File:Steroid biosynthesis pathway.png

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Steroid Biosynthesis Pathway

A simplified version of steroid biosynthesis highlighting the specific steroidogenic enzymes. Filled boxes highlight the steroidogenic enzymes examined by RT-qPCR in the original article.

Progesterone (P4)

  1. First, the transport protein, steroidogenic acute regulatory protein (StAR) is needed to facilitate the movement of cholesterol from the outer to inner mitochondrial membrane.
  2. Cholesterol is then converted to pregnenolone by the action of cytochrome side-chain cleaving enzyme (P450scc).
  3. Pregnenolone can then be converted to either 17α-hydroxypregnenolone by 17α-hydroxylase (P45017α) or to P4 by 3β-hydroxysteroid dehydrogenase (3β-HSD).
  4. P4 can either be a final product in this pathway or serve as a precursor in the synthesis of glucocorticoids, androgens, or estrogens.

17β-hydroxysteroid dehydrogenase (17β-HSD) functions in the conversion of weaker and stronger androgens and estrogens and was included in this study as a marker of upstream steroid enzyme activity.

Links: Endocrine System Development


Albergotti LC, Hamlin HJ, McCoy MW & Guillette LJ. (2009). Endocrine activity of extraembryonic membranes extends beyond placental amniotes. PLoS ONE , 4, e5452. PMID: 19424488 DOI.


© 2009 Albergotti et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Citation: Albergotti LC, Hamlin HJ, McCoy MW, Guillette, LJ Jr (2009) Endocrine Activity of Extraembryonic Membranes Extends beyond Placental Amniotes. PLoS ONE 4(5): e5452. doi:10.1371/journal.pone.0005452


Cite this page: Hill, M.A. (2024, May 20) Embryology Steroid biosynthesis pathway.png. Retrieved from

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G

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current20:35, 5 October 2009Thumbnail for version as of 20:35, 5 October 2009600 × 409 (101 KB)S8600021 (talk | contribs)Figure 1. Steroid biosynthesis pathway. A simplified version of steroid biosynthesis highlighting the specific steroidogenic enzymes investigated in this study. Filled boxes highlight the steroidogenic enzymes examined by RT-qPCR. Progesterone (P4) is hi