Development and application of a direct radioimmunoassay for aldosterone in saliva

Liquorice and glycyrrhetinic acid increase DHEA and deoxycorticosterone levels in vivo and in vitro by inhibiting adrenal SULT2A1 activity

The mineralocorticoid effects of liquorice are mediated by the inhibitory effects of one of its active components glycyrrhetinic acid on 11β-hydroxysteroid dehydrogenase type 2. However, liquorice is reputed to have many medicinal properties and also contains a number of other potentially biologically active compounds. Here we have investigated the wider effects of oral liquorice on steroidogenesis focussing particularly on possible inhibitory effects of glycyrrhetinic acid on adrenal sulfotransferase activity. Salivary steroids were profiled by ELISA in groups of normal male and female volunteers after consuming either liquorice-containing or non-liquorice-containing confectionary for one week. Cortisol and cortisone levels reflected expected inhibition of 11β-hydroxysteroid dehydrogenase type 2 by glycyrrhetinic acid. Salivary aldosterone was decreased but deoxycorticosterone, dehydroepiandrosterone and testosterone were increased. To assess whether glycyrrhetinic acid directly affected steroidogenesis, free and conjugated steroids were measured in incubates of adrenocortical H295 cells, firstly, in the presence or absence of forskolin and secondly, with radiolabeled deoxycorticosterone or dehydroepiandrosterone. Glycyrrhetinic acid inhibited cortisone and enhanced cortisol synthesis consistent with 11β-hydroxysteroid dehydrogenase type 2 inhibition. Basal and forskolin-stimulated syntheses of deoxycorticosterone and dehydroepiandrosterone conjugates were also inhibited in a dose-dependent manner; glycyrrhetinic acid inhibited the conjugation of deoxycorticosterone and dehydroepiandrosterone with IC50 values of 7 μM. Inhibition of deoxycorticosterone and dehydroepiandrosterone conjugation was apparent within 4 h of starting glycyrrhetinic acid treatment and was not associated with changes in the expression of SULT 2A1 mRNA. SULT2A1 encodes the enzyme sulfotransferase 2A1 which is responsible for the sulfonation of deoxycorticosterone and dehydroepiandrosterone as well as pregnenolone and 17-hydroxypregnenolone in human adrenal glands. We suggest that the glycyrrhetinic acid constituent of liquorice increases circulating and thereby, salivary levels of unconjugated deoxycorticosterone and dehydroepiandrosterone by inhibiting their conjugation at source within the adrenal cortex. This effect may contribute to the mineralocorticoid actions of glycyrrhetinic acid and gives substance to claims that liquorice also has androgenic properties.

Saliva as a medium for aldosterone measurement in repeated sampling studies

BACKGROUND

Saliva is a readily available biological fluid, making it convenient in diagnosis of diseases and in multi-sampling protocols. Several salivary steroids give a useful index of free plasma levels. Increased incidence of primary aldosteronism (PA) in approximately 10% of the hypertensive population has increased interest in the mineralocorticoid aldosterone.

METHODS

A biotinylated-aldosterone tracer and a commercially available antibody are used in a time-resolved fluorescence immunoassay (TR-FIA) to measure salivary aldosterone (SA). Saliva was collected in various multi-sampling protocols: Investigation of diurnal rhythm in healthy and PA patients, ACTH stimulation test and posture test in healthy subjects.

RESULTS

Method validation showed a sensitivity of 19 ng/L and intra-/inter-assay precision between 7.2-10.1% and 8.7-15.7%, respectively. SA correlated significantly (y = 0.2995x +/- 0.01, r(2)=0.60) to plasma aldosterone measured by a commercial radioimmunoassay. SA (median; 95%CI) was at 111 (95-127)ng/L in PA (n=84) and 50 (44-56)ng/L in healthy subjects (n=60). After change in posture, aldosterone increased in both, saliva (57 (47-63)ng/L to 95 (84-117)ng/L) and plasma (26 (26-41)ng/L to 135 (110-181)ng/L). Peak levels were reached after 1h, and were higher in females than in males.

CONCLUSIONS

SA correlates well to plasma aldosterone and mirrors responses during conditions of stress. SA is significantly higher in PA, and the diurnal rhythm seen in the healthy is blunted in PA. We additionally found gender-dependent differential responses to posture, with higher increases in females. Measurement of aldosterone in saliva presents a useful and convenient method for application in multi-sampling studies.

Salivary steroid assays – research or routine?

Salivary concentrations of unconjugated steroids reflect those for free steroids in serum although concentrations may differ because of salivary gland metabolism. Samples for salivary steroid analysis are stable for up to 7 days at room temperature, one month or more at 4°C and three months or more at −20°C. When assessed against strict criteria, the evidence shows that salivary cortisol in evening samples or following dexamethasone suppression provides a reliable and effective screen for Cushing's syndrome. Sequential salivary cortisol measurements are also extremely helpful for the investigation of suspected cyclical Cushing's syndrome. There is potential for the identification of adrenal insufficiency when used with Synacthen stimulation. Salivary 17-hydroxyprogesterone and androstenedione assays are valued as non-invasive tests for the home-monitoring of hydrocortisone replacement therapy in patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency. The diagnostic value of salivary oestradiol, progesterone, testosterone, dehydroepiandrosterone and aldosterone testing is compromised by rapid fluctuations in salivary concentrations of these steroids. Multiple samples are required to obtain reliable information, and at present the introduction of these assays into routine laboratory testing is not justified.

Clinical Use of Laboratory Tests for the Identification of Secondary Forms of Arterial Hypertension

The prevalence of secondary hypertension can be underestimated if appropriate tests are not performed. The importance of selecting patients with a high pre-test probability of secondary forms of hypertension is first discussed. The laboratory tests currently used for seeking a cause of hypertension are critically reviewed, with emphasis on their operative features and limitations. Strategies to identify primary aldosteronism, the most frequent form of secondary hypertension, and to determine its unilateral or bilateral causes are described. Treatment entails adrenalectomy in unilateral forms, and mineralocorticoid receptor blockade in bilateral forms. Renovascular hypertension is also a common, curable form of hypertension, that should be identified as early as possible to avoid the onset of cardiovascular target organ damage. The tests for its confirmation or exclusion are discussed. The various tests available for the diagnosis of pheochromocytoma, which is much rarer than the above but extremely important to identify, are also described, with emphasis on recent developments in genetic testing. Finally, the tests for diagnosing some rarer monogenic forms and other renal and endocrine causes of arterial hypertension are explored.

Development and validation of a simple and direct ELISA method for the determination of conjugated (glucuronide) and non-conjugated testosterone excretion in urine

BACKGROUND

Several methods are now available to estimate urinary testosterone levels that can only be performed in established big laboratories using GC/MS techniques. In clinical practice or for research projects, an inexpensive method that does not require skilled technicians would be useful. A simple, rapid and accurate ELISA method has been developed and applied in our laboratory to measure urinary non-conjugated and total testosterone.

METHODS

High affinity anti-testosterone antibody and HRP-Donkey anti-sheep IgG (Horse Radish Peroxidase) as enzyme tracer were used to develop the ELISA method. The assay was evaluated for specificity, sensitivity, parallelism, accuracy and imprecision by the established methods on samples obtained from healthy volunteers. The results from the direct ELISA were compared to those after enzyme hydrolysis plus solvent extraction and HPLC or commercial kits.

RESULTS

A satisfactory standard curve for the direct testosterone ELISA has been developed with good sensitivity. Cross-reactivity values of anti-testosterone antibody with major interfering steroids were minimal except for testosterone-3-glucuronide (58.8%). The validity of urinary testosterone assay was confirmed by the good correlation between the results obtained by the direct ELISA and those after enzyme hydrolysis and solvent extraction (Y = 0.987X + 0.398, R2 = 0.97). Accuracy studies, parallelism and imprecision data were determined and all found to be satisfactory. Urinary testosterone excretion values obtained by our direct ELISA from healthy volunteers were generally in agreement with those published by other workers. Male urinary total testosterone excretion (non-conjugated and testosterone glucuronide) ranged from 177.9 to 865.3 nmol/day, which was about 3-6 times more than the range for women urinary testosterone excretion (34.5-308.8 nmol/day).

CONCLUSION

A direct, reliable, easy to perform, sensitive and highly specific ELISA type assay for the measurement of total testosterone in urine samples (conjugated and non-conjugated) has been developed. The novel features of the assay are that it does not require an initial extraction step or involve time consuming procedures such as chromatography. A simple method has also been developed to measure non-conjugated urinary testosterone excretion after solvent extraction alone.

A new less-invasive and more informative low-dose ACTH test: salivary steroids in response to intramuscular corticotrophin

OBJECTIVE

The intravenous low-dose ACTH test has been proposed as a sensitive tool to assess adrenal function through circulating steroids. The aims of this study were to: (a) find the minimal intramuscular ACTH dose that induced serum and salivary cortisol and aldosterone responses equivalent to those obtained after a pharmacological dose of ACTH; and (b) define the minimum normal salivary cortisol and aldosterone responses in healthy subjects to that dose of ACTH. We also compared the performances of the standard- and low-dose ACTH intramuscular tests to screen patients with known hypothalamo-pituitary-adrenal impairments.

DESIGN

Rapid ACTH tests were performed in individuals using various intramuscular doses (12.5, 25 and 250 microg) at 2-week intervals.

SUBJECTS

Twenty-one healthy volunteers and 19 patients with primary (nine cases) and secondary (10 cases) adrenal insufficiency.

MEASUREMENT

Serum and salivary cortisol and aldosterone concentrations were measured at baseline and after ACTH. Serum cortisol > or = 552.0 nmol/l and aldosterone > or = 555.0 pmol/l concentrations at 30 min after 250 microg of ACTH were defined as normal responses.

RESULTS

In healthy volunteers cortisol and aldosterone responded to ACTH in a dose-dependent manner. The time to peak in saliva for each steroid was delayed as the dose of ACTH increased. The minimum ACTH dose that produced equivalent steroid responses at 30 min to 250 microg of ACTH (standard-dose test; SDT) was 25 microg (low-dose test; LDT). Saliva collection 30 min after LDT and SDT showed cortisol and aldosterone concentrations of at least 20.0 nmol/l and 100.0 pmol/l, respectively. These values were defined as normal steroid responses. Blunted salivary steroid responses to LDT and SDT were found in all patients with primary adrenal insufficiency. Subnormal salivary cortisol levels in response to LDT and SDT were found in all patients with secondary adrenal insufficiency. In five patients full recovery of adrenal function was demonstrated by both tests after steroid withdrawal. In the follow-up of four patients studied during the recovery period, subnormal SAF response after LDT and normal after SDT was demonstrated. Preservation of the adrenal glomerulosa was found in all the patients with secondary adrenal insufficiency through the normal rise in salivary aldosterone after both LDT and SDT.

CONCLUSIONS

Adrenal function can be accurately investigated with simultaneous measurements of salivary cortisol and aldosterone in response to 25 microg of corticotrophin injected into the deltoid muscle. Our data suggest that this may become a useful and relatively noninvasive clinical tool to detect subclinical hypoadrenal states.

The diagnostic applications of saliva--a review

This review examines the diagnostic application of saliva for systemic diseases. As a diagnostic fluid, saliva offers distinctive advantages over serum because it can be collected non-invasively by individuals with modest training. Furthermore, saliva may provide a cost-effective approach for the screening of large populations. Gland-specific saliva can be used for diagnosis of pathology specific to one of the major salivary glands. Whole saliva, however, is most frequently used for diagnosis of systemic diseases, since it is readily collected and contains serum constituents. These constituents are derived from the local vasculature of the salivary glands and also reach the oral cavity via the flow of gingival fluid. Analysis of saliva may be useful for the diagnosis of hereditary disorders, autoimmune diseases, malignant and infectious diseases, and endocrine disorders, as well as in the assessment of therapeutic levels of drugs and the monitoring of illicit drug use.