Endocrine Abstracts

Secondary causes of diabetes are uncommon. As 50-80% of patients with diabetes have co-existing hypertension, a high index of suspicion is required to exclude a secondary cause in patients presenting with both conditions. Atypical presentations may delay the diagnosis.

A 49 year old man presented with a one year history of polydipsia, polyuria and fatigue. Diabetes was diagnosed with a random blood glucose (RBG) of 12 mmol/l. Hypertension diagnosed 15 years back had been resistant to treatment. He also had a history of anxiety, depression and lethargy. Physical examination was normal. BMI was 26.87 kg/m2 and blood pressure was 170/100 mm Hg. RBG and glycated haemoglobin (HbA1c) were 4.4 mmol/l and 7.3% respectively.

The patient complained of fatigue, excessive thirst and visual blurring despite being on an oral hypoglycaemic drug. RBG during symptoms never exceeded 11 mmol/. An oral glucose tolerance test done to clarify his glycaemic status showed fasting plasma glucose of 7.2 mmol/l and a 2 hour value of 3.8 mmol/l. Though the results were not suggestive of diabetes, glycosuria persisted and RBG levels varied between 7 and 11 mmol/l.

Urine catecholamines were measured in view of the history of hypertension, headaches and variable glucose tolerance. Total urine metadrenalines were raised at 85.6 umol/24 hrs (normal 0-5.5). Urine noradrenaline levels were markedly elevated at 15388 umol/24 hrs (normal (90-600).MIBG scintigraphy and abdominal CT imaging showed a large pre-aortic phaechromocytoma.

Phaeochromocytomas are uncommon tumours accounting for hypertension in only 0.1% to 1% of hypertensive patients. They are a rare cause of glucose intolerance. In the absence of classical paroxysms, the presenting symptoms are often protean and non-specific. The diagnosis should be excluded in patients with diabetes or variable glucose tolerance who present with resistant or labile hypertension.