Mineralocorticoid response to low dose adrenocorticotropin infusion

Plasma Levels of Adrenocortical Steroids in CAPD and Hemodialysis Patients

CAPD patients appear to have higher levels of plasma renin activity than hemodialysis patients. Increased angiotensin n may result in increased secretion of 18-OH-B and aldosterone by the adrenal zona glomerulosa.

Differences in treatment design between continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis (HD) may affect secretion of adrenocorticosteroids. Ultrafiltration during CAPD is continuous and gradual. Therefore, CAPD patients experience only minor fluctuations in extracellular fluid volume and are usually at or near their estimated dry weight (EDW). In contrast, ultrafiltration in HD patients is rapid but intermittent. Hemodialysis patients approach their EDW only at the end of each treatment period. Hemodialysis patients, therefore, may remain significantly above their EDW for prolonged periods. CAPD allows patients to liberalize their dietary intake of potassium. Some CAPD patients may require potassium supplementation (I). In contrast, HD patients may need to restrict their dietary intake of potassium to prevent potentially lethal hyperkalemia. Heparin is routinely administered during HD but not during CAPD. The present study was designed to determine if these differences in treatment design produce greater stimulation of the adrenal zona glomerulosa in CAPD than in HD patients.

Defining contralateral adrenal suppression in primary aldosteronism: implications for diagnosis and outcome

OBJECTIVE

Unilateral primary aldosteronism (PA) should have a contralaterally normal and therefore suppressed adrenal zona glomerulosa. However, there is no validated definition of adrenal suppression. We created two biochemical hypotheses of adrenal suppression based upon measurements taken during adrenal vein sampling (AVS) to determine whether either proved useful for interpretation of AVS or prediction of hypertension outcome in operated cases.

DESIGN

Retrospective database analysis.

PATIENTS

Ninety-nine cases of PA from a tertiary hypertension unit.

MEASUREMENTS

Hypothesis 1 was the proportional suppression of the uninvolved/lowest adrenal(aldo/cortisol) to IVC(aldo/cortisol) ratio pre- and post cosyntropin. Hypothesis 2 was the absolute decrease in the uninvolved adrenal(aldo/cortisol) ratio after cortrosyn injection. ROC analysis performed using lateralization and hypertension resolution as the outcomes of interest.

RESULTS

Hypothesis 1 proved highly predictive of lateralization with a ROC AUC of 0.958, P < 0.0001, giving adrenal(aldo/cortisol):IVC(aldo/cortisol) <1.4 as the optimized criterion (sensitivity 90%, specificity 94%). For blood pressure outcomes in the surgical subgroup (n = 52), hypertension resolution was most commonly seen among subjects with adrenal suppression by both definitions although there was significant overlap with subjects requiring ongoing medication.

CONCLUSIONS

Post cosyntropin suppression of the uninvolved adrenal-to-IVC ratio is a highly useful definition of adrenal suppression that accurately predicts unilateral PA. This may be particularly useful in a case where AVS fails to catheterize one of the adrenal veins but suppression is seen on the other side. Adrenal suppression may also predict blood pressure outcome, however, a much larger PA database is likely necessary to determine the relative contribution of this predictor.

Addison disease presenting with acute neurologic deterioration: a rare presentation yields new lessons from old observations in primary adrenal failure

OBJECTIVE

To report a rare case of Addison disease presenting with acute neurologic deterioration, and to discuss previous reports and illustrative clinical lessons drawn from the case.

METHODS

We detail the clinical presentation and sequence of events leading to diagnosis of Addison disease in a 20-year-old man whose initial symptoms were those of acute neurologic deterioration.

RESULTS

A 20-year-old man presented with acute, rapid neurologic deterioration. The patient required intubation, but his condition responded very well to mannitol and dexamethasone. Head computed tomography showed a fourth ventricle reduced in size and basal cistern effacement, changes consistent with mild cerebral edema. Primary adrenal insufficiency was diagnosed after a low morning cortisol concentration prompted a corticotropin-stimulation test and serum aldosterone measurement (undetectable). The diagnosis was almost missed because of suspected confounders of dexamethasone and etomidate use. Subsequently, the patient tested positive for anti-21- hydroxylase antibodies. Cerebral edema rarely occurs with Addison disease and is most likely secondary to hyponatremia. Diagnosis in such cases may be complicated by resuscitative therapies; however, low cortisol levels should always be thoroughly investigated. This patient's presentation was also unique in that he maintained a normal electrolyte profile despite hypoaldosteronism, a phenomenon that may be explained by enhanced mineralocorticoid activity of exogenous cortisol.

CONCLUSIONS

The diagnosis of primary adrenal insufficiency may not be suspected in the absence of classic hyperpigmentation and hyperkalemia, but should remain in the differential diagnosis of acute confusion. While the use of dexamethasone and etomidate in initial resuscitation can transiently suppress adrenal function, any unusually low cortisol level merits thorough investigation.

Plasma aldosterone response to the low-dose adrenocorticotrophin (ACTH 1-24) stimulation test

BACKGROUND

Endocrine tests for adrenal insufficiency use pharmacological doses of stimulant such as ACTH. More physiological tests have often used high-dose protocols for sampling frequency.

AIMS

To evaluate the response of plasma aldosterone concentration to low doses (125, 250 and 500 ng/m(2) body surface area) of synthetic ACTH.

DESIGN

A randomised trial in six normal adult males aged 18-27 years.

MATERIALS AND METHODS

Aldosterone concentration was measured by radioimmunoassay in serum from blood samples taken at 10 min intervals for 90 min.

RESULTS

All three doses produced a significant rise in plasma aldosterone concentration (125 ng/m(2), P = 0.003; 250 ng/m(2), P < 0.001; 500 ng/m(2), P < 0.001) but there was no effect of dose on either the peak or incremental plasma aldosterone concentration. Mean time to peak was similar between the doses and the two higher doses were associated with a longer secretory profile (125 ng/m(2) 56 (26 SD) mins, 250 ng/m(2) 74 (19) mins, 500 ng/m(2) 77 (21) mins; F = 3.39; P = 0.04). Peaks of 100% were detected within 30 min of drug administration and peak response was associated with the prestimulation plasma aldosterone concentration (r = 0.45; P = 0.003). The between- and within-individual coefficients of variation for prestimulation concentrations were 37.0% and 32.8%, and for the peak response were 27.2% and 27.2%, respectively.

CONCLUSIONS

The response of plasma aldosterone concentrations to low-dose ACTH administration requires a blood sampling protocol of 0, 10, 20 and 30 min to capture concentrations near the peak response. The high-dose protocol would have missed the response. Over the dose range studied no dose-response was observed so the selection of dose should be based on the dose effective to release steroids in the glucocorticoid pathway if this study is to be used in conjunction with such evaluation.

Interaction Between Dexamethasone Treatment and the Corticotropin Stimulation Test in Septic Shock

OBJECTIVE:

To review dexamethasone interaction with corticotropin stimulation testing, particularly as it applies to treating septic shock.

DATA SOURCES:

Pertinent literature was identified through MEDLINE (1966–February 2004) using combinations of the key words dexamethasone, adrenocorticotropic hormone stimulation, and pretreat. Only articles written in the English language and evaluating human subjects were considered. Reference lists of identified articles were reviewed for additional citations.

DATA SYNTHESIS:

Accurate interpretation of the corticotropin stimulation test is important to identify patients with septic shock who may benefit from corticosteroid supplementation. In healthy volunteers, short-term dexamethasone administration prior to the corticotropin stimulation test may depress the baseline cortisol level, but does not inhibit the response to the corticotropin challenge. This may result in a slight increase in the difference between baseline and post-stimulation values.

CONCLUSIONS:

In 2 small trials in healthy adults, short-term, low-dose dexamethasone pretreatment decreased baseline cortisol levels, but values following corticotropin stimulation were unaffected. Accordingly, caution in interpreting corticotropin stimulation test results is warranted. However, the application of the findings from these studies to patients with septic shock is difficult, given the important differences in physiology between normal and septic patients. As of December 29, 2004, a dexamethasone dose >2 mg or prolonged dexamethasone therapy (>2 days, totaling 4 mg) preceding corticotropin stimulation has not been studied in any population.

Dexamethasone target sites in the central nervous system and their potential relevance to mental illness

1. The topical distribution of tritiated dexamethasone (DEX), a potent synthetic glucocorticoid of widespread use in the diagnosis and assessment of mental illness, was studied in rat CNS by autoradiography to obtain information on potential target sites for feedback and other centrally mediated effects of glucocorticoids. 2. The cells of the arcuate nucleus of the hypothalamus and the lateral thalamic nuclei displayed the most concentrated nuclear accumulation of silver grains. 3. Significant accumulation, exceeding that found in the hippocampal formation, also occurred in the cells of the ventromedial, periventricular, and paraventricular nuclei of the hypothalamus, the locus ceruleus, the nucleus tractus solitarii, and the area postrema, none of which are targeted by corticosterone, the native glucocorticoid of the rat. 4. Nuclear accumulation of silver grains was prominent in neural and glial cells of the cerebral cortex, the olfactory nucleus, the dorsolateral septum, the amygdala, the subfornical organ, the lateral parabrachial, medial trapezoid, and dorsal reticular nuclei, the nucleus centralis of the raphe, the cerebellum, and vascular tissues. 5. The localization of DEX in hypothalamic and brain-stem nuclei coincided with that of the glucocorticoid receptor, possibly implicating these sites in direct or modulating effects of glucocorticoids in various forms of mental disturbance, including depression, anxiety, panic disorders, and alcohol withdrawal. 6. The extent to which various CNS regions targeted by DEX feature in negative feedback control of adrenocortical secretion remains to be defined, as does the site of impaired feedback disclosed by the dexamethasone suppression test in psychiatric patients.

Investigation of the salivary 18-hydroxycorticosterone:aldosterone ratio in man using a direct assay

A method for the direct determination of 18-hydroxycorticosterone (18OHB) in human saliva has been developed and validated. Saliva was collected at 30 min and 1 h intervals between 0600 and 2200 h from healthy men and women for the determination of 18OHB (SHB), aldosterone (SA) and glucocorticoids (SGC = cortisol + cortisone). SHB was highly correlated with SA (r = 0.75; P less than 0.001) but even more highly with SGC (r = 0.89; P greater than 0.001). Multiple regression analysis confirmed that SGC was a more important determinant of SHB than was SA. Though the concentrations of 18OHB and aldosterone were highly correlated there was considerable variation in the 18OHB:aldosterone ratio during the period of saliva collection. This ratio tended to be highest in the morning and lowest in the evening and was weakly correlated with SGC level (r = 0.62; P less than 0.01). The 18OHB:aldosterone ratio in saliva approximates to, and is highly correlated with, that in plasma. We suggest that the fluctuations in SHB:SA ratio correspond to the relative rates of secretion of 18OHB and aldosterone and that this ratio is modulated either by ACTH or by cortisol. Whether this indicates that 18OHB is a by-product of glucocorticoid as well as aldosterone metabolism, or whether this implies a separate physiological role for the steroid remains to be clarified.

Hypertension in pseudohypoparathyroidism type I

PURPOSE

There is increasing evidence of a central role for the calcium ion in blood pressure regulation. By studying blood pressure control in disorders of calcium homeostasis, a better understanding of the role of the calcium ion and certain calcitrophic hormones in modulating arterial pressure in humans may be gained. Our goal was to examine levels of blood pressure in a group of patients with either type Ia or type Ib pseudohypoparathyroidism (PsHP), a disorder characterized by target organ resistance to parathyroid hormone.

PATIENTS AND METHODS

Forty-six patients with type I PsHP were recruited for the study (28 with type Ia and 18 with type Ib). Blood pressure was measured and the degree of obesity was assessed in all patients. Detailed measurements of hormones involved in blood pressure regulation were made in nine hypertensive patients with PsHP.

RESULTS

Elevated arterial pressure was present in 18 of the 46 patients with PsHP, which comprised 53 percent (18 of 34) of the adult subjects. Prevalence of hypertension was similar in PsHP type Ia (nine of 21) and type Ib (nine of 13; p not significant) and was not related to coexisting hypothyroidism or degree of hypocalcemia. However, hypertension in PsHP was strongly linked to severe obesity. Mean body weights of normotensive and hypertensive patients with PsHP were 64 +/- 2.8 (SEM) kg (125 +/- 6 percent ideal body weight) and 96 +/- 4.7 kg (172 +/- 10 percent ideal body weight), respectively. Compared with obese hypertensive non-PsHP persons, hypertensive subjects with PsHP had reduced basal and posture-stimulated renin activity (basal, 1.68 +/- 0.36 [n = 9] versus 3.97 +/- 0.61 ng/ml/hour [n = 9] [p less than 0.05]; upright posture, 2.11 +/- 0.42 versus 7.13 ng/ml/hour [p less than 0.05]; and lower basal and posture-stimulated plasma norepinephrine levels (basal, 236 +/- 52 versus 426 +/- 37 pg/ml [p less than 0.05]; upright posture, 424 +/- 62 versus 707 +/- 64 pg/ml [p less than 0.05]).

CONCLUSION

Our data suggest that hypertension is common in PsHP types Ia and Ib. This newly identified form of endocrine hypertension is strongly linked to excessive body weight but is associated with alterations in the renin-aldosterone and sympathetic nervous systems that are distinct from those encountered in obesity-related hypertension in the general population. The pathophysiologic basis for hypertension in these two distinctly different forms of PsHP remains to be determined.

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.

Hormone and blood pressure relationships in primary aldosteronism

We used continuous intra-arterial pressure monitoring and hourly venous hormone sampling over 24 hours in 5 patients with primary aldosteronism to study blood pressure and hormone regulation. Three patients were restudied under identical conditions of controlled diet electrolyte intake and body posture 3-7 months after removal of the aldosterone-secreting adrenal tumor. Prior to surgery there was no positive relationship of arterial pressure to renin or to aldosterone. Norepinephrine fluctuations showed positive correlations with arterial pressure but these 2 indices were more closely related after surgery. Plasma aldosterone levels paralleled those of cortisol both before and after cure of primary aldosteronism. Aldosterone/cortisol regression lines were steeper before surgery, and norepinephrine/renin regression lines were steepened in the post-operation studies. Our findings indicate that in established primary aldosteronism, fluctuations in arterial pressure are regulated in part by the sympathetic nervous system: the pattern of aldosterone secretion is controlled mainly by ACTH: aldosterone responsiveness to endogenous ACTH is enhanced: and sympathetic modulation of renin release in inhibited.

Glucocorticoid suppression enhances the 18-hydroxycorticosterone and aldosterone response to metoclopramide in man

18-Hydroxycorticosterone (18-OHB) is a precursor of aldosterone and is the only corticosteroid, other than aldosterone, that is synthesized predominantly in the zona glomerulosa. Administration of the dopamine antagonist, metoclopramide results in parallel rises in plasma 18-OHB and aldosterone levels without affecting the plasma levels of other aldosterone precursors. However, 18-OHB is a product of the zona fasciculata as well as the glomerulosa. Thus, it is possible that metoclopramide may stimulate zona fasciculata secretion of 18-OHB. In order to more selectively examine dopaminergic regulation of zona glomerulosa secretion of 18-OHB we have examined the effect of glucocorticoid suppression of the fasciculata on the 18-OHB and aldosterone responses to metoclopramide, 10 mg iv in 6 normal volunteers. Dexamethasone, 2 mg every 6 hours for 5 days, suppressed basal levels of cortisol, corticosterone, 18-OHB and aldosterone. Dexamethasone treatment had no effect on basal levels of PRA or PRA responses to metoclopramide. The 18-OHB and aldosterone responses to metoclopramide were enhanced (p less than .05) by dexamethasone suppression. The results suggest that dopaminergic mechanisms selectively suppress glomerulosa production of 18-OHB. Endogenous ACTH may inhibit zona glomerulosa production of 18-OHB and aldosterone in response to the dopamine antagonist, metoclopramide.

Plasma concentrations of 18-hydroxycorticosterone and aldosterone in continuous ambulatory peritoneal dialysis and hemodialysis patients

This study explores the hypothesis that the continuous ultrafiltration that accompanies continuous ambulatory peritoneal dialysis (CAPD) produces greater activation of the renin-angiotensin aldosterone axis than does the intermittent ultrafiltration that accompanies thrice weekly hemodialysis (HD). Plasma renin activity (PRA), active renin (AR), total renin (TR), inactive renin (IR), 18-hydroxycorticosterone (18-OH-B), aldosterone (PAC), and cortisol were measured in plasma from CAPD (n = 6) and HD (n = 10) patients. Blood from CAPD patients was sampled at 8 AM after overnight recumbency and at 12 noon after four hours ambulation. Blood from HD patients was sampled immediately pre-HD (8 AM) and post-HD (12 noon) at both 8 AM and 12 noon. PRA (P less than 0.01), AR (P less than 0.01), and AR/TR (100%; P less than 0.01) were higher in CAPD than in HD. IR and TR were not different in the two groups. Plasma 18-OH-B was normal in HD but markedly elevated in CAPD. 18-OH-B was higher in CAPD than in HD at 8 AM (P less than 0.05) and at 12 noon (P less than 0.05). Plasma cortisol was not different in the two groups. We conclude that the greater degree of renin activation in CAPD versus HD contributes to the higher levels of 18-OH-B and PAC observed in CAPD patients.

Effect of metoclopramide and domperidone on aldosterone, 18-hydroxycorticosterone and prolactin secretion in the rhesus monkey

This study was designed to investigate dopaminergic mechanisms in the control of corticosteroid secretion. Eight rhesus monkeys received metoclopramide (200 micrograms/kg) or domperidone (200 and 400 micrograms/kg) with 5% dextrose (vehicle), or with dopamine (4 micrograms/kg/min) infusions begun 60 min before administration of the dopamine antagonist. Metoclopramide, in the presence of vehicle, increased plasma aldosterone concentrations from 4.8 +/- 0.6 ng/dl to a maximum of 36 +/- 4.7 ng/dl and PRL concentrations from 7.6 +/- 1.1 ng/ml to a maximum of 120.5 +/- 8.0 ng/ml. Administration of metoclopramide resulted in a rise in plasma 18-hydroxycorticosterone from 10.2 +/- 1.3 ng/dl to a maximum concentration of 49.6 +/- 4.5 ng/dl. Plasma concentrations of electrolytes, PRA, plasma cortisol, 11-deoxycorticosterone, corticosterone, 18-hydroxy-11-deoxocorticosterone, were not altered by metoclopramide. Domperidone, in both doses, markedly increased plasma PRL concentrations but had no effect on plasma 18-OHB or aldosterone concentrations. Dopamine infusion inhibited the aldosterone response to metoclopramide and the prolactin response to metoclopramide and domperidone. The results of this investigation demonstrate that aldosterone responses to metoclopramide and prolactin responses to metoclopramide and domperidone are mediated by their antagonist activity at dopamine receptors.

Modulation of corticosteroid secretion by dopaminergic mechanisms in rhesus monkeys

This study was designed to investigate dopaminergic mechanisms in the control of corticosteroid secretion. Ten rhesus monkeys received metoclopramide (1.25 mg iv) or domperidone (1.25 mg iv) with 5% dextrose (vehicle) or with dopamine (4 micrograms.kg-1.min-1) infusions begun 60 min before administration of the dopamine antagonist. Metoclopramide, in the presence of vehicle, increased plasma 18-hydroxycorticosterone from 11.2 +/- 1.0 ng/dl to a maximum concentration of 50 +/- 5.1, plasma aldosterone from 5.4 +/- 0.7 ng/dl to a maximum of 38.2 +/- 4.9, and prolactin (PRL) concentrations from 8.5 +/- 1.2 ng/ml to a maximum of 114.6 +/- 7.2. Domperidone, in the presence of vehicle, increased plasma PRL concentrations from 8.6 +/- 1.2 ng/ml to a maximum of 148.7 +/- 7.8 but had no effect on plasma corticosteroids. Dopamine infusion inhibited the 18-hydroxycorticosterone, aldosterone, and PRL response to metoclopramide and the PRL response to domperidone. These results demonstrate that 18-hydroxycorticosterone and aldosterone responses to metoclopramide and PRL responses to metoclopramide and domperidone are mediated by their antagonist activity at dopamine receptors. Domperidone may fail to stimulate aldosterone secretion because it does not cross the blood-brain barrier or fails to act as an antagonist at the glomerulosa dopamine receptor through which dopaminergic modulation of corticosteroid secretion is mediated. A parallel time course of stimulation of 18-hydroxycorticosterone and aldosterone secretion without changes in other aldosterone precursors suggests that dopamine modulates the activity of the glomerulosa 18-hydroxylase enzyme.

Rapid increase of mineralocorticoids after furosemide in low-renin essential hypertension: evidence for 18-hydroxycorticosterone to be a better marker than aldosterone

The response of plasma renin activity (PRA), plasma aldosterone, 18-hydroxycorticosterone (18-OH-B), 18-hydroxydeoxycorticosterone (18-OH-DOC) and corticosterone to furosemide were compared in 20 normal control subjects, 16 patients with normal-renin essential hypertension (NREH) and 12 patients with low-renin essential hypertension (LREH). Analyses were performed before medication, and 15 min (supine) and 120 min (active orthostasis) after IV administration of 40 mg furosemide. In normotensive subjects PRA increased 15 min after administration of furosemide from 0.8 +/- 0.4 ng AI/ml . h (SD) to 3.4 +/- 1.4 (P less than 0.01), plasma aldosterone from 109 +/- 28 pg/ml to 139 +/- 40 (less than 0.01) and 18-OH-B from 199 +/- 90 to 279 +/- 85 (P less than 0.01). In patients with NREH, PRA increased significantly less (P less than 0.01) and no significant increase of plasma aldosterone or 18-OH-B was found. PRA of patients with LREH (0.2 +/- 0.1 ng AI/ml . h) remained practically unchanged 15 min after furosemide administration, but in contrast to NREH aldosterone increased from 111 +/- 37 to 160 +/- 66 (P less than 0.05) and 18-OH-B from 162 +/- 101 to 261 +/- 71 pg/ml (P less than 0.01). The relative increase in plasma 18-OH-B was significantly greater in patients with LREH than in patients with NREH. The plasma levels of aldosterone and 18-OH-B 120 min after furosemide administration were significantly higher in normotensive subjects than in either hypertensive group (P less than 0.01). Corticosterone and 18-OH-DOC levels were the same in all investigated groups and increased significantly (P less than 0.01) only at 120 min after furosemide erone and 18-OH-B 120 min after furosemide administration were significantly higher in normotensive subjects than in either hypertensive group (P less than 0.01). Corticosterone and 18-OH-DOC levels were the same in all investigated groups and increased significantly (P less than 0.01) only at 120 min after furosemide erone and 18-OH-B 120 min after furosemide administration were significantly higher in normotensive subjects than in either hypertensive group (P less than 0.01). Corticosterone and 18-OH-DOC levels were the same in all investigated groups and increased significantly (P less than 0.01) only at 120 min after furosemide administration combined with active orthostasis. In summary, our results support the concept that sensitivity of the mineralocorticoid-producing cells is enhanced in patients with LREH. Postfurosemide 18-OH-B seems to be a better marker of this phenomenon than aldosterone.