Acromegaly is characterized by chronic excessive growth hormone (GH) secretion by the pituitary gland. Feline acromegaly is most commonly caused by a functional pituitary tumor. Definitive diagnosis can be difficult because of the gradual disease onset, subtle clinical signs, unavailability of relevant laboratory tests, and client financial investment. The most significant clinical finding of acromegaly is the presence of insulin-resistant diabetes mellitus. Diagnosis is currently based upon brain imaging and measurement of serum GH and/or insulin-like growth factor-1 concentrations. Definitive treatment in cats is not well described, but radiation therapy appears promising.

A 10-year-old female spayed cat was diagnosed with acromegaly secondary to a pituitary tumour. At the time of diagnosis, the cat had insulin-resistant diabetes mellitus and its insulin-like growth factor-I levels were elevated. Clinical signs included polyuria, polydipsia and weight gain. Persistent hyperglycaemia and glucosuria were identified, and fructosamine levels remained elevated. Magnetic resonance imaging of the brain showed a pituitary tumour. Transsphenoidal cryohypophysectomy was used to treat the pituitary tumour. Postoperatively, the serum insulin-like growth factor-I levels decreased and the diabetes mellitus was controlled with routine levels of insulin. To the authors' knowledge, this is the second reported case of acromegaly treated with cryohypophysectomy, and the first that reports a favourable long-term outcome. Cryohypophysectomy may be a safe and effective treatment for cats with a pituitary mass resulting in acromegaly.

AcroCat comments: Transsphenoidal cryohypophysectomy refers to a surgical technique where the instruments are guided through the nose into the brain and a portion of the pituitary gland is frozen to kill any growths. The technique has been common in human brain surgery for many years.

In summary, the present study suggests there is no completely effective solitary diagnostic test for acromegaly in cats. Until other diagnostic tests have been developed, a combination of serum concentrations of IGF-1 and fGH and CT or MRI should be considered to establish an antemortem diagnosis. The prevalence of acromegaly in this study also suggests that acromegaly always should be considered a possible explanation for insulin-resistant diabetes in cats because many confirmed acromegalic cats in this study did not demonstrate the typical phenotype. Respiratory stridor was a prominent and common clinical finding, whereas hypertension, erythrocytosis, and hyperphosphatemia were less commonly observed than in previous reports.

A very interesting article suggesting feline acromegaly can be difficult to diagnose and that the disorder is probably underdiagnosed. The full text article can be accessed here in .pdf format. Included are some informative photographs. Please respect the copyright of this article and access it only for personal use.