Glucose is a simple sugar that forms more complex carbohydrates such as starch. It's also an important source of energy for the cells. After each meal, the digestive system breaks down carbohydrates and absorbs the glucose into the blood. This is the provenance of the term "blood sugar." If glucose levels rise, the pancreas releases a hormone called insulin that ushers the sugar into the cells for the production of energy. Measuring the ratio between glucose and insulin is sometimes useful as a diagnostic tool.
About Insulin Resistance
Insulin resistance is a physiological condition in which insulin becomes less effective at the task of lowering glucose levels in your blood because muscle, fat and liver cells do not respond properly to the presence of insulin. The pancreas attempts to keep up with the increased demand by producing more insulin. Diabetes eventually develops when it can no longer maintain the necessary level of production. If insulin fails to do its job properly, then high levels of glucose in the blood can damage tissue in the kidneys and nerves. Genetic and dietary factors, such as high blood levels of fat and sugar, may be to blame for insulin resistance.
About Glucose-to-Insulin Ratio
The glucose-to-insulin ratio is a measurement that directly compares the amount of blood glucose to the amount of insulin. It has become a popular method for assessing insulin sensitivity in certain medical conditions since its first description in 1998. A lower number denotes a higher degree of insulin resistance.
Screening Tool
Insulin resistance is a feature of a number of abnormal reproductive conditions, such as polycystic ovarian syndrome and premature adrenarche, and is a useful screening tool for these diseases. A 1998 study published in "The Journal of Clinical Endocrinology and Metabolism" by researchers from the Penn State University College of Medicine found that a glucose-to-insulin ratio of less than 4.5 is typical for women with polycystic ovarian syndrome. Another study published in a 2001 issue of the same journal suggests that a ratio of less than 7 in girls with premature adrenarche --- a condition characterized by early sexual maturation --- was largely associated with a large body mass index, higher levels of fasting insulin and other symptoms of the disease.
Limitations
Despite its potential usefulness as a screening tool, evidence suggests that the efficacy of the glucose-to-insulin ratio is somewhat limited. It may not be an appropriate measurement when fasting glucose levels are abnormal. This can occur in subjects with type 2 diabetes. In addition, it does not truly reflect the physiology underlying the factors that determine insulin sensitivity. The glucose-to-insulin ratio is relatively easy to measure, but there may be better measurements, such as the glucose clamp technique, in many circumstances.
References
- National Diabetes Information Clearinghouse; Insulin Resistance and Pre-Diabetes; October 2008
- Medical University of South Carolina: Assessing Insulin Sensitivity
- "The Journal of Clinical Endocrinology and Metabolism"; A Fasting Glucose to Insulin Ratio Is a Useful Measure of Insulin Sensitivity in Women with Polycystic Ovary Syndrome; R.S. Legro, et al.; August 1998
- "The Journal of Clinical Endocrinology and Metabolism"; Fasting Glucose Insulin Ratio: A Useful Measure of Insulin Resistance in Girls with Premature Adrenarche; P. Vuguin, et al.; October 2001
- "The Journal of Clinical Endocrinology and Metabolism"; Limitations of the Fasting Glucose to Insulin Ratio as an Index of Insulin Sensitivity; Michael J. Quon; October 2001
