Sunday, 28 September 2008

How does end-stage renal failure cause hypoglycaemia?

It is true that one of the rarer causes of hypoglycaemia is end-stage renal failure. In this regard, the kidney joins the liver and the heart as being organs that can disrupt glucose homeostasis when severely hypofunctional (there are probably others too).

We've covered the liver here, but how about the kidney? What is often forgotten is that the kidney is, like the liver, a site of gluconeogenesis, albeit a more minor one. Together they produce a maximum of 20% of the body's total gluconeogenesis, but this process is stimulated by adrenaline (epinephrine) entirely, not glucagon, which suggests that the kidneys are ever more crucial in maintaining normal blood glucose levels in conditions of bodily stress (like exercise, hypoglycaemia, and infections).

The kidneys don't store glycogen - that's done almost exclusively in the liver and muscles - but their gluconeogenic role is enough to explain why end-stage renal failure can sometimes lead to hypoglycaemia. However, there is another aspect to consider, and that is that the kidneys are a site of insulin clearance. As with gluconeogenesis, their role here is dwarfed by the liver's but it is still significant. The resulting increased half-life of insulin in end-stage renal disease can potentially cause hypoglycaemia too. In practice, however, insulin secretion is usually well suppressed as you approach hypoglycaemia, so it isn't clear how much this component contributes to renal failure's hypoglycaemia. It certainly causes headaches with regulating diabetic patient's overall glucose levels in this situation though!

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