Background

Acromegaly is a condition caused by excessive growth hormone, typically caused by a growth-hormone tumour in the region of the brain known as the pituitary. The consequences of this condition are increased hunger, high risk of developing diabetes mellitus which can be difficult to control, soft tissue growth and increased risk of heart disease.

There are limited treatment options for this condition, which include surgery to remove the brain tumour, radiation therapy of the brain tumour and medications which inhibit the release of growth hormone from the tumour. However, these options are costly and only the surgical option reliably results in disease control.

Cabergoline, a medication known to control acromegaly in some humans, could be used to control acromegaly in cats. Cabergoline can act on the growth hormone producing tumour to reduce growth hormone release and can shrink some pituitary tumours in humans.

Methods

Client owned cats with spontaneously occurring acromegaly and diabetes mellitus were enrolled. They all received daily oral liquid cabergoline in addition to their normal management of their diabetes at home. Their response to the treatment was assessed by determining if their diabetic control improved, whether a marker of growth hormone levels (IGF-1) decreased and whether their quality of life changed during the study. This study was performed under the Veterinary Surgeons Act because there is no licensed treatment for acromegaly in cats and this medication is available for the treatment of false pregnancy in dogs.

Results

Eight cats completed the study. The treatment was well tolerated, but there was no significant improvement of diabetic control, IGF1 levels or quality of life in the cats as a group. There was a trend for cats to need a higher dose of insulin to control their diabetes mellitus at the end of the study. There was one cat whose diabetic control improved, and insulin requirements reduced, and this was the cat with the lowest IGF1 levels consistent with ‘mild’ acromegaly.

Clinical Significance

Although cabergoline cannot be recommended for cats with very high IGF1 levels, there might be a subset of acromegalic cats with mild disease which benefit from this medication but further research is needed in this area.