16α-Hydroxyprogesterone

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-Hydroxyprogesterone

Names
IUPAC name (8S,9S,10R,13S,14S,16R,17R)-17-Acetyl-16-hydroxy-10,13-dimethyl-1,2,6,7,8,9,11,12,14,15,16,17-dodecahydrocyclopenta[a]phenanthren-3-one
Other names 16α-OHP; 16α-OH-PROG; 16α-Hydroxypregn-4-ene-3,20-dione
Identifiers
CAS Number	438-07-3
3D model (JSmol)	Interactive image
ChEBI	CHEBI:15826
ChEMBL	ChEMBL1908005
ChemSpider	213144
PubChem CID	243761
UNII	Y7JT9A46EO
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-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]