Successful Treatment of Acromegaly in a Diabetic Cat with Transsphenoidal Hypophysectomy

UNLABELLED: PATIENT AND SURGICAL TREATMENT: An 11-year-old, castrated male cat was referred for insulin-resistant diabetes mellitus. It had a ravenous appetite, increased body weight, polyuria/polydipsia and a dull hair coat. The cat was receiving 25 IU insulin four times daily but blood glucose concentrations remained elevated. Plasma concentrations of growth hormone (GH) (51 microg/l, reference range 0.8-7.2 microg/l) and insulin-like growth factor 1 (IGF-1) (3871 microg/l, reference range 39-590 microg/l) were highly elevated, whereas those of alpha-melanocyte-stimulating hormone, adrenocorticotropic hormone and cortisol were normal. Computed tomography revealed a thick palatum molle and an enlarged pituitary gland, indicating a pituitary neoplasm. Microsurgical transsphenoidal hypophysectomy was performed and microscopic examination of the surgical specimen revealed an acidophilic, infiltrative pituitary adenoma that showed positive immunostaining for GH. OUTCOME: The clinical signs resolved and 3 weeks after surgery the cat no longer required insulin administration. One year after hypophysectomy the plasma concentrations of GH and IGF-1 were 2.4 microg/l and 113 microg/l, respectively. PRACTICAL RELEVANCE: This is the first report detailing transsphenoidal hypophysectomy as a feasible and effective treatment for feline acromegaly due to a pituitary somatotroph adenoma. Moreover, in this patient, concurrent insulin-resistant diabetes mellitus resolved completely. The surgery is discussed in the context of human and other feline therapies for acromegaly.