Affecting Factors of Hypoglycaemia

There are various factors, closely connected with the necessary treatment of diabetes with insulin, which can affect hypoglycaemia.

Effect of Recurrent Hypoglycaemia and Hypoglycaemic Unawareness

Both insulin therapy for more than five years and lifelong diabetes itself, are likely eventually to cause defective counter-regulatory hormonal responses to hypoglycaemia, especially those involving glucagon. Normal brain function is critically dependent upon a good supply of glucose from the circulation at all times. The glucose is transported to the brain by specialized transporter proteins called GLUT 1. It has been found that previous and recurrent hypoglycaemia (such as nocturnal hypoglycaemia) alters the rate at which this occurs during subsequent attacks. There is an increased rate of glucose transfer to the brain during subsequent episodes of hypoglycaemia, which is an adaptive response.

The effect of both defective hormonal responses and adaptive changes in glucose transfer to the brain can be a loss or decreased awareness of hypoglycaemic symptoms. This is known as hypoglycaemic unawareness. When this is present, a person becomes aware of symptoms only at lower blood glucose levels or he or she may not notice them at all. Hence there is far less time to take restorative action and a much greater risk of loss of consciousness and the development of a severe attack. This is the situation that arises more frequently in tightly controlled, intensively treated Type 1 diabetes. Quite often, awareness of warning symptoms can be restored by returning to a less intensive treatment regime in which blood glucose is maintained at a higher level.

Effect of Insulin Type and Species

In the UK, there has been a considerable amount of debate about whether particular types of insulin may cause hypoglycaemic unawareness. This arose because a few people reported a decreased awareness when they changed from animal to human insulin. Although there is no scientific evidence for any problem with human insulin in this respect, it is known that individuals can react differently to particular type of insulin and that changes in dose may be needed if there is a switch from one kind to another. Diabetes clinical staff are always ready to listen to people's concerns about insulin and are happy to supply a particular type or suggest a change if this would seem to be beneficial.

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