Diagnosis and treatment of primary aldosteronism and isolated hypoaldosteronism

HYPOALDOSTERONISM IN A MATSCHIE'S TREE KANGAROO (DENDROLAGUS MATSCHIEI)

A 20-yr-old female Matschie's tree kangaroo (Dendrolagus matschiei) was diagnosed with hypoaldosteronism, a rare condition in which the body fails to produce normal amounts of the mineralocorticoid aldosterone. Aldosterone plays a key role in body salt homeostasis, increasing sodium reabsorption and promoting excretion of potassium. Hypoaldosteronism resulted in decreased appetite, lethargy, and weight loss in conjunction with hyponatremia, hyperkalemia, and hypercalcemia in this tree kangaroo. The animal was successfully managed with mineralocorticoid replacement using desoxycorticosterone pivalate. To the authors' knowledge this is the first report of hypoaldosteronism in a tree kangaroo and one of the few reports in the veterinary literature in any species.

Primary hyperaldosteronism: a case of unilateral adrenal hyperplasia with contralateral incidentaloma

Primary hyperaldosteronism is one of the most common causes of secondary hypertension but clear differentiation between its various subtypes can be a clinical challenge. We report the case of a 37-year-old African-American woman with refractory hypertension who was admitted to our hospital for palpitations, shortness of breath and headache. Her laboratory results showed hypokalaemia and an elevated aldosterone/renin ratio. An abdominal CT scan showed a nodule in the left adrenal gland but adrenal venous sampling showed elevated aldosterone/renin ratio from the right adrenal vein. The patient began a new medical regimen but declined any surgical options. We recommend clinicians to maintain a high level of suspicion to consider the less common subtypes of primary hyperaldosteronism, especially given the fact that the management greatly varies.

Adrenal incidentaloma

Because of the frequent use of computed tomography and other abdominal imaging modalities, clinicians more frequently see the incidentally discovered, clinically silent adrenal mass. Most adrenal incidentalomas should be evaluated for hormonal activity and assessed for their risk of malignancy. Adrenalectomy is indicated for hyperfunctioning tumors and for any potential primary malignant adrenal lesion. Nonfunctioning cortical adenomas < 4 to 5 cm in size should be followed clinically and radiographically. Laparoscopic adrenalectomy has been used increasingly as the preferred approach in patients who require surgical resection whereas open adrenalectomy is reserved for patients with large, malignant tumors. The indications for adrenalectomy in patients with nonfunctioning adrenal tumors should not be liberalized because of the laparoscopic approach.

Recent advances in the management of adrenal incidentalomas

Modern imaging techniques have made adrenal incidentaloma a relatively common diagnostic problem. When an incidental adrenal mass is found, the clinician must try to determine its etiology and functionality, and the likelihood of malignancy. This task is complicated further in patients with a history of extra-adrenal malignancy. In this article, we present a review of the literature and propose a diagnostic algorithm for management of adrenal incidentalomas.

Incidentalomas. A disease of modern technology

The optimal strategy for hormonal screening of a patient with any incidentally discovered adrenal or pituitary mass is unknown. Our review of the endocrinologic literature supports the view that such patients are at slightly increased risk for morbidity and mortality. There is a benefit of early diagnosis for at least for some of the disorders, suggesting the importance of case finding. The data in Tables 1 and 4 illustrate that clinically diagnosed hormone-secreting adrenal and pituitary tumors are far less common than incidentalomas. From a clinical perspective, our ability to determine accurately those at increased risk among the vast majority who are not at increased risk is poor. Given the limitations of diagnostic tests, effective hormonal screening requires a sufficiently high pretest probability to limit the number of false-positive results. This condition is met to varying degrees in the patient with an adrenal mass or small incidentally discovered pituitary mass but no signs or symptoms of hormone excess. Even the more common lesions such as pheochromocytoma and prolactinoma are relatively rare. Subjecting patients to unnecessary testing and treatment carries its own set of risks. Initial costs aside, testing may result in further expense and harm as false-positive results are pursued, producing the cascade effect described by Mold and Stein as a "chain of events (which) tends to proceed with increasing momentum, so that the further it progresses the more difficult it is to stop." The extensive evaluations performed in some patients with incidentally discovered masses may reflect the unwillingness of many physicians to accept uncertainty, even in the case of extremely unlikely diagnoses. This unwillingness may be driven, in part, by fear of potential malpractice liability, the failure to appreciate the influence of prevalence data on the interpretation of diagnostic testing, or other factors. Indeed, the major justification for further evaluation of these patients is not so much to avoid morbidity and mortality for rate patients who truly are at increased risk but rather to reassure those in whom further testing is negative (and to reassure ourselves). Physicians must take care not to create inappropriate anxiety in patients by overemphasizing the importance of an incidental finding unless it is associated with a realistic clinical risk. Our recommendations utilize currently available information to minimize the untoward effects of the cascade. As evidence accumulates, recommendations may need to be revised. The benefit of diagnosis of one of these adrenal or pituitary disorders must be considered in the context of the patient's overall condition. Studies are needed to analyze the utility in clinical practice of hormonal screening for these common radiologic findings. We need to use these studies to identify the critical gaps in our knowledge and to adopt the epidemiologic methods of evaluation of evidence that have been applied to preventive measures. We must be careful to recognize lead-time bias in which survival can seem to be lengthened when screening simply advances the time of diagnosis, lengthening the period of time between diagnosis and death without any true prolongation of life. Length bias refers to the tendency of screening to detect a disproportionate number of cases of slowly progressive disease and to miss aggressive cases that, by virtue of rapid progression, are present in the population only briefly. Endocrinologists must avoid the pitfalls of overestimation of disease prevalence and of the benefits of therapy resulting from advances in diagnostic imaging. Clinical judgment based on the best available evidence should be complemented and not replaced by laboratory data.

Idiopathic hyperplasia of the adrenal gland behaving like an aldosterone producing adenoma

Primary hyperaldosteronism (adrenal adenoma and idiopathic hyperplasia) is a disorder with hypertension, hypokalemia, elevated serum aldosterone and suppressed plasma renin activity. Hyperplasia is managed medically whereas adenomas are treated surgically. Selective adrenal venous catheterization and aldosterone measurement is a useful tool in making the distinction in 95% of cases. We report a case of bilateral idiopathic hyperplasia of the adrenal glands adequately treated with medications for 6 years followed by worsening. Selective catheterization was consistent with a right sided adenoma. Surgical removal of the right adrenal gland alleviated her symptoms. Pathological examination showed focal nodular hyperplasia. We propose that in the course of the disease the focal hyperplastic nodule became autonomous and behaved like an adenoma. Monitoring of patients with adrenal hyperplasia for recurrence of symptoms is prudent as surgery is beneficial in patients who develop an autonomous nodule.

Adrenal incidentaloma: subclinical Cushing's syndrome

Adrenal incidentalomas present a significant differential diagnostic challenge. All patients with an incidentally discovered adrenal lesion should be carefully considered and re-evaluated to exclude extra-adrenal malignancy. Tumours with hypersecretory syndromes require excision, whilst those tumours more than 6 cm in size, particularly if they exhibit other features of malignancy on computed tomography (CT), magnetic resonance imaging (MRI) or scintigraphy, should also be excised. In all cases screening for phaeochromocytomas should be performed, and in the context of hypertension and spontaneous hypokalaemia, a primary aldosterone-secreting tumour requires exclusion. However, the natural history and treatment regimens for those individuals demonstrating 'subclinical Cushing's syndrome' is far from clear. Size, as determined by CT or MR scanning, does not in itself reliably distinguish benign from malignant disease. Scintigraphy may be a useful adjunct, with discordant patterns suggesting malignant disease. Fine needle aspiration should not routinely be used but may be useful in cases of doubt about other extra adrenal malignancy.

Postural stimulation test in patients with aldosterone producing adenomas

OBJECTIVE

The purpose of this study was to evaluate the postural stimulation test before and after surgical treatment in patients with aldosterone-producing adenomas.

DESIGN

The retrospective study was made on patients with aldosterone producing adenomas.

PATIENTS

The postural stimulation test was analysed in 60 patients with surgically proven aldosterone producing adenoma and in 15 healthy volunteers.

MEASUREMENTS

The postural stimulation test was based on measurements of plasma aldosterone, cortisol and renin activity (PRA) at 0800 h and at noon after 4 hours ambulation.

RESULTS

The patients were divided into two groups according to the individual pattern of plasma aldosterone concentration following the postural test. Plasma aldosterone concentration decreased or did not change after 4 hours of standing in 42 patients (group 1, 70% of total) and increased in 18 patients (group 2, 30% of total). Mean plasma aldosterone was significantly higher in group 1 than in group 2 (1325 +/- 164 pmol/l (mean +/- SE) and 538 +/- 53 pmol/l, respectively). Mean plasma cortisol concentration after 4 hours of upright posture in both groups remained low (242 +/- 35 vs 401 +/- 63 nmol/l (group 1) and 317 +/- 46 vs 367 +/- 43 nmol/l (group 2)). Mean PRA in both groups was suppressed after 4 hours of upright posture (0.2 +/- 0.04 vs 0.2 +/- 0.04 pmol/l/s and 0.3 +/- 0.06 vs 0.1 +/- 0.02 pmol/l/s, respectively).

CONCLUSION

Diverse changes in plasma aldosterone and cortisol found in response to the postural test may indicate pathogenetic heterogeneity amongst patients with aldosterone producing adenomas and should be considered during diagnosis of primary aldosteronism.

Clinical and pathological diversity of primary aldosteronism, including a new familial variety

1. Of 93 patients with primary aldosteronism seen during a 20 year period, 52 had an aldosterone-producing adenoma (APA) removed (five more await surgery), 14 had bilateral adrenal hyperplasia (BAH), three had glucocorticoid-suppressible hyperaldosteronism (GSH), one had adrenal carcinoma and 18 are yet to be categorized. 2. Seventy-three presented with hypertension and hypokalaemia. Others had markedly suppressed renal venous plasma renin activity (PRA) or elevated plasma aldosterone (PA)/PRA ratio, in new or resistant hypertensives. 3. The PA/PRA ratio was the most reliable screening test. 4. Diagnosis depended on the failure of suppression of aldosterone by salt loading and fludrocortisone. 5. Differentiation of BAH from APA depended on adrenal venous sampling comparing adrenal and peripheral venous PA/cortisol ratios. 6. A new familial variety of primary aldosteronism is described, with two affected members in each of three families. 7. Primary aldosteronism should be looked for in resistant and low-renin hypertension as well as in hypertension with hypokalaemia, and other family members should have PA/PRA measured if they are hypertensive.

Primary hyperaldosteronism in England and Wales: a review of the use of a Supraregional Assay Service laboratory for the measurement of aldosterone and plasma renin activity

To ascertain the use being made of a Supraregional Assay Service laboratory in the diagnosis of primary hyperaldosteronism, follow-up data were obtained on 60 patients in whom the diagnosis was suggested by the biochemical results. In 36 patients an adrenal adenoma had been removed; 14 patients had evidence of an adenoma on CT scan; 10 patients were presumed to have bilateral adrenal hyperplasia. The data used to make the diagnosis of primary hyperaldosteronism and to assess the likelihood of the presence of an adenoma indicate that patients studied at 40 centres in the UK show results very similar to those of North American series where large numbers of patients have been described but all have been studied in the same centre. The majority of patients in our series were treated at the hospital at which the diagnosis was made, thus avoiding referral to a centre distant from the patient's home and indicating that the service was being used as originally intended when the Supraregional Assay Service was set up.

Aldosterone-producing tumors (Conn's syndrome)

Adenomas of the adrenal cortex which produce aldosterone (APA) are among the surgically correctible causes of hypertension accounting for 0.5 to 1.0% of all hypertensive etiologies. The adenomas have a 5:1 predilection for women and generally present with hypertension or profound hypokalemia. A low plasma renin activity completes the triad for primary hyperaldosteronism which could be caused by adrenocortical cancer, a neoplasm with an average diameter of 12 cm, or idiopathic hyperaldosteronism (IHA), a bilateral hyperplasia of the zona glomerulosa of the adrenal cortex which responds poorly to surgical resection. The adenomas are small (2 cm) but can be localized by imaging or selective venous sampling. Resection has a high success rate with minimal morbidity.

Primary hyperaldosteronism

Primary hyperaldosteronism is a challenging diagnosis because of its low incidence and variable pathophysiology. Serum potassium, properly done, is the routine screening test, but is not without its limitations. Confirmation of the diagnosis requires demonstration of abnormally high and nonsuppressible values for aldosterone in plasma and urine and low plasma renin activity. Sophisticated biochemical profiling and localization procedures often are required to identify those subtypes that will benefit from surgical management, including aldosterone-producing adenomas, primary adrenal hyperplasia, unilateral hyperplasia, and aldosterone-producing renin responsive adenomas. Glucocorticoid-suppressible hyperaldosteronism and isolated aldosterone-producing adrenal carcinoma are rare additional subtypes to be identified. Differentiation among these subtypes is a developing process that can be expected to continue to improve with new techniques and new understanding of underlying pathophysiology.