Question

Glycosuria occurs when Plasma glucose level exceeds

• A. . 120-140mg/dl
• B. . 160-180mg/dl
• C. . 130-150mg/dl
• D. . 100-120mg/dl

Hint:

Remember the normal fasting blood glucose levels (\textless 100 mg/dL) and the renal threshold for glucose (around 180 mg/dL). This helps understand conditions like diabetes and kidney function related to glucose.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks about the plasma glucose concentration threshold at which glycosuria (glucose in the urine) typically occurs.

Step 3: Detailed Explanation:
* Glycosuria: This condition refers to the excretion of glucose into the urine. Under normal circumstances, the kidneys reabsorb almost all the filtered glucose back into the bloodstream.
* Renal Threshold for Glucose: The kidneys have a maximum capacity to reabsorb glucose from the glomerular filtrate, known as the renal threshold for glucose. When the plasma glucose level exceeds this threshold, the renal tubules cannot reabsorb all of it, and the excess glucose is excreted in the urine.
* For most healthy individuals, the renal threshold for glucose is typically between 160-180 mg/dL (or approximately 9-10 mmol/L). In patients with diabetes mellitus, this threshold might be altered.
Therefore, glycosuria generally occurs when the plasma glucose level exceeds 160-180 mg/dL.

Step 4: Final Answer:
Glycosuria occurs when Plasma glucose level exceeds 160-180mg/dl.

Answer 2

Glycosuria appears once the blood carries more glucose than the kidneys can pull back out of the urine being formed, so the right answer is the glucose level at which this reabsorption system gets overloaded.

1. 120-140 mg/dl: This range sits close to the upper end of normal fasting and post-meal blood glucose, well within what the kidneys can fully reabsorb, so glucose would not yet appear in the urine at this level.
2. 160-180 mg/dl: This is the range at which the kidney's glucose reabsorbing transporters in the tubules become fully saturated, known as the renal threshold. Once blood glucose rises past this point, the excess glucose that cannot be reabsorbed spills into the urine.
3. 130-150 mg/dl: This is still below the point where the kidney's reabsorption capacity is maxed out, so it is too low to reliably cause glucose to appear in urine.
4. 100-120 mg/dl: This overlaps with normal fasting blood glucose levels, well under the level needed to overwhelm the kidneys, so glycosuria would not be expected here.

Since the kidney's capacity to reabsorb glucose is exceeded specifically in the 160-180 mg/dl range, this is the threshold at which glycosuria develops.

Therefore, the correct answer is 160-180 mg/dl.