Several classes of medication can lower estrogen levels or block estrogen’s effects in women, and the right choice depends on your menopausal status and the condition being treated. The main options include aromatase inhibitors, GnRH agonists, selective estrogen receptor modulators (SERMs), and progestins. Each works through a different mechanism, and most require a prescription tied to a specific diagnosis like hormone-receptor-positive breast cancer, endometriosis, or uterine fibroids.
Why Estrogen Lowering Is Prescribed
The most common reason for estrogen-suppressing medication is hormone-receptor-positive breast cancer, where the cancer cells have receptors that use estrogen or progesterone as fuel to grow. Roughly two-thirds of breast cancers fall into this category. Blocking or reducing estrogen after surgery and radiation significantly lowers the risk of recurrence.
Estrogen suppression is also used to manage endometriosis, adenomyosis, uterine fibroids (leiomyomas), and endometrial hyperplasia. All of these conditions are driven or worsened by estrogen activity, so reducing estrogen levels or counteracting its effects can shrink tissue growth, ease pain, and control heavy bleeding.
Aromatase Inhibitors
Aromatase inhibitors (AIs) block an enzyme called aromatase, which your body uses to convert androgens into estrogen. In postmenopausal women, this conversion in fat tissue, skin, and muscle is the primary remaining source of estrogen, since the ovaries are no longer active. By shutting down that enzyme, AIs suppress estrogen to very low levels.
The three AIs used in clinical practice are anastrozole, letrozole, and exemestane. Anastrozole is taken as a once-daily 1 mg tablet. Letrozole is taken as a once-daily 2.5 mg tablet. Both can be taken with or without food. These medications are primarily prescribed for postmenopausal women. Premenopausal women produce too much aromatase in their ovaries for these drugs to work on their own, so they need to be paired with a drug that suppresses ovarian function first.
Each AI carries slightly different considerations. Anastrozole and exemestane can raise blood pressure, so regular monitoring is important. Letrozole may affect cholesterol levels, making periodic lipid checks worthwhile. Exemestane is processed by a specific liver enzyme, which means other medications that speed up that enzyme’s activity can reduce exemestane’s effectiveness. Any product containing estrogen, including certain herbal supplements with phytoestrogens, can counteract the benefit of an AI and should be avoided during treatment.
GnRH Agonists for Premenopausal Women
Gonadotropin-releasing hormone (GnRH) agonists work by overriding the hormonal signals that tell your ovaries to produce estrogen. Normally, GnRH is released in pulses from the brain, stimulating the pituitary gland to trigger ovarian activity. GnRH agonists deliver a continuous dose instead. After an initial surge of hormones lasting one to two weeks, the receptors become desensitized and essentially shut down, leading to a profound drop in estrogen.
The two most commonly prescribed GnRH agonists are goserelin and leuprolide. They’re typically given as depot injections, meaning a slow-release formulation administered monthly or every few months. This approach is reversible: once the medication stops, ovarian function and estrogen production gradually return. GnRH agonists are the primary tool for suppressing ovarian estrogen in premenopausal women and are often combined with an aromatase inhibitor to achieve the deepest possible estrogen suppression. In breast cancer treatment, the goal is to push estradiol (the body’s main form of estrogen) below about 2.72 pg/mL, which is the threshold at which aromatase inhibitors can work at full effectiveness.
Beyond breast cancer, GnRH agonists are also used to manage endometriosis, adenomyosis, and uterine fibroids by temporarily creating a low-estrogen state that shrinks estrogen-dependent tissue and reduces pain and bleeding.
SERMs and SERDs
Selective estrogen receptor modulators (SERMs) take a different approach. Instead of lowering the amount of estrogen your body makes, they sit in estrogen receptors on cells and block estrogen from binding. In breast tissue, this stops estrogen from fueling cancer growth. The most widely used SERM is tamoxifen, which works in both premenopausal and postmenopausal women. Toremifene is another option, approved only for postmenopausal use.
SERMs are tissue-selective, which is an important distinction. Tamoxifen blocks estrogen in the breast but actually mimics estrogen in bone, which can help protect against bone loss. However, that same estrogen-like effect in the uterus means tamoxifen slightly increases the risk of endometrial changes, so it requires monitoring.
Selective estrogen receptor degraders (SERDs) go a step further. Rather than just blocking the receptor, they bind to it and destroy it entirely. Fulvestrant is the main SERD, used in postmenopausal women with breast cancer. It’s given as an injection rather than a daily pill.
Progestins to Counteract Estrogen
Progesterone naturally opposes estrogen’s effects on the uterine lining, and synthetic versions called progestins are widely used to manage estrogen-driven conditions. They work not by lowering estrogen production directly but by counterbalancing its stimulating effects on tissue growth.
Progestins are a frontline treatment for endometriosis, adenomyosis, uterine fibroids, and endometrial hyperplasia. Options include oral pills, injections, implants, and the levonorgestrel intrauterine device (LNG-IUD). The LNG-IUD is considered one of the most effective options across several of these conditions because it delivers progesterone directly to the uterus, often inducing amenorrhea (stopping periods entirely) with fewer body-wide side effects. It successfully stops heavy menstrual bleeding with anemia in up to 60% of premenopausal women with fibroids. For endometrial hyperplasia, long-term treatment with oral progestins resolves approximately 75% of cases, and the LNG-IUD has shown effectiveness in regressing hyperplasia within two years of insertion.
Oral contraceptive pills combining estrogen and progestin, or progestin-only formulations, are also commonly prescribed. For endometriosis specifically, these are effective at reducing chronic pelvic pain and painful periods, and they serve as a long-term management strategy rather than a short-term fix.
What Low Estrogen Feels Like
Regardless of which medication you take, suppressing estrogen comes with predictable effects. The most common are hot flashes, night sweats, vaginal dryness, joint stiffness, and mood changes. These mirror what happens during natural menopause, because the medications are essentially accelerating or deepening that hormonal shift.
Bone density loss is a significant concern with long-term estrogen suppression, particularly with aromatase inhibitors and GnRH agonists. Estrogen plays a protective role in maintaining bone strength, so removing it increases the risk of osteoporosis over time. Bone density scans are typically part of ongoing monitoring during treatment. Tamoxifen is a partial exception here, since its estrogen-like activity in bone can actually preserve density rather than erode it.
Which Medication Fits Which Situation
Your menopausal status is the single biggest factor in determining which medication is appropriate. Premenopausal women generally start with tamoxifen (a SERM) or a GnRH agonist, since the ovaries are still active and producing large amounts of estrogen. Aromatase inhibitors only work well when ovarian production has already been shut down, either naturally through menopause or medically through a GnRH agonist. Postmenopausal women have more options and are commonly prescribed aromatase inhibitors as a first-line approach for breast cancer.
For gynecological conditions like endometriosis and fibroids, progestins and GnRH agonists are the primary tools. The choice depends on symptom severity, whether you’re trying to preserve fertility, and how long treatment needs to last. GnRH agonists are potent but typically used for shorter durations because of bone loss concerns, while progestins like the LNG-IUD can be maintained for years.