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Conn Syndrome

Conn Syndrome

Article Author:
Malvinder Parmar
Article Editor:
Shikha Singh
9/18/2020 6:52:59 PM
For CME on this topic:
Conn Syndrome CME
PubMed Link:
Conn Syndrome


Conn syndrome was named after J. W. Conn who first described it in 1955, in a patient who had hypertension with an aldosterone-producing adenoma. The adenoma is characterized by increased aldosterone secretion from the adrenal glands, suppressed plasma renin, hypertension, and hypokalemia. Later, many other cases of adrenal hyperplasia with inappropriately elevated aldosterone secretion were described, and now the term primary hyperaldosteronism is used to describe Conn syndrome irrespective of whether the patient has an adenoma or not.[1][2]

The diagnosis of Conn syndrome is not always easy but recognition is important as this condition can help cure hypertension with surgical or medical management. However, it is important to distinguish aldosteronoma from idiopathic adrenal hyperplasia. Aldosteronomas are removed surgically, whereas idiopathic adrenal hyperplasia is managed with medications.  At the same time, one as to be aware that there are conditions that cause elevated aldosterone levels including familial disease, aldosterone-producing renin-responsive adenomas. ectopic secretion (from kidneys and ovary) and adrenocortical carcinomas.


The syndrome may be secondary to adrenal hyperplasia, adrenal adenoma, aldosterone-secreting adrenal carcinoma (1%), or familial hyperaldosteronism (FH).[3][4][5]

Various specific genetic alterations (see below) have been identified for rare familial forms of the disease. In a majority of these genetic alterations, the endpoint is Ca influx and membrane depolarization resulting in aldosterone hypersecretion.

  • Familial hyperaldosteronism (FH) type 1: Unequal crossing over between highly homologous CYP11B2 and CYP11B1 genes that code of aldosterone synthase and steroid 11 B-hydroxylase, resulting in a chimeric gene that is under adrenocorticotrophin (ACTH) rather than RAS control.
  • Familial hyperaldosteronism (FH) type 2: Autosomal dominant, heterogeneous, no response to dexamethasone suppression, possibly link with chromosome 7p22.
  • Familial hyperaldosteronism (FH) type 3: Mutations in the gene encoding the inwardly rectifying potassium channel Kir3.4 (KCNJ5 gene). Specific mutations in the KCNJ5 gene, like those altering the G151E amino acid, are associated with a milder form of aldosteronism, compared to those with a G151R mutation that have a more severe form.

Mutations in three other genes encoding for membrane proteins (Na/K-ATPase (ATP1A), ca ATPase (ATP2B3) and Ca1.3 (CACNAID) are associated with Ca influx and/or activated calcium signaling pathways leading to increased production of aldosterone by CYP11B2 gene.

Recently, a single-nucleotide polymorphism (c.-2G>C) of the NR3C2 gene that codes for mineralocorticoid receptor (MR) has been shown to be associated with increased activation of RAS and increased blood pressure in the general population.

In most cases, the aldosteronomas arise from the zona fasciculata. There is often significant glandular hyperplasia.


Primary hyperaldosteronism is the most common cause of secondary hypertension and occurs in about 6% to 20% of adult hypertensive patients, higher in patients with resistant hypertension. The prevalence of 10% was noted when consecutive patients with hypertension were evaluated. However, the prevalence increased to 30% when aldosterone to renin ratio (ARR) was used as a screening method in general practice.

Aldosterone-producing adenoma is present in 50% to 60%, and the remaining is idiopathic or bilateral adrenal hyperplasia. It is about two times more common in women than in men.


Primary hyperaldosteronism is caused by aldosterone-producing adenomas, bilateral idiopathic adrenal hyperplasia, aldosterone-producing adrenal carcinoma, and familial aldosteronism. The increased amount of aldosterone potentiates renal sodium reabsorption and water retention, and potassium excretion. The increased sodium reabsorption by the kidneys results in plasma volume expansion which is the primary initiating mechanism for hypertension. This may induce tissue inflammation and heightened sympathetic drive, with subsequent development of fibrosis in vital organs, such as heart, kidneys, and vasculature. As a result, this may lead to the development of chronic kidney disease, atrial fibrillation, stroke, ischemic heart disease, and congestive heart failure.[6][7]

Besides the elevation in sodium, patients often develop hypokalemia and metabolic alkalosis. Nearly 1/5th of patients with Conn syndrome have impairment in glucose tolerance which is due to the inhibitory effects of hypokalemia on insulin secretion


Histopathology is often heterogeneous ranging from micronodular or macronodular hyperplasia with adenoma formation, with atrophy or diffuse or nodular hyperplasia of the adjacent adrenal cortex.

History and Physical

Often, the patients are asymptomatic but may present with symptoms of fatigue, muscle weakness, cramping (secondary to potassium wasting), headaches, and palpitations. They can also have polydipsia and polyuria from hypokalemia-induced nephrogenic diabetes insipidus.

Many patients are discovered to have Conn syndrome as a result of persisting hypokalemia and hypertension. Others may present with serious arrhythmias after being started on diuretics for hypertension. Finally, there are some patients who present with hypertension that is refractory to treatment.

Physical findings:

  • Hypertension
  • Abdominal distension
  • Ileus associated with hypokalemia
  • Hypertension associated bruits, altered mental status, retinopathy

It is important to note that Conn syndrome is not associated with edema because of spontaneous natriuresis.


Hypokalemia in a hypertensive patient is the most common clue for primary hyperaldosteronism. However, normal serum potassium may be present in up to 38% of patients, especially in patients with adrenal hyperplasia or familial aldosteronism.[8][9]

Blood work will reveal hypokalemia, hypernatremia and metabolic alkalosis due to the actions of aldosterone on the distal convoluted tubule.

  • Urinary potassium excretion is elevated (more than 30 mmol/day).
  • Diagnosis depends on the demonstration of expanded extracellular fluid (ECF) volume (suppressed plasma renin) and non-suppressible aldosterone secretion.
  • ARR (aldosterone: renin ratio): The lack of uniform assay method and diagnostic protocols in assessing the results creates a high variability in cut-off values among various investigators. A ratio of 40 or more (20 ng/dL/h to 40 ng/dL/h) or more than 135 (68 pmol/mU to 135 pmol/mU) has a sensitivity of 73% to 93% and a specificity of 71% to 84%, indicating the need for further confirmatory studies with salt-loading (failure to lower plasma aldosterone level less than 10 ng/dL), fludrocortisone suppression test, or captopril suppression test. The Endocrine Society's clinical practice guidelines do not specify which of these confirmatory tests should be regarded as the gold standard to confirm or exclude the diagnosis; therefore, different tests are performed by different centers.
  • Once autonomous aldosterone production is established, the next step is to evaluate for possible adenoma. CT scan may show an adenoma that accounts for 70% cases, but as milder forms are being recognized now, idiopathic hyperaldosteronism is the most common cause. However, CT may provide incorrect diagnosis because of the common occurrence of non-functional adrenal adenomas (incidentalomas) that may be present in 4% of the general population.
  • The studies to confirm unilateral nature of adrenal hypersecretion (lateralization) either by adrenal venous sampling (invasive, difficult and possible complications) or by
    iodocholesterol adrenal scan have limitations. 
  • Plasma 18-hydroxycorticosterone is elevated in adenoma and normal in adrenal hyperplasia.
  • A plasma aldosterone response to a two-hour upright position shows a normal increase in adrenal hyperplasia but a paradoxical decrease in adrenal adenoma.

Prior to measuring aldosterone levels it is important to know the diurnal rhythm of the hormone. The lowest levels of aldosterone are observed around midnight and the highest values are seen in the morning between 7-8 am. This diurnal rhythm is preserved in patients with Conn syndrome but rare in idiopathic adrenal hyperplasia. 

When to screen?

  • Patients with stage 2 or stage 3 hypertension
  • Resistant hypertension
  • Hypertension with spontaneous or diuretic-induced hypokalemia
  • Hypertension with adrenal incidentaloma
  • Hypertension with a family history of early-onset hypertension or cerebrovascular disease
  • Patients with first-degree relatives diagnosed with Primary aldosteronism
  • Any patient with suspected secondary hypertension


Treatment / Management

The goals of treatment include normalizing blood pressure, electrolytes and aldosterone levels. The treatment depends on the cause

Unilateral adrenalectomy in patients with a unilateral adenoma (Conn syndrome) cures hypertension in 30% to 60% of cases, but the mean cure rate is only 19% after unilateral or bilateral adrenalectomy in patients with idiopathic hyperaldosteronism whose treatment mainly is medical. This treatment includes aldosterone antagonists such as spironolactone or eplerenone or other potassium-sparing diuretics like amiloride.

To decrease risks of elevated blood pressure during surgery, patients need to be optimized preoperatively. Aldosterone antagonists like eplerenone and spironolactone are associated with survival benefits.

To lower blood pressure, spironolactone is preferred as it also normalizes serum potassium levels and plasma volume. In a small group of patients with glucocorticoid-mediated hyperaldosteronism, low doses of corticosteroids can help with blood pressure control.

Nonsurgical treatment is an option for patients who are frail and have numerous comorbidities. In addition, bilateral adrenal hyperplasia is also managed medically.

Adrenalectomy is used to excise unilateral lesions. Prior to surgery, the patient has to be treated with spironolactone for 4-6 weeks. Today, laparoscopic adrenalectomy is widely used to excise the adrenal gland.


About 2/3rd of patients become normotensive after surgery but the blood pressure may take 6-12 months to stabilize. Over 5 years, only about 50% of patients will remain normotensive. Those who fail to respond to spironolactone prior to surgery will most likely continue to be hypertensive after surgery.

Differential Diagnosis

  • Hypertension
  • Metabolic alkalosis
  • Renal artery stenosis
  • Malignant hypertension
  • Preeclampsia
  • Licorice intake
  • Gitelman syndrome
  • Barter syndrome
  • Adrenal carcinoma


Conn syndrome is associated with high morbidity and mortality if it is left untreated. The primary cause of the morbidity is linked to hypertension and hypokalemia, the latter is known to cause cardiac arrhythmias that can be fatal.


Complications are often related to the underlying chronic hypertension that can cause acute myocardial infarction, stroke and heart failure. Most important, hypertension can also lead to retinopathy and end-stage renal disease. The surgery for Conn syndrome can also lead to complications.

Postoperative and Rehabilitation Care

After surgery, the blood pressure has to be monitored for many months. Some patients may develop significant hyperkalemia that may require treatment with diuretics.

A low salt diet is recommended especially since it helps in the management of hypertension.

Pearls and Other Issues

  • Normal serum potassium level does not exclude primary hyperaldosteronism. Several studies have shown that 7% to 38% of patients with primary hyperaldosteronism have normal baseline.
  • Serum potassium levels, especially patients with hypertension who are often advised to restrict their salt intake. The hypokalemia becomes evident with the liberalization of dietary sodium intake.



Enhancing Healthcare Team Outcomes

The diagnosis and management of Conn syndrome is best done with an interprofessional team. The disorder can be difficult to diagnose because of the lack of standardized tests. In addition, the ARR may be falsely elevated in patients with chronic kidney disease, patients on potassium supplements or beta-blockers. Diuretics, angiotensin-converting enzyme inhibitors, and angiotensin receptor blockers may cause false-negative results. If the clinical suspicion is high, ARR should be repeated after holding these agents for two weeks.

Unilateral adrenalectomy in patients with a unilateral adenoma (Conn syndrome) cures hypertension in 30% to 60% of cases, but the mean cure rate is only 19% after unilateral or bilateral adrenalectomy in patients with idiopathic hyperaldosteronism whose treatment mainly is medical. This treatment includes aldosterone antagonists such as spironolactone or eplerenone or other potassium-sparing diuretics like amiloride.

Due to the challenges of managing this disease, the pharmacist should be involved in diuretic selection and dosing. The pharmacist should check for drug-drug interaction and report back to the clinical interprofessional team concerns. The nurses monitoring the patient should be familiar with the pathophysiology and expected abnormalities in laboratory testing. Due to the precarious challenges of abnormal potassium, the nurse should be prepared to report to the clinical team quickly any untoward abnormalities as daily lab screens are reported. Only through interprofessional team involvement and close monitoring can the best results be achieved. [Level 5][10]


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