Endocrine Abstracts

Fasting blood glucose is key to diagnosing diabetes, whilst the Oral Glucose Tolerance Test (OGTT) is a valuable adjunct when diagnosis is borderline or inconclusive. The OGTT is often used to detect early changes in glucose tolerance and predict a likely path to overt Diabetes Mellitus for example in gestational diabetes.

A 42 year old female, referred to the Endocrine services for episodes of symptomatic hypoglycaemia. Past medical history included pyloroplasty & vagotomy in 1985. Hypoglycaemia was repeatedly documented in the post-prandial situation. A diagnosis of dumping syndrome was made. The patient was placed on regular pre-prandial Octreotide injections 50–100 mcg (sc). Her glucose handling was then re-evaluated.

Investigations: • HBA1C 5.7%

• Islet cell Antibody – negative

• Anti GAD AND Insulin Antibody – negative

Dynamic tests: • Extended OGTTT(Off Octreotide)

• Extended OGTTT (On Octreotide)

Discussion: We see a contrasting picture of insulin production and glycaemia on and off Octreotide. Octreotide is effectively suppressing the first phase insulin secretion and preventing post-prandial hypoglycaemia but at the expense of causing hyperglycaemia in response to a standard 75 g oral glucose load. Off Octreotide there is a heightened first phase of insulin release indicative of the disordered insulin response seen in the dumping syndrome.

Conclusion: Does the patient have diabetes? Despite raised blood glucose at 2 hrs which would normally be diagnostic of diabetes – in this situation it more likely reflects altered insulin dynamics.

Pre-prandial Octreotide injections are clearly efficacious in the dumping syndrome but we need to be aware of alterations in glucose dynamics the long term effects of which are uncertain. It is reassuring that fasting blood glucose remains normal on and off octreotide and that a normal HbAlc is maintained.