Hypderaldosteronism is an underdiagnosed disorder of cats that often presents with signs similar to to chronic renal disease; including hypertension and a low blood potassium. There are several other steroid hormones that are intermediates in aldosterone synthesis that have been theorized to also be increased in cases of hyperaldosteronism, such as progesterone and corticosterone. The purpose of this study was to investigate abnormalities in adrenal corticosteroids including progesterone, corticosterone, and cortisol, in cats undergoing measurement of baseline aldosterone concentrations.
This study was performed at a reference laboratory that is the primary center assaying feline aldosterone levels in North America. In a two year period, samples of plasma or serum submitted for aldosterone assay also had other hormones levels tested if samples sizes permitted. No exclusion criteria were present.
In addition to aldosterone, cortisol, corticosterone, and progesterone levels were assayed using standard analyzers. OF the 122 cats with information suggesting a clinical history of hyperaldosteronism, 76 cats had markedly increased aldosterone (>3000pmol/L), 71 severely increased (1000-2999pmol/L), 59 moderately increased (500-999pmol/L), and 92 normal to mildly increased (<500pmol/L) 585 samples were submitted for analysis, of which 297 had sufficient volume for additional assays. The median age (where available) was 13 years, with only variable information provided by submitting veterinarians. Cats with elevated aldosterone levels showed higher levels of progesterone and corticosterone, but not cortisol (which in fact was lower in cats with higher aldosterone levels). Over 30% of cats with aldosterone concentrations over 3000pmol/L had significant increases in progesterone (>10npmol/L). These cats also have corticosterone concentrations 10x the reference level. The authors theorize that these increases may be due to close proximity within synthetic pathways, but may be due to the prescience of multiple tumors.
Elevated corticosterone and progesterone are relevant due to their significant association with diabetes mellitus, polyphagia, and other potential clinical signs.
There were some limitations to this paper. Data collection was retrospective, and performed at a laboratory that may not have had full patient information available. As such, complete interpretation of findings may not be valid. Not all intermediates were assayed; for example 17-OH progesterone may also have been measured.
This manuscript suggests that cats with hyperaldosteronism may suffer from multiple endocrine issues, and investigation for hyperestrogenism in particular should be pursued. Conversely, it raises questions as to whether cats with diabetes mellitus and hypokalemia should be investigated for adrenal disease.
Schulman RL. Feline primary hyperaldosteronism. Vet Clin North Am Small Anim Pract. 2010; 40: 353- 359.
Harvey AM, Refsal KR. Feline hyperaldosteronism. In: CT Mooney, ME Peterson, eds. BSAVA Manual of Canine and Feline Endocrinology. 4th ed. Glouchester, UK: BSAVA; 2012: 204- 214.
Ash RA, Harvey AM, Tasker S. Primary hyperaldosteronism in the cat; a series of 13 cases. J Feline Med Surg. 2005; 7: 173- 182.
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