Peculiarities of feline hyperadrenocorticism: Update on diagnosis and treatment

Abstract

Practical relevance: Hyperadrenocorticism (HAC) is a relatively uncommon endocrinopathy of older cats, with a mean age at diagnosis of 10 years. In addition to pituitary-dependent and adrenal-dependent hypercortisolism, clinical signs of HAC can result from adrenal sex steroid-producing tumours. Clinical challenges: While HAC in cats has many similarities to canine HAC, there are key differences in presentation, diagnosis and response to therapy. Most, but not all, cats with HAC have concurrent diabetes mellitus, which is often insulin resistant. Up to a third of cats with HAC have extreme skin fragility and are at high risk of debilitating iatrogenic skin tears during diagnostic or therapeutic interventions. Infections of the skin and nail beds, and urinary, respiratory and gastrointestinal tract, secondary to cortisol-induced immune suppression, are also common. Cats respond differently to dogs to adrenal function tests including adrenocorticotropic hormone (ACTH) stimulation and dexamethasone suppression tests; a 10-fold higher dose of dexamethasone is recommended in cats to screen for HAC. Curative treatment options include adrenalectomy or transsphenoidal hypophysectomy. Radiation or medical treatment may improve clinical signs. The response to mitotane therapy is poor. While trilostane is the medical treatment of choice based on retrospective studies, investigations into the pharmacokinetics of this drug in cats are lacking. Global importance: Feline HAC occurs worldwide and is not associated with any purebreed predisposition. Although uncommon, adrenal sex steroid-producing tumours have a higher prevalence in cats than in dogs. Evidence base: The information in this review is drawn from over 180 reported cases of feline HAC. Reports investigating clinical presentation, clinicopathological findings and treatment outcomes are observational, retrospective multiple case series (EBM grade III) or single case reports (EBM grade IV). While most endocrine testing studies for diagnosis are cohort controlled analytical studies (EBM grade III), prospective, randomised, placebo-controlled studies have been performed (EBM grade I).

Diabetes mellitus en hypercortisolisme bij een kat

“…In some cases, this test can also allow to make a differentiation between pituitary-dependent (PDH) and adrenal-dependent HC (ADH) based on the level of suppression of cortisol. In this case, there was suppression after four hours (<40 nmol/L) and an escape of suppression after eight (Feldman, 2014;Boland and Barrs, 2017). This finding was compatible with the clinical signs and the poorly controlled DM.…”

“…However, few cases with normal sized adrenal glands or mild asymmetric enlargement, as described in this case report, have been reported. (Combes et al, 2013;Valentin et al 2014;Boland and Barrs, 2017). In cats with ADH, the most important finding is a unilateral adrenal mass, with normal or small contralateral gland (Valentin et al, 2014;d'Anjou and Penninck, 2015;Boland and Barrs, 2017).…”

“…The pituitary gland can be visualized by CT and MRI. About 50 % of pituitary tumors are large enough in size to visualize (Chiaramonte and Greco, 2007;Niessen et al, 2013;Boland and Barrs, 2017). Generally, tumors smaller than 10 mm in height are considered microtumors, whereas the larger masses are macrotumors.…”

“…In the current case, the cat developed progressive azotemia during treatment. It should be emphasized that before treatment, the urine specific gravity (USG) was 1.015 although the majority of cats with HC have a USG of >1.020 (Feldman, 2014;Boland and Barrs, 2017). It is unclear if the azotemia was caused by therapy or if the CKD had already been developing before treatment.…”

“…Trilostane is the medical treatment recommended above all other medical options because of its superior efficacy, relative lack of side effects and ease of use. Other medical treatment options are mitotane, ketoconazole, aminoglutethimide and metyrapone but they are not recommended due to the lack of efficacy in some cats, their adverse effects and the difficulty of sourcing them (Niessen et al, 2013;Boland and Barrs, 2017).…”