Carbohydrate metabolism: glucokinase and MODY: 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 · Carbohydrate metabolism: glucokinase and MODY

Sample item

A 22-year-old woman has a fasting plasma glucose of 118 mg/dL on three occasions, HbA1c 6.4% and a 2-hour OGTT glucose of 150 mg/dL. She is lean and asymptomatic, her father and a sister have similar mild values, and islet autoantibodies are negative. Genetic testing shows a heterozygous inactivating glucokinase mutation. What is the most appropriate management?

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

The answer and the reasoning

D. Reassurance and observation without pharmacological treatment

Glucokinase acts as the beta-cell glucose sensor, and a heterozygous loss of function raises the glucose threshold for insulin release. This causes mild, stable fasting hyperglycaemia present from birth (GCK-MODY) with a small rise after meals and very low risk of complications. Treatment does not change glycaemia, so it is unnecessary except sometimes in pregnancy decisions made by specialists.

Option by option

  • A. Lifelong basal insulin

    Insulin is not needed and the regulatory set point simply resets glucose upward.

  • B. Sulfonylurea at low dose

    Sulfonylureas are first-line in HNF1A and HNF4A MODY, not in glucokinase MODY, where they are ineffective.

  • C. Metformin and weight-reduction programme

    Metformin and weight loss are for type 2 diabetes with insulin resistance and do not alter the glucokinase set point.

  • D. Reassurance and observation without pharmacological treatment (correct)

    Correct. GCK-MODY needs no drug treatment because glycaemia is mild, stable and does not cause complications.

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, Reassurance and observation without pharmacological treatment. Glucokinase acts as the beta-cell glucose sensor, and a heterozygous loss of function raises the glucose threshold for insulin release.

Why is "Lifelong basal insulin" not the answer?

Insulin is not needed and the regulatory set point simply resets glucose upward.

Why is "Sulfonylurea at low dose" not the answer?

Sulfonylureas are first-line in HNF1A and HNF4A MODY, not in glucokinase MODY, where they are ineffective.

Why is "Metformin and weight-reduction programme" not the answer?

Metformin and weight loss are for type 2 diabetes with insulin resistance and do not alter the glucokinase set point.

What concept does this question test?

It tests Carbohydrate metabolism: glucokinase and MODY in Biochemistry. This causes mild, stable fasting hyperglycaemia present from birth (GCK-MODY) with a small rise after meals and very low risk of complications. Treatment does not change glycaemia, so it is unnecessary except sometimes in pregnancy decisions made by specialists.

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 Carbohydrate metabolism: glucokinase and MODY?

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.