Endocrinology and diabetes: Kallmann 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 and diabetes: Kallmann syndrome

Sample item

A 17-year-old boy has absent pubertal development, small testes and anosmia. Serum LH, FSH and testosterone are all low, other pituitary function is normal and MRI of the sella is normal. What is the underlying defect?

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

The answer and the reasoning

B. Failed olfactory-placode migration of GnRH neurones

In Kallmann syndrome, GnRH neurones fail to migrate with the olfactory placode into the hypothalamus. This gives hypogonadotropic hypogonadism with anosmia or hyposmia. Treatment is gonadotropin or testosterone replacement.

Option by option

  • A. Deficiency of 5-alpha reductase in target tissues

    5-alpha reductase deficiency causes ambiguous genitalia with normal testosterone.

  • B. Failed olfactory-placode migration of GnRH neurones (correct)

    Correct. Failure of GnRH neurone migration explains low gonadotrophins with anosmia.

  • C. Extra X chromosome causing primary testicular failure

    An extra X gives high gonadotrophins from primary testicular failure.

  • D. Pituitary tumour compressing gonadotrophs

    A sellar tumour would show on MRI and affect other hormones.

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 B, Failed olfactory-placode migration of GnRH neurones. In Kallmann syndrome, GnRH neurones fail to migrate with the olfactory placode into the hypothalamus.

Why is "Deficiency of 5-alpha reductase in target tissues" not the answer?

5-alpha reductase deficiency causes ambiguous genitalia with normal testosterone.

Why is "Extra X chromosome causing primary testicular failure" not the answer?

An extra X gives high gonadotrophins from primary testicular failure.

Why is "Pituitary tumour compressing gonadotrophs" not the answer?

A sellar tumour would show on MRI and affect other hormones.

What concept does this question test?

It tests Endocrinology and diabetes: Kallmann syndrome in General Medicine. This gives hypogonadotropic hypogonadism with anosmia or hyposmia. Treatment is gonadotropin or testosterone replacement.

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 and diabetes: Kallmann 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.