Differential diagnosis in primary aldosteronism

Analysis of screening and confirmatory tests in the diagnosis of primary aldosteronism: need for a standardized protocol

BACKGROUND

The upright serum aldosterone/upright plasma renin activity ratio (ARR) has been recommended as a screening tool for the diagnosis of primary aldosteronism.

OBJECTIVE

We reviewed the data collected from hypertensive patients in order to define retrospectively the cut-off values and evaluate the reliability of the ARR and of the saline infusion test in the diagnosis of primary aldosteronism.

PATIENTS

In 157 patients referred to our unit with a suspicion of primary aldosteronism, 61 of whom had confirmed primary aldosteronism [26 aldosterone-producing adenoma (APA); 35 idiopathic hyperaldosteronism], the supine and upright ARR, and the ARR after the administration of captopril and losartan were calculated, and the results of the saline infusion test were analysed.

RESULTS

Choosing 40 as the cut-off value, the upright ARR had 100% sensitivity and 84.4% specificity. The post-captopril and post-losartan ARR were slightly more specific, but at the cost of a lower sensitivity. A cut-off value of 7 ng/dl for serum aldosterone at the end of the saline infusion in patients with an upright ARR of 40, gave 100% specificity and a positive predictive value. Furthermore, APA patients showed increased mean levels of aldosterone/cortisol ratio after the saline infusion test.

CONCLUSION

Our data reinforce the superiority of a standardized upright ARR as a screening test in the diagnosis of primary aldosteronism, identifying 40 as an ideal cut-off value. Saline infusion represents a useful test to confirm such a diagnosis, with a serum aldosterone level of 7 ng/dl as a satisfactory cut-off value. Some more information is obtained when the aldosterone/cortisol ratio is considered.

The Role of Adrenal Venous Sampling in the Surgical Management of Primary Aldosteronism

OBJECTIVE

Primary aldosteronism is the most common endocrine form of secondary hypertension, but no single test or imaging method always identifies it. Identification of a unilateral overproduction of aldosterone due to Conn's adenoma or unilateral hyperplasia is of utmost importance to the surgeon.

MATERIALS AND METHODS

We reviewed our experience with primary aldosteronism in 46 consecutive patients who had undergone adrenalectomy at the Surgical Pathology Institute, University of Padua since 1993. All the patients underwent a CT scan. Adrenal venous sampling was performed in those patients with negative or equivocal findings on imaging studies.

RESULTS

Computed tomography was non-contributory in 12 patients and frankly misleading in 2 patients, demonstrating a probable mass lesion in the contralateral but not in the ipsilateral adrenal. Eighteen patients had selective venous sampling that was successful in altering the management of 14 cases. Eleven patients who biochemically had an adrenal adenoma, had normal/equivocal CT, while the remaining 3 had bilateral or contralateral adrenal masses. Venous sampling localized aldosterone secretion and an adenoma, less than 1 cm in diameter, was removed, curing their hypertension. Eleven patients were treated by open adrenalectomy and 35 by the lateral transperitoneal laparoscopic approach. Histological examination revealed 45 Conn's adenomas, of which 13 had a diameter of less than 1 cm (range 0.3-0.8), and 1 case of nodular hyperplasia.

CONCLUSIONS

Patients who have equivocal or unexpected CT findings should proceed to hormonal localization. Adrenal venous sampling is essential in patients with equivocal CT scans to avoid unnecessary and inappropriate adrenalectomy.

Adrenocortical hypertension

Primary aldosteronism, congenital adrenal hyperplasia, Cushing's syndrome, glucocorticoid-remediable aldosteronism, and corticotropin-dependent forms of adrenal pathology can cause hypertension by excessive production of adrenocortical hormones. Although traditional biochemical assays continue to be used, genetic testing has simplified the diagnosis of glucocorticoid-remediable aldosteronism. Also new interventional radiologic approaches for the diagnosis and treatment of corticotropin-dependent forms of Cushing's syndrome are available. Medical and surgical approaches, however, still remain viable options for treatment.

Adrenocortical hypertension

Primary aldosteronism, congenital adrenal hyperplasia, Cushing's syndrome, glucocorticoid-remediable aldosteronism, and corticotropin-dependent forms of adrenal pathology can cause hypertension by excessive production of adrenocortical hormones. Although traditional biochemical assays continue to be used, genetic testing has simplified the diagnosis of glucocorticoid-remediable aldosteronism. Also, new interventional radiologic approaches for the diagnosis and treatment of corticotropin-dependent forms of Cushing's syndrome are available. Medical and surgical approaches, however, still remain viable options for treatment.

A case of unilateral adrenal hyperplasia: the diagnostic dilemma of hyperaldosteronism

OBJECTIVE

To report the successful laparoscopic surgical management of a case of right unilateral adrenal hyperplasia.

METHODS

We present a case of unilateral adrenal hyperplasia and review the pertinent literature. The effectiveness of surgical treatment of unilateral adrenal hyperplasia is evaluated.

RESULTS

A 50-year-old man had a 7-year history of hypertension, which had been treated with antihypertensive medications. On initial assessment, he was taking long-acting diltiazem, 240 mg twice a day, and his blood pressure was 150/84 mm Hg. He was noted to have recurrent hypokalemia, low plasma renin activity, increased plasma aldosterone concentration, and high urinary aldosterone levels. Magnetic resonance imaging of the adrenal glands revealed a normal left adrenal gland and fullness of the right adrenal gland. Selective adrenal vein catheterization showed findings consistent with a right-sided adrenal gradient. Surgical removal of the right adrenal gland laparoscopically alleviated his symptoms and cured his hypertension and hypokalemia. Pathologic examination of the right adrenal gland revealed diffuse hyperplasia of the zona fasciculata and zona reticularis. Plasma aldosterone, renin, and potassium levels returned to normal postoperatively, and his blood pressure declined to 120/70 mm Hg. At 1-year follow-up, the patient remained normotensive without the need for antihypertensive agents.

CONCLUSIONS

This rare type of hyperaldosteronism, known as unilateral adrenal hyperplasia, is difficult to categorize not only because it fails to typify a conventional subtype but also because it is difficult to confirm the pathologic diagnosis. Recognition of the variety of provocative, biochemical, and imaging results that may be seen in this disorder is important in making the correct diagnosis. Determining unilaterality of disease by selective adrenal vein sampling can result in a cure of hypertension and hypokalemia by surgical resection.

Management approaches to adrenal incidentalomas. A view from Ancona, Italy

The definition of adrenal incidentaloma encompasses a heterogeneous spectrum of pathologic entities, including primary adrenocortical and medullary tumors, benign or malignant lesions, hormonally active or inactive lesions, metastases, and infections. This article provides an overview of the diagnostic clinical approach and management of the incidentally discovered adrenal masses. Approaches are based on data collected in more than 1000 cases of the Collaborative Study Group on Adrenal Incidentaloma of the Italian Society of Endocrinology and the authors' experience.

Screening for primary aldosteronism with a logistic multivariate discriminant analysis

OBJECTIVE

Primary aldosteronism (PA) is the most common endocrine cause of curable hypertension, but no single test unequivocally identifies it. Accordingly, we investigated the usefulness of a logistic multivariate discriminant analysis (MDA) approach for PA screening.

DESIGN

Generation of a logistic MDA function based on retrospective analysis of biochemical tests in a large cohort of referred patients with/without confirmed Conn's adenoma (CA), followed by prospective validation of the model.

PATIENTS

We investigated 574 selected hypertensives: 206 (32 with and 174 without CA) retrospectively, 48 (with a 13% prevalence of CA) prospectively for the validation of the model, and 320 referred hypertensives (with a 3.4% prevalence of CA) similarly evaluated. Patients were referred to a specialised centre for hypertension (4th Clinica Medica--University of Padua) and to a department of Internal Medicine of a regional hospital (Reggio Emilia).

MEASUREMENTS

In all patients we measured several demographic and biochemical variables and performed a captopril test. A stepwise analysis of variance, based on a model fitted with several different variables, identified baseline (sALDO) and captopril-suppressed plasma aldosterone (cALDO), supine plasma renin activity (sPRA) and K+ as the most informative. Therefore, two models of logistic MDA with sPRA, K+, and either sALDO (model A) or cALDO (model B) were developed and used. ROC analysis was also performed to assess the optimal cut-off values.

RESULTS

The model B of MDA provided the best performance and identified CA with 100% sensitivity and 81% accuracy. When used prospectively it showed 100% sensitivity, both in the Padua (88% accuracy) and in the Reggio Emilia series (90% accuracy). However, at both institutions most patients with idiopathic hyperaldosteronism (IHA) were also detected.

CONCLUSIONS

Thus, although developed from patients with confirmed Conn's adenoma, a strategy based on multivariate discriminant analysis can be used prospectively for accurate screening for primary aldosteronism. Furthermore, it was proven to be accurate and applicable to patients tested with similar modalities at a different institution. Although this approach did not provide a clear-cut discrimination of Conn's adenoma from idiopathic hyperaldosteronism, it may avoid unnecessary and costly further testing in patients with a low probability of primary aldosteronism.

Hypothesis: aldosterone is synthesized by an alternative pathway during severe sodium depletion. 'A new wine in an old bottle'

1. The last three steps of aldosterone biosynthesis, 11 beta-hydroxylation, 18-hydroxylation and 18-oxidation, have been demonstrated to be catalysed by one enzyme, which is the cytochrome P450(11 beta) (CYP11B) in cow, pig, sheep and bullfrog or cytochrome P450aldo (CYP11B2) in rat, human, mouse and hamster. 2. The related enzyme P450(11 beta) (CYP11B1) from rat, human, mouse and hamster adrenals displays 11 beta-hydroxylation and 18-hydroxylation activities, but not 18-oxidation activity in vitro. No such enzyme has been reported in the cow, pig or sheep to date. 3. Data showing the dissociation of aldosterone secretion from plasma angiotensin II (AngII) levels indicate the presence of other factor(s) that regulate aldosterone biosynthesis in response to changes in body sodium status. Thus, we propose the existence of a 'sodium status factor' that regulates aldosterone biosynthesis in addition to AngII, K+, adrenocorticotropic hormone and atrial natriuretic peptide. 4. We propose that during severe sodium deficiency there is a switch in the aldosterone pathway to a pathway using 18-hydroxy-deoxycorticosterone (18-OH-DOC) rather than corticosterone as an intermediate. This switch may be mediated via the putative 'sodium status factor'. 5. Two models of the hypothesis will be discussed in this paper: (i) a 'one-enzyme' model; and (ii) a 'two-enzyme' model. 6. The one-enzyme model proposes that P450aldo (P450(11 beta) as in the case of the cow, sheep and pig) changes its enzymatic activity during severe sodium deficiency (i.e. switching to the alternative aldosterone biosynthesis pathway). 7. The two-enzyme model proposes that, under normal circumstances, P450aldo synthesizes aldosterone from deoxycorticosterone, while during severe sodium deficiency the P450(11 beta) provides the substrate (i.e. 18-OH-DOC) for the P450aldo.

Angiotensin II receptors in cortical and medullary adrenal tumors

Several pieces of evidences suggest that angiotensin II (Ang II) has mitogenic effects, and a link between Ang II receptors and adrenal tumors can be suggested. In various adrenal tumors, aldosterone-producing adenoma (APA), Cushing's adrenal adenomas (Cush), pheochromocytomas (Pheo), and adrenal carcinomas, we studied the density, affinity, and subtype of Ang II receptors. Ang II binding was tested in cell membrane homogenates. [125I]Ang II was used as ligand, and Losartan and CGP 42112 were used as selective Ang II type 1 and type 2 antagonists, respectively. In APA, Ang II receptor density was 178.5 +/- 82.7 fmol/mg: however, due to the high degree of variability, the receptor density was not significantly higher than that in nontumorous adrenal cortex (59.3 +/- 8.4 fmol/mg). In Cush, the receptor density (27.6 +/- 8.2 fmol/mg; P < 0.05) was significantly lower than that in controls, whereas in Pheo and cortical carcinoma, Ang II binding was very low and in several cases almost undetectable. There was no remarkable difference in the Ang II receptor affinity among all tissues tested. The ratio between type 1 and type 2 Ang II receptors showed a large prevalence of type 1 in controls, APA, and three cases of Cush; in two cases of Cush, this ratio was reversed. In conclusion, our data indicate that Ang II receptors are normally expressed in APA and can also be detected in Cush, whereas they have a very low density in Pheo and adrenal carcinoma. Therefore, Ang II receptors are not involved in the lack of response to Ang II that is characteristic of APA; additionally, a reduction of Ang II receptors can be associated with dedifferentiation or malignancy of adrenal tumors. Further investigation of the expression and functional characterization of Ang II receptors is required to better clarify their possible role in adrenal tumorigenesis.

Secondary hypertension: evaluation and treatment

Most patients with hypertension in the United States have essential (primary) hypertension (95%), the cause of which is unknown. The remaining 5% of adults with hypertension have the secondary form of hypertension, the cause and pathophysiologic process of which are known. Internists and other primary care physicians refer to this as treatable or curable hypertension, because the hypertension can be managed or even controlled with medications. Similarly, the condition is called surgical hypertension by surgeons in the belief that once the cause is determined and identified, surgical intervention will result in cure of hypertension. Secondary causes of hypertension include renal parenchymal disease, renovascular diseases, coarctation of the aorta, Cushing's syndrome, primary hyperaldosteronism, pheochromocytoma, hyperthyroidism, and hyperparathyroidism. Occasionally included in this category are alcohol- and oral contraceptive-induced hypertension and hypothyroidism, but these conditions are not discussed herein. The evaluation of secondary hypertension is of interest and can bring together different facets of anatomy, physiology, pharmacology, and radiology in the medical and surgical treatment of these disorders. Despite enthusiasm that can be generated in the evaluation of these conditions, evaluation can be expensive and should not be conducted for all patients with hypertension. Features that aid in the diagnosis of secondary hypertension include the following: 1. Onset of hypertension before the age of 20 or after the age of 50 years. The presence of hypertension at a young age may suggest coarctation of the aorta, fibromuscular dysplasia, or an endocrine disorder. Hypertension found for the first time after the age of 50 years may suggest the presence of renovascular hypertension caused by atherosclerosis. 2. Markedly elevated blood pressure or hypertension with severe end-organ damage, as in grade III or IV retinopathy. These findings suggest the presence of renovascular hypertension or pheochromocytoma. 3. Specific body habitus and ancillary physical findings. For example, truncal obesity and purple striae occur with hypercortisolism, and exophthalmos is associated with hyperthyroidism. 4. Resistant or refractory hypertension (poor response to medical therapy usually necessitating use of more than three antihypertensive medications from three different classes). 5. Specific biochemical test that suggest the existence of certain disorders, such as hypercalcemia in hyperparathyroidism, hyperglycemia in Cushing's syndrome and pheochromocytoma, and unprovoked hypokalemia with renin-producing tumors, primary hyperaldosteronism, or renin-mediated renovascular hypertension. 6. Other characteristics that may suggest secondary hypertension such as abdominal diastolic bruits (renovascular hypertension), decreased femoral pulses (coarctation of the aorta), or bitemporal hemianopias (Cushing's disease). A combination of a good history and physical examination, astute observation, and accurate interpretation of available data usually are helpful in the diagnosis of a specific causation.

Case report: failure of adrenal scintigraphy to exhibit 131I cholesterol uptake in a CT-demonstrated, surgically proven aldosteronoma

This is the case of a large 2 x 1.5 cm adrenal tumor demonstrated on CT scan that was proven biochemically and surgically to be an aldosteronoma and that did not concentrate 6-beta(131I)-iodo-methyl-19-norcholesterol (NP-59). Before the publication of this case, all CT-identified aldosteronomas of greater than 1 cm have concentrated NP-59. Previously, an adrenal mass of greater than 1 cm that failed to concentrate NP-59 was excluded from being an aldosteronoma. This concept must be reevaluated with the publication of this case.

Long-term treatment of mineralocorticoid excess syndromes

Recognition of the pathogenesis of secondary forms of hypertension is often considered the key to appropriate choice of treatment. We here present the results of a prolonged clinical follow-up (from 1 to 20 years) of a large number of patients with mineralocorticoid excess syndromes (MES), including over 100 patients with primary aldosteronism (PA), 3 cases with dexamethasone-suppressible aldosteronism (DSA), 3 cases of apparent mineralocorticoid excess (AME) Type II, and 4 patients with 17-hydroxylase deficiency (17OHDS). The patients with PA have been divided in two subgroups, one of 69 cases followed between 1973 and 1982, and the second of 37 patients studied between 1983 and 1992; 33 further cases were not evaluated due to poor compliance. In group I, 26 patients underwent surgery (23 unilateral adenoma, 1 primary hyperplasia, 2 bilateral nodular hyperplasia); at 5 years 50% had normal blood pressure, 25% had mild hypertension and 25% had moderate to severe hypertension. Forty-three patients with either adenoma (APA) or idiopathic aldosteronism (IHA) received long-term spironolactone treatment. Among them, 13 required the addition of thiazide and/or beta-blockers, while 13 were switched to an amiloride/thiazide combination (+/- beta blockers) due to side-effects to spironolactone (gynecomastia 6/20 males, menstrual upset or breast pain in 7/23 females). In group II, 12 patients underwent surgery (11 adenoma, 1 primary hyperplasia) with a similar outcome at 3 years as in group I; 25 patients were put on either K canrenoate (11) or Ca++ channel blockers (14) with or without KCl supplementation; in 8 cases these two drugs were combined according to blood pressure levels achieved during the follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)