Renal: glucose handling: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · Renal: glucose handling

Sample item

A diabetic patient on an SGLT2 inhibitor has glycosuria although plasma glucose is 100 mg/dL. What is the explanation?

ARaised GFR delivers more glucose than the transport maximumBBlockade of SGLT1 in the distal tubule increases glucose lossCInhibition of sodium-glucose cotransport in the early proximal tubule lowers the renal threshold for glucoseDBlockade of basolateral GLUT2 prevents glucose entering the tubular cell

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Inhibition of sodium-glucose cotransport in the early proximal tubule lowers the renal threshold for glucose

Normally the proximal tubule reabsorbs all filtered glucose by SGLT2 (about 90%) and SGLT1 until the plasma level exceeds the threshold of about 180 mg/dL. An SGLT2 inhibitor lowers the effective transport capacity and glucose appears in urine at normal plasma levels. This causes osmotic diuresis and a risk of genital mycotic infection.

Option by option

A. Raised GFR delivers more glucose than the transport maximum
The filtered load at normal GFR is not above the maximum without the inhibitor, and GFR is not raised.
B. Blockade of SGLT1 in the distal tubule increases glucose loss
SGLT1 is mostly intestinal and in the S3 segment, not distal.
C. Inhibition of sodium-glucose cotransport in the early proximal tubule lowers the renal threshold for glucose (correct)
Correct. Reduced apical glucose uptake lowers the threshold so glycosuria appears at normal plasma glucose.
D. Blockade of basolateral GLUT2 prevents glucose entering the tubular cell
GLUT2 is not the target of these drugs.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is C, Inhibition of sodium-glucose cotransport in the early proximal tubule lowers the renal threshold for glucose. Normally the proximal tubule reabsorbs all filtered glucose by SGLT2 (about 90%) and SGLT1 until the plasma level exceeds the threshold of about 180 mg/dL.

Why is "Raised GFR delivers more glucose than the transport maximum" not the answer?

The filtered load at normal GFR is not above the maximum without the inhibitor, and GFR is not raised.

Why is "Blockade of SGLT1 in the distal tubule increases glucose loss" not the answer?

SGLT1 is mostly intestinal and in the S3 segment, not distal.

Why is "Blockade of basolateral GLUT2 prevents glucose entering the tubular c…" not the answer?

GLUT2 is not the target of these drugs.

What concept does this question test?

It tests Renal: glucose handling in Physiology. An SGLT2 inhibitor lowers the effective transport capacity and glucose appears in urine at normal plasma levels. This causes osmotic diuresis and a risk of genital mycotic infection.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Renal: glucose handling?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.