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Question 491
Endocrinology → General
Classification
Question
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Placental steroidogenesis differs from steroidogenesis in the ovary because the placenta depends on precursor supply from the maternal-foetal unit. Which statement best distinguishes placental progesterone synthesis from placental oestrogen synthesis?
Question Stem
Select the single best answer.
Options
A
Progesterone synthesis requires fetal precursors to the same extent as oestrogen synthesis
B
Progesterone is synthesized only from fetal adrenal precursors
C
Progesterone synthesis requires placental conversion of testosterone to dihydrotestosterone
D
Progesterone synthesis does not require fetal precursors in the way that oestrogen synthesis does
E
Progesterone cannot be synthesized from maternally derived cholesterol
Explanation
The placenta cannot undertake steroidogenesis independently in the same way as the ovary and uses precursors from fetal and maternal sources. However, fetal precursors are not required for progesterone synthesis in the way that they are for oestrogen production. Maternal LDL cholesterol can be used to form pregnenolone and subsequently progesterone.
Option Validity
A) Fetal precursors are not required for placental progesterone synthesis to the same extent as for oestrogen production.
B) Progesterone is not synthesized exclusively from fetal adrenal precursors.
C) Conversion of testosterone to dihydrotestosterone is not the pathway described for placental progesterone synthesis.
E) Maternal LDL cholesterol provides substrate for placental progesterone synthesis.
Further Reading
Saxena, MRCOG-1 Basic Sciences, Endocrinology: Hormones Produced by the Maternal-Foetal-Placental Unit, p. 299.