Girth to Height Ratio (GHR) is Inversely Correlated to Plasma Glucose to Insulin Ratio (GIR), a Measurement of Insulin Resistance, in Horses

Abstract

Insulin resistance, most often caused by obesity and associated with increased age, occurs when insulin‐dependent tissues have a diminished sensitivity to the effects of insulin. In horses, insulin resistance increases the risk for developing a severe lameness condition, laminitis. The aim of this study was to determine if accessible external measurements of obesity could facilitate detection of insulin resistance in horses, possibly preventing the onset of laminitis through early intervention. We hypothesized that the progression of insulin resistance would directly correlate with quantitative assessment of physical parameters of obesity, such as body condition score (BCS), girth to height ratio (GHR), and neck circumference to height ratio (NCHR). Insulin resistance was determined by fasting plasma glucose to insulin ratio (GIR) in horses (n=23) of varying body conditions. GIR was inversely correlated to age (p = 0.003) and GHR (p = 0.048). There was no relationship between GIR and BCS or NCHR. As the quantitative measurement of GIR is inversely correlated to insulin resistance, these results indicate that older horses and those with greater GHR were more likely to be insulin resistant. In conclusion, GHR predicts insulin resistance as determined by GIR, but other physical parameters of obesity, such as the subjective assessment of BCS and the objective measurement of NCHR, are not reliable predictors of insulin resistance. Therefore, GHR could be used as a parameter to indicate if further assessment of insulin resistance should be conducted in individual horses.