| Poorly controlled diabetes may lead to life-threatening diabetic ketoacidosis
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Ketoacidosis develops predominantly in persons with type 1 diabetes who have no, or very little, insulin in plasma. Because of this they have a low insulin-to-glucagon concentration ratio. Lack of insulin does not allow glucose to enter insulin-dependent tissues, such as adipose tissue and muscle. Glycolysis and lipogenesis are inhibited, and glycogenolysis, lipolysis, ketogenesis, and gluconeogenesis are stimulated (Fig. 20.16). The key phenomenon is that the liver becomes a net producer of glucose. Increased endogenous glucose production, together with impaired glucose transport, lead to fasting hyperglycemia. Simultaneously, unopposed lipolysis produces an excess of acetyl-CoA. Ketogenesis is stimulated. In a decompensated patient, ketonemia and ketonuria develop (Fig. 20.17). Overproduction of acetoacetic and b-hydroxybutyric acids decrease the pH of blood, and causes metabolic acidosis (see Chapter 23). In a type 1 diabetic patient, ketoacidosis can develop quickly, even after missing a single insulin dose. In type 2 diabetes, ketoacidosis is relatively rare but may be precipitated by a major stress, such as myocardial infarction.
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| Because glucose is osmotically active, its increased renal excretion causes water loss (osmotic diuresis). Poorly controlled diabetic patients complain of having to drink a lot of fluid (polydypsia) and of passing large volumes of urine (polyuria). The fluid loss eventually leads to dehydration (see Chapter 22).
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| Hypoglycemia is the most common complication of diabetes
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| Hypoglycemia, described earlier in this chapter, is the most common acute complication of diabetes. It develops when the balance between insulin dose, carbohydrate supply, and physical activity becomes disrupted. Thus, hypoglycemia may occur as a result of taking too much insulin or missing a meal. Exercise increases tissue glucose uptake independently of insulin; therefore diabetic patients must decrease their insulin dose before strenuous exercise to prevent hypoglycemia. In mild hypoglycemia, having a sweet drink or several lumps of sugar to eat is enough to control it. Many diabetic patients sense the early symptoms of hypoglycemia and should carry sweets to prevent severe events. Severe hypoglycemia, however, is a medical emergency that requires immediate treatment with either intravenous glucose or glucagon.
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