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16α-Hydroxyprogesterone
Names
	IUPAC name 16α-Hydroxypregn-4-ene-3,20-dione
	Systematic IUPAC name (1R,2R,3aS,3bS,9aR,9bS,11aS)-1-Acetyl-2-hydroxy-9a,11a-dimethyl-1,2,3,3a,3b,4,5,8,9,9a,9b,10,11,11a-tetradecahydro-7H-cyclopenta[a]phenanthren-7-one
	Other names 16α-OHP; 16α-OH-PROG
Identifiers
CAS Number	438-07-3;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:15826;
ChEMBL	ChEMBL1908005;
ChemSpider	213144;
PubChem CID	243761;
UNII	Y7JT9A46EO;
CompTox Dashboard (EPA)	DTXSID001017030 ;
	InChI InChI=1S/C21H30O3/c1-12(22)19-18(24)11-17-15-5-4-13-10-14(23)6-8-20(13,2)16(15)7-9-21(17,19)3/h10,15-19,24H,4-9,11H2,1-3H3/t15-,16+,17+,18-,19+,20+,21+/m1/s1 Key: LOVNYFVWYTXDRE-RMWFXKKMSA-N;
	SMILES CC(=O)[C@H]1[C@@H](C[C@@H]2[C@@]1(CC[C@H]3[C@H]2CCC4=CC(=O)CC[C@]34C)C)O;
Properties
Chemical formula	C21H30O3
Molar mass	330.468 g·mol−1
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

16α-Hydroxyprogesterone (16α-OHP), also known as 16α-hydroxypregn-4-ene-3,20-dione, is a minor endogenous progestogen steroid hormone and a metabolite of progesterone that is formed in lower amounts than 17α-hydroxyprogesterone (17α-OHP).^[1] It occurs in micromolar concentrations and its physiological relevance hence is questionable.^[1] However, it may accumulate in target tissues and could have a physiological role in the reproductive system and mammary gland development as well as the cardiovascular and central nervous systems.^[1]

16α-OHP is formed from progesterone via 16α-hydroxylation primarily by CYP17A1 and primarily in steroidogenic tissues including the adrenal glands, testes, and ovaries.^[1] It is also synthesized from progesterone during pregnancy by hepatic cytochrome P450 enzymes like CYP3A4 and CYP1A1 in the fetal liver as well as placenta.^[1] It appears to be an end metabolite of progesterone and does not seem to be further metabolized.^[1]

16α-OHP has approximately 67% and 43% of the affinity of progesterone for the PR-A and PR-B, respectively, and acts as an agonist of these receptors similarly to progesterone.^[1] It was found to produce natriuresis similar to that produced by spironolactone when administered to humans, suggesting that it also has antimineralocorticoid activity similarly to progesterone.^[1] However, surprisingly, 16α-OHP showed low affinity for the mineralocorticoid receptor (MR) of greater than 1 μM (compared to 1 nM for progesterone) and showed no antagonism of the MR at up to a concentration of 1 μM (whereas progesterone shows potent such activity).^[1] However, the findings of another study suggested that 16α-OHP antagonizes the effects of aldosterone via the MR, and it may still be possible that 16α-OHP has significant antimineralocorticoid activity in some cells in spite of its weak MR affinity.^[1]

References

^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Storbeck KH, Swart P, Africander D, Conradie R, Louw R, Swart AC (2011). "16α-hydroxyprogesterone: origin, biosynthesis and receptor interaction". Mol. Cell. Endocrinol. 336 (1–2): 92–101. doi:10.1016/j.mce.2010.11.016. PMID 21095220. S2CID 5503049.