Hyperglycemia is a condition involving too much glucose in the blood. "Hyper" means "too much" or "excessive"; "glyc" refers to glucose; and the suffix "emia" means "in the blood." Diabetes mellitus, stress, critical illness and certain drugs are culprits in the development of hyperglycemia. While glucose may be somewhat elevated immediately after a meal, this is a natural response to the ingestion of food. Whatever the cause, chronic hyperglycemia may lead to blood vessel damage.
Diabetes
Diabetes mellitus is a major cause of hyperglycemia. In fact, frequent hyperglycemia is a hallmark of the disease. Diabetes mellitus involves insulin, a hormone produced by the pancreas to lower the body's blood sugar.
In type 1 diabetes, or insulin-dependent diabetes, the pancreas is unable to produce insulin. This is because an autoimmune disorder has destroyed the beta cells of the pancreas. The beta cells function as the insulin production center of the pancreas. In type 2 diabetes, or noninsulin-dependent diabetes, insulin is still produced by the pancreas, but the body is resistant to its effects and cannot adequately respond to it. In the absence of insulin or an effective response to it, nothing is able to stimulate liver, fat and muscle cells to remove glucose from the blood and store it as glycogen. Consequently, the glucose level stays elevated without medical intervention.
Medications
According to the Mayo Clinic, a class of drugs called glucocorticoids can cause hyperglycemia. These drugs include prednisone, methylprednisolone, betamethasone, dexamethasone and hydrocortisone. Naturally occurring glucocorticoids stimulate the liver to release glucose, conserve glucose by preventing its uptake by muscle and fat cells, and enhance production of chemicals used in synthesizing glucose. Glucocorticoids received as a synthetic drug have a similar effect.
Stress
When the body undergoes physical or emotional stress, the "flight or fight" response is engaged. The body perceives any threat to physical or emotional integrity as a stressor. In preparation to meet a threat, the adrenal glands release a class of hormones called catecholamines, which engage the sympathetic nervous system, according to AJP - Endocrinology and Metabolism. One of the effects of catecholamines is to increase glucose production to fuel the increased metabolic needs in managing the threat.
Critical Illness
A combination of factors contribute to hyperglycemia in critically ill patients. Though a person might not feel stressed, illness is still a threat, and organ systems react accordingly to neutralize it. According to The Journal of Clinical Endocrinology and Metabolism, increased fat metabolism, glucose production by the liver and skeletal muscles, and production of what are called inflammatory mediators cause resistance to insulin in an effort to make glucose more readily available. These inflammatory mediators include tumor necrosis factor and interleukin.
References
- Journal of Clinical Endocrinology and Metabolism: Hyperglycemia in Children with Meningococcal Sepsis and Septic Shock: The Relation between Plasma Levels of Insulin and Inflammatory Mediators
- Mayo Clinic: Glucocorticoid-Induced Diabetes Mellitus
- AJP Endocrinology and Metabolism: Islet function and stress hyperglycemia: plasma glucose and epinephrine interaction
