further, ACTH levels can be measured by radioimmunoassay (RIA) or immunoradiometric assay (IRMA). The aims of the present study were to perform a reappraisal of the diagnostic accuracy of the CRH test taking these different testing modalities into consideration and to study the correlation between basal ACTH and cortisol levels and their responses to CRH in patients with Cushing's disease. PATIENTS: The study population comprised 148 patients with Cushing's disease and 12 patients with ectopic ACTH secretion collected through an Italian multicentre study. DESIGN: Patients were submitted to stimulation with 100 microg human or ovine CRH (36% and 64% of subjects, respectively) and ACTH measured either by RIA or IRMA (28% and 72%, respectively). A 50% increase in ACTH and cortisol levels was considered indicative of Cushing's disease. RESULTS: Mean peak ACTH levels measured by RIA and IRMA were comparable, as was the diagnostic accuracy of the test with the two assays (87% for IRMA and 84% for RIA, ns). In patients with Cushing's disease, stimulation with ovine CRH induced greater hormonal responses compared to testing with human CRH although only the cortisol response reached statistical significance (ACTH: 247.5 +/- 28.0% vs. 168.5 +/- 21.3% over baseline, P = 0.06; cortisol: 89.3 +/- 8.5% vs. 60.8 +/- 9.6% over baseline, P < 0.05 for ovine and human CRH, respectively). No appreciable rise in ACTH and cortisol levels was registered among patients with ectopic ACTH secretion. Diagnostic accuracy of the cortisol response was significantly greater with the ovine than with human peptide (71% vs. 49%, P < 0.05, for ovine and human CRH, respectively) while the ACTH response yielded equal diagnostic accuracy (86% vs. 87%, ns, for the ovine and human peptide, respectively). Interestingly, the correlation between ACTH and cortisol peak responses in patients with Cushing's disease was significantly greater for human than for ovine CRH (r = 0.68 vs. r = 0.41, P < 0.01, respectively). In addition, baseline cortisol levels exhibited a significant negative correlation with both the ACTH and cortisol response to CRH suggesting the persistence of the negative cortisol feedback in patients with Cushing's disease. CONCLUSIONS: (A) Both RIA and IRMA can be used indifferently for the assessment of the ACTH response to CRH. (B) Human and ovine CRH provide the same diagnostic accuracy as regards the ACTH response which, incidentally, represents the most accurate criterion for the evaluation of the CRH test; ovine CRH is superior to the human peptide in the evaluation of the cortisol response. (C) In patients with Cushing's disease, endogenous cortisol maintains the ability to negatively modulate CRH-stimulated corticotropin secretion.