Integrated concentration of plasma aldosterone in normal subjects: correlation with cortisol

The Expanding Spectrum of Primary Aldosteronism: Implications for Diagnosis, Pathogenesis, and Treatment

Primary aldosteronism is characterized by aldosterone secretion that is independent of renin and angiotensin II and sodium status. The deleterious effects of primary aldosteronism are mediated by excessive activation of the mineralocorticoid receptor that results in the well-known consequences of volume expansion, hypertension, hypokalemia, and metabolic alkalosis, but it also increases the risk for cardiovascular and kidney disease, as well as death. For decades, the approaches to defining, diagnosing, and treating primary aldosteronism have been relatively constant and generally focused on detecting and treating the more severe presentations of the disease. However, emerging evidence suggests that the prevalence of primary aldosteronism is much greater than previously recognized, and that milder and nonclassical forms of renin-independent aldosterone secretion that impart heightened cardiovascular risk may be common. Public health efforts to prevent aldosterone-mediated end-organ disease will require improved capabilities to diagnose all forms of primary aldosteronism while optimizing the treatment approaches such that the excess risk for cardiovascular and kidney disease is adequately mitigated. In this review, we present a physiologic approach to considering the diagnosis, pathogenesis, and treatment of primary aldosteronism. We review evidence suggesting that primary aldosteronism manifests across a wide spectrum of severity, ranging from mild to overt, that correlates with cardiovascular risk. Furthermore, we review emerging evidence from genetic studies that begin to provide a theoretical explanation for the pathogenesis of primary aldosteronism and a link to its phenotypic severity spectrum and prevalence. Finally, we review human studies that provide insights into the optimal approach toward the treatment of primary aldosteronism.

Circadian rhythm in plasma aldosterone concentration and its seasonal modulation in the camel (Camelus dromedarius) living in the Algerian Sahara desert

Five male camels dwelling in the Algerian Sahara were studied for circadian rhythmicity in plasma aldosterone concentration and its seasonal modulation. Blood was sampled at a frequency of 1 h or less for a span of 27 h during each season of the year. The mean plasma aldosterone concentration exhibited a significant circadian rhythmicity in every season of the year. Plasma aldosterone concentration was lowest in the morning, increased in the afternoon, and generally highest in the late evening. The peak of the circadian rhythm exhibited seasonal variation; it occurred at 20:04h in October, 16:41h in December, 20:40h in March, and 24:16h in June. The rhythm's 24h mean also exhibited seasonal variability, being significantly higher in March and June compared to October.

Detection of primary aldosteronism by the 6-hour integrated aldosterone/renin ratio

An outpatient diagnostic procedure measuring the 6-hour integrated plasma concentration of aldosterone and plasma renin activity was used to detect primary aldosteronism in 12 patients with low renin hypertension, including six with mild hypertension and normal urinary excretion and spot plasma levels of aldosterone. The ratio of integrated plasma concentration of aldosterone to plasma renin activity in the 12 patients (mean, 339; range, 116-700; p less than 0.0001) did not overlap with that measured in 105 normotensive controls (mean, 27.8; range, 5-97) or in 87 subjects with essential hypertension (mean, 29.2; range, 4-67). Eight patients had surgically proven adenomas (3 of which measured less than 5 mm) with normalization of blood pressure following adrenalectomy. The four remaining patients had bilateral hyperplasia. The 6-hour integrated plasma concentration of aldosterone to plasma renin activity ratio was found to be a useful new outpatient diagnostic tool for evaluation of primary hyperaldosteronism.

The diagnostic value of the 24 hour integrated concentration of plasma aldosterone

The 24-hour urinary excretion rate of aldosterone, the 24-hour integrated concentration of plasma aldosterone (IC-ALDO) and the morning plasma aldosterone levels from a single, discrete venipuncture of 92 subjects (30 normal subjects, 62 patients with mild, essential hypertension) were compared, using the variance ratio method, to 12 patients with primary aldosteronism. The variance of the IC-ALDO was significantly lower than the respective variances of the 24-hour urinary excretion of aldosterone (P less than 0.01) and of the discrete, morning plasma levels of aldosterone (P less than 0.01). The clinical usefulness of this diagnostic procedure depends on its ability to discriminate between healthy subjects and various hypertensive patients. Because of its narrower variance and enhanced discriminatory ability, the 24-hour IC-ALDO may have useful application in diagnosis of various disorders of aldosterone secretion. We have found the IC-ALDO completely separated 11 of 12 primary aldosteronism patients (mean 36 +/- 17) from essential hypertensive controls (mean 9.6 +/- 4.1) (P less than 0.01). When IC-ALDO was combined with integrated concentration of plasma renin activity in an ALDO/RENIN ratio, all 12 primary aldosteronism patients were diagnosed.

Circadian as well as circannual rhythms of circulating aldosterone have decreased amplitude in aging women

Age differences in the characteristics of the circadian rhythm in circulating radioimmunoassayable aldosterone were studied on nine 20 to 26 year-old and ten 70 to 78 year-old women and ten 23 to 26 year old and ten 70 to 80 year old men in Würzburg, West Germany. These diurnally active-nocturnally resting subjects were sampled every 3 hours for 15 hours. A classical analysis of variance and a multivariate analysis of rhythm characteristics revealed major effects of age exerted on the circadian aldosterone amplitude in women (p = 0.003) but not in concomitantly sampled men. These observations complement the study of circadian and circannual rhythms in 8 young adults (15-21 years), 10 mature adults (29-36 years) and 10 post-menopausal (44-59 years) North American women, sampled at 100 minute intervals for 24 hours, once in each season, and document that the adrenocortical aldosterone-producing system remains rhythmic with at least two frequencies up to the late decades of human life, although in women it may be characterized by a reduction in the extent of spectral change after 70 years of age.

Diurnal and ultradian variations of plasma concentrations of eleven adrenal steroid hormones in human males

The diurnal variations of the plasma concentrations of eleven steroid hormones and of corticotropin (ACTH) were studied in ten young healthy males. The plasma steroids progesterone, pregnenolone, deoxycorticosterone, 17-OH-progesterone, 17-OH-pregnenolone, deoxycortisol, 18-OH-deoxycorticosterone, corticosterone, aldosterone, cortisol and 18-OH-corticosterone, as well as plasma ACTH, were measured at 30-min intervals in the morning and in the evening and at 2-h intervals during the rest of the day. Steroids were extracted from 1 ml plasma, fractionated by high-pressure liquid chromatography (HPLC) and finally quantified by radioimmunoassay (RIA). Plasma concentrations of ACTH were radioimmunoassayed after extraction from 2 ml plasma. More or less pronounced circadian and episodic variations were apparent for plasma levels of all steroids studied, as well as of ACTH. According to related profiles of diurnal variations of plasma concentrations, three different categories of steroids were tentatively crystallized. Category 1 includes 17-OH-pregnenolone, deoxycortisol, corticosterone, 18-OH-deoxycorticosterone, deoxycorticosterone, cortisol and 18-OH-corticosterone, exhibiting a rhythm partly synchronous with that of the pituitary secretory activity of ACTH. Category 2, including progesterone, pregnenolone and 17-OH-progesterone, exhibited a time course of plasma concentrations assuming a regulation predominantly dictated by the testicular secretory activity. Lastly, aldosterone exerted a variation of plasma concentrations which was obviously regulated by the renin-angiotensin system under the present conditions.

Studies of diurnal changes in plasma renin activity, and plasma noradrenaline, aldosterone and cortisol concentrations in man

Diurnal studies were performed on ten normal volunteers taking a normal sodium diet. Half-hourly blood samples were taken throughout 25 h and assayed for plasma renin activity (PRA) and the plasma concentrations of noradrenaline, aldosterone and cortisol. Sleep was recorded polygraphically and scored by standard criteria. Circadian rhythms were demonstrated for plasma cortisol, aldosterone and noradrenaline concentrations, but not for plasma renin activity. The nadir of the rhythm for the noradrenaline concentration appeared to be related to sleep itself rather than to any chronological index. Only PRA was effected by the stage of sleep, falling sharply during periods of REM sleep. Plasma cortisol and aldosterone concentrations showed a positive correlation over the 24 h. There was, however, no correlation between PRA and plasma aldosterone concentrations, except when the subjects arose after their night's recumbency. Plasma noradrenaline concentration did not correlate with the concentration of any of the other hormones measured.

Adrenoleukodystrophy: elevated C26 fatty acid in cultured skin fibroblasts

Because postmortem brain and adrenal tissue from patients with adrenoleukodystrophy (ALD) or adrenomyeloneuropathy (AMN) have been shown to contain abnormally large amounts of very long chain fatty acids (C24 through C30), we searched for such an abnormality in cultured skin fibroblasts. Total lipid extracts of cultured fibroblasts were hydrolyzed, their fatty acid composition was determined by gas-liquid chromatography, and the ratio of C26 to C22 fatty acids was calculated. In 29 control cell lines this ratio was 0.064 +/- 0.019. In 5 patients with autopsy-proved ALD the ratio was 0.778 +/- 0.139; in 6 patients with clinical features typical of ALD it was 0.764 +/- 0.092; in 2 patients with autopsy-proved AMN, 0.890 +/- 0.02; and in 2 patients with clinical features typical of AMN, 0.560 +/- 0.079. Abnormal ratios were observed in 4 of 5 ALD heterozygotes. In 3 patients in whom the diagnosis of ALD was suspected, an abnormal ratio (0.860) was observed in 1 and normal ratios (0.06 and 0.074) in the 2 others.

Influence of sodium balance on ACTH/adrenal corticosteroid dose-response curves in the dog

In order to define short-term ACTH/corticosteroid dose-respone characteristics, we infused ACTH for 1 h at each of five incremental rates into pedigreed male beagle dogs in four different states of sodium balance. Progressive sodium depletion was associated with progressive increased in basal (pre-ACTH) plasma levels of renin, angiotensin II, aldosterone, 18-hydroxycorticosterone (18-OH-B), and 18-hydroxy-11-deoxycorticosterone (18-OH-DOC). Administration of dexamethasone significantly reduced the preinfusion levels of cortisol, aldosterone, 18-OH-B, and 18-OH-DOC. The threshold dose of ACTH required to elicit an aldosterone response during low-sodium intake was similar to that for cortisol, but was higher during normal or high-sodium intake. Steepest portions of the dose-response curves were at lower rates of ACTH infusion for cortisol than for aldosterone, and maximum increment was much greater for cortisol (60-fold) than for aldosterone (12-fold). Whereas the slopes of ACTH/aldosterone and ACTH/18-OH-B dose-response curves were steepened by lower sodium diets, the ACTH/cortisol response was significantly flattened by severe sodium depletion. We conclude that ACTH is a potent and direct-acting short-term regulator of aldosterone secretion, subject to modification by altered sodium balance.

Dissociation of the diurnal variation of aldosterone and cortisol in anephric subjects

Diurnal variation of plasma aldosterone and cortisol concentration in man was studied in 13 anephric subjects and 7 normal subjects. All subjects were ambulatory and active throughout the study except during an 8-hour sleep period. Six anephric subjects received Kayexalate (sodium polystyrene sulfonate) during the studies to prevent potassium accumulation and increase in plasma potassium concentration. Diurnal variation of plasma aldosterone concentration with peak and nadir concentrations at 12:00 noon and 12:00 midnight respectively was demonstrated in the studies on normal subjects. Changes in plasma aldosterone concentration were not significantly correlated with changes in plasma concentration but were highly correlated with changes in PRA (P less than 0.001). There was a highly significant correlation between plasma aldosterone and potassium concentration in the anephric subjects studied without Kayexalate administration (P less than 0.001). In the anephric subjects who received Kayexalate, plasma aldosterone and potassium concentration remained stable, and no correlation could be demonstrated. No diurnal variation of plasma aldosterone concentration could be demonstrated in either group of anephric subjects, whereas plasma cortisol concentration varied as in the studies on normal subjects. Conclusion. Diurnal variation of plasma aldosterone concentration is dependent on continued stimulation by the renin-angiotensin system. Loss of this stimulation has no demonstrable effect on the diurnal variation of plasma cortisol concentration.

Regulation of aldosterone secretion in dehydrated babies

The factors controlling aldosterone secretion were measured in 12 patients with moderate to severe dehydration during the first year of life. Secondary hyperaldosteronism was present in all cases (mean plasma aldosterone concentration 414.6 ng/dl), as well as increased plasma cortisol levels (mean 49.7 microgram/dl). Plasma cortisol, an indirect parameter of stimulation of the adrenal cortex by ACTH, showed the highest correlation with plasma aldosterone (r = 0.82). Despite a mean elevation of 168 ng AT/ml/h the plasma renin concentration did not seem to play the dominant role in the regulation of aldosterone secretion in these infants. High serum sodium concentrations have a clearly inhibiting effect on aldosterone secretion as shown by the negative correlation coefficient of r = 0.80.

24 hour profile of 18-hydroxy-11-deoxycorticosterone in normal supine man: relationship with cortisol and aldosterone

Daily profiles of plasma 18-hydroxy-11-deoxycorticosterone (18-OH-DOC) were studied in four normal supine men on a normal sodium intake. Blood was taken every hour from 01.00 to 24.00 hours. Plasma cortisol (F) and aldosterone (A) were determined hourly for comparative studies. 18-OH-DOC fluctuated considerably during the 24 h period of investigation, the highest values being found during the early morning hours in synchrony with F. The episodic secretions of 18-OH-DOC were also significantly correlated with those of A, which in turn paralleled those of F. We conclude that ACTH, plays a definite role in the regulation of 18-OH-DOC in normal supine men on a normal sodium diet.

Measurement of the 24 hour integrated plasma concentration of growth hormone, in assessing the response of acromegalic patients to treatment

The integrated concentration of growth hormone (ICGH) has been measured in fourteen acromegalic patients, and compared with the basal plasma growth hormone concentration (BGH). Seven patients were treated by trans-sphenoidal pituitary surgery, and in these, similar percentage reductions of BGH and ICGH occurred after treatment. The other seven patients were treated with bromocriptine alone, and in these the percentage reduction of ICGH was significantly less than that of BGH. Measurements of basal plasma growth hormone concentration may be unreliable in assessing the response of acromegalic patients to treatment with bromocriptine. The ICGH can be measured easily on a single blood specimen obtained by continuous sampling over 24 h, and may be more reliable for this purpose.

Plasma and urinary aldosterone measurement in healthy subjects with a radioimmunoassay kit not requiring chromatography

We examined the application of a radioimmunoassay kit, not requiring chromatography, to the measurement of aldosterone in healthy human subjects. Plasma aldosterone, urinary aldosterone, and plasma renin activity measurements were performed on samples from 47 subjects under conditions in which dietary sodium intake, posture, and times of sample collection were rigidly controlled. Nomograms are presented to illustrate the continuous, rather well defined, inverse relationship between 24 h sodium excretion and aldosterone measurements in plasma and urine. Mean plasma and urinary aldosterone values for subjects on normal sodium diets were 0.332+/-0.211 nmol/liter and 36.6+/-18.6 nmol/24 h and agreed well with previously reported values. A significant (p less than 0.05 increase in 24 h urinary aldosterone, plasma aldosterone and plasma renin activity resulted with decreased dietary sodium intake and conversely, a significant (p less than 0.05) decrease in each hormone occurred with increased dietary sodium intake. Rising from the supine to upright position resulted in a 230% increase in plasma aldosterone concentrations and a 284% increase in plasma renin activity.