Is primary aldosteronism underdiagnosed in clinical practice?

SFE/SFHTA/AFCE Consensus on Primary Aldosteronism, part 2: First diagnostic steps

In patients with suspected primary aldosteronism (PA), the first diagnostic step, screening, must have high sensitivity and negative predictive value. The aldosterone-to-renin ratio (ARR) is used because it has higher sensitivity and lower variability than other measures (serum potassium, plasma aldosterone, urinary aldosterone). ARR is calculated from the plasma aldosterone (PA) and plasma renin activity (PRA) or direct plasma renin (DR) values. These measurements must be taken under standard conditions: in the morning, more than 2hours after awakening, in sitting position after 5 to 15minutes, with normal dietary salt intake, normal serum potassium level and without antihypertensive drugs significantly interfering with the renin-angiotensin-aldosterone system. To rule out ARR elevation due to very low renin values, ARR screening is applied only if aldosterone is>240pmol/l (90pg/ml); DR values<5mIU/l are assimilated to 5mIU/l and PRA values<0.2ng/ml/h to 0.2ng/ml/h. We propose threshold ARR values depending on the units used and a conversion factor (pg to mIU) for DR. If ARR exceeds threshold, PA should be suspected and exploration continued. If ARR is below threshold or if plasma aldosterone is<240pmol/l (90pg/ml) on two measurements, diagnosis of PA is excluded.

Aldosterone and arterial hypertension

In the setting of primary aldosteronism, elevated aldosterone levels are associated with increased blood pressure. Aldosterone concentrations within the normal range, however, can also alter blood pressure. Furthermore, the aldosterone-to-renin ratio, an indicator of aldosterone excess, is associated with hypertension, even in patients without excessive absolute aldosterone levels. In this Review we assess the data on the role of aldosterone in the development and maintenance of hypertension. We provide an overview of the complex crosstalk between genetic and environmental factors, and about aldosterone-mediated arterial hypertension and target organ damage. The discussion is organized according to major targets of aldosterone action: the collecting duct in the kidney, the vasculature and the central nervous system. The antihypertensive efficacy of mineralocorticoid-receptor blockers, even in patients with aldosterone values in the normal range, supports the evidence that aldosterone plays a part in blood pressure elevation in the absence of primary aldosteronism.

Management of adrenal incidentaloma

Clinically inapparent adrenal masses, or adrenal incidentalomas, are discovered inadvertently in the course of work-up or treatment of unrelated disorders. Cortical adenoma is the most frequent tumour detected incidentally, but adrenocortical cancer, phaeochromocytoma and metastasis are not rare. Two critical questions should be answered before trying to outline the management of adrenal incidentaloma: (1) which tumours may cause harm to the patient, and (2) can we recognize and effectively treat such tumours? Based on the available scientific evidence, two major recommendations should be made: (1) identify either primary (adrenocortical cancer) or secondary (adrenal metastasis) malignancy; (2) identify phaeochromocytoma. Radiological evaluation is the key to the differential diagnosis of benign and malignant tumours. Endocrine testing is necessary to exclude phaeochromocytoma in all patients with an adrenal incidentaloma because this tumour may remain undiagnosed after imaging studies. The management of clinically inapparent adrenal adenomas may vary depending whether or not they are functioning. It is reasonable to screen for primary aldosteronism all hypertensive patients and recommend adrenalectomy when an aldosterone-producing adenoma is confirmed. A subset of adenomas secretes cortisol autonomously and may lead to mild hypercortisolism, a condition defined as subclinical Cushing's syndrome. The criteria for defining subclinical Cushing's syndrome are controversial, and we currently do not have sufficient evidence to define a gold standard for screening. Also the management of this condition is largely empirical, and data are insufficient to indicate the superiority of a surgical or non-surgical approach to managing patients with subclinical Cushing's syndrome.

Lesions of the adrenal cortex

CONTEXT

In surgical pathology practice adrenal cortical tumors are rare. However, in autopsy series adrenal cortical nodules are found frequently. These are now being identified more commonly in life when the abdomen is scanned for other disease. It is important to differentiate between benign and malignant lesions as adrenal cortical carcinoma is an aggressive tumor. Molecular genetic investigations are providing new information on both pathogenesis of adrenal tumors and basic adrenal development and physiology.

OBJECTIVE

To provide an overview of current knowledge on adrenal cortical development and structure that informs our understanding of genetic diseases of the adrenal cortex and adrenal cortical tumors.

DATA SOURCES

Literature review using PubMed via the Endnote bibliography tool.

CONCLUSIONS

The understanding of basic developmental and physiologic processes permits a better understanding of diseases of the adrenal cortex. The information coming from investigation of the molecular pathology of adrenal cortical tumors is beginning to provide additional tests for the assessment of malignant potential in diagnosis but the mainstay remains traditional histologic analysis.

A diagnostic approach to adrenal cortical lesions

The adrenal gland is not a common specimen in surgical pathology practice as, until recently, adrenal tumors were recognized in life only if associated with hypersecretion of hormones or evidence of malignancy. However, adrenal nodules are not uncommon at autopsy, and the number of these found in life is now increasing as they are identified when the abdomen is scanned for the investigation of other diseases using computed tomography or magnetic resonance imaging. It is therefore becoming increasingly important for the surgical pathologist to be aware of the range of pathology in the gland and to understand how to approach the specimens. This short review will deal with lesions of the adrenal cortex.

Noninvasive adrenal imaging in hyperaldosteronism: is it accurate for correctly identifying patients who should be selected for surgery?

BACKGROUND AND AIMS

The most common causes of hyperaldosteronism (HA) are bilateral idiopathic hyperaldosteronism (IHA), aldosterone-producing adenoma (APA), and unilateral primary adrenal hyperplasia (PAH). We evaluated if non-invasive preoperative imaging studies are able to reliably differentiate these causes of hyperaldosteronism.

METHODS

The medical records of 50 consecutive patients with HA were reviewed. Follow up was obtained by outpatient consultation or phone contact.

RESULTS

Thirty-five patients (70%) underwent successful adrenalectomy for APA, basing on the computed tomography (CT) scan results only. All these patients were biochemically cured. The remaining 15 patients underwent dexamethasone suppression adrenal cortical scintiscan (ACS) because of equivocal or inconclusive CT scan. In 11 of these patients, ACS showed a bilateral uptake, suggesting IHA. They were followed-up. In the remaining four patients, ACS showed a unilateral uptake. These patients underwent adrenalectomy. Final histology showed APA in three patients and PAH in one. They were biochemically cured. Sensitivity of combined non-invasive imaging procedures (CT and ACS) in detecting histologically proven and biochemically cured APA and PAH was 100%.

CONCLUSION

Non-invasive adrenal imaging studies are accurate in distinguishing between IHA and APA/PAH. Invasive diagnostic tests (adrenal venous sampling) should be indicated only when they do not conclusively localize hypersecretion.

Hypokalemia and Uncontrolled Hypertension

In a 45-year-old female with chronic uncontrolled hy-pertension complicated by hypokalemia, laboratory and radiological findings were consistent with an aldosterone producing adenoma (APA). Diagnosis of Conn's syndrome was confirmed by histopathology. The hypokalemia re-solved and her hypertension improved after laparoscopic adrenalectomy. Discussion of the case, diagnosis and treat-ment are presented.

The current epidemic of primary aldosteronism

Until recently, primary aldosteronism was considered to be a rare cause of identifiable or secondary hypertension. Over the past 10 years, a steadily growing number of reports have claimed that this condition is much more common, present in 5-40% of all hypertensive patients, which translates into many millions of patients. The primary basis for this current epidemic is the application of a relatively simple screening test, the plasma aldosterone to renin ratio (ARR). Despite growing recognition that the ARR is neither sensitive nor specific, its advocates recommend that it should be a routine procedure in evaluation of all hypertensives. Evidence is provided that this recommendation will lead to massive increases in costs, both in money and in morbidity, while providing benefit to only a very small number of patients who would not be aided by continuation of previous diagnostic protocols.

The 45-year story of the development of an anti-aldosterone more specific than spironolactone

At the early stage of its development in 1957, the daily dose of spironolactone necessary to improve various pathological conditions was not precisely determined and dose-dependent sexual side effects limited its long-term use. Prescription of high daily doses and absence of selectivity for the mineralocorticoid receptor explain these limitations. The 9-11alpha epoxy group added to mexrenone by the Ciba-Geigy chemists in 1984 and improved chemical synthesis at Searle, permitted the original international clinical development of a selective antagonist for high blood pressure and congestive heart failure treatment. This review deals with the main methodological issues of a 20-year biological and clinical development of eplerenone, the second antimineralocorticoid drug. The investigation of a large range of daily doses (25-400mg) initially selected in normal volunteers by the 9alpha-fluorohydrocortisone test has led to the conclusion that 50-100mg q.i.d. doses of eplerenone offer a favorable benefit/risk ratio in various patient populations by neutralization of the aldosterone effects on blood pressure and target organ damage. The absence of sexual side-effects has confirmed the clinical relevance of the initial biological hypothesis on the need for more selectivity at the androgen and progestogen receptor sites. Widening the distance between efficacy and adverse effects of an anti-mineralocorticoid drug will facilitate the long-term maintenance of a moderately negative sodium balance and a slightly positive potassium balance, while minimizing the direct effects of salt and aldosterone on the heart, vessels, brain, and kidneys. Wide use in unselected patients and additional controlled clinical trials are necessary to confirm the benefits expected from animal and clinical research given that a 45-year interval also characterizes the story of the Na-Cl cotransporter (NCC) blocker, chlorthalidone, from its initial clinical use to the demonstration of its beneficial effects on cardiovascular morbidity and mortality.

Hyperaldosteronism among black and white subjects with resistant hypertension

Recent reports suggesting that the prevalence of primary hyperaldosteronism may be higher than historically thought have relied on an elevated plasma aldosterone concentration/plasma renin activity ratio to either diagnose or identify subjects at high risk of having primary hyperaldosteronism and have not included suppression testing of all evaluated subjects. In this prospective study of 88 consecutive patients referred to a university clinic for resistant hypertension, we determined the 24-hour urinary aldosterone excretion during high dietary salt ingestion, baseline plasma renin activity, and plasma aldosterone in all subjects. Primary hyperaldosteronism was confirmed if plasma renin activity was <1.0 ng/mL per hour and urinary aldosterone was >12 microg/24-hour during high urinary sodium excretion (>200 mEq/24-hour). Eighteen subjects (20%) were confirmed to have primary hyperaldosteronism. The prevalence of hyperaldosteronism was similar in black and white subjects. Of the 14 subjects with confirmed hyperaldosteronism who have been treated with spironolactone, all have manifested a significant reduction in blood pressure. In this population, an elevated plasma aldosterone/plasma renin activity ratio (>20) had a sensitivity of 89% and a specificity of 71% with a corresponding positive predictive value of 44% and a negative predictive value of 96%. These data provide strong evidence that hyperaldosteronism is a common cause of resistant hypertension in black and white subjects. The accuracy of these results is strengthened by having done suppression testing of all evaluated subjects.