Reproduction: two-cell theory of oestrogen synthesis: 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: two-cell theory of oestrogen synthesis

Sample item

In the follicular phase, theca interna cells under LH stimulation make androstenedione. Where is it converted to oestradiol, and under which hormone?

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

The answer and the reasoning

C. Granulosa cells, by aromatase induced by FSH

In the two-cell, two-gonadotrophin model, LH stimulates theca cells to make androgens. These diffuse into the granulosa cells, where FSH induces aromatase, which converts androstenedione to oestrone and testosterone to oestradiol. FSH also induces LH receptors on granulosa cells before ovulation.

Option by option

  • A. Corpus luteum cells, by 21-hydroxylase induced by hCG

    21-hydroxylase is a step in corticosteroid synthesis, and hCG acts on the luteal body only in pregnancy.

  • B. Granulosa cells, by 5-alpha reductase induced by LH

    5-alpha reductase makes dihydrotestosterone, not oestradiol.

  • C. Granulosa cells, by aromatase induced by FSH (correct)

    FSH drives aromatase in granulosa cells, which complete oestradiol production.

  • D. Theca cells, by aromatase induced by LH

    Theca cells lack significant aromatase, so they only supply androgen substrate.

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 C, Granulosa cells, by aromatase induced by FSH. In the two-cell, two-gonadotrophin model, LH stimulates theca cells to make androgens.

Why is "Corpus luteum cells, by 21-hydroxylase induced by hCG" not the answer?

21-hydroxylase is a step in corticosteroid synthesis, and hCG acts on the luteal body only in pregnancy.

Why is "Granulosa cells, by 5-alpha reductase induced by LH" not the answer?

5-alpha reductase makes dihydrotestosterone, not oestradiol.

Why is "Theca cells, by aromatase induced by LH" not the answer?

Theca cells lack significant aromatase, so they only supply androgen substrate.

What concept does this question test?

It tests Reproduction: two-cell theory of oestrogen synthesis in Physiology. These diffuse into the granulosa cells, where FSH induces aromatase, which converts androstenedione to oestrone and testosterone to oestradiol. FSH also induces LH receptors on granulosa cells before ovulation.

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 Reproduction: two-cell theory of oestrogen synthesis?

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.