Title: Feline hyperaldosteronism

{{Short description |Hormonal disorder in cats}}
{{about|hyperaldosteronism in cats|the disease in humans|Hyperaldosteronism}}
'''Feline hyperaldosteronism''' is a disease in cats. The symptoms are caused by abnormally high concentrations of the hormone [[aldosterone]],&lt;ref name=JFMS/&gt;  which is secreted by the [[adrenal gland]]. The high concentrations of aldosterone may be due directly to a disorder of the adrenal gland (primary hyperaldosteronism), or due to something outside of the adrenal gland causing it to secrete excessive aldosterone (secondary hyperaldosteronism).

==Causes==
===Primary hyperaldosteronism===
Primary hyperaldosteronism (PHA) is a disorder of the [[adrenal cortex]] that causes increased circulating aldosterone levels. There are two types of PHA. One type is caused by a unilateral aldosterone-producing [[adenoma]] or [[adenocarcinoma]]. The other type, known as [[idiopathic]] hyperaldosteronism, occurs with bilateral [[adrenal hyperplasia]].&lt;ref name=JFMS&gt;{{cite journal|last=Djajadiningrat-Laanen |first=S.| last2=Galac |first2=S. |last3=Kooistra |first3=Hans |title=Primary Hyperaldosteronism: Expanding the diagnostic net |journal=Journal of Feline Medicine and Surgery |year=2011 |volume= 13 |issue=9 |pages=641–650 |doi=10.1016/j.jfms.2011.07.017|pmc=10832666 }}&lt;/ref&gt;

===Secondary hyperaldosteronism===
Secondary hyperaldosteronism is a normal physiological response to decreased arterial blood volume, wherein [[hypovolemia]] activates the [[renin–angiotensin system]] to stimulate aldosterone synthesis and thus increase [[Water retention (medicine)|fluid retention]].&lt;ref name=Kooistra&gt;{{cite conference|last=Kooistra |first=Hans S. |title=Hyperaldosteronism in Cats. |conference=World Small Animal Veterinary Association World Congress Proceedings| year=2006 |url=http://www.vin.com/proceedings/Proceedings.plx?CID=WSAVA2006&amp;PID=15793&amp;O=Generic}}&lt;/ref&gt;

==Mechanism==
[[Aldosterone receptor]]s are present on the [[epithelial cell]]s of the distal [[nephron]] in the [[kidney]]. Aldosterone activates [[sodium channel]]s that result in sodium resorption from the urine.&lt;ref name=JFMS/&gt; Increased sodium and water retention results in systemic [[arterial hypertension]].&lt;ref name=Kooistra/&gt; This increase in active [[sodium reabsorption]] generates an [[electrochemical gradient]] that leads to passive transfer of [[potassium]] from the [[tubular cell]]s into the [[urine]]. This causes a lower total body concentration of potassium and potentially, [[hypokalemia]].&lt;ref name=JFMS/&gt; Hypokalemia affects polarization of nerve and muscle membranes, which causes episodic [[muscle weakness]].&lt;ref name=Kooistra/&gt;

==Symptoms==
Symptoms primarily relate to the effects of hypokalemia (potassium depletion) and systemic arterial hypertension (elevated blood pressure).&lt;ref name=&quot;Feldman 2015&quot; /&gt; As the disease progresses, affected cats will present muscular weakness and/or ocular signs of [[hypertension]]. Signs of muscle weakness can include a [[plantigrade]] stance of the hindlimbs, cervical ventroflexion, inability to jump, lateral recumbency, or collapse. Ocular signs of arterial hypertension include [[mydriasis]], [[hyphema]], or [[blindness]] due to [[retinal detachment]] and/or [[intraocular hemorrhage]]s.&lt;ref name=JFMS/&gt; A palpable mass in the cranial abdomen is another potential finding.&lt;ref name=Kooistra/&gt;

==Diagnosis==
Persistently increased [[blood pressure]] may also be due to [[kidney disease]] or [[hyperthyroidism]]. When a cause is not readily apparent, and especially when hypokalemia is identified, [[hyperaldosteronism]] should be considered. [[Diagnostic imaging]], usually beginning with abdominal ultrasound, may identify that one or both [[adrenal gland]]s are enlarged.  Imaging may also detect [[metastasis]] and usually includes [[radiograph]]s of the chest in addition to abdominal ultrasound and/or [[computerized tomography]] (CT).&lt;ref name=JFMS/&gt;

The ratio of plasma aldosterone concentration (PAC) to [[plasma renin activity]] (PRA) can be used as a screening test for PHA. In cats with unilateral or bilateral [[zona glomerulosa]] tumors, the PAC may be very high while the PRA is completely suppressed. In cats with idiopathic bilateral nodular hyperplasia of the zona glomerulosa, the PAC may be slightly elevated or high normal. In the presence of hypokalemia even a mildly elevated aldosterone should be considered inappropriately high. A high-normal or elevated PAC with a low PRA indicates persistent aldosterone synthesis in the presence of little or no stimulation of the renin–angiotensin system.

==Treatment==
Unilateral primary hyperaldosteronism due to an [[adrenocortical adenoma]] or adrenocarcinoma can be potentially cured surgically. Unilateral [[adrenalectomy]] is the treatment of choice for unilateral PHA. Potential complications include [[hemorrhage]] and postoperative hypokalemia. With complete removal of the tumor, prognosis is excellent.&lt;ref name=JFMS/&gt;

Bilateral primary hyperaldosteronism due to [[hyperplasia]] of the zona glomerulosa or metastasized adrenocortical adenocarcinoma should be treated medically. Medical therapy is aimed at normalizing blood pressure and plasma potassium concentration. [[Mineralocorticoid receptor]] blockers, such as spironolactone, coupled with potassium supplementation are the most commonly used treatments. Specific therapy for treating high blood pressure (e.g., [[amlodipine]]), should be added if necessary.&lt;ref name=Kooistra/&gt;

==Epidemiology==
Most affected cats are over 10 years old. No breed or sex is predisposed to hyperaldosteronism.&lt;ref name=&quot;Feldman 2015&quot;&gt;{{cite book|last1=Feldman|first1=EC|editor1-last=Feldman|editor1-first=EC|editor2-last=Nelson|editor2-first=RW|editor3-last=Reusch|editor3-first=C|editor4-last=Scott-Moncrieff|editor4-first=JC|title=Canine and Feline Endocrinology|date=2015|publisher=Elsevier, Saunders|isbn=9781455744565|pages=478–481|edition=4th|chapter=Primary hyperaldosteronism in cats}}&lt;/ref&gt;

==References==
{{Reflist}}

[[Category:Cat diseases]]