Lecture notes compiled by Rebecca A. Price MD. Lecture given by Deborah Greco DVM PhD ACVIM at the MVMA Seminar in Telluride, Colorado, March 2005. These notes are the interpretation of Dr. Price and any errors within are her sole responsibility.
Acromegaly: Case History and Discussion
10 year old male cat with a 2 year history of diabetes mellitus unresponsive to insulin therapy. Diet: Free choice dry cat food. Insulin: 12 U NPH BID injected in dorsum of neck. Owner complains of cat being lethargic and having behavior changes plus severe polydipsia and polyuria.
On physical examination, weight was 11 kg (24.2 pounds). The tongue was enlarged (macroglossia) and separation between the incisor teeth was noted. The cat had a heart murmur and a thyroid nodule, both kidneys were enlarged and the cat appeared dull and depressed.
Laboratory work showed BUN and creatinine (kidney function labs) were slightly increases and the glucose was 25 mmol/L (450 mg/dl). Fructosamine was 900 micromoles/L and the T4 (thyroid) was normal. Xrays included a normal chest xray, an abdominal x-ray that showed enlarged kidneys and liver and some bone abnormalities in the spine (bridging spondylosis). A skull x-ray showed thickened bones. An echocardiogram revealed enlargement of the left ventricle and some mild overall enlargement of the heart.
The cat was treated with the following:
Four weeks later the cat was rechecked. There had been a 50% reduction in PU/PD occurring after the changes in insulin and diet. The cat was still lethargic and a slight plantigrade (leg neuropathy) stance was noted. Lab work showed mild hyperglycemia and fructosamine was decreased to 540 micromoles/L. A CT scan showed a large pituitary adenoma resulting in a diagnosis of acromegaly.
The cat had a 3 week course of cobalt irradiation with a decreasing insulin dosage. A low dose of prednisone (steroid) was given to counteract any brain swelling caused by the irradiation. The cat responded well and one year later was still off insulin with a normal personality.
The causes of insulin resistance include: