Causes of Hypoglycaemia

Immediate Causes of Hypoglycaemia

In the short-term, hypoglycaemia has two main causes relating either to the supply of carbohydrate or to the amount of available insulin. Very often, a hypo is caused either by inadequate carbohydrate intake as in a missed, late or small meal, or by an increase in the rate at which glucose is utilized due to a greater demand for energy. The latter situation generally results from increased physical exercise or activity, which can be something as simple as gardening or spring-cleaning. Alternatively, a hypo may be caused by excess treatment. This may either be the direct result of too much insulin being injected or, in the case of sulphonylureas, an excess dose provoking a greater than normal release of insulin from beta cells. In both cases, the net effect can be a fall in the circulating level of glucose, and if this descends too low, the development of hypogly-caemia. Other immediate causes or factors which can contribute to an attack include a higher than normal intake of alcohol, change of injection site, and hot weather (which affects insulin/glucose metabolism). It may be that there is no obvious cause for a particular 'hypo' but after recovery, it is always worthwhile to undertake a mental review of previous events and to try and discover the reason why it may have happened. Usually, some seemingly minor factor, possibly something that has not been a problem before, turns out to be the most likely cause. The purpose of the 'postmortem' is to try and avoid a recurrence in the future, even though this may not always be easy.

Longer-term Causes of Hypoglycaemia

There are a number of other, longer-term causes of hypoglycaemia, which generally cause it to be recurrent, rather than a single episode that happens due to one recent event. These include:

• The 'honeymoon period' in Type 1 diabetes, when there may be an initial apparent recovery of islet cells (invariably short-lived) following the initiation of insulin treatment. The honeymoon period usually comes to an abrupt end, often coinciding with a period of illness. A person in this position is usually carefully monitored and maintained on a minimal dose of insulin in order to avoid hypoglycaemia, rather than insulin treatment being stopped altogether.
• Alteration or change in insulin sensitivity, for example, the resolution of insulin resistance following childbirth or after withdrawal of steroid therapy
• Development of kidney or severe liver disease, underactive pituitary or thyroid gland, Addison's disease, disorders affecting absorption of nutrients, e.g. coeliac disease
• Severe weight loss or eating disorders.

These disorders may affect different people in various ways with regard to hypoglycaemia. Treatment of the primary cause, rather than hypoglycaemia as such, usually removes or lessens the risk of attacks.

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