Oral Glucose Tolerance Test (OGTT)

Oral glucose tolerance test (OGTT) measures the body ability to use glucose and indirectly reveals about production, activity and function insulin in body. Oral glucose tolerance test is fairly dependable with ambulatory patients that do not suffer from any other severe chronic conditions. The test-OGTT- is better be proceeded by at least 3 days of adequate carbohydrate diet in order to obtain proper result, and should be performed in morning after the subject has fasted for about 8-14 hours.

Result as shown in table above was fairly remote or far-away rather than being within normal blood glucose ranges. It only came once in normal blood glucose range when it showed 7.5 entering with acceptable readings. Although our subject had fasted all these hours for about 14 hours his readings was out of the normal ranges. This indicates diabetic risk or threat. Impaired glucose tolerance is category of oral glucose tolerance test curve which is significantly abnormal values but not sufficient or enough to make diagnose as diabetes.

This involves fasting blood glucose level less than 140mg/100ml (7.77 mmol/L) and a single point on the OGTT curve at or above 200mg/100 ml (11.1 mmol/L). Impaired glucose tolerance can not be diagnosed diabetes as once; it shows a condition between normality and diabetic and diabetic risk or possibility. However in our case it can’t be said impaired glucose tolerance because Fasting blood glucose is higher than 140 mg/100 ml (7.77 mmol/L) and OGTT curve is above 200mg/100ml (11.1 mmol/L) in more than one single point. Therefore the subject should undergo through further diabetic tests to figure out if there is any problem.

Oral glucose tolerance test (OGTT) is not the best way to establish a diagnosis of diabetes mellitus. In fact it has relatively few indications that can also be considered as other types of diagnosis established from OGTT. These indications include 1) borderline fasting or postprandial blood glucose, 2) persistent glycosuria, 3) glycosuria in pregnant women. Oral glucose tolerance test is of little use or value in hospitalized patients or with patient immediately after a severe disease. There are several factors that can affect and alter OGTT readings, they are: bilirubin values more than 20mg/dl, triglycerides in vitro lipemic samples >5000mg/dl, hematocrit values <20%>65% at blood glucose concentrations <200mg/dl,>10mg/dl and glucose value <70mg/dl>8mg/dl, galactose >10mg/dl and maltose >16mg/dl may give falsely elevated results, situation of decreased peripheral blood flow, finger stick may not be appropriate to reflect the true physiological state.

In hyperglycaemia glucose metabolism is severely distorted, body cells can not take up glucose from blood although they are starving. Then great amount of glucose will be present in blood, kidneys reabsorb some of this huge amount and the rest is excreted through urine. Liver plays an important role in glucose metabolism, in normal feeding state glucose flows through blood from intestine to liver which in turn starts performing his storage of glucose to glycogen. Fasting cycle begins as soon as nutrients flow from intestine diminishes. As blood glucose and insulin level fall back to normal glucagon is released, this promotes glycogenolysis and gluconeogenesis in liver. If this fasting is prolonged for overnight several metabolic strategies maintain blood glucose levels.

Under starvation condition which is extremely prolonged fasting, the body makes metabolic changes to ensure that adequate amounts of blood glucose are available to sustain energy production in the brain and other glucose-requiring cells. Furthermore fatty acid and ketone bodies from liver are mobilized to sustain the other tissue.