Outline the physiological consequences of an inability to produce insulin.
Most candidates were able to detail how insulin allowed influx of glucose into insulin dependent
cells, in combination with potassium. Good candidates were able to explain how the inability to
produce insulin allowed hypovolaemia and electrolyte loss, with the ensuing tachycardia and
hypotension. Few candidates mentioned insulin’s action on hormone sensitive lipase (HSL), and
that deficiency of insulin leads to increased activity of this enzyme. The fact that when insulin is not
produced, the liver cells carry out -oxidation of the fatty acid (released peripherally by the action
of HSL) releasing acetyl CoA which is coalesced into acetoacetic acid was mentioned by only a
few. However, the fact that ketone bodies in the form of acetoacetic acid, -hydroxybutyric acid
and acetone accumulate and cause a metabolic (anion gap) acidaemia, appeared to be well
known. Few, went on to describe that a compensatory respiratory alkalosis will be generated and
detail how and why this occurred.
Syllabus: N2a&b, E2,F1, C1g 2b
References: Guyton and Hall Textbook of Medical Physiology 10th Ed, pg 888