**Question:** Impaired oral GTT indicated by

A. Increased fasting blood glucose levels
B. Decreased peak glucose levels after oral glucose load
C. Delayed glucose absorption
D. Absence of hyperglycemic peak after oral glucose load

**Core Concept:** Oral Glucose Tolerance Test (OGTT) is a diagnostic test used to evaluate an individual's glucose tolerance status. It measures how well the body can use glucose, a key component of blood sugar regulation. The normal OGTT involves fasting for 8-14 hours, then consuming a glucose load (75g of glucose), followed by blood glucose measurements at 0 (baseline), 30, 60, 90, and 120 minutes. Impaired glucose tolerance indicates a higher risk of developing type 2 diabetes mellitus.

**Why the Correct Answer is Right:** An impaired OGTT, particularly D, indicates that an individual has difficulty controlling their blood glucose levels after consuming glucose. This is a sign of impaired glucose tolerance (IGT) and is a risk factor for developing type 2 diabetes mellitus. The absence of a hyperglycemic peak after oral glucose load (D) signifies that the body is unable to effectively regulate glucose levels, which is a crucial aspect of glucose tolerance assessment.

**Why Each Wrong Option is Incorrect:**

A: Increased fasting blood glucose levels (A) might be considered abnormal, but it is not specific to an impaired glucose tolerance. Increased fasting glucose levels can be seen in various conditions like polycystic ovary syndrome, Cushing's syndrome, or non-alcoholic fatty liver disease, among others.

B: Decreased peak glucose levels after oral glucose load (B) might indicate impaired glucose tolerance, but option D is more specific as it directly assesses the post-load glucose response.

C: Delayed glucose absorption (C) is not directly linked to impaired glucose tolerance. Delayed absorption could be due to various factors like gastrointestinal issues or medication use, not necessarily indicative of IGT.

In summary, impaired glucose tolerance is indicated by a normal or high fasting glucose level (A) and an absent or delayed hyperglycemic peak (D) during the oral glucose tolerance test (OGTT).