Clinical biochemistry: hyperglycaemic emergencies: practice question

A Biochemistry 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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Biochemistry · Clinical biochemistry: hyperglycaemic emergencies

Sample item

A 74-year-old man with type 2 diabetes is drowsy and dehydrated after a week of infection. Plasma glucose is 900 mg/dL, effective osmolality 340 mOsm/kg, pH 7.36 and bicarbonate 22 mmol/L, with trace ketones. Why is ketosis minimal despite severe hyperglycaemia?

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

The answer and the reasoning

D. Residual insulin is enough to restrain lipolysis and ketogenesis but not hepatic glucose output

Hyperosmolar hyperglycaemic state occurs when insulin is deficient or ineffective but still present in an amount that suppresses adipose lipolysis and hepatic ketogenesis. It is not enough to restrain gluconeogenesis and glycogenolysis, so glucose rises extremely, causing osmotic diuresis and dehydration. In diabetic ketoacidosis insulin is almost absent.

Option by option

  • A. A defect in hepatic carnitine palmitoyltransferase I

    CPT-I failure would impair ketogenesis, but it is not a feature of this condition.

  • B. Rapid ketone use by the brain lowers blood levels

    The brain cannot remove enough ketone bodies to hide ketosis, and ketone use would not prevent the formation seen in ketoacidosis.

  • C. Complete absence of insulin with very high glucagon

    Absent insulin with high glucagon describes diabetic ketoacidosis, which has acidosis and heavy ketosis.

  • D. Residual insulin is enough to restrain lipolysis and ketogenesis but not hepatic glucose output (correct)

    Correct. Low-level insulin action suppresses ketogenesis while hyperglycaemia continues.

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.

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Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is D, Residual insulin is enough to restrain lipolysis and ketogenesis but not hepatic glucose output. Hyperosmolar hyperglycaemic state occurs when insulin is deficient or ineffective but still present in an amount that suppresses adipose lipolysis and hepatic ketogenesis.

Why is "A defect in hepatic carnitine palmitoyltransferase I" not the answer?

CPT-I failure would impair ketogenesis, but it is not a feature of this condition.

Why is "Rapid ketone use by the brain lowers blood levels" not the answer?

The brain cannot remove enough ketone bodies to hide ketosis, and ketone use would not prevent the formation seen in ketoacidosis.

Why is "Complete absence of insulin with very high glucagon" not the answer?

Absent insulin with high glucagon describes diabetic ketoacidosis, which has acidosis and heavy ketosis.

What concept does this question test?

It tests Clinical biochemistry: hyperglycaemic emergencies in Biochemistry. It is not enough to restrain gluconeogenesis and glycogenolysis, so glucose rises extremely, causing osmotic diuresis and dehydration. In diabetic ketoacidosis insulin is almost absent.

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 Clinical biochemistry: hyperglycaemic emergencies?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry 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.