Endocrine Abstracts

Humans with hypopituitarism post-pituitary surgery can develop altered emotional behaviour and hyperphagia, consistent with reduced oxytocin levels. Almost all cats diagnosed with acromegaly have concurrent diabetes mellitus (DM). Hypophysectomy provides the most favourable quality of life and endocrine outcomes. However, approximately 66% experience persistent diabetes insipidus and require long-term DDAVP supplementation, and experience a median weight gain of 1.2kg by 12 months post-hypophysectomy. The effects of hypophysectomy on serum oxytocin concentrations have not been described. The current study evaluated the effect of hypophysectomy on serum oxytocin concentration in cats treated for acromegaly. Paired serum samples from cats with acromegaly and DM pre- and post-hypophysectomy were analysed using a commercial ELISA validated for the measurement of feline oxytocin. Patient descriptive and outcome data were recorded, including serum IGF1 concentration and remission of DM. Serum oxytocin concentration pre- and post-hypophysectomy was compared using Wilcoxon matched pairs signed-rank test. Relationships between oxytocin and DDAVP requirement, and oxytocin and percent bodyweight change were analysed using Mann-Whitney U test and Spearman’s correlation respectively. Twelve paired samples were included with 11/12 cats achieving normalisation of serum IGF1 concentration and resolution of DM following hypophysectomy. There was no difference between pre- and post-hypophysectomy oxytocin concentrations (pre-hypophysectomy median 16 pg/mL, range 0 - 61 and post-hypophysectomy median 22 pg/mL, range 0 – 42, P=.65), no relationship between post-hypophysectomy oxytocin concentration and requirement for long-term DDAVP supplementation (P=0.81), and no correlation between post-hypophysectomy oxytocin concentration and percentage change in bodyweight at 3 to 6 months (P=0.70). This study suggests that cats continue to produce and secrete oxytocin following hypophysectomy, and oxytocin deficiency is not a contributor to post-operative weight gain.