Combined administration of human corticotropin-releasing factor and lysine vasopressin induces cortisol escape from dexamethasone suppression in healthy subjects

Inadequate suppression of plasma cortisol after 1-2 mg dexamethasone is frequently observed in depressive patients. To further investigate the pathophysiology underlying cortisol nonsuppression after dexamethasone we compared cortisol and corticotropin (ACTH) response to human corticotropin-releasing factor (h-CRF), lysine vasopressin (LVP), and a concurrent administration of both peptides after pretreatment with 1.5 mg dexamethasone in six male controls. Neither h-CRF nor LVP were able to produce a marked elevation of dexamethasone suppressed plasma cortisol and ACTH. If both peptides were administered in combination, a substantial escape of plasma cortisol from dexamethasone suppression was observed. ACTH responses changed in concordance with those of cortisol indicating that the LVP-CRF interaction takes place at the pituitary level. Our finding is consistent with a multihormonal control of pituitary-adrenal activity and bears several implications for interpretation of dexamethasone suppression test results in depressive illness.     

Hyper-responsiveness of adrenal gland to vasopressin resulting in enhanced plasma cortisol in patients with adrenal nodule(s)

Hyper-responsiveness of plasma cortisol to vasopressin has been demonstrated in ACTH-independent bilateral macronodular adrenocortical hyperplasia (AIMAH) and some adrenal adenomas with Cushing's syndrome (CS). However, the clinical significance of hyper-responsiveness of plasma cortisol to vasopressin has not been investigated systematically in adrenal nodule(s). The aim of this study was to clarify the prevalence of hyper-responsiveness of plasma cortisol to vasopressin (vasopressin responder) and their clinical characteristics in terms of hormonal secretion using vasopressin-loading test in the patients with adrenal nodule(s) except pheochromocytomas. A vasopressin-loading test was performed on 61 consecutive patients with adrenal nodules (CS: 33, aldosterone-producing adenoma: 10, non-functional tumor: 18). Vasopressin responders were observed in 36.1% of adrenal nodule(s), 42.4% of CS and 28.5% of non-CS. In responders with CS, eight patients had bilateral nodules that were diagnosed as AIMAH, and the remaining six patients had a unilateral nodule. These patients had lower plasma cortisol than non-responders at both morning (P<0.01) and midnight (P<0.05), as well as the morning following overnight dexamethasone suppression at 1mg (P<0.05) and 8mg (P<0.05). Hyper-responsiveness of the adrenal gland to vasopressin resulting in enhanced plasma cortisol was frequently observed among patients with adrenal nodule(s). The vasopressin responders among the patients with adrenal nodule(s) frequently had CS with low autonomous cortisol secretion.     

Cortisol responsiveness to insulin-induced hypoglycemia in Cushing's syndrome with huge nodular adrenocortical hyperplasia

A 51-yr-old male patient with a 3 yr history of Cushing's syndrome is described. The baseline plasma cortisol level was elevated, while the plasma ACTH levels remained at an undetectable level. Dynamic testing of pituitary-adrenal function revealed no suppression after 8 mg of dexamethasone, and there was no response to metyrapone or CRF, while plasma cortisol showed a hyperresponse to synthetic ACTH. Plasma cortisol responded to insulin-induced hypoglycemia without an obvious ACTH response. These and the computerized tomography data suggested a "huge" bilateral nodular adrenocortical hyperplasia which was later confirmed by surgery. The left and right adrenal glands weighed 55 and 76 g, respectively. In vitro experiments, using the adrenal tissue, showed that there was an adrenal cortisol response to 1-39 ACTH but not to regular insulin, arginine vasopressin, angiotensin II, norepinephrine or epinephrine. These results indicate that plasma cortisol responded to a slight hypoglycemia-induced plasma ACTH change which was not detected in the ACTH radioimmunoassay or to factors other than ACTH which might be induced by hypoglycemia.     

Effects of a kappa-opioid agonist on adrenocorticotropic and diuretic function in man

Although kappa-opiate receptors represent an important fraction of the total opiate receptor capacity in human brain their endocrine function is unknown. We determined the effects of a kappa-opiate receptor agonist on the secretion of vasopressin, ACTH and cortisol and on diuresis. The racemic benzomorphan kappa agonist MR 2033 or its opiate active (-)-isomer, MR 2034, inhibited the release of cortisol and ACTH in 12 trials in a naloxone reversible manner; plasma levels of vasopressin were not altered. The (+)-isomer, MR 2035, did not affect the secretion of cortisol or ACTH. Surprisingly, in five other subjects large increases were observed in vasopressin, ACTH and cortisol following the kappa-agonist, which were probably elicited indirectly by aversive effects of the opioid. The subjects in whom vasopressin release was not altered by MR 2033 and MR 2034 displayed large decreases in urine osmolality which were not antagonized by naloxone. The opiate inactive (+)-isomer, MR 2035, caused no diuretic response. Subjects in whom vasopressin release was stimulated did not show decreases in urine osmolality indicating that vasopressin is capable of antagonizing the diuretic action of the kappa-agonist. Our data show that a kappa-agonist inhibits secretion of cortisol and ACTH by acting at stereospecific opiate receptors and elicits diuresis by acting at stereospecific, but naloxone-insensitive non-classical opioid receptors. These data support the concept that different types of kappa-receptors can be distinguished in man.     

The changes in plasma cortisol and urinary free cortisol by an overnight dexamethasone suppression test in patients with Cushing's disease

We studied the suppressibility of cortisol secretion in 15 patients with Cushing's disease by measuring morning plasma cortisol level as well as the 24-hour urinary free corisol (UFC) excretion following single doses of increasing amounts of dexamethasone (ranging from 0.5 to 32 mg) given at 11 p.m. The mean plasma cortisol level in patients with Cushing's disease was twice as high as in normal subjects, whereas the mean UFC in these patients was 6 times as high. Plasma cortisol in seven patients were suppressed by less than 4 mg of dexamethasone (in 2 cases, less than 0.5 mg; in 3 cases, less than 2 mg; and in 2 cases less than 4 mg). In these cases, basal plasma cortisol and UFC were less than 25 micrograms/dl and 350 micrograms/day, respectively. Among the other eight patients, plasma cortisol was partially suppressed in 5 cases and not suppressed in 3 cases by high doses of dexamethasone (16-32 mg). In these cases the basal plasma cortisol and UFC were more than 25 micrograms/dl and 350 micrograms/day, respectively. There was a significant correlation between the basal plasma cortisol and UFC (r = 0.687, p less than 0.01). These data suggest that the suppression by increasing amounts of dexamethasone in most cases with Cushing's disease was related to the severity of hypercortisolism.     

Cortisol-suppressible dexamethasone-nonsuppressible cyclic Cushing's disease with evidence of clinical and biochemical remission with bromocriptine.

We report a rare case of a 57-year-old female patient with Cushing's disease who had clinically and biochemically proven cyclicity. There were periodic increases in plasma ACTH and cortisol and urinary free cortisol and 17-OHCS. Plasma CRH was undetectable and plasma ACTH responded to exogenous CRH when basal plasma cortisol was relatively low. Neither plasma ACTH nor cortisol responded to dexamethasone (oral and intravenous) but plasma ACTH was clearly suppressed by cortisol infusion. With 40 mg/day bromocriptine, the periodic hypercortisolemia disappeared and the patient was maintained on remission. The response of plasma cortisol to dexamethasone suppression test was also normalized.     

Studies on the "low dose" suppressible Cushing's disease.

Diagnosis of Cushing's disease in most cases can be established by the standard dexamethasone suppression test without difficulty. However, some cases were known to be normally suppressed by the standard low dose of dexamethasone (2 mg daily). The case we encountered recently was also normally suppressed by either the rapid (Nugent) or the standard (Liddle) method. This fact prompted us to study the usefulness of a single dose of 0.5 mg of dexamethasone to suppress the plasma cortisol in the normal. It was concluded that the single oral dose of 0.5 mg of dexamethasone given at 11 p.m. on the previous night suppressed the plasma cortisol efficiently the following morning in the normal, thus making the differentiation of particular cases of Cushing's disease from the normal possible. The disappearance of plasma dexamethasone did not differ significantly between the normal and the Cushing's disease.     

Regulation of aldosterone secretion in primary aldosteronism.

Plasma aldosterone, plasma renin activity and plasma cortisol were determined in patients with primary aldosteronism in response to posture and at short-time intervals overnight while the patient were supine. In the 5 patients with an aldosterone-producing adenoma postural changes in plasma aldosterone were paralleled by those in cortisol while plasma renin activity was generally undetectable indicating an ACTH-dependent secretion of aldosterone. This concept was supported by the observation that in 3 of these patients who were tested overnight 1. episodic secretion of plasma aldosterone was paralleled by those of cortisol and 2. episodic secretion of plasma aldosterone could be blunted by dexamethasone. In the patient with idiopathic adrenal hyperplasia concomittant changes in plasma aldosterone and plasma renin activity occurred. The assumption that in this patient the fluctuations in plasma aldosterone were mediated through changes in renal renin secretion was supported by the finding that episodic secretion of plasma aldosterone persisted under suppression of ACTH-secretion by dexamethasone. Our results indicate, that the described procedures may all serve as diagnostic criteria to differentiate between aldosterone-producing adenoma and idiopathic adrenal hyperplasia.     

Effect of naloxone on plasma concentrations of prolactin and LH in lactating sows

Six lactating sows were injected through an indwelling vena cava cannula with naloxone (2.5 mg/kg body weight) on Day 15 post partum. Blood samples were collected through the cannulas at 10-min intervals for 8 h before and 10 h after naloxone administration. Plasma prolactin and LH concentrations were measured by radioimmunoassay. Naloxone caused a marked suppression of plasma prolactin concentrations lasting 4-6 h. LH concentrations were also affected by naloxone: LH rose to reach maximum values 20-50 min after naloxone treatment. Pretreatment values were recorded 200-300 min after the treatment. These results indicate that endogenous opioids are involved in causing the endocrine patterns occurring during lactation, i.e. high prolactin and low LH concentrations.     

Opioid action on luteinizing hormone secretion in newborn pigs: paradoxical effect of naloxone

German Landrace piglets, 6-7 days of age, received either saline (9 males, 8 females), 0.5 mg naloxone/kg body weight (7 males, 7 females), 2.0 mg naloxone/kg (7 males, 8 females) or 0.5 mg DADLE (potent leu-enkephalin analog)/kg (7 males, 7 females) through a catheter inserted into the jugular vein 2-4 days previously. Male or female piglets were allocated randomly, within litter, to the different experimental groups. Blood samples were withdrawn for a period of 240 min at 10-min intervals for the first 60 min following injection and at 20-min intervals for the rest of the test period. Piglets were separated from their mother via a detachable wall and were allowed to suckle every 50 min. DADLE failed to alter plasma levels of LH in both males and females. Naloxone induced a significant (P less than 0.01) decrease in LH concentrations in females 10 to 60 min after injection (saline: 2.3 +/- 0.2 ng/ml plasma (SEM); 0.5 mg naloxone/kg: 1.0 +/- 0.2 ng/ml plasma and 2 mg naloxone/kg 1.2 +/- 0.4 ng/ml plasma). In males low doses of naloxone reduced plasma LH levels 10 to 40 min after injection (saline: 2.0 +/- 0.3 ng/ml plasma and 0.5 ng naloxone/kg: 1.1 +/- 0.3 ng/ml), whereas a decrease in plasma LH levels occurred 80 to 140 min after injection of high doses of naloxone (saline: 2.1 +/- 0.2 ng/ml and 2 mg naloxone/kg: 1.0 +/- 0.2 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of alpha-2 adrenoreceptor blockade by yohimbine on the hormonal response to hypoglycaemic stress in normal man

In order to evaluate the effect of alpha-2 adrenoreceptor blockade on the ACTH response to insulin-induced hypoglycaemia, six normal men were studied with and without yohimbine (30 mg p.o.) premedication. Despite a similar hypoglycaemic stimulus and significant suppression of the growth hormone response (P less than 0.05), no change was observed in basal or stimulated plasma ACTH, cortisol, arginine vasopressin (AVP) or prolactin responses following yohimbine. We conclude that alpha-2 adrenoceptor blockade with yohimbine does not significantly affect the ACTH response to hypoglycaemia in man.     

Overnight (1 mg) dexamethasone suppression testing reliably distinguishes non-cushingoid obesity from Cushing's syndrome.

To determine the sensitivity of the overnight 1-mg dexamethasone suppression test in diagnosing Cushing's syndrome, we evaluated the cortisol responses of 55 subjects (25 non-obese individuals with body mass index less than 25 kg/m2, 20 obese individuals with body mass index greater than 30 kg/m2, and 10 patients with surgically proven Cushing's syndrome) following ingestion of 1 mg dexamethasone at midnight. The basal 8 AM plasma cortisol levels among non-obese and obese individuals and patients with Cushing's syndrome were 310 +/- 85, 377 +/- 91, and 813 +/- 270 nmol/L, respectively. Following 1 mg of dexamethasone, Cushing's syndrome patients showed minimal suppression of cortisol to 609 +/- 180 nmol/L (P = 0.79). Non-obese and obese individuals suppressed to 18.7 +/- 6.0 nmol/L (P less than 0.001) and 22 +/- 7.1 nmol/L (P = 0.003), respectively. The results demonstrated similar cortisol responses to overnight dexamethasone suppression in obese and non-obese groups, and clearly distinguished these subjects from those with Cushing's syndrome. Obesity is not a confounding factor in the 1-mg dexamethasone suppression test.     

Dexamethasone suppressibility of plasma pregnenolone or dehydroepiandrosterone in gonadectomized patients.

The 9 AM dexamethasone suppression test was carried out in gonadectomized patients, and plasma pregnenolone or dehydroepiandrosterone (DHA) was radioimmunoassayed following various amounts of dexamethasone administration. Pregnenolone, as well as the plasma ACTH level, was completely suppressed with 1 mg dexamethasone, whereas 4 mg or 8 mg of dexamethasone was needed to induce a complete DHA suppression. These findings suggest that the gonads alone contribute to the poor dexamethasone suppressibility of pregnenolone in normal subjects, and that adrenal DHA secretion might be also regulated by an unidentified factor other than ACTH, which would be suppressed with large doses of dexamethasone.     

Evidence for direct inhibitory effects of dopamine on zona glomerulosa secretion of 18-hydroxycorticosterone in rhesus monkeys

This study was designed to more selectively investigate the dopaminergic regulation of 18-hydroxycorticosterone (18-OHB) and aldosterone production by the adrenal zona glomerulosa. Mature rhesus monkeys received either an infusion of dopamine (2 micrograms/kg/min) or 5% dextrose (0.2 ml/min) over a 60 min period (N=6). Dopamine had no effect on plasma levels of renin activity, cortisol, corticosterone, aldosterone or blood pressure. However, dopamine suppressed (p less than 0.05) plasma 18-OHB levels from a baseline of 31.6 +/- 3.5 ng/dl to 23.6 +/- 2.1 ng/dl at 60 min after onset of infusion. This observation is in agreement with some studies in humans but differs from others in which no depression in 18-OHB was observed following dopamine infusion. Dopamine infusion markedly (p less than 0.001) suppressed plasma PRL levels by 30 min after onset of infusion. Corticosteroid responses to metoclopramide (200 micrograms/kg) after dexamethasone 1 mg im every 6 h X 5 days or placebo treatment (vehicle im every 6 h X 5 days) was then evaluated. Dexamethasone significantly suppressed basal cortisol, corticosterone, 18-OHB and aldosterone. Although dexamethasone blunted the prolactin response, it did not inhibit the aldosterone response to metoclopramide. The 18-OHB response to metoclopramide was increased (p less than 0.01) following dexamethasone treatment. Following dexamethasone suppression, 18-OHB levels were still lowered (p less than 0.05) by dopamine infusion. These results suggest that dopamine selectively inhibits zona glomerulosa production of 18-OHB and aldosterone in rhesus monkeys.     

beta-Endorphin controls vasopressin release during foot shock-induced stress in the rat

This study tested the possibility that beta-endorphin is involved in the regulation of vasopressin release during stress induced by inescapable electric foot shock. To this end, a specific anti-beta-endorphin antiserum or a control serum lacking the specific anti-beta-endorphin antibodies was administered to male rats. Plasma vasopressin concentrations, measured by radioimmunoassay, were not affected by brief foot shock stress in control rats, but were raised significantly by the stress in animals which had received an intracerebroventricular (i.c.v.) injection of the anti-beta-endorphin antiserum. In contrast, when the same volume of the anti-beta-endorphin antiserum was injected into a tail vein, foot shock stress produced only a slight effect on vasopressin release. I.c.v. injection of the antiserum changed neither basal nociceptive threshold nor stress-induced analgesia as revealed by the tail-flick latency. Vasopressin release induced by an osmotic stimulus was not influenced by the anti-beta-endorphin antiserum given i.c.v. The opiate antagonist naloxone or the glucocorticoid dexamethasone raised plasma vasopressin concentration in stressed rats which had received the control serum (i.c.v.); however, after i.c.v. injection of the anti-beta-endorphin antiserum neither naloxone nor dexamethasone elevated the plasma vasopressin concentration beyond the level reached by the anti-beta-endorphin antiserum (i.c.v.) alone. These results suggest that beta-endorphin inhibits the release of vasopressin during foot shock-induced stress in the rat.     

Single-dose four hour dexamethasone suppression test in normal men and its application for the diagnosis of cushing's syndrome

As a four hour morning test, plasma cortisol levels were radioimmunoassayed before and at two and four hours after dexamethasone (0, 0.5 mg, 1.0 mg or 2.0 mg) was administered at 8–9 a.m. in 20 normal subjects. The 1.0 mg four hour test was most effective in suppression of cortisol and it showed the same suppressibility as the widely used single-dose overnight test. With the 1.0 mg four hour test, 2 patients with Cushing's syndrome due to adrenal hyperplasia could be differentiated from normal and obese subjects.The four hour morning test would be more useful than the widely used overnight test from the reasons; i) it shows the same suppressibility as the overnight test, ii) it obviates the need for bothersome midnight administration of dexamethasone, iii) because it takes only one morning to perform, it can save a day, iv) and it might be applicable for the differential diagnosis of Cushing's syndrome because 4.0 mg morning test resulted in complete suppression of plasma cortisol in a tested Cushing's syndrome, whereas with even 8.0 mg, plasma cortisol was not suppressed in the overnight test in 2 such patients examined.     

Serum concentrations of deoxycorticosterone in women during the luteal phase of the ovarian cycle are not suppressed by dexamethasone treatment

We determined the serum levels of deoxycorticosterone (DOC) in plasma of six healthy, apparently ovulatory women during the mid-follicular and mid-luteal phases of their ovarian cycles; and we evaluated the effect of dexamethasone (1 mg by mouth) on the concentrations of DOC and cortisol in serum at times when plasma progesterone levels were high or low. The serum levels of DOC, unlike those of cortisol, did not vary significantly in single blood samples obtained in the morning (8-10 a.m.) and afternoon (3-5 p.m.); and serum DOC levels in women were significantly higher (P less than 0.05) during the mid-luteal phase than during the mid-follicular phase of the cycle. There were unmistakable diurnal variations in serum levels of cortisol, and cortisol concentrations were reduced to less than 20% of pretreatment levels after the ingestion of 1 mg dexamethasone during the mid-follicular or mid-luteal phase. The serum concentrations of DOC were reduced only to approx 70% of pretreatment levels after dexamethasone ingestion during the follicular phase. The serum levels of DOC did not decline significantly after administration of dexamethasone during the mid-luteal phase, when progesterone levels in serum are high (14-16 ng/ml). Blood samples also were obtained at hourly intervals during the 24 h before and after dexamethasone administration in one woman during the follicular phase and in another woman the during the early luteal phase (progesterone levels = 1-3 ng/ml) of the ovarian cycle. DOC levels (pre-dexamethasone) fluctuated in synchrony with those of cortisol in the woman studied during the follicular phase but not in the woman studied during the early luteal phase of the cycle. In the post-dexamethasone period, plasma cortisol levels were suppressed for at least 24 h in both women whereas DOC levels were decreased only partially. We conclude that plasma DOC is derived from both adrenal secretion and from extraadrenal 21-hydroxylation of progesterone--the latter source of DOC is not affected by dexamethasone suppression of ACTH secretion.     

Cortisol response and ovarian hormones in juvenile and cycling female Cebus monkeys: effect of stress and dexamethasone

We examined cortisol profiles in relation to ovarian hormones and their response to a repeated composite stressor with and without dexamethasone suppression. To evaluate the day-to-day changes in circulating cortisol relative to ovarian hormones, we subjected five adult female Cebus apella monkeys daily to restraint, sedation, transport to a neighboring room for femoral venipuncture, and return to the cage throughout the menstrual cycle. The cortisol response to the repeated stressor for blood collection, its relationship with the ovarian function, and the effects of dexamethasone were evaluated in six juveniles (18-24 months old) and five adult females in the luteal phase. Blood was sampled at time 0; then the monkeys received the vehicle and their blood was sampled again at 1, 2, 4, and 24 hr. This experiment was repeated 3 weeks later, with dexamethasone (i.m. 2 mg/Kg) injected instead of vehicle. Plasma aliquots were assayed for cortisol, progesterone, and estradiol. The results revealed that from middle infancy and throughout adulthood, hypercortisolism is the norm in female Cebus monkeys. The high cortisol values remained unchanged across the cycle despite the cyclic changes in estradiol and progesterone levels. Juvenile monkeys exhibited a higher cortisol response to stress than adults, and both juvenile and adult monkeys exhibited the typical suppression by dexamethasone. A rapid suppression of progesterone co-occurred in parallel with cortisol after dexamethasone injection in juvenile monkeys, suggesting that most circulating progesterone originates in the adrenals. In contrast, adult females exhibited an overincrement of progesterone levels, in parallel with a rise in cortisol, in response to the stressor, and this effect was exacerbated by dexamethasone. The findings suggest that hypercortisolism is insufficient to disrupt ovarian development toward a normal cyclical function, and that ovarian steroids have no influence on day-to-day circulating cortisol levels. On the other hand, the overincrement of progesterone levels induced by stress and/or glucocorticoids during the early luteal phase is unlikely to interfere with the development of this phase and implantation in this monkey species.     

Effect of naloxone on the secretion of LH in infantile and prepubertal Holstein bull calves

Administration of naloxone (100 mg i.v.; approximately 1.21 mg/kg body weight0.75) to 10 intact calves (24 weeks of age) caused an acute release of LH that was similar in amplitude and duration to spontaneous discharges of LH that occur at the same age. The naloxone-induced release of LH was abolished in 9/10 calves (intact and castrated) treated with oestradiol-17 beta. To determine the ontogeny of opioid control of secretion of LH, 12 calves were randomly assigned to receive saline or naloxone (1.21 mg/kg body weight0.75, i.v.) at 3, 5, 7, 9, 11, 13, 17 and 21 weeks of age. At each age, blood was collected at 10-min intervals for 4 h and saline or naloxone was administered (i.v.) after collection of the 120-min sample. Before administration of naloxone, plasma LH values increased with age (P less than 0.01) but did not differ between the control and naloxone groups (age x treatment, P greater than 0.05). Administration of naloxone caused concentrations of plasma LH to increase at 3, 11, 13, 17 and 21 weeks of age (treatment x time, P less than 0.001). Concentrations of LH (saline vs naloxone, ng/ml) reached a maximum within 20 min after treatment at Weeks 3 (0.3 vs 1.2), 11 (0.6 vs 2.6), 13 (0.6 vs 3.7), 17 (1.1 vs 2.6), and within 40 min after treatment at Week 21 (1.0 vs 3.5).(ABSTRACT TRUNCATED AT 250 WORDS)     

Circadian cortisol secretion and circadian adrenal responses to ACTH are maintained in dexamethasone suppressed capuchin monkeys (Cebus apella)

We tested the hypothesis that the capuchin monkey adrenal (Cebus apella) gland has oscillatory properties that are independent of adrenocorticotropic hormone (ACTH) by exploring under ACTH suppression by dexamethasone: (i) maintenance of a circadian rhythm of plasma cortisol and (ii) clock time dependency of plasma cortisol response to exogenous ACTH. The capuchin monkey had a clear ACTH and plasma cortisol rhythm. Dexamethasone treatment resulted in low non-rhythmic ACTH levels and decreased cortisol to 1/10 of control values; nevertheless, the circadian rhythm of plasma cortisol persisted. We found that cortisol response to exogenous ACTH was clock time-dependent. The maximal response to ACTH occurred at the acrophase of the cortisol rhythm (0800 h). These results suggest that the capuchin monkey adrenal cortex may possess intrinsic oscillatory properties that participate in the circadian rhythm of adrenal cortisol secretion and in the circadian cortisol response to ACTH.