A 27-year-old woman presented with a 6-week history of weight loss, excessive thirst, nocturia and lethargy. She had no significant past medical or family history. At presentation she was unwell, tachycardic and had a blood pressure of 174/100 mm Hg. Physical examination was otherwise unremarkable. Her urine dipstick was strongly positive for glucose and ketones. The plasma glucose was 21.7 mmols/l. An arterial blood gas showed a pH of 7.35 and bicarbonates of 23. She was treated as a new onset type-I diabetic. In view of the hypertension and tachycardia, a 24-hour urine collection for catecholamines was done which showed raised adrenaline (539 nmol), noradrenaline (3161 nmol) and normal dopamine levels. MRI showed a left adrenal mass consistent with pheochromocytoma. There were no other features suggestive of multiple endocrine neoplasia. Anti-islet cell and anti-glutamic acid decarboxylase (GAD) antibodies were negative. Initial treatment with alpha and beta-blockers reduced her blood pressure, and the daily insulin requirement from around 50 to 30units. Following adrenalectomy her insulin requirement rapidly tailed off. After stopping insulin, an oral glucose tolerance test was normal.
Glucose intolerance in pheochromocytoma requiring high doses of insulin is rare. There have been 4 cases of diabetic ketoacidosis secondary to pheochromocytoma reported so far. Glucose intolerance in pheochromocytoma is due to decrease in insulin secretion and increase in peripheral resistance to insulin action. Catecholamine action on alpha-2 receptors on the pancreatic islet cells cause decrease secretion of insulin. Increased insulin resistance is mainly affected by catecholamine stimulation of beta-2 receptors in the peripheral tissues.
This case highlights the importance of considering pheochromocytoma in a young patient presenting with diabetes mellitus and hypertension.
06 - 07 Nov 2006
Society for Endocrinology