Our digestive system breaks down carbohydrates from foods such as rice, bread, pasta, fruits and vegetables into various forms of simple sugars. One of these sugars is glucose, the body’s main source of energy.
Normal blood glucose ranges from 70 to 100 mg per deciliter (mg/dl) or 3.9 to 5.6 millimoles per liter (mmol/l). Blood glucose levels rise after a meal. Prompted by the elevated level of glucose in the bloodstream, the beta cells of the pancreas secrete the hormone insulin. Insulin facilitates the entry of glucose into the body’s cells and tissues. Any excess glucose is stored in the liver and muscles in the form of glycogen. This process lowers the level of glucose in the bloodstream and prevents it from rising to dangerously high levels (hyperglycemia). As blood glucose levels return to normal, insulin secretion by the pancreas tapers off.
In between meals, particularly during the overnight fast between dinner and breakfast, blood glucose levels drop. Any dip in blood glucose levels signals the alpha cells of the pancreas to secrete the hormone glucagon. Glucagon prompts the liver to break down stored glycogen (glycogenolysis) and release glucose back into the bloodstream. This keeps blood sugar level within a normal range until the next meal.
Aside from glycogenolysis, the body also has the ability to manufacture glucose through gluconeogenesis. Occurring primarily in the liver, this process also takes place in the kidneys and intestine. Gluconeogenesis utilizes various glucose precursors (e.g., pyruvate, lactate, glycerol, amino acids, fatty acids) to manufacture glucose and help maintain blood glucose levels within the normal range.
Hypoglycemia or abnormally low blood glucose is a condition commonly associated with the treatment of diabetes. Insulin and oral diabetes medications that increase insulin production (e.g., sulfonylureas, gliptins, meglitinides) can cause hypoglycemia. Liraglutide (brand name Victoza), a once-daily injectable medication for adults with type 2 diabetes mellitus, mimics the action of an intestinal hormone called GLP-1 that stimulates the beta cells in the pancreas to release insulin when blood sugar is too high after meals. GLP-1 also helps to lower the amount of glucose produced by the liver. It may cause hypoglycemia when taken with a sulfonylurea or insulin. Hypoglycemia may also develop if, after taking your diabetes medications, you eat less than usual (ingest less glucose) or exercise more than you normally would (use up more glucose).
Rarely, hypoglycemia can be caused by other conditions. Excessive alcohol consumption can block the liver from releasing stored glucose into the bloodstream. Severe illnesses of the liver, such as severe hepatitis, can cause hypoglycemia. A rare tumor of the pancreas called insulinoma may cause insulin overproduction resulting in hypoglycemia.
Common signs and symptoms of hypoglycemia include confusion, double/blurred vision, heart palpitations, shakiness, anxiety, sweating, hunger, and tingling sensation around the mouth. Because the primary energy source of neurons (brain cells) is glucose, hypoglycemia has a profound effect on the brain. Untreated, hypoglycemia can result in seizures, loss of consciousness, and death. Watch out for next week’s column, which will discuss ways to prevent and treat hypoglycemia.
CONTEST: Glucose is a carbohydrate. True or False? E-mail your answer to [email protected] and get the chance to win a prize! Congratulations to Joaguin Ong! Your correct answer to the question in the September 7, 2013 column was chosen as this week’s winner in the Diabetes Trivia Contest. You will receive an e-mail on how to claim your prize.
Dr. Elizabeth Paz-Pacheco is an Associate Professor at the University of the Philippines College of Medicine and Chief of the Section of Endocrinology, Diabetes and Metabolism, UP-Philippine General Hospital. A Consultant Endocrinologist at The Medical City, she is also the editor in chief of the Journal of the Asean Federation of Endocrine Societies. The “Changing Diabetes” column commemorates the 92nd anniversary of insulin’s discovery. It aims to increase awareness on diabetes prevention, diagnosis and management. Novo Nordisk supports “Changing Diabetes.” Headquartered in Denmark, Novo Nordisk is a global healthcare company with 90 years of innovation and leadership in diabetes care. For questions or comments, e-mail [email protected]