Mineralocorticoid Administration Research Articles

A7813 Variations in abundance of urinary exosomal renal sodium transporters in response to mineralocorticoid administration and oral salt loading and in relation to baseline plasma aldosterone and potassium

Objectives: To quantify changes in abundance of sodium transporters [Na-Cl cotransporter (NCC), its phosphorylated form (pNCC), Na-K-Cl cotransporter (NKCC2) and epithelial sodium channel g-subunit (g-ENaC)] and prostasin in urinary exosomes in response to mineralocorticoid administration and oral salt loading, and explore associations with plasma aldosterone (aldo) and K+, in patients undergoing fludrocortisone suppression testing (FST).Methods: Baseline (D0) and day 4 (D4) morning urine samples were collected from 13 patients, including 10 with hypertension and raised aldo/renin ratio undergoing FST to confirm or exclude primary aldosteronism (PA; confirmed in 9) and 3 cured of PA by unilateral adrenalectomy. Urinary exosomes were isolated by ultracentrifugation and analysed by immunoblotting.Results: Increases in abundance of NCC (1.48 fold, p = 0.03) and pNCC (1.52 fold, p = 0.04) and trends towards increases in prostasin (p = 0.07), NKCC2 (p = 0.09) and cleaved g-ENaC (p = 0.11) were observed among the 13 subjects after 4 days FST. Abundance of cleaved g-ENaC rose significantly (p = 0.02) in the 10 non-operated subjects. Among the 13 subjects, D0 aldo and K+ did not correlate significantly with abundance of the target proteins, although D0 pNCC showed a trend towards positive correlation with aldo (p = 0.09). In the 10 non-operated subjects, D0 pNCC showed a negative correlation with plasma K+ that almost reached significance (p = 0.06).Conclusion: FST is associated with significant increases in NCC and pNCC and trends towards increases in ENaC, prostasin and NKCC2. The negative correlation between baseline plasma K+ and abundance of pNCC observed in adrenal-intact subjects suggests a possible role for K+ in the regulation of tubular salt handling and blood pressure.

Hyperkalemic Forms of Renal Tubular Acidosis: Clinical and Pathophysiological Aspects.

In contrast to distal type I or classic renal tubular acidosis (RTA) that is associated with hypokalemia, hyperkalemic forms of RTA also occur usually in the setting of mild-to-moderate CKD. Two pathogenic types of hyperkalemic metabolic acidosis are frequently encountered in adults with underlying CKD. One type, which corresponds to some extent to the animal model of selective aldosterone deficiency (SAD) created experimentally by adrenalectomy and glucocorticoid replacement, is manifested in humans by low plasma and urinary aldosterone levels, reduced ammonium excretion, and preserved ability to lower urine pH below 5.5. This type of hyperkalemic RTA is also referred to as type IV RTA. It should be noted that the mere deficiency of aldosterone when glomerular filtration rate is completely normal only causes a modest decline in plasma bicarbonate which emphasizes the importance of reduced glomerular filtration rate in the development of the hyperchloremic metabolic acidosis associated with SAD. Another type of hyperkalemic RTA distinctive from SAD in which plasma aldosterone is not reduced is referred to as hyperkalemic distal renal tubular acidosis because urine pH cannot be reduced despite acidemia or after provocative tests aimed at increasing sodium-dependent distal acidification such as the administration of sodium sulfate or loop diuretics with or without concurrent mineralocorticoid administration. This type of hyperkalemic RTA (also referred to as voltage-dependent distal renal tubular acidosis) has been best described in patients with obstructive uropathy and resembles the impairment in both hydrogen ion and potassium secretion that are induced experimentally by urinary tract obstruction and when sodium transport in the cortical collecting tubule is blocked by amiloride.

Abstract 195: Sulforaphane Protects Against Subarachnoid Hemorrhage and Alters the Expression of Inflammatory and Extracellular Matrix Remodeling Genes in a Mouse Model of Intracranial Aneurysm

Introduction: Oxidative stress has been shown to play an important role in the pathogenesis of intracranial aneurysm (IA). Sulforaphane is an isothiocyanate that exhibits antioxidant properties via the Nrf2 transcription factor. We tested whether sulforaphane would protect against IA formation and subarachnoid hemorrhage (SAH) in a mouse model. Methods: C57BL/6 mice were treated intraperitoneally with either 0.5mg/kg/day of sulforaphane (treatment group, n = 32) or a vehicle solution (control group, n = 26) prior to being subjected to a well-established IA induction protocol involving unilateral nephrectomy, mineralocorticoid administration, and intracranial injection of elastase. Sulforaphane/vehicle treatments were begun seven days prior to elastase injection, and continued daily for the duration of the experiment. Animals were followed for 14 days until sacrifice, with measurement of the number of aneurysms formed and ruptured in each animal. Intracranial vessel tissue was collected, pooled, and analyzed using real-time PCR (RT-PCR) with experiments performed in triplicate (n = 3). Results: There was a lower incidence of IA in the treatment group (1.06 +/- 0.24 per animal) than in the control group (1.54 +/- 0.33), but this trend did not reach significance. The incidence of SAH in the treatment group (0.53 +/- 0.09 per animal) was approximately 50% lower than in the control group (1.08 +/- 0.21, p = 0.012). RT-PCR showed significant (p < 0.05) differences in the expression of interferon gamma, matrix metalloproteinase 9, collagen Ia2, interleukin-6, myosin heavy chain, and SM22 between the treatment and control groups. Conclusions: Treatment with sulforaphane resulted in a significantly lower incidence of SAH in a mouse model of IA. The expression of genes involved in inflammation and extracellular matrix remodeling were altered by sulforaphane administration.

OS 05-06 IN PRIMARY ALDOSTERONISM, MINERALOCORTICOIDS AND POTASSIUM INFLUENCE ABUNDANCE OF THE THIAZIDE SENSITIVE SODIUM-CHLORIDE COTRANSPORTER

Background: Distal tubular sodium retention is a potent driver of hypertension, with the thiazide sensitive sodium-chloride cotransporter (NCC) a key player. The upstream modulators of NCC are unclear, but recent evidence has revealed the kinases ‘with-no-lysine kinase 4’ (WNK4) and ‘STE20/SPS1-related, proline alanine-rich kinase’ (SPAK) to be involved. The wider role of mineralocorticoids is poorly understood, but animal models implicate aldosterone as a potent regulator, possibly via effects on plasma potassium. We therefore studied the effects of fludrocortisone on NCC, pNCC, WNK4 and SPAK in human urinary exosomes. Methods: Daily morning urine samples were collected from 26 patients undergoing fludrocortisone suppression testing (100mcg q6h) to diagnose or exclude primary aldosteronism (PA). Exosomes were isolated by ultracentrifugation and NCC, pNCC, WNK4 and SPAK expression quantified by immunoblot. Results: We observed a rise in NCC (3.68 fold increase, P < 0.01) and median pNCC (2.73 fold increase, P < 0.01) during fludrocortisone administration. The ratio of pNCC/NCC however dropped by 48% (P < 0.01). Abundance of WNK4 also increased by 3.23 fold (P < 0.01) but changes in SPAK were not significant once corrected for changes in exosome marker abundance. Patients without PA (n = 6) had lower baseline aldosterone levels (144 vs 643 pmol/l, P < 0.01) than those with PA (n = 20) and a lower abundance of NCC (p = 0.03), pNCC (p = 0.027) and WNK4 (p = 0.002). Plasma potassium was unchanged during the test, but at baseline there was a very strong negative correlation between NCC, pNCC and WNK4 abundance (P < 0.01 for all), which was stronger than the relationship with aldosterone. Conclusions: Mineralocorticoid administration causes a rapid and progressive increase in abundance and phosphorylation of NCC in humans. NCC abundance is stimulated to a greater extent than phosphorylation, possibly via stimulation of the WNK4 pathway. These effects may be driven by changes in plasma potassium.

In Primary Aldosteronism, Mineralocorticoids Influence Exosomal Sodium-Chloride Cotransporter Abundance.

Distal tubular sodium retention is a potent driver of hypertension, and the thiazide-sensitive sodium-chloride cotransporter (NCC) has a key role in this process. In humans, factors regulating NCC are unclear, but in animal models, aldosterone is a potent regulator, possibly via effects on plasma potassium. We studied the effects of the mineralocorticoid fludrocortisone on the abundance of NCC and its phosphorylated form (pNCC) as well as WNK lysine deficient protein kinase 4 (WNK4) and STE20/SPS1-related, proline alanine-rich kinase (SPAK) in human urinary exosomes. We isolated exosomes from daily urine samples in 25 patients undergoing fludrocortisone suppression testing (100 μg every 6 hours for 4 days) to diagnose or exclude primary aldosteronism. Over the course of the test, NCC levels increased 3.68-fold (P<0.01) and pNCC levels increased 2.73-fold (P<0.01) relative to baseline. The ratio of pNCC/NCC dropped by 48% (P<0.01). The abundance of WNK4 increased 3.23-fold (P<0.01), but SPAK abundance did not change significantly (P=0.14). Plasma potassium concentration strongly and negatively correlated with pNCC, NCC, and WNK4 abundance (P<0.001 for all). This study shows that, in humans, mineralocorticoid administration is associated with a rapid increase in abundance of NCC and pNCC, possibly via the WNK pathway. These effects may be driven by changes in plasma potassium.

Natriuretic Hormone

Until about 1957 it was generally accepted that the regulation of renal sodium excretion was dependent solely upon changes in(a) glomerular filtration rate (Factor 1) and(b) the activity of the renin-angiotensin-aldosterone system (Factor 2).coupled with the effect of changes in intrarenal haemodynamics and physical factors, such as hydrostatic pressure surrounding renal tubules, and plasma protein osmotic pressure in peritubular capillaries.Since that time, however, evidence has gradually been accumulated to suggest that these are not the only factors which are relevant in this context, and the existence of a humoral inhibitor of renal sodium reabsorption has therefore been postulated. This ‘third factor' has been given the name of natriuretic hormone, and indications of its presence have been found in two principal situations. These are(a) 'Sodium escape’ during chronic mineralocorticoid administration(b) Volume expansion with (i) isotonic saline (ii) blood

The child with difficult to control Congenital Adrenal Hyperplasia: is there a place for continuous subcutaneous hydrocortisone therapy

The treatment of congenital adrenal hyperplasia requires administration of glucocorticoid and mineralocorticoid to replace the deficit resulting from the enzymatic block. During puberty, cortisol metabolism changes with an increase in clearance, which may lead to unstable control. This may require an increase in dosing frequency, and if this proves problematic, continuous subcutaneous hydrocortisone delivery using insulin pump technology can be valuable. The potential indications for such therapy along with some practical considerations are detailed in this Clinical Question report.

Chronic hyperaldosteronism in Cryptochrome-null mice induces high-salt- and blood pressure-independent kidney damage in mice

Although aldosterone has an essential role in controlling electrolyte and body fluid homeostasis, aldosterone also exerts certain pathological effects on the kidney. Several previous studies have attempted to examine these deleterious effects. However, the majority of these studies were performed using various injury models, including high-salt treatment and/or mineralocorticoid administration, by which the kidney changes observed were not only due to aldosterone but also due to prior injury caused by salt and hypertension. In the present study, we investigated aldosterone's pathological effect on the kidney using a mouse model with a high level of endogenous aldosterone. We used cryptochrome-null (Cry 1, 2 DKO) mice characterized by high aldosterone levels and low plasma renin activity and observed that even under normal salt exposure conditions, these mice showed increased albumin excretion and kidney tubular injury, decreased nephrin expression and increased reactive oxygen species production in the absence of hypertension. Exposure to high salt levels exacerbated the kidney damage observed in these mice. Moreover, we noted that decreasing blood pressure without blocking aldosterone action did not provide beneficial effects to the kidney in high-salt-treated Cry 1, 2 DKO mice. Thus, our findings support the hypothesis that aldosterone has deleterious effects on the kidney independent of high-salt exposure and high blood pressure.

Adrenal Hemorrhage Causing Adrenal Insufficiency in a Patient with Antiphospholipid Syndrome: Increased Adrenal 18F-FDG Uptake

45-yr-old woman with antiphospholipid syndrome (APS) and a history of recurrent thromboembolic events was admitted with hematothorax while on acenocoumarol. Recovery was complicated by cardiacarrestandhypotensionrequiringresuscitation.She subsequently developed fever and abdominal distress coincided by hyponatremia, hyperkalemia, and eosinophilia. An insufficient rise in serum cortisol after synthetic ACTH (20 nmol/liter maximally), together with an undetectable aldosterone and elevated ACTH (278 ng/liter) confirmed primary adrenal insufficiency. Glucocorticoid and mineralocorticoid administration improved her condition. Antiadrenal antibodies were absent. Plasma metanephrines were normal. Integrated 2-[fluorine 18] fluoro-2-deoxy-D glucose ( 18 F-FDG) positron emission tomography/computed tomography (CT)wasperformedinsearchofaninflammatoryfocus. 18 F-FDG uptake was increased in both adrenal glands,

Membranous Nephropathy With Renal Salt Wasting: Role of Neurohumoral Factors in Sodium Retention

The role of neurohumoral factors in the sodium retention of nephrotic syndrome is controversial. We report a case with abrupt onset of severe nephrotic-range proteinuria and hypoalbuminemia due to membranous glomerulonephritis that was associated with renal salt wasting and hypovolemia without edema. Further evaluation showed hypoaldosteronism, hyporeninemia, and primary autonomic failure principally affecting the sympathetic nervous system, determined by the Valsalva maneuver. Administration of exogenous mineralocorticoid and oral salt caused edema and accelerated hypertension. The severe hypoaldosteronism likely was due to use of the angiotensin-converting enzyme inhibitor lisinopril, and it improved after this drug treatment was discontinued. The nephrotic proteinuria resolved after treatment with cyclosporine and prednisone, but the primary autonomic failure with hyporeninemic hypoaldosteronism persisted. The case shows that intratubular factors activated by nephrotic proteinuria are not sufficient to produce sodium retention in the absence of aldosterone and an intact sympathetic nervous system.

Hyponatremia and antidiuresis syndrome

Antidiuretic hormone (ADH), or arginine vasopressin (AVP), is primarily regulated through plasma osmolarity, as well as non-osmotic stimuli including blood volume and stress. Links between water-electrolyte and carbohydrate metabolism have also been recently demonstrated. AVP acts via the intermediary of three types of receptors: V1a, or V1, which exerts vasoconstrictive effects; pituitary gland V1b, or V3, which participates in the secretion of ACTH; and renal V2, which reduces the excretion of pure water by combining with water channels (aquaporin 2). Antidiuresis syndrome is a form of euvolaemic, hypoosmolar hyponatraemia, which is characterised by a negative free water clearance with inappropriate urine osmolality and intracellular hyper-hydration in the absence of renal, adrenal and thyroid insufficiency. Ninety percent of cases of antidiuresis syndrome occur in association with hypersecretion of vasopressin, while vasopressin is undetectable in 10% of cases. Thus the term “antidiuresis syndrome” is more appropriate than the classic name “syndrome of inappropriate ADH secretion” (SIADH). The clinical symptoms, morbidity and mortality of hyponatraemia are related to its severity, as well as to the rapidity of its onset and duration. Even in cases of moderate hyponatraemia that are considered asymptomatic, there is a very high risk of falls due to gait and attention disorders, as well as rhabdomyolysis, which increases the fracture risk. The aetiological diagnosis of hyponatraemia is based on the analysis of calculated or measured plasma osmolality (POsm), as well as blood volume (skin tenting of dehydration, oedema). Hyperglycaemia and hypertriglyceridaemia lead to hyper- and normoosmolar hyponatraemia, respectively. Salt loss of gastrointestinal, renal, cutaneous and sometimes cerebral origin is hypovolaemic, hypoosmolar hyponatraemia (skin tenting), whereas oedema is present with hypervolaemic, hypoosmolar hyponatraemia of heart failure, nephrotic syndrome and cirrhosis. Some endocrinopathies (glucocorticoid deficiency and hypothyroidism) are associated with euvolaemic, hypoosmolar hyponatraemia, which must be distinguished from SIADH. Independent of adrenal insufficiency, isolated hypoaldosteronism can also be accompanied by hypersecretion of vasopressin secondary to hypovolaemia, which responds to mineralocorticoid administration. The causes of SIADH are classic: neoplastic (notably small-cell lung cancer), iatrogenic (particularly psychoactive drugs, chemotherapy), lung and cerebral. Some causes have been recently described: familial hyponatraemia via X-linked recessive disease caused by an activating mutation of the vasopressin 2 receptor; and corticotropin insufficiency related to drug interference between some inhaled glucocorticoids and cytochrome p450 inhibitors, such as the antiretroviral drugs and itraconazole, etc. SIADH in marathon runners exposes them to a risk of hypotonic encephalopathy with fatal cerebral oedema. SIADH treatment is based on water restriction and demeclocycline. V2 receptor antagonists are still not marketed in France. These aquaretics seem effective clinically and biologically, without demonstrated improvement to date of mortality in eu- and hypervolaemic hyponatraemia. Obviously treatment of a corticotropic deficit, even subtle, should not be overlooked, as well as the introduction of fludrocortisone in isolated hypoaldosteronism and discontinuation of iatrogenic drugs.

Experimental Cardiac Hypertrophy Induced by Oral Administration of Mineralocorticoid and Saline in Rats

We suggest a new, easily applicable way of myocardial hypertrophy induction in rats. Forty randomized age-matched male Wistar rats were divided into 2 groups of 20 each: a control group and an orally administered fludrocortisone/salt group. Myocardial hypertrophy was estimated by measuring body weight, heart-weight-to-body-weight ratio and ventricular free wall thickness. Moderate myocardial hypertrophy without heart failure was established in fludrocortisone/salt group in 4 weeks. Our method is effective and low cost, and it provides a model of hypertrophic heart.

S1-1 The Role and Regulation of Mineralocorticoid Receptor Activation in Heart Failure

Mineralocorticoid receptor (MR) activation by either administration of exogenous mineralocorticoids, or by endogenous glucocorticoids, promotes oxidative stress, vascular inflammation and cardiac fibrosis in experimental animals. These studies suggest potential mechanisms for the benefits observed in recent large scale clinical trials investigating the cardioprotective effects of MR antagonists given in conjunction with current best practice. Given that few patients showed elevated plasma aldosterone, novel mechanisms involved in activating the MR in the failing heart are now being investigated. We have investigated the contribution of specific cell types to MR-mediated cardiac pathology using Cre-Lox technology to create tissue specific MR knockouts mice. Our data suggests that MR signalling in macrophages contributes to the regulation of proinflammatory and profibrotic genes associated with the onset of cardiac fibrosis. Importantly, macrophage MR null mice given DOC/salt for 8 weeks show no increase in cardiac fibrosis and systolic blood pressure, in contrast to wild type littermates. Given that macrophage recruitment is equivalent in MR macrophage knockout mice and wild type mice these data suggest that macrophage MR may play a distinct role in tissue remodelling but that MR activation elsewhere in the cardiovascular system is also important. Selective modulators of the MR that are specifically directed towards non-epithelial cardiovascular tissue would increase tissue protection without the side effects associated with renal MR blockade. Moreover, activation of the MR by other ligands would argue for the use of MR antagonists in renal and cardiovascular protection even when plasma aldosterone is normal.

The Janus effect: two faces of aldosterone

Inhibition of the nitric oxide pathway by N(omega)-nitro-l-arginine methyl ester (l-NAME) is well known to produce hypertension and proteinuria, but the mechanisms are less straightforward. Prolonged administration of mineralocorticoids mimics the pathological findings produced by l-NAME. Ikeda and colleagues provide a clue to the mechanism by showing that exposure to l-NAME increases plasma aldosterone 50-fold, and that spironolactone markedly attenuates the renal changes. Thus, chronic l-NAME exposure may turn out to be a model of mineralocorticoid excess.

Mineralocorticoid Signaling in Transition to Heart Failure With Normal Ejection Fraction

Heart failure with normal ejection fraction occurs in elderly patients with hypertensive heart disease. We hypothesized that, in such patients, mineralocorticoid receptor activation accelerates the types of ventricular and vascular remodeling and dysfunction believed important in the transition to heart failure. We tested this hypothesis by administering deoxycorticosterone acetate (DOCA) without salt loading or nephrectomy to elderly dogs with experimental hypertension. Elderly dogs were made hypertensive by renal wrapping. After 5 weeks, dogs were randomly assigned to DOCA (1 mg/kg per day IM; old hypertensive [OH]+DOCA; n=11) or not (OH; n=11) for 3 weeks. At week 8, conscious echocardiography and hemodynamic assessment under anesthesia were performed. DOCA resulted in further increases in conscious blood pressure (P<0.05) without increases in cardiac output or diastolic volume. In the conscious state, effective arterial elastance (P<0.05) and systemic vascular resistance (P=0.06) were increased, and systemic arterial compliance (P<0.05) was decreased in OH+DOCA animals. After anesthesia, instrumentation, and autonomic blockade, blood pressure was lower, whereas left ventricular (LV) systolic elastance, LV diastolic stiffness, and ex vivo myofiber diastolic stiffness were increased in OH+DOCA animals. LV collagen was increased in OH+DOCA animals (P<0.05 for all), but LV mass, LV brain natriuretic peptide, and titin isoform profiles were not. Neither aortic stiffness nor aortic structure was altered in OH+DOCA animals. These findings suggest that age and hypertensive heart disease enhance sensitivity to exogenous mineralocorticoid administration and that mineralocorticoid receptor activation could contribute to the transition to heart failure in elderly persons by promoting increases in LV diastolic and systolic stiffness.

Recent advances in diagnosis, treatment, and outcome of congenital adrenal hyperplasia due to 21-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21-OHD) is an autosomal-recessive disease causing cortisol deficiency, aldosterone deficiency and hyperandrogenism. Diagnosis of 21-OHD is confirmed by steroid analysis in newborn screening or later on. Standard medical treatment consists of oral glucocorticoid and mineralocorticoid administration in order to suppress adrenal androgens and to compensate for adrenal steroid deficiencies. However, available treatment is far from ideal, and not much is known about the long-term outcome in CAH as trials in patients in adulthood or old age are rare. Here we briefly describe the pathophysiology, clinical picture, genetics and epidemiology of 21-OHD. This is followed by a comprehensive review of the recent advances in diagnosis, treatment and outcome. Novel insights have been gained in the fields of newborn screening, specific steroid measurement utilizing mass spectrometry, genetics, glucocorticoid stress dosing, additive medical therapy, prenatal treatment, side-effects of medical treatment, adrenomedullary involvement, metabolic morbidity, fertility and gender identity. However, many issues are still unresolved, and novel questions, which will have to be answered in the future, arise with every new finding.

Mineralocorticoid receptor activation and cardiac fibrosis

MR (mineralocorticoid receptor) activation by either administration of exogenous mineralocorticoids or by allowing endogenous glucocorticoids to activate the MR has been shown to produce oxidative stress and vascular inflammation at the earliest stages of the development of cardiac fibrosis in experimental animals. These studies suggest potential mechanisms for the benefits observed in recent large scale clinical trials investigating the cardioprotective effects of MR antagonists given in conjunction with current best practice therapy for moderate-to-severe heart failure and heart failure post-myocardial infarction. Given that few patients had elevated plasma aldosterone, novel mechanisms involved in activating the MR in the failing heart are now being investigated.

Long-term Follow up of Congenital Adrenal Hyperplasia Patients with Hyponatremia

Congenital adrenal hyperplasia (CAH) caused by 21-hydroxylase deficiency is an autosomal recessive disease, which leads to cortisol and aldosterone deficiency and hyperandrogenism. Typical medical treatment includes oral glucocorticoid and mineralocorticoid administration to suppress adrenal androgens and to compensate for adrenal steroid deficiencies. However, some patients stopped taking medicine without the doctor's consent. Among these patients, four cases of CAH patients showing the presence of hyponatremia as an initial electrolyte disorder were found with adrenal adenoma. Hypersecretion of adrenocorticotrophic hormone and chronic poor compliance to therapy appears to be associated with the development of the adrenal tumor. Two cases were managed with adrenalectomy because of increasing adrenal tumor size and virilization. Whereas the other two cases did not increase in size and were observed without adrenalectomy. Therefore, it is important that patients with CAH maintain steroid medication to avoid the appearance of adrenal tumor.

Isolated corticotrophin deficiency

Isolated ACTH deficiency (IAD) is a rare disorder, characterized by secondary adrenal insufficiency (AI) with low or absent cortisol production, normal secretion of pituitary hormones other than ACTH and the absence of structural pituitary defects. In adults, IAD may appear after a traumatic injury or a lymphocytic hypophysitis, the latter possibly due to autoimmune etiology. Conversely, a genetic origin may come into play in neonatal or childhood IAD. Patients with IAD usually fare relatively well during unstressed periods until intervening events spark off an acute adrenal crisis presenting with non specific symptoms, such as asthenia, anorexia, unintentional weight loss and tendency towards hypoglycemia. Blood chemistry may reveal mild hypoglycemia, hyponatremia and normal-high potassium levels, mild anemia, lymphocytosis and eosinophilia. Morning serum cortisol below 3 microg/dl are virtually diagnostic for adrenal insufficiency. whereas cortisol values comprised between 5-18 microg/dl require additional investigations: insulin tolerance test (ITT) is considered the gold standard but-when contraindicated-high or low dose-ACTH stimulation test with serum cortisol determination provides a viable alternative. Plasma ACTH concentration and prolonged ACTH infusion test are useful in differential diagnosis between primary and secondary adrenal insufficiency. For some patients with mild, near-to-asymptomatic disease, glucocorticoid replacement therapy may not be required except during stressful events; for symptomatic patients, replacement doses i.e., mean daily dose 20 mg (0.30 mg/kg) hydrocortisone or 25 mg (0.35 mg/kg) cortisone acetate, are usually sufficient. Administration of mineralocorticoids is generally not necessary as their production is maintained.

Aldosterone-sensitive NTS neurons are inhibited by saline ingestion during chronic mineralocorticoid treatment

The nucleus of the solitary tract (NTS) contains a unique subpopulation of neurons that express the enzyme 11-β-hydroxysteroid dehydrogenase type 2 (HSD2). These neurons are mineralocorticoid-sensitive and are activated in association with salt appetite during sodium deficiency. In the absence of sodium deficiency, the HSD2 neurons and sodium appetite are both stimulated by chronic mineralocorticoid administration. After 7 days of treatment with deoxycorticosterone (2 mg/day), an increased number of HSD2 neurons became immunoreactive for the neuronal activity marker c-Fos. When given access to concentrated saline (3% NaCl), deoxycorticosterone-treated rats drank eight times more than vehicle-treated rats. Saline ingestion increased neuronal activation within the medial subdivision of the NTS, but the number of c-Fos-immunoreactive HSD2 neurons was reduced. This finding suggests that the HSD2 neurons are inhibited by signals directly related to saline ingestion, and not simply by the alleviation of sodium deficiency, which does not occur during mineralocorticoid administration.