Endocrinology: dawn phenomenon: 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 · Endocrinology: dawn phenomenon

Sample item

A man with type 1 diabetes on basal insulin has a fasting glucose of 190 mg/dL, but a 3 a.m. glucose of 105 mg/dL, with a steady rise after about 4 a.m. Which physiological change best explains the early-morning rise?

AFalling hepatic glucose output during the nightBRebound hyperglycaemia after nocturnal hypoglycaemiaCSlow absorption of the evening mealDPre-dawn GH and cortisol surges antagonise insulin

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

The answer and the reasoning

D. Pre-dawn GH and cortisol surges antagonise insulin

The dawn phenomenon results from nocturnal growth hormone pulses and the early-morning cortisol rise, which antagonise insulin and increase hepatic glucose output. A normal 3 a.m. value separates it from the Somogyi effect, in which nocturnal hypoglycaemia precedes the rise.

Option by option

A. Falling hepatic glucose output during the night
Hepatic glucose output rises, not falls, in the pre-dawn hours.
B. Rebound hyperglycaemia after nocturnal hypoglycaemia
This is the Somogyi effect and would require a low reading in the early hours, which was not found.
C. Slow absorption of the evening meal
A meal eaten the evening before cannot sustain a rise that begins only after 4 a.m. from a normal 3 a.m. level.
D. Pre-dawn GH and cortisol surges antagonise insulin (correct)
Correct. Counter-regulatory hormones peak before waking and raise glucose despite basal insulin.

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, Pre-dawn GH and cortisol surges antagonise insulin. The dawn phenomenon results from nocturnal growth hormone pulses and the early-morning cortisol rise, which antagonise insulin and increase hepatic glucose output.

Why is "Falling hepatic glucose output during the night" not the answer?

Hepatic glucose output rises, not falls, in the pre-dawn hours.

Why is "Rebound hyperglycaemia after nocturnal hypoglycaemia" not the answer?

This is the Somogyi effect and would require a low reading in the early hours, which was not found.

Why is "Slow absorption of the evening meal" not the answer?

A meal eaten the evening before cannot sustain a rise that begins only after 4 a.m. from a normal 3 a.m. level.

What concept does this question test?

It tests Endocrinology: dawn phenomenon in Physiology. A normal 3 a.m. value separates it from the Somogyi effect, in which nocturnal hypoglycaemia precedes the rise.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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: dawn phenomenon?

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.