Peri-operative Hormone Plasma Profiles Predict Recurrence After Transsphenoidal Hypophysectomy in Dogs with Corticotroph Pituitary Adenomas

Introduction
Pituitary-dependent hypercortisolism (PDH) is a common endocrinopathy in dogs, with an estimated prevalence of 1-2 per 1000 dogs/year. It is caused by an adrenocorticotropic hormone (ACTH) secreting adenoma in the pars distalis or pars intermedia of the pituitary gland. In dogs, transsphenoidal hypophysectomy has been performed for 15 years in the Netherlands and has been shown to be an effective treatment for dogs with PDH. Despite high initial remission rates, long-term recurrence does occur. The aim of the present study was to evaluate the predictive value of the early postoperative plasma ACTH, cortisol and a-MSH concentrations for recurrence of hypercortisolism after transsphenoidal hypophysectomy in dogs with PDH.

Materials and Methods
55 dogs with PDH underwent transsphenoidal hypophysectomy as primary treatment. Diagnosis was based upon urinary corticoid: creatinine ratios (UCCRs) combined with a high dose dexamethasone suppression test. All surgeries were performed by the same neurosurgeon. After surgery, oral hormone substitution therapy was started. Plasma hormone levels of ACTH, cortisol and a-MSH were measured before surgery and 1,2,3,4,5, and 24 to 48 hours after surgery. Dogs with persistent disease were readily identified with the perioperative profile and were excluded from further analysis. Absolute values and the degree of decrease were analysed for their prognostic value of recurrence. Variables were analyzed with univariate and multivariate Cox’s proportional-hazard analysis.  [...]