Conn's syndrome

In Conn's syndrome there are high aldosterone levels in the absence of activation of the renin-angiotensin system.

• first described by Conn in 1955 in a patient presenting with resistant hypertension and hypokalemia who was found to have an aldosterone-secreting adrenal adenoma
  • the adenoma is characterized by increased aldosterone secretion from the adrenal glands, suppressed plasma renin, hypertension, and hypokalemia

Classical Conn's syndrome should be considered in a patient who is not on diuretics who has the following features (1,2):

• hypertension
• hypokalaemia
• alkalosis

Sodium is usually mildly elevated or normal.

Consider primary aldosteronism in patients with moderate to severe hypertension, resistant hypertension, hypertension with an adrenal mass, or hypokalaemia

Unilateral disease is treated with adrenalectomy; bilateral disease is treated with a mineralocorticoid receptor antagonist

There is an increasing frequency in the diagnosis of primary aldosteronism (1,2):

• principal reason for the increasingly frequent diagnosis of this disease, once viewed as rare, is that normokalemic Conn's syndrome is now recognized as an independent disease entity
• normal serum potassium is present in the majority of patients with primary hyperaldosteronism, especially in patients with adrenal hyperplasia or familial aldosteronism
• found in 5% to 18% of patients with high blood pressure (1)
• screening test of choice is plasma aldosterone-to-renin ratio (ARR) but testing may not be accurate (due to interfering medications) or consider temporary medication changes before screening or a therapeutic trial of a mineralocorticoid receptor antagonist in these contexts (2)
• primary aldosteronism is estimated to result from bilateral adrenal hyperplasia in two-thirds of patients, and from unilateral aldosterone-secreting adenoma in approximately one-third
  • although ARR is regarded as the ideal screening tool, there exists some controversy regarding the clinical conditions under which the ARR is obtained, as well as the test's diagnostic accuracy
  • certain drugs, including beta-blockers, angiotensin-converting enzyme inhibitors (ACE-I), selective-serotonin reuptake inhibitors and oral contraceptives, have been shown to affect the results of the test
  • ideal testing conditions involve discontinuation of such medications two weeks prior
  • for further advice regarding use of an ARR then seek advice from a hypertension specialist or endocrinologist
  • in adults with hypertension and a positive screening test for primary aldosteronism, referral to a hypertension specialist or endocrinologist is recommended for further evaluation and treatment (3)

Reference:

• Aronova A, Fahey TJ III, Zarnegar R. Management of hypertension in primary aldosteronism. World J Cardiol. 2014 May 26;6(5):227-33
• Choy K W, Fuller P J, Russell G, Li Q, Leenaerts M, Yang J et al. Primary aldosteronism BMJ 2022; 377 :e065250 doi:10.1136/bmj-2021-065250
• Whelton PK et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. J Am Coll Cardiol. 2018 May 15;71(19):2199-2269