Endocrinology: Klinefelter syndrome: practice question

A General Medicine 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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General Medicine · Endocrinology: Klinefelter syndrome

Sample item

A 22-year-old tall man with long limbs has gynaecomastia, sparse facial hair, and small firm testes of 3 mL. Semen analysis shows azoospermia. Testosterone is low and LH and FSH are markedly raised. What is the most likely karyotype?

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

The answer and the reasoning

C. 47,XXY

Klinefelter syndrome (47,XXY) causes primary testicular failure with small firm testes, hypergonadism-type raised gonadotrophins, low testosterone, azoospermia, gynaecomastia and tall eunuchoid habitus. It carries increased risk of breast cancer, osteoporosis and metabolic syndrome. Testosterone replacement treats androgen deficiency but not infertility.

Option by option

  • A. 47,XYY

    47,XYY men are tall but have normal testes and fertility, and normal hormones.

  • B. 46,XY with an androgen receptor mutation

    Androgen insensitivity leads to high testosterone with a female or undervirilised phenotype, not low testosterone.

  • C. 47,XXY (correct)

    Primary hypogonadism with tall stature and gynaecomastia indicates 47,XXY.

  • D. 45,X

    45,X is Turner syndrome, which gives a short female phenotype with streak ovaries.

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 General Medicine question

What is the answer to this General Medicine question?

The best answer is C, 47,XXY. Klinefelter syndrome (47,XXY) causes primary testicular failure with small firm testes, hypergonadism-type raised gonadotrophins, low testosterone, azoospermia, gynaecomastia and tall eunuchoid habitus.

Why is "47,XYY" not the answer?

47,XYY men are tall but have normal testes and fertility, and normal hormones.

Why is "46,XY with an androgen receptor mutation" not the answer?

Androgen insensitivity leads to high testosterone with a female or undervirilised phenotype, not low testosterone.

Why is "45,X" not the answer?

45,X is Turner syndrome, which gives a short female phenotype with streak ovaries.

What concept does this question test?

It tests Endocrinology: Klinefelter syndrome in General Medicine. It carries increased risk of breast cancer, osteoporosis and metabolic syndrome. Testosterone replacement treats androgen deficiency but not infertility.

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: Klinefelter syndrome?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General Medicine 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.