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Conn Syndrome

Conn Syndrome is primary hyperaldosteronism, a disorder caused by excessive, autonomous production of aldosterone from the adrenal cortex. It leads to sodium retention, potassium loss, and hypertension.

Also called

Primary Hyperaldosteronism,

ICD-10

E26.0

Specialty

Endocrine

Onset

Chronic

Reviewed

August 2026

On This Page

Overview

-Conn Syndrome is an important and potentially treatable cause of secondary hypertension.

 

-The two major causes of Conn Syndrome are:

  • Bilateral adrenal hyperplasia
  • Unilateral aldosterone-producing adrenal adenoma

 

–Excess aldosterone causes sodium and water retention → hypertension, while promoting potassium and hydrogen ion excretion → hypokalemia and metabolic alkalosis.

Etiology & Risk Factors

The major causes include:

 

-Bilateral Adrenal Hyperplasia

  • Usually causes bilateral aldosterone overproduction.
  • It is an important cause of primary aldosteronism.

 

-Aldosterone Producing Adrenal Adenoma

  • Usually unilateral.
  • Historically known as the classic cause of Conn Syndrome.

 

-Risk Factors

  • Resistant hypertension
  • Severe hypertension
  • Hypertension at a young age
  • Hypokalemia
  • Adrenal incidentaloma
  • Family history of primary aldosteronism

Pathophysiology

Autonomous aldosterone secretion → increased renal sodium reabsorption → increased water retention → increased extracellular fluid volume → hypertension

Excess aldosterone → increased potassium and hydrogen ion secretion → hypokalemia + metabolic alkalosis

Volume expansion → suppression of renin secretion → low plasma renin → high aldosterone-to-renin ratio

Clinical Presentation

-Symptoms:

  • Many patients are asymptomatic and are diagnosed during evaluation of hypertension.

 

-Possible symptoms include:

  • Headache
  • Muscle weakness
  • Muscle cramps
  • Fatigue
  • Palpitations
  • Excessive thirst
  • Frequent urination

 

-Signs:

  • Hypertension
  • Resistant hypertension
  • Hypokalemia
  • Muscle weakness
  • Cardiac arrhythmias in severe hypokalemia

History Taking

-Ask about:

  • Duration of hypertension
  • Blood pressure readings
  • Resistant hypertension
  • Current antihypertensive medications
  • Number of medications required for blood-pressure control
  • Previous hypokalemia
  • Muscle weakness
  • Muscle cramps
  • Palpitations
  • Polyuria
  • Polydipsia
  • Nocturia
  • Headaches

Physical Examination

–General Examination

  • Blood pressure
  • Heart rate
  • Body mass index
  • Assessment of volume status

 

Look for:

  • Persistent hypertension
  • Severe hypertension
  • Signs of cardiovascular complications

 

-System-Specific Examination:

 

-Cardiovascular

Assess for:

  • Hypertension
  • Arrhythmias
  • Signs of heart failure
  • Evidence of hypertensive cardiovascular disease

 

-Neuromuscular

Assess for:

  • Muscle weakness
  • Reduced muscle strength
  • Abnormal reflexes in severe hypokalemia

Investigations

-Biochemistry / Specific Tests

  • Typical findings may include:
  • Low plasma renin
  • High plasma aldosterone
  • Increased aldosterone-to-renin ratio
  • Hypokalemia
  • Metabolic alkalosis

 

-Aldosterone-to-Renin Ratio

  • The aldosterone-to-renin ratio (ARR) is the main screening test for Conn Syndrome.
  • A positive screen generally requires:
  • Inappropriately elevated aldosterone
  • Suppressed renin
  • Elevated ARR
  • Exact cutoff values vary according to the assay and laboratory.

 

–Imaging

Adrenal CT

Used after biochemical diagnosis to assess:

  • Adrenal adenoma
  • Adrenal nodules
  • Adrenal hyperplasia
  • Adrenal carcinoma

Diagnosis

-Primary aldosteronism (Conn Syndrome) is suspected when there is:

  • Inappropriately high aldosterone + suppressed renin → elevated aldosterone-to-renin ratio

The diagnosis is confirmed according to the clinical context and appropriate confirmatory testing.

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Management

1. Definitive Treatment

Treatment depends on whether aldosterone excess is unilateral or bilateral.

 

-Unilateral Disease

Laparoscopic adrenalectomy is generally the preferred definitive treatment in suitable surgical candidates.

 

-Bilateral Disease

Usually treated medically with a mineralocorticoid receptor antagonist.

 

2. Medical Treatment

Mineralocorticoid Receptor Antagonists

 

-Spironolactone

  • Commonly used
  • Effective in reducing aldosterone-mediated effects
  • Can cause gynecomastia and sexual adverse effects

 

–Eplerenone

  • More selective for the mineralocorticoid receptor
  • Often better tolerated regarding sex-hormone-related adverse effects
  • May require twice-daily dosing

 

-Potassium Replacement

Used when hypokalemia is present, particularly while definitive treatment is being established

 

-Antihypertensive Therapy

Additional antihypertensive agents may be required depending on blood-pressure control.

Complications

  • Resistant hypertension
  • Hypokalemia
  • Metabolic alkalosis
  • Cardiac arrhythmias
  • Left ventricular hypertrophy
  • Heart failure
  • Coronary artery disease
  • Stroke
  • Chronic kidney disease
  • Increased cardiovascular risk

Prognosis

The prognosis is generally excellent when primary aldosteronism is recognized and appropriately treated.

-Treatment can substantially improve:

  • Blood pressure
  • Potassium levels
  • Cardiovascular risk
  • Renal outcomes

Key Points / Clinical Pearls

  • Conn Syndrome is primary hyperaldosteronism.
  • It is caused by autonomous aldosterone secretion from the adrenal glands.
  • Major causes are bilateral adrenal hyperplasia and aldosterone-producing adrenal adenoma.
  • Excess aldosterone causes sodium retention and potassium loss.
  • Classic laboratory findings are high aldosterone, suppressed renin, hypokalemia, and metabolic alkalosis.
  • Normal potassium does not exclude primary aldosteronism.
  • Consider it in resistant or severe hypertension.
  • The aldosterone-to-renin ratio (ARR) is the main screening test.
  • Antihypertensive medications can interfere with interpretation of the ARR.
  • Adrenal CT is used after biochemical evaluation but cannot reliably distinguish unilateral from bilateral disease.
  • Adrenal venous sampling may be required before surgery to establish lateralization.
  • Unilateral disease can often be treated definitively with laparoscopic adrenalectomy.
  • Bilateral disease is generally treated with spironolactone or eplerenone.
  • Funder JW, Carey RM, Mantero F, et al. The Management of Primary Aldosteronism: Case Detection, Diagnosis, and Treatment: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2016;101(5):1889-1916. Journal of Clinical Endocrinology & Metabolism .
  • Williams TA, Reincke M. Management of Endocrine Disease: Diagnosis and Management of Primary Aldosteronism: The Endocrine Society Guideline. Eur J Endocrinol. 2018;179(1):R19-R29. European Journal of Endocrinology .
  • Monticone S, Burrello J, Tizzani D, et al. Prevalence and Clinical Manifestations of Primary Aldosteronism Encountered in Primary Care Practice. J Am Coll Cardiol. 2017;69(14):1811-1820.
  • Vaidya A, Mulatero P, Baudrand R, Adler GK. The Expanding Spectrum of Primary Aldosteronism: Implications for Diagnosis, Pathogenesis, and Treatment. Endocr Rev. 2018;39(6):1057-1088.
  • National Library of Medicine (NIH). Hyperaldosteronism . StatPearls.
  • National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Primary Aldosteronism . National Institutes of Health.