In clinical, medical terms, four grades of hypoglycaemia are recognized.
- Grade 1: its existence can be detected biochemically but it does not produce symptoms.
- Grade 2: produces only mild symptoms and can be easily treated by the affected person.
- Grade 3: produces more severe symptoms and requires the assistance of another person.
- Grade 4: very severe, producing unconsciousness, coma and/or convulsions and requiring emergency treatment in hospital.
In practice, people who experience hypoglycaemia or who are considered to be at risk are given advice on how to treat three categories designated mild, moderate and severe. The treatment for these is described below.
The symptoms of hypoglycaemia can be attributed to two main causes. Involvement of the autonomic nervous system (the part of the nervous system that is not under conscious control) and the release of hormones from the adrenal glands, produces 'fright', 'flight' and 'fight' symptoms. These typically include anxiety, trembling, sweating, shivering, pallor, palpitations and a raised heartbeat rate, and dizziness. These are called adrenergic symptoms. The brain is very soon affected by the inadequate energy supply, as blood glucose levels fall during hypoglycaemia, producing the second category of neuroglycopenic symptoms. These include inability to concentrate, confusion, irrational, aggressive or uncharacteristic behaviour, speech disturbance, refusal to co-operate, drowsiness, and eventual loss of consciousness. If treatment is not provided, there is a risk of convulsions and eventual permanent brain damage or, in extreme circumstances, death. A third group of symptoms, which do not directly belong to either category but are commonly experienced, include hunger, disturbance of vision, transient headache, and feelings of weakness.
In experimental conditions of induced hypoglycaemia, adrenergic symptoms are produced first at a higher level of blood glucose while neuroglycopenic ones begin as the level continues to descend. Many people learn to recognize adrenergic symptoms as an early warning of hypoglycaemia and are able to take action to rectify the situation. However, there are circumstances where this is not the case, and in any particular hypoglycaemic episode not all symptoms maybe present, or there maybe neuroglycopenic ones appearing at the same time as adrenergic ones, so that the situation is not always clear cut.
Events within the Body during Hypoglycaemia
As blood glucose levels fall during hypoglycaemia, the body responds by activating a sequence of counter-regulatory hormones to try and reverse the decline. The hormones are secreted in a particular sequence, namely, glucagon (from pancreatic alpha cells), adrenaline and noradrenaline (secreted by an area of the adrenal glands called the medulla whose normal function is to prepare the body for 'fright', 'flight' or 'fight'), Cortisol (released by the cortex of the adrenal glands and involved in glucose metabolism and stress responses), and growth hormone (from the pituitary gland). Glucagon, adrenaline and noradrenaline stimulate the processes of glycogenolysis and gluconeo-genesis which results in the production and release of glucose from the liver. Cortisol and growth hormone are less involved in acute hypoglycaemia but are important in the later restoration of glucose levels. However, when secretion of these hormones is impaired for any reason, as in pituitary gland disorders (this gland controls adrenal production of Cortisol) and Addison's disease, which affects the adrenal glands themselves, hypoglycaemia is likely to occur. Addison's disease can itself be a complicating feature of Type 1 diabetes. When insulin or sulphonylureas are needed to treat diabetes, the counter-regulatory hormonal responses are often inadequate to prevent hypoglycaemia.
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