Health Benefit Of Estriol – Dosage, Side Effects

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Health Benefit Of Estriol/Estriol is a metabolite of estrone metabolized via 16alpha-hydroxy estrone through the enzyme 16alpha-hydroxysteroid dehydrogenase or to 2- or 4-hydroxy estrone (catechol estrogens) by the action of catechol-O-methyltransferase. The latter metabolites can be formed in the brain and may compete with receptors for catecholamines. Metabolites are conjugated with sulfate or glucuronide before excretion by the kidney. During pregnancy, estriol constitutes 60-70% of the total estrogens, increasing to 300-500-fold in relation to non-pregnant women. The late-term human fetus produces relatively large amounts of 16 alpha-hydroxy DHEA, which serves the mother as a precursor of estriol. It has been shown that 90% of the precursors for the formation of estriol are of fetal origin. If abnormal maternal serum screening results, specifically low levels of unconjugated estriol in the second trimester are detected, a diagnosis of Smith-Lemli-Opitz syndrome (SLOS), or RSH is suspected. SLOS is an autosomal recessive disorder caused by mutations of the gene encoding 7-dehydrocholesterol reductase

Estriol (E3), also spelled oestriol, is a steroid, a weak estrogen, and a minor female sex hormone. It is one of three major endogenous estrogens, the others being estradiol and estrone. Levels of estriol in women who are not pregnant are almost undetectable. However, during pregnancy, estriol is synthesized in very high quantities by the placenta and is the most produced estrogen in the body by far, although circulating levels of estriol are similar to those of other estrogens due to a relatively high rate of metabolism and excretion.[rx][rx] Relative to estradiol, both estriol and estrone have far weaker activity as estrogens.[rx]

Mechanism of Action of Estriol

Estriol levels can be measured to give an indication of the general health of the fetus. DHEA-S is produced by the adrenal cortex of the fetus. This is converted to estriol by the placenta. If levels of “unconjugated estriol” are abnormally low in a pregnant woman, this may indicate a problem with the development of the child. The drug interacts with a target cell receptor. When the estrogen receptor has bound its ligand it can enter the nucleus of the target cell, and regulate gene transcription which leads to the formation of messenger RNA. The mRNA interacts with ribosomes to produce specific proteins that express the effect of estriol upon the target cell. Estrogens increase the hepatic synthesis of sex hormone-binding globulin (SHBG), thyroid-binding globulin (TBG), and other serum proteins and suppress follicle-stimulating hormone (FSH) from the anterior pituitary.

Uses Indications of Estriol

  • Used as a test to determine the general health of an unborn fetus
  • The treatment of hormone-dependent urinary incontinence due to sphincter mechanism incompetence in ovariohysterectomised bitches.
  • Estriol is indicated as hormone replacement therapy for the treatment of atrophic vaginitis and kraurosis in post-menopausal women.
  • Estriol is indicated for the treatment of pruritus vulvae and dyspareunia associated with atrophic vaginal epithelium.
  • Estriol is used in menopausal hormone therapy to treat menopausal symptoms, such as hot flashes, vulvovaginal atrophy, and dyspareunia (difficult or painful sexual intercourse). The benefits of estriol on bone mineral density and osteoporosis prevention have been inconsistent and are less clear. Estriol has been found to reduce the risk of urinary tract infections and other uEstriolrogenital symptoms.[rx][rx]
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Contraindications of Estriol

  • Allergic (hypersensitive) to any of the ingredients of estriol
  • Estriol contains cetyl alcohol and stearyl alcohol. This may cause local skin reactions (
  • Known hypersensitivity to estriol or any of the excipients.
  • Known, past or suspected cancer of the breast
  • Known or suspected estrogen-dependent malignant tumors (eg endometrial cancer)
  • Undiagnosed genital bleeding
  • Untreated endometrial hyperplasia
  • Previous or current venous thromboembolism (deep venous thrombosis, pulmonary embolism)
  • Known thrombophilic disorders (eg protein C, protein S, or antithrombin deficiency, see section 4.4)
  • Active or recent arterial thromboembolic disease (eg angina, myocardial infarction)
  • Acute liver disease, or a history of liver disease as long as liver function tests have failed to return to normal
  • Porphyria.

In medicine, a contraindication is a condition or factor that serves as a reason to withhold a certain medical treatment due to the harm that it would cause the patient.

Dosage of Estriol

Adult menopausal and postmenopausal females

  • 0.5 mg to 2 mg PO once daily. Usual initial dose: 1 or 2 mg PO once daily. Less than 1 mg/day PO may suffice for vaginal/vulvar symptoms only; however, in such patients, consider vaginal therapy alone.
  • Use the lowest effective dose. The administration should be cyclic (e.g., 3 weeks on and 1 week off). In women with an intact uterus, estrogen may be given cyclically or combined with progestin for at least 10 to 14 days per month to minimize the risk of endometrial hyperplasia.

Menopausal and postmenopausal females

  • 1 patch (delivering 0.025 mg, 0.0375 mg, 0.05 mg, 0.06 mg, 0.075 mg, or 0.1 mg per day) applied and replaced every 7 days. Usual initial dose is 0.0375 mg/day or 0.05 mg/day.
  • Use the lowest effective dose. A switch between transdermal system types can be done immediately; if on oral therapy, begin 1 week after oral treatment is discontinued or when symptoms reappear.

Topical dosage (topical gel only)

Adult menopausal and postmenopausal females
  • Initially, apply 1 actuation of the pump (0.87 grams estriol gel containing 0.52 mg of estradiol and delivering 12.5 mcg/day of estradiol systemically) once daily to the upper arm. Adjust based upon the individual patient response. The usual dose range is 1 to 2 pump actuation per day.

Vaginal dosage ( vaginal ring; Femring only)

Adult menopausal and postmenopausal females
  • Insert 1 vaginal ring (delivering either 50 or 100 mcg per 24 hours) vaginally into the upper third of the vaginal vault; keep in place continuously for 3 months, then remove. If appropriate, insert a new ring. Use the lowest effective dose. While Femring may be used to treat isolated genitourinary symptoms, consider other vaginal products of lower estradiol dosage first.
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  • The cream can be started any time after the manifestation of atrophic vaginitis or associated symptoms (eg dyspareunia, pruritus). The recommended initial daily dose is one applicator full per day.
  • A maintenance dose of one applicator full twice a week may be used after restoration of the vaginal mucosa has been achieved.
  • For initiation and continuation of treatment of postmenopausal symptoms, the lowest effective dose for the shortest duration should be used. Attempts to discontinue medication should be made at three to six-month intervals following a physical examination.
  • The cream is to be applied to the vagina, using an applicator. The applicator holds 5ml of a cream containing 0.5mg estriol. The filled applicator should be inserted high into the vagina and emptied, preferably in the evening.
  • Remove the cap from a new tube and use the top of the cap to pierce the metal seal on the tube.
  • One end of the applicator is fitted with a plunger. Ensure the plunger is fully inserted into the applicator. Screw the other end of the applicator onto the tube. Squeeze the tube, so that the barrel of the applicator fills with cream. Unscrew the applicator and replace the cap on the tube.
  • Lie down, with knees bent and spread apart. Gently insert the open end of the applicator well into the vagina. Push the plunger firmly but gently as far as it will go to empty the cream into the vagina.
  • Keeping the plunger pressed down firmly, grip the applicator by the barrel and remove it. There is no relevant indication for use of Gynest in children

Missed Dose

  • When a dose is inadvertently forgotten, resume dosing when the omission is realized.

Side Effects of Estriol

The Most Common 

  • Breast tenderness may sometimes occur as a side effect of estriol. Local reactions with vaginal estriol such as discomfort (irritation, burning, itching) and discharge may occur.
  • Nausea, vomiting,
  • Vaginal bleeding, and reversible feminization.
  • Breast enlargement,
  • Headache,
  • Abdominal tenderness, or persistent upper abdominal pain
  • Breast lumps
  • Changes in menstrual periods
  • Fluid retention, and edema among others.[rx]
  • Estriol may produce endometrial hyperplasia similarly to estradiol and other estrogens[rx][rx]
  • However, it appears that typical clinical dosages of vaginal estriol are not associated with an important risk of endometrial proliferation or hyperplasia.[rx][rx]
  • Increased risk of blood clots,
  • Cardiovascular disease, and, when combined with most progestogens,
  • Breast cancer.
  • Estrogens can cause breast development
  • Feminization
  • Infertility
  • Low testosterone levels,
  • Sexual dysfunction among others.

More Common

  • signs of depression (e.g., poor concentration, changes in weight, changes in sleep, decreased interest in activities, thoughts of suicide)
  • signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
  • acne
  • breast pain
  • darkening of the skin
  • decreased interest in sexual activity
  • fatigue
  • fluid retention
  • hair loss
  • irritability
  • migraine headaches
  • increased blood pressure
  • nausea
  • problems wearing contact lenses
  • unexpected vaginal bleeding
  • vomiting
  • nausea
  • nervousness
  • stomach cramps and bloating
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  • a problem caused by growth of the womb lining outside the womb (fibroids or endometriosis)
  • any problem with your heart or circulation(including high blood pressure or risk factors for a blood clot.
  • relatives who have had a blood clot
  • asthma
  • diabetes
  • migraine or severe headaches
  • epilepsy (fits)
  • gallstones
  • liver or kidney problems
  • a rare problem called ‘systemic lupus
  • erythematosus’ (SLE)
  • otosclerosis (a hearing disorder).

Drug Interactions of Estriol Cream

Estriol may interact with following drugs, supplements & may change the efficacy of drugs

  • anastrozole
  • angiotensin-converting enzyme inhibitors (ACEIs; e.g., captopril, enalapril, ramipril)
  • angiotensin receptor blockers (ARBs; e.g., candesartan, irbesartan, losartan)
  • aripiprazole
  • atorvastatin
  • axitinib
  • “azole” antifungals (e.g., itraconazole, ketoconazole, voriconazole)
  • barbiturates (e.g., pentobarbital, phenobarbital)
  • beta-adrenergic blockers (e.g., atenolol, propranolol, sotalol)
  • calcium channel blockers (e.g., amlodipine, diltiazem, nifedipine, verapamil)
  • carbamazepine
  • carvedilol
  • celecoxib
  • corticosteroids (e.g., dexamethasone, hydrocortisone, prednisone)
  • cyclosporine
  • dexamethasone
  • diabetes medications (e.g., chlorpropamide, glipizide, glyburide, insulin, metformin, nateglinide, rosiglitazone)
  • dipyridamole
  • diuretics (water pills; e.g., furosemide, hydrochlorothiazide, triamterene)
  • grapefruit juice
  • heparin
  • levothyroxine
  • macrolide antibiotics (e.g., clarithromycin, erythromycin)
  • nilotinib
  • oxcarbazepine
  • phenytoin
  • prazosin
  • progesterone
  • propranolol
  • saw palmetto
  • saxagliptin
  • somatropin
  • St. John’s wort
  • tacrolimus
  • tamoxifen
  • theophylline
  • tocilizumab
  • trazodone
  • ursodiol
  • verapamil
  • vinblastine
  • vitamin C
  • warfarin

Pregnancy Category of Estriol Cream

  • FDA Pregnancy Category  – X 
  • AU TGA Pregnancy Category – B 3


Estriol should not be used during pregnancy, as it may be harmful to the developing baby. If you become pregnant while taking this medication, contact your doctor immediately.


Taking estriol while breast-feeding may decrease the amount and quality of breast milk. Estriol is also passed through breast milk to your breastfeeding child. Women who are breast-feeding should not take this medication. The safety and effectiveness of this medication have not been established for use by children.


Health Benefit Of Estriol

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