The fetal-placental unit cooperatively produces estriol during pregnancy. The immediate precursor (dehydroepiandrosterone sulphate, DHEA-S) for estriol synthesis is derived from which source?

• A Maternal adrenal cortex
• B Fetal adrenal cortex ✓
• C Placental trophoblast
• D Maternal ovary

Explanation

Estriol synthesis requires the fetal-placental unit: the fetal adrenal cortex produces DHEA-S, which is hydroxylated by the fetal liver (16-alpha hydroxylase) and then aromatised by the placental sulphatase and aromatase to estriol. Neither maternal tissues nor the placenta alone can complete this pathway. Low maternal estriol in pregnancy suggests fetal adrenal hypoplasia or anencephaly.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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