Insulin Toxicity Can Cause Laminitis

A controlled experimental trial was conducted using nine clinically normal ponies to determine the effects of high blood insulin levels on lamellar integrity and laminitis in normal ponies with normal blood glucose levels. Five ponies were administered high levels of insulin over a 72-hour period while keeping their blood glucose levels within the normal range and controls received saline placebos over the same time period. The ponies were monitored and treated for signs of laminitis that developed and they were sacrificed after about 72 hours to examine the hoof lamellae microscopically.

All the ponies in the high insulin group developed clinical as well as microscopic signs of laminitis in all four feet while none of the controls were affected. This occurred despite all ponies receiving a normal diet and having normal blood glucose levels.

This is the first time a direct link between high insulin levels alone and laminitis has been made in the absence of other factors such as high blood glucose or concurrent Cushing’s disease. The authors point out that high insulin blood levels might be useful to identify horses at increased risk of laminitis from grazing lush pastures or other metabolic disease. The results also suggest insulin and glucose could have important, independent effects on laminar blood flow related to laminitis.

—Asplin et al. The Veterinary Journal 2007;174:530-535.

Palmar Imaging Findings Compared

A case series of 258 horses affected by lameness localized to the foot was used to compare findings from radiographs…