Reproduction: Kallmann syndrome: 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 · Reproduction: Kallmann syndrome

Sample item

A 17-year-old boy has no pubertal development and cannot smell. Testosterone, LH and FSH are all low, other pituitary hormones are normal and pituitary MRI is normal. Gonadotropins rise after repeated pulsatile GnRH. What is the underlying defect?

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

The answer and the reasoning

D. Failed migration of GnRH neurons from the olfactory placode to the hypothalamus

In Kallmann syndrome GnRH neurons fail to migrate with the olfactory neurons, so anosmia accompanies hypogonadotropic hypogonadism. The pituitary is intact and responds to pulsatile GnRH after priming. Treatment is gonadotropins or pulsatile GnRH to induce puberty and fertility.

Option by option

  • A. Defective androgen receptor

    Androgen insensitivity gives high LH and high testosterone.

  • B. Primary failure of Leydig cells

    Primary Leydig failure would give high LH and FSH.

  • C. Destruction of pituitary gonadotrophs

    Destroyed gonadotrophs could not respond to pulsatile GnRH.

  • D. Failed migration of GnRH neurons from the olfactory placode to the hypothalamus (correct)

    Correct. A migration defect explains anosmia with GnRH deficiency.

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 Physiology question

What is the answer to this Physiology question?

The best answer is D, Failed migration of GnRH neurons from the olfactory placode to the hypothalamus. In Kallmann syndrome GnRH neurons fail to migrate with the olfactory neurons, so anosmia accompanies hypogonadotropic hypogonadism.

Why is "Defective androgen receptor" not the answer?

Androgen insensitivity gives high LH and high testosterone.

Why is "Primary failure of Leydig cells" not the answer?

Primary Leydig failure would give high LH and FSH.

Why is "Destruction of pituitary gonadotrophs" not the answer?

Destroyed gonadotrophs could not respond to pulsatile GnRH.

What concept does this question test?

It tests Reproduction: Kallmann syndrome in Physiology. The pituitary is intact and responds to pulsatile GnRH after priming. Treatment is gonadotropins or pulsatile GnRH to induce puberty and fertility.

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 Reproduction: Kallmann syndrome?

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.