Endocrinology: biphasic insulin secretion: 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.

Try it

Physiology · Endocrinology: biphasic insulin secretion

Sample item

After an intravenous glucose load in a healthy person, insulin secretion shows a sharp peak within 5 to 10 minutes followed by a slower, sustained rise. What does the first phase represent?

ANewly synthesised insulin from increased transcriptionBInsulin released from the liver after first-pass bindingCRelease of proinsulin from the alpha cellsDRelease of pre-formed insulin from stored granules

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

The answer and the reasoning

D. Release of pre-formed insulin from stored granules

The first phase is exocytosis of insulin granules docked near the beta cell membrane, triggered by calcium entry after closure of the ATP-sensitive potassium channel. The second phase involves mobilisation of reserve granules and new synthesis. Loss of the first phase is an early abnormality in type 2 diabetes.

Option by option

A. Newly synthesised insulin from increased transcription
New synthesis supports the slower second phase.
B. Insulin released from the liver after first-pass binding
The liver removes insulin and does not secrete it.
C. Release of proinsulin from the alpha cells
Alpha cells secrete glucagon, not proinsulin.
D. Release of pre-formed insulin from stored granules (correct)
Correct. The early peak comes from pre-formed granules.

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 D, Release of pre-formed insulin from stored granules. The first phase is exocytosis of insulin granules docked near the beta cell membrane, triggered by calcium entry after closure of the ATP-sensitive potassium channel.

Why is "Newly synthesised insulin from increased transcription" not the answer?

New synthesis supports the slower second phase.

Why is "Insulin released from the liver after first-pass binding" not the answer?

The liver removes insulin and does not secrete it.

Why is "Release of proinsulin from the alpha cells" not the answer?

Alpha cells secrete glucagon, not proinsulin.

What concept does this question test?

It tests Endocrinology: biphasic insulin secretion in Physiology. The second phase involves mobilisation of reserve granules and new synthesis. Loss of the first phase is an early abnormality in type 2 diabetes.

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 Endocrinology: biphasic insulin secretion?

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.