Successful treatment of acromegaly in a diabetic cat with transsphenoidal hypophysectomy

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.

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.

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.