Estradiol

Estradiol	Last updated: 16/09/2025
(Also known as: oestradiol; 17beta oestradiol; beta-estradiol)

GENERAL INFORMATION

Description

A semisynthetic estrogenic hormone with veterinary applications

Examples of veterinary uses

Mainly used as a hormone replacement therapy in conditions of inadequate estrogen production

Examples of species treated

Horses; Cattle; Cats; Dogs

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

Estradiol exhibits stereoisomerism, primarily due to the configuration of its hydroxyl groups and the orientation of its steroid backbone. The most biologically active form is 17beta-estradiol, where the hydroxyl group at carbon 17 is in the beta position. Its stereoisomer, 17alpha-estradiol, has the hydroxyl group in the alpha position and is significantly less potent in estrogenic activity. Additionally, estradiol can undergo glucuronidation at either the 3-hydroxyl or 17-hydroxyl positions, forming estradiol-3-glucuronide and estradiol-17-glucuronide, which are regioisomers with distinct metabolic pathways and biological roles.

Chemical formula

C₁₈H₂₄O₂

Canonical SMILES

CC12CCC3C(C1CCC2O)CCC4=C3C=CC(=C4)O

Isomeric SMILES

C[C@]12CC[C@H]3[C@H]([C@@H]1CC[C@@H]2O)CCC4=C3C=CC(=C4)O

International Chemical Identifier key (InChIKey)

VOXZDWNPVJITMN-ZBRFXRBCSA-N

International Chemical Identifier (InChI)

InChI=1S/C18H24O2/c1-18-9-8-14-13-5-3-12(19)10-11(13)2-4-15(14)16(18)6-7-17(18)20/h3,5,10,14-17,19-20H,2,4,6-9H2,1H3/t14-,15-,16+,17+,18+/m1/s1

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
estradiol hemihydrate	Hydrate
estradiol	-
ethinyl estradiol	Variant

General status

Veterinary substance type

Medicinal drug; Hormone

Substance groups

Steroid hormone

Minimum active substance purity

Known relevant impurities

Substance origin

Semi-synthetic

Mode of action

Substance binds to its specific intracellular receptor and regulates DNA transcription for protein formation

Molecular targets

[Estrogen receptor alpha, Agonist], [Estrogen receptor beta, Agonist], [Beclin-1, Binder], [ATP synthase subunit a, Inhibitor], [Nuclear receptor subfamily 1 group I member 2, Binder], [Neuronal acetylcholine receptor subunit alpha-4, Binder], [G-protein coupled estrogen receptor 1, Binder]

CAS RN

17916-67-5

EC number

200-023-8

CIPAC number

US EPA chemical code

PubChem CID

5757

Therapeutic Class

Estrogens: Natural and semisynthetic estrogens, plain

ATCvet Code

QG03CA03

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

272.4

PIN (Preferred Identification Name)

IUPAC name

(8R,9S,13S,14S,17S)-13-methyl-6,7,8,9,11,12,14,15,16,17-decahydrocyclopenta[a]phenanthrene-3,17-diol

CAS name

3,17β-dihydroxy-1,3,5(10)-estratriene

Forever chemical

Other status information

Relevant Environmental Water Quality Standards

Physical state

White crystalline solid

Related substances & organisms

estradiol benzoate

estradiol cyprionate

ethinyl estradiol

Commercial

Property

Value

Availability status

Current

Introduction & key dates

1929, first isolated; 1930s, clinical use began; 1950s, veterinary adoption

Example manufacturers & suppliers of products using this active now or historically

Pfizer Animal Health

Example products using this active

ECP (Estradiol Cypionate)
Estroject
Estrus
Estra-D
Premarin

Formulation and application details

Typically supplied as a sterile oil-based solution for intramuscular injection

Commercial production

The commercial production of estradiol typically begins with a steroidal precursor, such as estrone or testosterone, which undergoes a series of chemical transformations to yield the active estrogen compound. These steps include oxidation, reduction, and selective hydroxylation, often facilitated by catalysts and solvents that ensure high purity and yield. Advanced methods may incorporate continuous flow chemistry, allowing for more efficient and scalable synthesis. Historically, some estrogen products were derived from pregnant mare urine, but modern estradiol is almost exclusively synthesised chemically to avoid variability and ethical concerns.

Impact on climate of production and use

Published GHG data is not available for most pharmaceuticals. However, according to industry, global averages suggest producing 1 kg of a typical active pharmaceutical ingredient can range from 10 to 100 kg CO₂e for small molecule drugs and potentially up to 1000 kg CO₂e for complex biologicals such as vaccines, depending on the drug type, its formulation, complexity of synthesis, solvent recovery, and energy sources used

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

Solubility - In water at 20 °C (mg l⁻¹)

3.6

Low

Solubility - In organic solvents at 20 °C (mg l⁻¹)

Melting point (°C)

173

Boiling point (°C)

445.9

Degradation point (°C)

Flashpoint (°C)

Octanol-water partition coefficient at pH 7, 20 °C

1.02 X 10⁰⁴

Calculated

Log P

4.01

High

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.2

Dissociation constant pKa) at 25 °C

10.46

Vapour pressure at 20 °C (mPa)

Henry's law constant at 25 °C (Pa m³ mol⁻¹)

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

Maximum UV-vis absorption L mol⁻¹ cm⁻¹

Surface tension (mN m⁻¹)

Refractive Index

Environmental release

Degradation

Property

Value

Source; quality score; and other information

Interpretation

Soil degradation (days) (aerobic)

DT₅₀ (typical)

DT₅₀ (lab at 20 °C)

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

Note

Manure DT₅₀ (days)

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Note

Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7

Value

Note

Water-sediment DT₅₀ (days)

Water phase only DT₅₀ (days)

Sediment phase only DT₅₀ (days)

Air degradation

As this parameter is not normally measured directly, a surrogate measure is used: ‘Photochemical oxidative DT₅₀’. Where data is available, this can be found in the Fate Indices section below.

Decay in stored produce DT₅₀

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d (mL g⁻¹)

K_oc (mL g⁻¹)

Notes and range

Freundlich

K_f (mL g⁻¹)

K_foc (mL g⁻¹)

¹/_n

Notes and range

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

Bio-concentration factor

BCF (l kg⁻¹)

CT₅₀ (days)

Known metabolites

None

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

960

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

(ppm diet)

Mammals - Chronic 21d NOAEL (mg kg⁻¹ bw d⁻¹)

Birds - Acute LD₅₀ (mg kg⁻¹)

Birds - Short term dietary (LC₅₀/LD₅₀)

Birds - Chronic 21d NOEL (mg kg⁻¹ bw d⁻¹)

Earthworms - Acute 14 day LC₅₀ (mg kg⁻¹ dw soil)

Earthworms - Chronic NOEC, reproduction (mg kg⁻¹ dw soil)

Soil micro-organisms

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

Non-target plants

Vegetative vigour ER₅₀ (g ha⁻¹)

Seedling emergence ER₅₀ (g ha⁻¹)

Honeybees (Apis spp.)

Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Unknown mode acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Chronic

Notes

Bumblebees (Bombus spp.)

Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Mason bees (Osmia spp.)

Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Other bee species (1)

Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)

Mode of exposure

Other bee species (2)

Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)

Mode of exposure

Beneficial insects (Ladybirds)

Beneficial insects (Lacewings)

Beneficial insects (Parasitic wasps)

Beneficial insects (Predatory mites)

Beneficial insects (Ground beetles)

Aquatic ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Temperate Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

Temperate Freshwater Fish - Chronic 21 day NOEC (mg l⁻¹)

Tropical Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

Temperate Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)

> 0.139

Daphnia magna

Moderate

Temperate Freshwater Aquatic invertebrates - Chronic 21 day NOEC (mg l⁻¹)

Tropical Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)

Aquatic crustaceans - Acute 96 hour LC₅₀ (mg l⁻¹)

Sediment dwelling organisms - Acute 96 hour LC₅₀ (mg l⁻¹)

Sediment dwelling organisms - Chronic 28 day NOEC, static, water (mg l⁻¹)

Sediment dwelling organisms - Chronic 28 day NOEC, sediment (mg kg⁻¹)

Aquatic Plants (free-floating, fonds growth, fresh) - 7 day (mg l⁻¹)

Aquatic plants (rooted, growth rate, fresh) - 14 day (mg l⁻¹)

Algae - Acute (growth rate, fresh; mg l⁻¹) (EC₅₀)

> 2.48

Desmodesmus subspicatus

Moderate

Algae - Chronic (growth rate, fresh; mg l⁻¹)

Mesocosm study data

NOEAEC mg l⁻¹

Marine bivalves

HUMAN HEALTH AND PROTECTION

General

Property

Value

Source; quality score; and other information

Interpretation

Threshold of Toxicological Concern (Cramer Class)

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

960

Rat

Moderate

Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)

Mammals - Inhalation LC₅₀ (mg l⁻¹)

Other Mammal toxicity endpoints

ADI - Acceptable Daily Intake (mg kg⁻¹ bw day⁻¹)

ARfD - Acute Reference Dose (mg kg⁻¹ bw day⁻¹)

AAOEL - Acute Acceptable Operator Exposure Level (mg kg⁻¹ bw day⁻¹)

AOEL - Acceptable Operator Exposure Level - Systemic (mg kg⁻¹ bw day⁻¹)

Dermal penetration studies (%)

Dangerous Substances Directive 76/464

Exposure Routes

Public

Occupational

Mammalian dose elimination route and rate

Primarily eliminated from the body through hepatic metabolism followed by renal and fecal excretion

Health issues

Specific human health issues (hazard-based)

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

No data found

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

No data found

Respiratory tract irritant

Skin irritant

Skin sensitiser

Eye irritant

Phototoxicant

No data found

General human health issues

CPL data: suspected of causing cancer

Handling issues

Property

Value and interpretation

General

May emit acrid smoke and irritating fumes if heated to decomposition
IMDG Transport Hazard Class 9

CLP classification 2013

Health: H351, H360fd, H362
Environment: H410

WHO Classification

Not listed (Not listed)

UN Number

UN3077

Waste disposal & packaging

Packaging group III (minor danger)

Shelf-life, storage, stability and reactivity

Chemically stable under standard ambient conditions

TRANSLATIONS

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English

estradiol

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Record last updated:	16/09/2025
Contact:	aeru@herts.ac.uk
Please cite as:	Lewis, K.A., Tzilivakis, J., Warner, D. and Green, A. (2016) An international database for pesticide risk assessments and management. Human and Ecological Risk Assessment: An International Journal, 22(4), 1050-1064. DOI: 10.1080/10807039.2015.1133242