Growth and development: delayed puberty with anosmia: practice question

A Pediatrics 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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Pediatrics · Growth and development: delayed puberty with anosmia

Sample item

A 16-year-old boy has no pubertal development and is unable to smell. Testes are prepubertal, and serum LH, FSH and testosterone are all low, with otherwise normal pituitary function and a normal karyotype. What is the underlying defect?

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

The answer and the reasoning

C. Failed migration and deficient secretion of GnRH neurons

Kallmann syndrome is isolated hypogonadotropic hypogonadism with anosmia or hyposmia, caused by failure of GnRH neurons to migrate with the olfactory placode. LH, FSH and testosterone are all low. Midline defects, renal agenesis and cryptorchidism may accompany it.

Option by option

  • A. Primary testicular failure due to an extra X chromosome

    In 47,XXY the gonadotropins are high because the testes have failed, and anosmia is absent.

  • B. Prolactin excess from a pituitary adenoma

    A prolactinoma is rare at this age and does not explain a lifelong absent sense of smell.

  • C. Failed migration and deficient secretion of GnRH neurons (correct)

    Correct. Deficient GnRH with anosmia defines Kallmann syndrome.

  • D. Constitutional delay with a late-maturing hypothalamic axis

    Constitutional delay can lower hormones temporarily but does not cause anosmia.

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 Pediatrics question

What is the answer to this Pediatrics question?

The best answer is C, Failed migration and deficient secretion of GnRH neurons. Kallmann syndrome is isolated hypogonadotropic hypogonadism with anosmia or hyposmia, caused by failure of GnRH neurons to migrate with the olfactory placode.

Why is "Primary testicular failure due to an extra X chromosome" not the answer?

In 47,XXY the gonadotropins are high because the testes have failed, and anosmia is absent.

Why is "Prolactin excess from a pituitary adenoma" not the answer?

A prolactinoma is rare at this age and does not explain a lifelong absent sense of smell.

Why is "Constitutional delay with a late-maturing hypothalamic axis" not the answer?

Constitutional delay can lower hormones temporarily but does not cause anosmia.

What concept does this question test?

It tests Growth and development: delayed puberty with anosmia in Pediatrics. LH, FSH and testosterone are all low. Midline defects, renal agenesis and cryptorchidism may accompany it.

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 Growth and development: delayed puberty with anosmia?

Memorise milestones and the vaccine schedule as tables and revise them often. Then use the flashcards and the other Pediatrics 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.