ATC Code G03CA04, G03CC06, G03CD01
Formula C18H24O3
Molar Mass (g·mol−1) 288,3814
Physical State solid
Density (g·cm−3) 1,27
Melting Point (°C) 82-86
PKS Value 10,54
CAS Number 50-27-1
PUB Number 5756
Drugbank ID DB04573
Solubility insoluble in water


Estriol or estriol is a female sex hormone of the estrogen group. It is a metabolic product of the estrogen estradiol and therefore exhibits a weaker estrogen effect. A large amount of estriol is produced by the placenta during pregnancy.

It is used to relieve vaginal discomfort and in hormone replacement therapy during menopause. Estriol is mostly applied vaginally as a cream or administered in tablet form.



Estriol binds to the estrogen receptor in the nucleus, thereby stimulating cells to produce proteins. Increased sex hormone-binding globulin and thyroid hormone-binding globulin are synthesized and follicle-stimulating hormone is suppressed. The proteins formed mediate the effect of estriol on the target cell. It also positively affects the microflora of the vagina and alleviates the discomfort of vaginal mucosal involution.


Estriol is rapidly and completely absorbed, with only 1-2% of the ingested dose entering the systemic circulation. Metabolism occurs in the liver and intestine. In plasma, it circulates at 91% protein-bound, with maximum plasma concentration reached after 5 hours. In relation to other estrogens, the effect lasts shorter and is weaker. Estriol is almost entirely excreted renally.


Estriol should not be used in case of:

  • Hypersensitivity
  • Breast cancer
  • estrogen-dependent tumors
  • Endometriosis
  • Thromboembolic diseases
  • severe renal failure
  • Liver disease
  • Pregnancy and lactation

Drug interactions

Estriol may interact with drugs that affect the CYP450 enzyme, resulting in either increased or decreased plasma estriol levels. Systemic interactions are unlikely when used topically.


Side effects

The following side effects are common during estriol therapy:

  • Itching
  • Discharge
  • breast pain or tenderness
  • Edema
  • Nausea

Toxicological data

LD50 (rat, oral): >2000 mg/kg