CID 5994

C₂₁H₃₀O₂

Progesterone

C 21
H 30
O 2

Ball-and-stick Stick Space-filling

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53 atoms, 56 bonds.

IUPAC name: (8S,9S,10R,13S,14S,17S)-17-acetyl-10,13-dimethyl-1,2,6,7,8,9,11,12,14,15,16,17-dodecahydrocyclopenta[a]phenanthren-3-one
Molar mass: 314.469(50) g/mol
Atoms: 53
SMILES: CC(=O)C1CCC2C1(CCC3C2CCC4=CC(=O)CCC34C)C
InChIKey: RJKFOVLPORLFTN-LEKSSAKUSA-N
PubChem CID: 5994

Made of

C H O

Structural formula of progesterone. Each unlabelled corner is a carbon atom, and the 21 hydrogens on carbon are not drawn. Wedges come toward you, hashes go back. It shows which atoms are joined to which, not the shape. The model above shows the shape.

Once an ovary has released an egg, the empty follicle left behind, the corpus luteum, starts making progesterone. One signal sets off both events, the US Office on Women’s Health explains: luteinising hormone triggers ovulation and prompts the corpus luteum to make the hormone. MeSH, the US National Library of Medicine’s subject vocabulary, names the corpus luteum and the placenta as the main secretors.

ChEBI, the Chemical Entities of Biological Interest database, classes progesterone as a C21-steroid hormone. The formula C₂₁H₃₀O₂ counts 21 carbon atoms beside 30 of hydrogen and two of oxygen, and a mole weighs 314.5 g.

The pure compound forms white, odourless crystals or powder, the US Occupational Safety and Health Administration records. The Hazardous Substances Data Bank (HSDB) lists two crystal forms that readily interconvert: alpha melts at 127–131 °C and beta at 121 °C. CAMEO Chemicals, a hazard database, calls it insoluble in water.

Structure and bonding

Both oxygen atoms of progesterone are double-bonded to carbon, and neither holds a hydrogen: all 30 hydrogens sit on carbon. Labels puts an O symbol at each end of the molecule. One C=O is in the end six-membered ring, beside the only C=C double bond. The other is in an acetyl group, a C=O carbon carrying a methyl group, CH₃, on the five-membered ring.

The Stick view shows four rings fused in a row, three of six carbons and one of five, the frame the cholesterol page describes. MeSH gives steroids a shared nucleus of 17 carbon atoms in fused rings, to which most add two methyl groups and a side chain. This model has all three: 17 ring carbons, two methyls on carbons shared between rings, and the acetyl group.

In Ball-and-stick, the four double-bonded carbons each lie flat among three neighbours: the angles around each add to 360° in PubChem’s computed model. The other 17 carbons each make four single bonds, tetrahedrally arranged in Chem1’s account. Seen edge-on, the ring carbons stay within 0.6 Å of one plane, both ring methyls on one face.

Where it turns up

Besides the ovaries, the adrenal glands normally make small amounts, MedlinePlus notes. HSDB lists the testis among the tissues that form progesterone and records its secretion in males.

Progesterone is also a way-station. MeSH describes it as made from pregnenolone and as an intermediate in making the steroid hormones of the ovaries and testes and the adrenal corticosteroids. An enzyme made from the CYP17A1 gene turns it into 17-hydroxyprogesterone, MedlinePlus Genetics explains. Further processing yields sex hormones and glucocorticoids, which help maintain blood sugar; the cortisol page follows that branch. Without that enzyme activity, progesterone goes to mineralocorticoids, which help regulate salt and water balance.

HSDB records it as obtained from animal ovaries, or synthesised from stigmasterol or from diosgenin, extracted from the Mexican yam Dioscorea mexicana. Medicines carry it dissolved in oil for injection, in pessaries and suppositories, and in an intrauterine device. Cosmetics may contain it as a skin or hair conditioner, the California Safe Cosmetics Program notes.

Why it matters

In the second half of the menstrual cycle, once the egg is released, progesterone rises and readies the lining of the uterus for a fertilised egg, MedlinePlus explains. Without a pregnancy the hormone falls and the lining thins. HSDB holds the abrupt decline principally responsible for menstruation beginning. The Office on Women’s Health names very low levels of both oestrogen and progesterone as the signal.

Inside cells, progesterone binds the progesterone receptor, which may cause the cells to grow, the US National Cancer Institute (NCI) notes. The NCI Thesaurus credits it with cutting the number of oestrogen receptors and stopping further follicles from developing. The liver breaks most of it down, and HSDB puts its plasma half-life at several minutes.

NCI lists birth control and the treatment of menstrual disorders, infertility and menopause symptoms among progesterone’s uses. Combined menopausal hormone therapy pairs oestrogen with a progestin, a synthetic form of progesterone. The two Women’s Health Initiative trials of hormone therapy were stopped early, in 2002 and 2004, over health risks; the estradiol page gives NCI’s findings on the therapy.

Properties

Properties of progesterone Molar mass summed from IUPAC/CIAAW 2024 standard atomic weights; formula, atom and bond counts and PubChem's molecular weight from PubChem CID 5994.
Property	Value	Unit	Source
Molecular formula (Hill order)	C₂₁H₃₀O₂
Molar mass	314.469(50) g/mol	g/mol	IUPAC/CIAAW 2024
Carbon atoms	21
Hydrogen atoms	30
Oxygen atoms	2
Bonds	56
Single bonds	53
Double bonds	3
PubChem molecular weight	314.5 g/mol	g/mol	PubChem

Safety

Suspected of causing cancer is the hazard statement on 87.1% of the classifications companies have filed for progesterone with the European Chemicals Agency. May cause cancer appears on 12.2%, and may damage fertility or the unborn child on 64.6%. CAMEO Chemicals adds that the chemical may be taken up through the skin. The PubChem Laboratory Chemical Safety Summary for progesterone gathers these classifications.

Questions

What functional groups does progesterone have?

Two ketone groups and no alcohol group. CAMEO Chemicals, a hazard database, places progesterone in its Ketones group, and ChEBI, a chemical database, describes oxo groups, oxygens double-bonded to carbon, at positions 3 and 20 of its pregnane skeleton. In the 3D model each oxygen is double-bonded to a carbon that holds two other carbons, and neither oxygen carries a hydrogen. All 30 hydrogens of C₂₁H₃₀O₂ are bonded to carbon, leaving no O–H group anywhere.

What does progesterone do in pregnancy?

It keeps rising. In a cycle without pregnancy the hormone falls again; once a pregnancy begins, MedlinePlus explains, progesterone goes on climbing to support it. At the high levels of pregnancy it keeps the uterus from contracting and bringing on pre-term labour. It also helps ready the breasts to make milk, the Office on Women's Health notes. MeSH, a US medical vocabulary, names the placenta beside the corpus luteum as a main secretor.

Is the hormone in birth control pills progesterone?

Not in the pill prescribed most often in the United States, which holds synthetic versions of oestrogen and progesterone, the National Cancer Institute (NCI) explains. The mini pill holds only a progestin. NCI's dictionary counts any natural or laboratory-made substance with some or all of progesterone's biological effects as a progestin, and the NCI Thesaurus keeps the word for synthetic steroid hormones that act like progesterone. The pills stop ovulation and keep sperm from passing the cervix.

Is progesterone linked to cancer?

The US National Toxicology Program has listed progesterone since 1985 under 'reasonably anticipated to be a human carcinogen'. The listing rests on sufficient evidence from studies in experimental animals, where it caused tumours in the mammary gland and the female genital tract. The body's own oestrogen and progesterone stimulate some cancers to develop and grow, the National Cancer Institute states. Long exposure to the ovaries' hormones, or to high levels, is linked to a higher risk of breast cancer.

Made of the same elements

C₂₁H₃₀O₅ Cortisol 56 atoms, 59 bonds.
C₁₉H₂₈O₂ Testosterone 49 atoms, 52 bonds.
C₁₈H₃₄O₂ Oleic acid 54 atoms, 53 bonds.
C₁₆H₃₂O₂ Palmitic acid 50 atoms, 49 bonds.
C₁₈H₂₄O₂ Estradiol 44 atoms, 47 bonds.
C₂₀H₁₄O₄ Phenolphthalein 38 atoms, 41 bonds.
C₁₅H₁₆O₂ Bisphenol A 33 atoms, 34 bonds.
C₁₃H₁₈O₂ Ibuprofen 33 atoms, 33 bonds.

All 51 compounds made of carbon, hydrogen and oxygen

C₂₇H₄₄O Cholecalciferol 72 atoms, 74 bonds.
C₁₀H₂₀O Menthol 31 atoms, 31 single bonds.
C₂₇H₄₆O Cholesterol 74 atoms, 77 bonds.
C₁₄H₁₄O₃ Naproxen 31 atoms, 32 bonds.
C₁₂H₂₂O₁₁ Lactose 45 atoms, 46 single bonds.
C₁₂H₂₂O₁₁ Sucrose 45 atoms, 46 single bonds.
C₉H₈O₄ Aspirin 21 atoms, 21 bonds.
C₈H₈O₃ Methyl salicylate 19 atoms, 19 bonds.
C₈H₈O₃ Vanillin 19 atoms, 19 bonds.
C₆H₁₂O₆ Fructose 24 atoms, 24 single bonds.
C₆H₁₂O₆ Glucose 24 atoms, 24 single bonds.
C₄H₉OH 1-Butanol 15 atoms, 14 single bonds.
C₆H₅COOH Benzoic acid 15 atoms, 15 bonds.
C₂H₅OC₂H₅ Diethyl ether 15 atoms, 14 single bonds.
C₆H₅CHO Benzaldehyde 14 atoms, 14 bonds.
C₃H₇COOH Butyric acid 14 atoms, 13 bonds.
CH₃COOC₂H₅ Ethyl acetate 14 atoms, 13 bonds.
C₇H₆O₃ Salicylic acid 16 atoms, 16 bonds.
C₄H₈O Butanone 13 atoms, 12 bonds.
C₆H₅OH Phenol 13 atoms, 13 bonds.
C₃H₈O₂ Propylene glycol 13 atoms, 12 single bonds.
C₃H₇OH 1-Propanol 12 atoms, 11 single bonds.
C₆H₈O₆ Ascorbic acid 20 atoms, 20 bonds.
C₃H₈O₃ Glycerol 14 atoms, 13 single bonds.
C₃H₈O Isopropyl alcohol 12 atoms, 11 single bonds.
C₆H₈O₇ Citric acid 21 atoms, 20 bonds.
C₂H₅COOH Propionic acid 11 atoms, 10 bonds.
C₃H₆O Acetone 10 atoms, 9 bonds.
C₂H₆O₂ Ethylene glycol 10 atoms, 9 single bonds.
C₃H₆O₃ Lactic acid 12 atoms, 11 bonds.
CH₃OCH₃ Dimethyl ether 9 atoms, 8 single bonds.
C₂H₅OH Ethanol 9 atoms, 8 single bonds.
C₄H₆O₅ Malic acid 15 atoms, 14 bonds.
CH₃COOH Acetic acid 8 atoms, 7 bonds.
C₄H₆O₆ Tartaric acid 16 atoms, 15 bonds.
CH₃CHO Acetaldehyde 7 atoms, 6 bonds.
C₂H₄O Ethylene oxide 7 atoms, 7 single bonds.
C₂H₄O₃ Glycolic acid 9 atoms, 8 bonds.
CH₃OH Methanol 6 atoms, 5 single bonds.
HCOOH Formic acid 5 atoms, 4 bonds.
H₂CO₃ Carbonic acid 6 atoms, 5 bonds.
CH₂O Formaldehyde 4 atoms, 3 bonds.
H₂C₂O₄ Oxalic acid 8 atoms, 7 bonds.