Hypoadrenocorticism in dogs presenting to a tertiary veterinary clinic in Switzerland: overall prevalence, clinical signs, laboratory changes and outcome.

Hypoadrenocorticism (HAD) is a relatively uncommon endocrinopathy and dogs often present with non-specific clinical signs. The laboratory database of a tertiary referral center was blinded for review and retrospectively searched between March 2015 and March 2023, for dogs with suspected HAD and then categorized according to basal cortisol measurements and/or an adrenocorticotropic hormone stimulation test (ACTH-STIM). Diagnosis of HAD was based on abnormal results of an ACTH-STIM (post-ACTH-STIM cortisol < 2ug/dl). HAD was diagnosed in 54 dogs, representing 9,6 % of the screened population (n = 564). Dogs without HAD had significantly higher sodium (p < 0,001), lower creatinine (p = 0,007), and lower phosphates (p < 0,001) concentrations than dogs with HAD. Most common breeds diagnosed with HAD included: mix breed (n = 16), Jack Russel Terrier (n = 5) and Bernese Mountain Dog (n = 3). Median age at diagnosis was 5 years (IQR: 3-8,75, range: 1-14). Twenty-nine dogs were male and 26 dogs were female. Most common clinical signs were combinations of hypo-/anorexia (n = 37, 68,5 %), lethargy (n = 35, 64,8 %), and vomiting (n = 31, 57,4 %). Only two of 54 dogs (3,7 %) had resting cortisol values > 0,5 µg/dl (> 13,79 nmol/l) (max. 0,63 µg/dl [17,38 nmol/l]) whereas six dogs (11,1 %) had post-ACTH-STIM cortisol values > 0,5 µg/dl (median: 0,82 µg/dl [22,62 nmol/l], IQR 0,51-0,96 [14,07-26,48]). Dogs with eunatremic, eukalemic hypoadrenocorticism (EEH) were more likely to present with anemia (OR: 14,19, 95 % CI, 2,71-74,22), whereas dogs with typical HAD were more likely to present with hyperphosphatemia (OR: 23,33, 95 % CI, 2,68-203,14). Forty-three dogs (79,6 %) had hyponatremic and/or hyperkalemic HAD and the remaining 11 dogs had EEH. In-house mortality was 5 % (3/55). One dog with EEH developed typical HAD seven weeks after initial diagnosis. Among dogs with HAD, the proportion diagnosed with EEH was similar to previous studies. In contrast to previous reports in which females were overrepresented, more males than females were affected in this cohort. No significant difference in age at presentation was observed between dogs with typical HAD and EEH.