ABSTRACT
This chapter discusses carbohydrate metabolism and its abnormalities, with emphasis on diabetes mellitus and hypoglycaemia. The main monosaccharide hexoses are reducing sugars. Naturally occurring polysaccharides are long-chain carbohydrates composed of glucose subunits. Insulin is the most important hormone controlling plasma glucose concentrations. Insulin binds to specific cell surface receptors on muscle and adipose tissue, thus enhancing the rate of glucose entry into these cells. Insulin-induced activation of enzymes stimulates glucose incorporation into glycogen (glycogenesis) in liver and muscle. The entry of glucose into liver and cerebral cells is not directly affected by insulin, but depends on the extracellular glucose concentration. The liver modifies the potential hyperglycaemic effect of a high-carbohydrate meal by extracting relatively more glucose than in the fasting state from the portal plasma. High urinary glucose concentrations produce an osmotic diuresis and therefore polyuria. Glycosuria can be defined as a concentration of urinary glucose detectable using relatively insensitive, but specific, screening tests.
