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etx-pediatric-ch24-fig5

Published November 11, 2023 at 758 × 608 in Ambiguous Genitalia in the Newborn.
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Figure 5. Steroid metabolic pathways in the fetal-placental-maternal unit, also known as the fetal-placental unit. The main function of the FZ of the fetal adrenal is the production of DHEA-S from cholesterol, which is transported to the placenta, desulfated to DHEA, and sequentially metabolized by placental 3β-hydroxysteroid dehydrogenase type 1 (3βHSD1), 17β-hydroxysteroid dehydrogenases (17βHSD) and cytochrome P450 aromatase (CYP19A1), to androstenedione (A4), testosterone (T) and estradiol (E2), respectively. E2 is then transported from the placenta into the maternal circulation. A4 is additionally also a substrate for placental CYP19A1, producing estrone (E1). Fetal adrenal DHEA-S is also metabolized by the fetal liver to 16α-hydroxy-DHEA-S by cytochrome P450 family 3 subfamily A member 7 (CYP3A7), which is metabolized to estriol (E3), the estrogen marker of pregnancy. Abbreviations: PREG, pregnenolone; 17OHPREG, 17α-hydroxypregnenolone; PROG, progesterone; DHEA, dehydroepiandrosterone; DHEA-S, dehydroepiandrosterone-sulfate; CYP11A1, cytochrome P450 cholesterol side chain cleavage; StAR, steroidogenic acute regulatory protein; CYP17A1, cytochrome P450 17α-hydroxylase/17,20-lyase; SULT2A1, sulfotransferase; CYP3A7, cytochrome P450 family 3 subfamily A member 7; CYP19A1, cytochrome P450 aromatase; HSD17B, 17β-hydroxysteroid dehydrogenase; HSD3B1, 3β-hydroxysteroid dehydrogenase type 1; HSD11B2, 11β-hydroxysteroid dehydrogenase type 2; STS, sulfatase.
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