Feline acromegaly (hypersomatropism or HST) is a spontaneously occurring condition caused by a growth hormone (GH) secreting pituitary tumor (somatotrophinoma). Studies estimate 1 in 3 to 1 in 5 diabetic cats have acromegaly (HST)-induced diabetes mellitius. Cats with high levels of growth hormone exhibit insulin resistance, arthropathy, general abdominal organ enlargement, and cardiovascular disease. Diabetic cats affected by acromegaly are frequently difficult to control with insulin alone, and controlling glucose levels will not manage other aspects of the disease.
In humans with HST, treatment options include surgical removal of the pituitary tumor, radiation treatment and medical treatment. One form of medical treatment is the use of somatostatin analogs, the drug form of choice in most patients. To date, there has been no successful management of HST in cats by drug inhibition of pituitary GH secretion. The authors questioned whether cats with somatotrophinomas express somatostatin receptors (SSTR) consistently; therefore, possibly a drug with high binding affinity for SSTRs. One such drug for consideration is pasireotide. The goal was to determine is a subcutaneous injection of pasireotide given every 12 hours would improve control of acromegaly in cats and also improve control of their diabetes.
Twelve cats completed the study. All were diagnosed diabetics diagnosed with HST by serum insulin-like growth factor-1 (ILGR-1) concentrations >1000 ng/mL by radioimmunoassay and pituitary enlargement. While receiving the pasireotide, ILGR-1 levels were measured and glycemic control assessed using a 12-hour blood glucose curve on days 1 and 5.
This study is the first to report effective medical treatment of acromegaly in cats. The drug, pasireotide, was well tolerated and all cats had decreased ILGR-1 concentrations. Any adverse effects in 3 of 12 cats were reported as mild gastrointestinal disturbances.
Further, insulin sensitivity improved in almost all the cats despite the short, 5-day treatment time. Eleven of the 12 cats completing the study had a lower insulin dose on day 5 than on day 1 to avoid hypoglycemia. All of the clients whose cats completed this short term trial opted to re-enroll in a long-acting pasireotide compound trial which was started shortly after this study was finished.
