Chapter 12: Carbohydrate Metabolism

Carbohydrate Metabolism provides an in-depth analysis of carbohydrate metabolism, focusing on the essential biochemical processes that regulate blood glucose levels and the pathological consequences of their disruption. It begins by examining the chemistry of sugars, from simple monosaccharides like glucose to complex storage polysaccharides such as animal glycogen and plant starch. The narrative highlights the physiological necessity of glucose as a primary energy source, particularly for the brain, which lacks significant storage capacity and remains highly sensitive to extracellular concentrations. Central to this discussion is the hormonal control of glucose homeostasis, detailing how insulin facilitates cellular uptake and storage through glycogenesis while suppressing gluconeogenesis, and how counter-regulatory hormones like glucagon, growth hormone, and adrenaline mobilize energy via glycogenolysis. A significant portion of the text is dedicated to the clinical pathology of diabetes mellitus, categorizing it into Type 1 autoimmune-mediated deficiency, Type 2 insulin resistance, and specialized forms such as gestational diabetes and maturity-onset diabetes of the young (MODY). Beyond diagnostics, the chapter explores chronic vascular complications, metabolic syndrome, and acute medical emergencies like diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS). It also provides critical insights into the monitoring of glycaemic control using glycated haemoglobin (HbA1c) and the investigation of hypoglycaemia, covering Whipple’s triad and the differential diagnosis of insulinomas through C-peptide analysis.