Estrogen Therapy/Estrogen Therapy (ET)is a form of hormone replacement therapy (HRT), that are a useful in case of deficiency of estrogen therapy that indicates uncomfortable symptoms accompany menopause-related disease conditions.[rx] The Women’s Health Initiative trial has made the use of estrogen therapy obsolete in terms of preventing vasomotor symptoms, osteoporosis, and cardiovascular diseases. Localized estrogen treatment often relieves these symptoms and significantly increases the quality of life, which includes life-changing improvements in sexuality, the incidence of urinary tract infections, and incontinence.[rx] The method of estrogen delivery is vital in assessing its benefits and uses. For example, the use of estrogen transdermally, in stark contrast to orally, has been linked to a lower risk of deep vein thrombosis, cholecystitis, osteoporosis, and stroke. The use of estrogen therapy has also been beneficial in a patient with an increased risk of osteoporotic fractures with long-term use.
Mechanism of Action of Estrogen Therapy
The primary use of estrogen therapy lies in its treatment of menopausal symptoms. Although there is a reduction in the use of estrogen therapy as a preventative treatment, it is still routinely used to treat menopausal symptoms locally. Typically, drugs administered vaginally are used mainly for their local effects, but they can also have systemic effects. Estrogen is a steroid hormone that plays a central role in the reproductive system by altering the transcription of genes in specific organs and tissues, primarily the uterus and vagina. The genes undergo alteration through the act of estrogen on certain receptors, known as nuclear transcription factors. These nuclear transcription factors, once bound by estrogen, are then able to bind to promoter regions in sequences of specific genes and are therefore able to regulate these genes [rx]. Once these genes get transcribed, this allows for the development, regulation, and maintenance of the uterus and vagina. One important function of estrogen is its influence on the acid pH in the vaginal canal. The pH of the vaginal lumen in the years preceding menopause typically ranges between 4.5 and 6.0, as it varies relative to the menstrual cycle. Estrogen is responsible for decreasing the pH of the vaginal lumen by acting on the vaginal-ectocervical epithelial cells to increase proton secretion [rx]. Once a woman experiences menopause, there is a decrease in estrogen, causing an alkalinization of the vaginal canal to about 6.5-7.0. A pH of above 6.5 correlates with an increased risk of vaginal infections, UTIs, dryness, pruritus, and dyspareunia, all of which contribute to the symptoms of menopause. Furthermore, alkalinization of the vaginal lumen has associations with the tendency of forming tumors within the cervix.
Indications Of Estrogen Therapy
The indications of estrogen therapy 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.[rx] 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
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.[rx]
Overview of actions
- Anabolic: Increases muscle mass and strength, speed of muscle regeneration, and bone density, increased sensitivity to exercise, protection against muscle damage, stronger collagen synthesis, increases the collagen content of connective tissues, tendons, and ligaments, but also decreases the stiffness of tendons and ligaments (especially during menstruation). Decreased stiffness of tendons gives women much lower predisposition to muscle strains but soft ligaments are much more prone to injuries (ACL tears are 2-8x more common among women than men).
- Anti-inflammatory properties
- Mediate formation of female secondary sex characteristics
- Accelerate metabolism
- Increased fat storage in some body parts such as breasts, buttocks, and legs but decreased abdominal and visceral fat (androgenic obesity).Estradiol also regulates energy expenditure, body weight homeostasis, and seems to have much stronger anti-obesity effects than testosterone in general.
Women tend to have lower base strength but on average have about the same increases of muscle mass in responses to resistance training as men and far faster relative increases in strength
- Stimulate endometrial growth
- Increase uterine growth
- Increase vaginal lubrication
- Thicken the vaginal wall
- Maintenance of vessel and skin
- Reduce bone resorption, increase bone formation
- Protein synthesis
- Increase hepatic production of binding proteins
- Increase circulating level of factors 2, 7, 9, 10, plasminogen
- Decrease antithrombin III
- Increase platelet adhesiveness
- Increase vWF (estrogen -> Angiotensin II -> Vasopressin)
- Increase PAI-1 and PAI-2 also through Angiotensin II
- Increase HDL, triglyceride
- Decrease LDL, fat deposition
- Fluid balance
- Salt (sodium) and water retention
- Increase cortisol, SHBG
- Gastrointestinal tract
- Reduce bowel motility
- Increase cholesterol in bile
- Increase pheomelanin, reduce eumelanin
- Support hormone-sensitive breast cancers
- Lung function
- Promotes lung function by supporting alveoli (in rodents but probably in humans).
- Uterus lining
- Estrogen together with progesterone promotes and maintains the uterus lining in preparation for implantation of fertilized egg and maintenance of uterus function during the gestation period, also upregulates oxytocin receptor in the myometrium
- Surge in estrogen level induces the release of luteinizing hormone, which then triggers ovulation by releasing the egg from the Graafian follicle in the ovary.
- Sexual behavior
- Promotes sexual receptivity in estrus, and induces lordosis behavior. In non-human mammals, it also induces estrus (in heat) prior to ovulation, which also induces lordosis behavior. Female non-human mammals are not sexually receptive without the estrogen surge, i.e., they have no mating desire when not in estrus.
- Regulates the stereotypical sexual receptivity behavior; this lordosis behavior is estrogen-dependent, which is regulated by the ventromedial nucleus of the hypothalamus.
- Sex drive is dependent on androgen levels only in the presence of estrogen, but without estrogen, free testosterone level actually decreases sexual desire (instead of increases sex drive), as demonstrated for those women who have hypoactive sexual desire disorder, and the sexual desire in these women can be restored by administration of estrogen (using oral contraceptive). In non-human mammals, mating desire is triggered by estrogen surge in estrus.
- Estrogens are responsible for the development of female secondary sexual characteristics during puberty, including breast development, widening of the hips, and female fat distribution. Conversely, androgens are responsible for pubic and body hair growth, as well as acne and axillary odor.
Contraindications Of Estrogen
Hormone replacement therapy, which includes estrogen therapy taken either orally or transdermally, has several contraindications that correlate with the adverse effects and relative toxicity of estrogen-based formulations. These include patients who have a known or suspected history of any form of breast or uterine cancer, a history of deep vein thrombosis or pulmonary embolism, a history of stroke or myocardial infarction, or a history of blood clotting disorders. Those patients who have a history of stroke, particularly ischemic stroke events, might benefit from estrogen therapy as the current literature on the contraindication in stroke patients is controversial.[rx] These contraindications do not apply to estrogen taken transvaginally, as in the form of creams or suppositories, as the serum level of estrogen via this route is too low to cause any effect.
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
History of dementia or neurocognitive disorders
History of tobacco use