Elevated blood glucose is a common medical condition most often associated with the disease diabetes mellitus. There are many potential causes for high sugar, however, including other disease processes and medications. A single episode of elevated sugar should prompt the consideration of a broad differential, or list of possible diagnoses, in order to find the true cause.
Diabetes Mellitus
Diabetes mellitus is a disease which causes the body to either lack the hormone insulin—necessary for normal glucose metabolism—or develop a resistance to it. There are two types of diabetes mellitus: type I and type II. In type I, a person is born with an inherited condition which causes the immune system to begin attacking insulin-producing cells in the pancreas. In type II, the body develops a resistance to the hormone after years of unhealthy dieting and lack of exercise. In either case, glucose can not move from the bloodstream into cells where it is needed to produce energy. Elevated blood sugar, or hyperglycemia, results.
Gestational Diabetes
Diabetes mellitus is not the only form of diabetes. Pregnant women can often develop a form of the disease known as gestational diabetes. It is similar to type II diabetes mellitus as described above in that the body develops a resistance to the hormone insulin. This occurs because of the increased metabolic stresses placed upon a pregnant woman's body while the fetus fights for nutrients. Blood sugar levels typically return to normal upon resolution of the pregnancy, but according to Current Diagnosis and Treatment Obstetrics and Gynecology, there is a 60 percent chance of recurrence in subsequent pregnancies. In addition, women who have developed gestational diabetes are at a higher risk of developing type II diabetes later in life and should see their doctors to discuss diet and exercise changes.
Cushing's Disease
Cushing's disease is caused by a small tumor on an organ near the brain called the pituitary gland. The pituitary gland secretes hormones such as ACTH, TSH, GH and prolactin. These control the various hormonal organs in the body such as the thyroid gland. Excessive secretion of ACTH by the tumor causes elevated levels of cortisol. Cortisol is a stress hormone with a wide range of effects, one of which is insulin resistance similar to type II diabetes mellitus. Cushing's disease causes elevated blood sugar along with other signs and symptoms such as truncal obesity, osteoporosis, thin extremities and purple striae on the skin.
Hemochromatosis
Hemochromatosis results from a genetic predisposition to increased iron absorption by the intestines. This inappropriately high level of iron absorption causes excess iron to be deposited throughout the body. Deposition in the skin causes a metallic or slate gray hue, accumulation in the liver causes cirrhosis and liver failure, and iron in the pancreas damages the cells which produce insulin. This results in a form of hyperglycemia similar to type I diabetes mellitus, in which there is a lack of the hormone insulin because of destruction of the cells that produce it.
Medications
A variety of medications can also cause hyperglycemia. The most common culprits are glucocorticoids. These medications are used to treat chronic inflammatory conditions such as asthma or autoimmune conditions. The mechanism of glucocorticoid-induced hyperglycemia is insulin resistance. The seizure medication phenytoin, cholesterol medication niacin and oral contraceptives all can cause elevated blood sugar levels as well.
References
- "Current Medical Diagnosis & Treatment 2010, 49th Edition"; Stephen J. McPhee, Maxine A. Papadakis, Eds.; 2010
- "Current Diagnosis & Treatment: Emergency Medicine, Sixth Edition"; C. Keith Stone, Roger L. Humphries; 2008
- "Greenspan's Basic & Clinical Endocrinology, Eighth Edition"; David G. Gardner and Dolores Shoback; 2007
- "Current Diagnosis & Treatment Obstetrics & Gynecology, 10th Edition"; Alan H. DeCherney and Lauren Nathan; 2007
