Glucose is the simplest form of carbohydrates that are usable by the body's cells. Glucose is also the preferred source of energy for the brain and skeletal muscle. Glucose is absorbed through the intestinal cells and eventually makes its way into the bloodstream. In order for it to be utilized for the energy it contains, the monosaccharide must make its way out of the blood and into the cells. The transporter known as insulin helps glucose make this transition. If the body cannot properly make this transition, impaired glucose tolerance, also known as pre-diabetes, can result.
Acanthosis Nigrans
Acanthosis nigrans is the darkening of the skin in areas of the knuckles, neck, armpits, elbows and knees. This condition can result from prediabetes, or impaired glucose tolerance, according to mayoclinic.com. The condition is not concerning in any other way except for its physical presentation, but its usefulness lies in its ability to prompt early testing for diabetes. It is one of the few signs of this condition and the American Heart Association notes that early diagnosis of a pre-diabetic state can stave off and prevent full blown Type 2 diabetes by up to 58 percent with changes in lifestyle.
Increased Urination and Thirst
Impaired glucose tolerance is the result of the body's inability to properly move glucose out of the blood stream and into the cells. This measurement is determined by giving the patient a drink containing 75 g of glucose and testing her blood after two hours. The oral glucose tolerance test (OGTT), as it is called, expects a normal increase in blood sugar levels up to 139 mg/dl. When a person has an OGTT level between 140 and 199 mg/dl, he is believed to have impaired glucose tolerance or the inability to properly move sugar from the bloodstream into the cells.
When the body is unable to maintain normal levels of glucose in the blood, the sugar begins to enact its osmotic forces. Glucose, or sugar, is capable of drawing water toward it, affecting the movement of water within and surrounding the cells as well as the movement of water out of the body. High blood sugar levels, according to the American Diabetes Association, can cause excess water to be released from the body, thereby increasing the frequency of urination. Because so much water is being lost in the urine, the body attempts to compensate by excessively stimulating the thirst centers in the brain. As the intolerant state worsens, the symptoms of increased urination and thirst become more evident.
Fatigue
Reduced cellular energy production is the result of having too little glucose, or sugar, inside of the cells. Each gram of glucose can be burned to create 4 kcals of energy, according to anatomy and physiology authors Gerard Tortora and Bryan Derrickson in their book "Introduction to the Human Body." The brain and muscle cells depend on glucose as their primary energy source. Without sufficient amounts of it, secondary to the impaired tolerance to glucose that can be determined with the oral glucose tolerance test (OGTT), the cells quickly become fatigued. The worse the tolerance to glucose, or the progression of the prediabetic state, the more likely the fatigue that is being experienced on a cellular level will become noticeable on a larger scale.
Mild Visual Changes
High levels of glucose in the circulation can cause the molecules to become unstable and act as free radicals. Blurred vision can result from the damage that the free radicals have on the optic nerve--the nerve responsible for vision, notes the American Diabetes Association. Pre-diabetes or impaired glucose tolerance can lead to mild visual changes, as the OGTT and fasting blood sugar test levels approach diabetes cutoffs.
References
- American Diabetes Association: Pre-Diabetes FAQs
- Mayo Clinic: Prediabetes -- Symptoms
- "Introduction to the Human Body"; Gerard Tortora and Bryan Derrickson; 2010
