Decreased insulin sensitivity and glucose tolerance in spontaneous canine hyperadrenocorticism

Alterations in carbohydrate metabolism were evaluated in 60 dogs with untreated hyperadrenocorticism by measuring basal concentrations of plasma glucose and insulin and performing glucose and insulin tolerance tests. The 60 dogs could be divided into four groups based on paired glucose and insulin concentrations. Eight dogs had normal concentrations of both glucose and insulin. Twenty-four dogs (40 per cent) were euglycaemic with mild to moderate hyperinsulinaemia whereas 23 (38 per cent) had moderate hyperglycaemia with moderate to severe hyperinsulinaemia. The five dogs (8 per cent) with overt ketoacidotic diabetes mellitus had relative insulin deficiency. Of eight dogs tested, six had intravenous glucose intolerance; all of the dogs had increased total insulin secretion during glucose tolerance testing. Resistance to the hypoglycaemic effect of exogenous insulin was demonstrated in six of the seven dogs tested. In 20 dogs that had basal glucose and insulin again determined after correction of hyperadrenocorticism, mean concentrations of both glucose and insulin decreased into the normal range.