Glucose Intolerance and Diabetes Mellitus in Endocrine Disorders - Two Case Reports and a Review

Impaired glucose tolerance and diabetes mellitus are a manifestation of several well recognised endocrine disorders. Hyperglycaemia subsides upon removal of the underlying cause in these conditions - usually a hormone secreting tumour. We describe two subjects who were cured of their poorly controlled diabetes mellitus following surgical removal of a phaeochromocytoma and a cortisol secreting adrenal adenoma and review the mechanisms underlying glucose intolerance in endocrine disorders. The reported incidence of diabetes is variable in these conditions and may range between 2- 95%. The severity is also variable as some affected individuals have only minor glucose intolerance while others have frank symptomatic diabetes mellitus which forms a major manifestation of their illness. The mechanisms causing hyperglycaemia are (a) insulin resistance, (b) increased hepatic glucose production and output, (c) decreased insulin production and release and (d) increased intestinal glucose absorption. Multiple intermediate mechanisms which include electrolyte perturbations and hormone receptor and post receptor mediated effects are responsible for these abnormalities. An understsanding of these mechanisms and diagnostic strategies is important as these may be used to advantage in managing these patients. We describe some of these in greater detail below.