Basal glucose metabolism and peripheral insulin sensitivity in equine pituitary pars intermedia dysfunction.

BACKGROUND

Glucocorticoids are suggested to precipitate laminitis and induce insulin resistance in horses.

HYPOTHESIS/

OBJECTIVES

To assess insulin sensitivity and the basal amount of glucose metabolized in equine pituitary pars intermedia dysfunction (PPID).

ANIMALS AND

METHODS

The euglycaemic hyperinsulinaemic clamp (EHC) technique was performed in seven horses with a diagnosis of PPID based on the presence of hypertrichosis and positive dexamethasone suppression-test results comprising one gelding and six mares with a mean age of 21.1 ± 5.8 (SD; range 15-34) years. Results were compared with those from five negative (healthy) controls comprising two geldings and two mares with a mean age of 10.0 ± 2.5 (range 7-13) years and six positive (diseased) controls comprising two geldings and four mares with a mean age of 12.5 ± 4.5 (range 8-21) years examined during the same period. Differences were assessed by means of the Mann-Whitney U test.

RESULTS

Mean basal rate of glucose metabolism (9.0 ± 4.2 versus 16.0 ± 5.2 µmol/kg BW/min; p = 0.030) and mean glucose metabolism rate-to-plasma insulin concentration ratio (2.9 ± 1.6 versus 6.2 ± 2.7 × 10(-6); p = 0.048) were significantly lower in PPID horses than in negative controls, respectively. No differences were found between both control groups.

CONCLUSIONS AND CLINICAL

IMPORTANCE

In horses suffering from PPID it seems important to reduce the insulin resistance, thereby potentially decreasing the risk of laminitis as being a major complication of equine PPID. Plasma glucose concentration following fasting might be considered in the screening of horses for PPID.