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Primary hyperaldosteronism
Synonym(s): Conn, Conn's
Introduction
- Hyperaldosteronism is defined by an elevated plasma aldosterone concentration, exceeding the upper limit of the reference range, or in the case of primary hyperaldosteronism an increased ratio of plasma aldosterone to plasma renin activity.
- Aldosterone is normally secreted by the zona glomerulosa of the adrenal gland in response to stimulation of the renin-angiotensin-aldosterone system.
- Aldosterone has effects on mineralocorticoid receptors in the distal renal tubules, colon and salivary glands to stimulate sodium re-absorption, and potassium and hydrogen excretion.
- Hyperaldosteronism can be primary or secondary.
- Primary hyperaldosteronism is characterized by elevated plasma aldosterone in the face of suppressed plasma renin activity, and occurs as the result of an aldosterone secreting adrenal tumor or adrenal hyperplasia.
- Secondary hyperaldosteronism describes an increase in aldosterone production, occurring as a normal response to activation of the renin-angiotensin-aldosterone system, such as occurs with congestive heart failure Heart: congestive heart failure , severe hepatic dysfunction and renal failure Kidney: acute renal failure.
Presenting signs
- Generalized muscle weakness, eg cervical ventroflexion, limb weakness, ataxia Ataxia.
- Episodic weakness.
- Ocular manifestations of hypertension Hypertension, eg hyphema Hyphema, blindness Blindness.
- Other manifestations of hypertension, eg behavioral changes, neurological signs.
- Less commonly: dysphagia, episodic stiffness, polyuria, polydipsia, polyphagia.
Acute presentation
- Generalized muscle weakness.
- Collapse.
- Sudden onset blindness Blindness.
Age predisposition
- Middle aged to older cats.
Breed/Species predisposition
- No known breed predisposition.
Cost considerations
- Endocrine assays.
- Medication and monitoring during medical therapy.
- Surgery and post-operative care.
Special risks
- Anesthesia: hypokalemia Hypokalemia and hypertension should be stabilized prior to considering surgical management.
- Surgery: significant risk of severe and possibly fatal intra- or peri-operative hemorrhage following resection of adrenal masses.
Pathogenesis
Etiology
- Aldosterone secreting adrenal adenoma.
- Aldosterone secreting adrenal carcinoma.
- Bilateral adrenal hyperplasia.
Pathophysiology
- In primary hyperaldosteronism there is dissociation of the renin-angiotensin-aldosterone system. Increased, autonomous aldosterone secretion occurs → independently from renin secretion, with loss of negative feedback.
- Increased aldosterone causes retention of sodium, and excretion of potassium.
- Retention of sodium results in expansion of extracellular fluid volume, leading to hypertension.
- Excretion of potassium results in hypokalemic polymyopathy.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Rose S A, Kyles A E, Labelle P et al (2007) Adrenalectomy and caval thrombectomy in a cat with primary hyperaldosteronism. JAAHA 43 (4), 209-14 PubMed.
- Ash R A, Harvey A M, Tasker S (2005) Primary hyperaldosteronism in the cat: a series of 13 cases. J Feline Med Surg 7 (3), 173-182 PubMed.
- Javadi S, Djajadiningrat-Laanen S C, Kooistra H S et al (2005) Primary hyperaldosteronism, a mediator of progressive renal disease in cats. Domest Anim Endocrinol 28 (1), 85-104 PubMed.
Other sources of information
- Refsal K R & Harvey A M (2009) Primary hyperaldosteronism. In: August's Consultations in Feline Internal Medicine. August J R (ed). 6th edn. Chapter 24, pp 254-267.