Abstract
The common causes of hyperadrenocorticism (HAC) are pituitary ACTH-secreting corticotroph tumours, known as pituitary-dependent hyperadrenocorticism, and cortisol-secreting adrenal tumours. The only licensed medical treatment in the UK is trilostane. This treatment improves the clinical signs of HAC in the majority of cats and dogs. There are a number of alternative treatment options that are available for use in non-responders or as first-line treatment instead of trilostane. After a diagnosis of HAC is made, each option should be discussed with clients. This article discusses medical, surgical and radiotherapy options that should be considered to create an individualised treatment plan for each patient and owner.
Highlights
Medical ManagementTrilostane (Vetoryl, Dechra, Shrewsbury, UK) has been shown to be extremely useful in the management of pituitary-dependent hyperadrenocorticism (PDH)
The common causes of hyperadrenocorticism (HAC) are pituitary ACTH-secreting corticotroph tumours, known as pituitary-dependent hyperadrenocorticism, and cortisol-secreting adrenal tumours
Macroadenomas often protrude out of the bony indentation that houses the pituitary at the base of the brain, the sella turcica, and are >10 mm, classification based on a cut-off size of 10 mm has questionable utility in veterinary medicine (Meij et al, 2002; Wood et al, 2007)
Summary
Trilostane (Vetoryl, Dechra, Shrewsbury, UK) has been shown to be extremely useful in the management of PDH. The complete mechanism of action of mitotane is un- known, it is primarily adrenolytic, by induction of free radicals, and inhibits 11β hydroxylase and desmolase in the adre- nal gland, thereby reduce steroid synthesis (Figure 1) (Veytsman et al, 2009) This drug successfully improves clinical signs of HAC in up to 87% of dogs and 50% of cats, but mitotane-associated side-effects occur in up to 42% dogs, and clinical relapse following dose adjustments is common (Lorenz, 1982; Nelson et al, 1988; Kintzer and Peterson, 1991; Schwedes, 1997). Its efficacy is underwhelming, especially in light of better medical options being available, despite some reports suggesting it to be relatively effective, with improvement of HAC-associated clinical signs in 43 of 48 dogs and survival times comparable to mitotane and trilostane (median survival 810 vs 622 to 852 days, respectively) (Barker et al, 2005; Lien and Huang, 2008; Fracassi et al, 2014). Other medical management options are of- ten either less effective or more frequently associated with detrimental side-effects
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