The hormones estrogen and progesterone are produced by the ovaries in premenopausal women and by some other tissues, including fat and skin, in both premenopausal and postmenopausal women. Estrogen promotes the development and maintenance of female sex characteristics and the growth of long bones. Progesterone plays a role in the menstrual cycle and pregnancy.
Estrogen and progesterone can also promote the growth of some breast cancers, which are called hormone-sensitive (or hormone-dependent) breast cancers. Hormone-sensitive breast cancer cells contain proteins known as hormone receptors that become activated when hormones bind to them. The activated receptors cause changes in the expression of specific genes, which can lead to the stimulation of cell growth.
To determine whether breast cancer cells contain hormone receptors, doctors test samples of tumor tissue that have been removed by surgery. If the tumor cells contain estrogen receptors, the cancer is called estrogen receptor-positive (ER-positive), estrogen-sensitive, or estrogen-responsive. Similarly, if the tumor cells contain progesterone receptors, the cancer is called progesterone receptor-positive (PR- or PgR-positive). Approximately 70 percent of breast cancers are ER-positive. Most ER-positive breast cancers are also PR-positive.
Breast cancers that lack estrogen receptors are called estrogen receptor-negative (ER-negative). These tumors are estrogen-insensitive, meaning that they do not use estrogen to grow. Breast tumors that lack progesterone receptors are called progesterone receptor-negative (PR- or PgR-negative).
Several strategies have been developed to treat hormone-sensitive breast cancer, including the following:
Blocking ovarian function: Because the ovaries are the main source of estrogen in premenopausal women, estrogen levels in these women can be reduced by eliminating or suppressing ovarian function. Blocking ovarian function is called ovarian ablation.
Ovarian ablation can be done surgically in an operation to remove the ovaries (called oophorectomy) or by treatment with radiation. This type of ovarian ablation is usually permanent.
Alternatively, ovarian function can be suppressed temporarily by treatment with drugs called gonadotropin-releasing hormone (GnRH) agonists, which are also known as luteinizing hormone-releasing hormone (LH-RH) agonists. These medicines interfere with signals from the pituitary gland that stimulate the ovaries to produce estrogen.
Blocking estrogen production: Drugs called aromatase inhibitors can be used to block the activity of an enzyme called aromatase, which the body uses to make estrogen in the ovaries and in other tissues. Aromatase inhibitors are used primarily in postmenopausal women because the ovaries in premenopausal women produce too much aromatase for the inhibitors to block effectively. However, these drugs can be used in premenopausal women if they are given together with a drug that suppresses ovarian function.
Examples of aromatase inhibitors approved by the FDA are anastrozole (Arimidex) and letrozole (Femara), both of which temporarily inactivate aromatase, and exemestane (Aromasin), which permanently inactivates the enzyme.
Blocking estrogen’s effects: Several types of drugs interfere with estrogen’s ability to stimulate the growth of breast cancer cells:
Selective estrogen receptor modulators (SERMs) bind to estrogen receptors, preventing estrogen from binding. Examples of SERMs approved by the FDA are tamoxifen (Nolvadex), raloxifene (Evista), and toremifene (Fareston). Tamoxifen has been used for more than 30 years to treat hormone receptor-positive breast cancer.
Because SERMs bind to estrogen receptors, they can potentially not only block estrogen activity (serve as estrogen antagonists) but also mimic estrogen effects (i.e., serve as estrogen agonists). Most SERMs behave as estrogen antagonists in some tissues and as estrogen agonists in other tissues. For example, tamoxifen blocks the effects of estrogen in breast tissue but acts like estrogen in the uterus and bone.
Other antiestrogen drugs, such as fulvestrant (Faslodex), work in a somewhat different way to block estrogen’s effects. Like SERMs, fulvestrant attaches to the estrogen receptor and functions as an estrogen antagonist. However, unlike SERMs, fulvestrant has no estrogen agonist effects. It is a pure antiestrogen. In addition, when fulvestrant binds to the estrogen receptor, the receptor is targeted for destruction.
An oral non-steroidal aromatase inhibitor, Letrozole is routinely prescribed by medical practitioners to patients with hormonally responsive breast cancer after surgery. Also known as Femara and Liquifem, the antiestrogen is also used by budding and professional sportsmen on anabolic steroids to keep off estrogenic side effects such as oily skin, acne, gynecomastia, and bloating at bay while reaping the optimum benefits of steroids during an anabolic steroid cycle.
Letrozole is considered as one of the most potent drugs for stimulating metabolic rate of the body and promoting burning of fat. It is also useful in reducing the levels of LDL (bad) cholesterol and promoting the level of spermatogenesis in male patients suffering from non-obstructive azoospermia and treat endometriosis. The third-generation selective oral aromatase inhibitor, Letrozole, is also used to stimulating dramatic enhancements in terms of growth hormone, cortisol, SHBG, hepatic production of binding proteins, HDL, and growth and development of sexual characteristics. If that was not all, Femara also has the ability to promote healthy immune function, healthy cholesterol levels, joint health, cognitive function, and muscle growth while reducing or even eliminating estrogenic side effects such as oily skin, gynecomastia, and fluid retention.
The medication may even be recommended by medical practitioners to treat certain types of breast cancer (such as hormone-receptor-positive breast cancer) in women after menopause or preventing the cancer from making a return. By reducing the amount of estrogens in the body, Letrozole helps in slowing or reversing the growth of these breast cancers.
The use of Letrozole, for a period of three to six weeks, is also associated with restoration of natural products of hormones, like testosterone. If that was not all, one 2.5 mg tablet of Femara is good enough to inhibit side effects of estrogens by as much as 80 percent.
The ideal dosage of Letrozole is 2.5 mg once a day for treating patients with breast cancer. Sportsmen use Letrozole in dosages of 0.5-1.0 mg every day, with or without meals. It is very important to note that this is a prescription drug and must be used and purchased only with a prescription. Moreover, its use should always be followed by a medical recommendation for the same after careful and complete evaluation of medical reports and history. At no point of time, two dosages of the drug can be taken together, even if missed accidentally. In case the first dose has been missed, it should be skipped and the next dose should be taken at its scheduled time.
Letrozole use is not recommended to pregnant and breastfeeding women and children or those having allergies to the drug or any of its ingredients. Those suffering with prostate, breast, or testicular cancer or treated for high blood pressure, liver damage, stroke, and kidney damage should avoid using the drug. Patients making use of drugs such as Prasterone, Tamoxifen, DHEA, and Androstenedione should avoid using Letrozole unless the same is specifically approved by a qualified medical practitioner.
The abuse of Letrozole can lead to side effects and thus best avoided. When abused or of a low grade, it can lead to side effects such as hot flushes, night sweats, vomiting, bone pain, loss of appetite, headache, stomach pain, cough, and breast pain. Use of Letrozole should not be made by individuals treated for high blood fats (cholesterol), bone problems (such as osteopenia, osteoporosis), stroke or blood clots, heart disease (such as chest pain, heart attack, heart failure), high blood pressure, kidney problems, and liver problems.
In rare cases, Femara use may cause severe health complications such as chest/jaw/left arm pain, confusion, coughing up blood, sudden dizziness/fainting, pain/swelling/warmth in the groin/calf, tingling/weakness/numbness in the arms/legs, weakness on one side of the body, vision changes, sudden/severe headache, slurred speech, bone fractures, mental/mood changes (such as depression, anxiety), swelling of arms/legs, and blurred vision. Drugs such as estrogens (such as ethinyl estradiol, conjugated estrogens), estrogen blockers (such as anastrozole, tamoxifen) may interfere with functioning and action mechanism of Letrozole and this may cause serious side effects or may cause the medications not to work correctly. The consumption of alcoholic beverages should be reduced, if the same cannot be completely eliminated, while Letrozole is being used.