Estrogen Drug – Uses, Dosage, Side Effects, Interaction

Estrogen Drug – Uses, Dosage, Side Effects, Interaction

Estrogen is a special type of sex hormone that is responsible for a female to the development and regulation of the female reproductive system and secondary sexual characteristics. There are three major endogenous estrogens that have estrogenic hormonal activity: estrone (E1), estradiol (E2), and estriol (E3). Estradiol, an estrane, is the most potent and prevalent. Another estrogen called estetrol (E4) is produced only during pregnancy

Estrogen binds to and activates specific nuclear receptors, which, in turn, bind to estrogen response elements (EREs) in target genes, resulting in histone acetylation, alteration of chromatin conformation, and initiation of transcription. (NCI04).

Estrogen is a steroid hormone associated with the female reproductive organs and is responsible for the development of female sexual characteristics. Estrogen is often referred to the following structures as either estrone, estradiol, and estriol. Of the previously mentioned forms of estrogen, estradiol is the most common form of estrogen hormone for hormone replacement therapy (HRT) in the treatment of symptoms of menopause. The use of estrogen for hormone replacement therapy has been heavily researched in medicine and remains a controversial topic. According to early studies, estrogen as hormone replacement therapy for postmenopausal women showed promising benefits of decreased risk of osteoporosis, coronary arterial disease, and mortality. Later studies conducted by the Women’s Health Initiative concluded that risk was greater than the benefit of hormone replacement therapy in postmenopausal women.

Mechanism of Action of Estrogen

Estrogen enters the systemic circulation as a free hormone or protein-bound, either as sex hormone-binding globulin (SHBG) or albumin. Non-protein-bound estrogen has the property to diffuse into cells freely with no regulation. The initiation of cellular physiological response to estrogen begins in the cell cytoplasm with the binding of estrogen to either alpha-estrogen receptor or beta-estrogen receptor. The activated estrogen-estrogen receptor complex then crosses into the nucleus of cells to induce transcription of DNA by binding to nucleotide sequences known as estrogen response elements (ERE) to enact a physiological response. Estrogen hormone levels in the body are regulated by the negative feedback effect of estrogen on the hypothalamus and pituitary gland. An example of negative feedback can be observed during the menstrual cycle. Estrogen metabolic activity primarily takes place within the liver hepatocytes CYP3A4 and excreted from the body in the urine.

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Estrogens have an important role in the reproductive, skeletal, cardiovascular, and central nervous systems in women, and act principally by regulating gene expression. The biologic response is initiated when estrogen binds to a ligand-binding domain of the estrogen receptor resulting in a conformational change that leads to gene transcription through specific estrogen response elements (ERE) of target gene promoters; subsequent activation or repression of the target gene is mediated through 2 distinct transactivation domains (ie, AF-1 and AF-2) of the receptor. The estrogen receptor also mediates gene transcription using different response elements (ie, AP-1) and other signal pathways. Recent advances in the molecular pharmacology of estrogen and estrogen receptors have resulted in the development of selective estrogen receptor modulators (eg, clomiphene, raloxifene, tamoxifen, toremifene), agents that bind and activate the estrogen receptor but that exhibit tissue-specific effects distinct from estrogen. Tissue-specific estrogen-agonist or -antagonist activity of these drugs appears to be related to structural differences in their estrogen receptor complex (eg, specifically the surface topography of AF-2 for raloxifene) compared with the estrogen (estradiol)-estrogen receptor complex. A second estrogen receptor also has been identified, and the existence of at least 2 estrogen receptors (ER-alpha, ER-beta) may contribute to the tissue-specific activity of selective modulators. While the role of the estrogen receptor in bone, cardiovascular tissue, and the CNS continues to be studied, emerging evidence indicates that the mechanism of action of estrogen receptors in these tissues differs from the manner in which estrogen receptors function in reproductive tissue

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Indications of Estrogen

The indications of estrogen are

  • Conjugated estrogen therapy is indicated in the treatment of moderate to severe vasomotor symptoms due to menopause.
  • Conjugated estrogen therapy is indicated in the treatment of moderate to severe symptoms of vulvar and vaginal atrophy due to menopause. When prescribing solely for the treatment of symptoms of vulvar and vaginal atrophy, topical vaginal products should be considered.
  • Conjugated estrogen therapy is indicated in the treatment of hypoestrogenism due to hypogonadism, castration or primary ovarian failure.
  • Conjugated estrogen therapy is indicated in the treatment of breast cancer (for palliation only) in appropriately selected women and men with metastatic disease.
  • Conjugated estrogen therapy is indicated in the treatment of advanced androgen-dependent carcinoma of the prostate (for palliation only).
  • The FDA approves of estrogen for hormone replacement therapy in the treatment of symptoms of menopause. Synthetic estrogen is also available for clinical use with the purpose of having increase absorption and effectiveness by alteration of the estrogen chemical structure for topical or oral administration.
  • Synthetic steroid estrogens include Ethinyl estradiol, estradiol valerate, estropipate, conjugate esterified estrogen, and quinestrol. Ethinyl estradiol is a commonly used synthetic estrogen to prevent pregnancy as a component of the oral contraceptive pill approved by the FDA. Some nonsteroidal synthetic estrogens include dienestrol, diethylstilbestrol, benzestrol, megestrol, and hexestrol.

Clinically, the use of estrogen includes the following FDA-approved indications

  • Primary ovarian insufficiency
  • Female hypogonadism
  • Symptoms associated with menopause including vulvovaginal atrophy, dyspareunia, hot flashes and night sweats, and prevention of osteoporosis
  • Oral contraceptive pill (OCP) to prevent pregnancy
  • Moderate acne vulgaris
  • Prostate cancer with advanced forms of metastasis

Estrogen/synthetic estrogen has the following non-FDA-approved indication for polycystic ovarian syndrome for the relief of symptoms of hyperandrogenism and amenorrhea.

The effects of estrogen on various systems of the body are described below
  • Breast – Estrogen is responsible for the development of mammary gland tissue and parenchymal and stromal changes in breast tissue at puberty in females. Estrogen is also responsible for the development of mammary ducts during puberty, and during pregnancy, functions to secrete breast milk in postpartum lactation.
  • Uterus – In the uterus, estrogen helps to proliferate endometrial cells in the follicular phase of the menstrual cycle, thickening the endometrial lining in preparation for pregnancy.
  • Contraception – Ethinyl estradiol, an ingredient of OCPs, functions to suppress the hypothalamus release of gonadotropin-releasing hormone (GnRH) and pituitary release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in preventing ovulation during the menstrual cycle.
  • Vagina – Estrogen supports the proliferation of epithelial mucosa cells of the vagina and the vulva. In the absence of estrogen, the vaginal and vulvar mucosal epithelium becomes thin and presents with symptoms of dryness known as vulvovaginal atrophy.
  • Bone – During puberty, estrogen aides in the development of long bones and fusion of the epiphyseal growth plates. Estrogen protects bones by inactivating osteoclast activity, preventing osteoporosis in both estrogen-deficient and postmenopausal women.
  • Cardiovascular – Estrogen affects plasma lipids by increasing high-density lipoproteins (HDL) and triglyceride levels while decreasing low-density lipoproteins (LDL) and total plasma cholesterol and reduce the risk of coronary artery disease in early use in postmenopausal women.

Contraindications of Estrogen

The following are contraindications for the use of natural estrogen and synthetic estrogen derivatives:

  • Estrogen hormone receptor sensitive malignancies including breast cancer, ovarian cancer, and endometrial cancers
  • Coronary arterial disease
  • History of thromboembolism or thrombophlebitis
  • History of hypercoagulable disease (Factor V Leiden syndrome, Protein C or Protein S deficiencies and metastatic disease)
  • History of ischemic stroke
  • Migraine headaches
  • Seizure disorder
  • History of dementia or neurocognitive disorders
  • Hypertension
  • Uterine leiomyomas
  • Endometriosis
  • Urinary incontinence
  • Hyperlipidemia
  • Gallbladder disease
  • Liver disease
  • History of tobacco use

Dosage and Administration of Estrogen

Estrogen hormone therapy may be prescribed in the following combinations as either estrogen-only medication or estrogen and hormone combination medication to treat symptoms of menopause, prevention of osteoporosis, prevention of pregnancy, hypoestrogenism, and metastatic breast and advance prostate cancers.

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Available Estrogen Preparations

Oral

  • Estrogen: Conjugated may be prescribed in the dosage of 0.3-mg, 0.625-mg, 0.9-mg, and 1.25-mg tablets
  • Estradiol may be prescribed in the dosage of 0.5-mg, 1-mg, and 2-mg tablets
  • Norethindrone/ethinyl estradiol 1.5 mg/30 mcg tablets for oral contraception

Vaginal Ring

  • Combination estrogen-etonogestrel/ethinyl estradiol hormone vaginal ring for contraception: 0.12 mg/0.015 mg per day.
  • Estradiol only vaginal ring for vulvovaginal atrophy: 7.5 mcg per day

Intramuscular Injection

  • Estradiol valerate administered as an intramuscular injection in the dosage of 10 mg per mL, 20 mg per mL, and 40 mg per mL for vasomotor symptoms of menopause, vulvovaginal atrophy,  and hypoestrogenism. Recommendations for advanced prostate cancer palliative treatment is more than 30-mg intramuscular injection.
  • Estradiol cypionate administered as an intramuscular injection in the dosage of 5 mg per mL for treatment of moderate-to-severe symptoms of menopause.

Transdermal

Available as a topical cream, topical spray, vaginal cream, vaginal tablet insert, and transdermal patch

  • Estradiol topical gel (0.006%): 0.52 mg per pump
  • Estradiol topical spray applied to the inner surface of the forearm: 1.53 mg per actuation
  • Estradiol hemihydrate tablet for vaginal insert may be prescribed at the following dosage: 10-mcg, 25-mcg tablet
  • Estrogen, conjugated vaginal cream: 0.625 mg per gram applied intravaginally
  • Estradiol transdermal patch may be prescribed at the following dosage: 0.025 mg, 0.05 mg, 0.075 mg, or 0.1 mg per day.

Adverse Effects of Estrogen

Natural estrogen and synthetic estrogen may cause the following common adverse effects: breast tenderness, nausea, vomiting, bloating, stomach cramps, headaches, weight gain, hyperpigmentation of the skin, hair loss, vaginal itching, abnormal uterine bleeding also known as breakthrough bleeding, and anaphylaxis.

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Weight gain may be a reported adverse effect of the oral contraceptive pill (OCP) containing ethinyl estradiol, but studies conducted on short-term and long-term use of OCPs resulted in no weight gain association.

More severe side effects of estrogen include hypertension, cerebrovascular accident, myocardial infarction, venous thromboembolism, pulmonary embolism, exacerbation of epilepsy, irritability, exacerbation of asthma, galactorrhea and nipple discharge, hypocalcemia, gallbladder disease, hepatic hemangioma and adenoma, pancreatitis, breast hypertrophy, endometrial hyperplasia, vaginitis, vulvovaginal candidiasis (intravaginal preparations), enlargement of uterine fibroids, and risk of cervical cancer and breast cancer.

US Preventive Services Task Force (USPSTF) Score: D

Using estrogen-alone or combined estrogen and progestin use to prevent a chronic condition in postmenopausal women with or without a uterus is not recommended by the US Preventive Services Task Force (USPSTF).

Pregnancy and Lactation

  • Estradiol use in pregnancy is classified as pregnancy risk factor category X, and the use of esterified estrogens are contraindicated for use during pregnancy

Box Warnings

The use of estrogen without progestins increased the risk of endometrial cancer. The use of estrogen with and without progestins resulted in an increased risk of myocardial infarction, stroke, pulmonary emboli, and deep vein thrombosis in postmenopausal women (50 to 79 years old) and an increased risk of invasive breast cancer in postmenopausal women (50 to 79 years old) with oral conjugated estrogens with medroxyprogesterone by studies established by the Women’s Health Initiative. The use of oral conjugated estrogens plus medroxyprogesterone acetate increased the risk of developing dementia in postmenopausal women older than 65 years of age have been established by the Women’s Health Initiative Memory Study.

References

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