A single depot injection of leuprolide acetate, sold under the brand name Lupron Depot, can shrink uterine fibroids by roughly 36 percent in just 12 weeks. Clinical trials show that 77 percent of women treated with leuprolide achieved more than a 25 percent reduction in uterine volume, with the most dramatic shrinkage — around 30 percent — happening during the first treatment cycle alone. For the millions of women living with fibroids, that kind of rapid reduction can mean the difference between uncontrolled bleeding and walking into surgery with a body that is better prepared to heal. Uterine fibroids affect up to 70 to 80 percent of women by age 50, making them the most common benign tumors in women of reproductive age.
Yet many women endure years of heavy periods, pelvic pressure, and anemia before learning that an injectable treatment exists that can offer meaningful relief in a matter of months. The catch — and there is always a catch — is that this injection was never designed to be a permanent fix. It is primarily a bridge to surgery, and fibroids tend to grow back once the medication stops. This article walks through exactly how GnRH agonist injections work, what the clinical data actually shows, who benefits most, what the side effects look like, and how newer oral medications are changing the landscape. If you or someone you care for is weighing treatment options for fibroids, this is the practical breakdown you need before that next appointment.
Table of Contents
- How Does the Injection That Shrinks Uterine Fibroids in Three Months Actually Work?
- What the Clinical Evidence Shows — and Where It Falls Short
- Pre-Surgical Strategy — Why Doctors Prescribe Injections Before the Operating Room
- Oral Alternatives That Are Changing the Conversation
- Side Effects and the Bone Density Question
- Emerging Research — Collagenase Injections and Direct Fibroid Targeting
- Updated Guidelines and What Comes Next
- Conclusion
- Frequently Asked Questions
How Does the Injection That Shrinks Uterine Fibroids in Three Months Actually Work?
Lupron Depot belongs to a class of drugs called gonadotropin-releasing hormone agonists, or GnRH agonists. The mechanism is straightforward but aggressive: the injection suppresses estrogen production by the ovaries, effectively starving fibroids of the hormone that fuels their growth. Estrogen is the engine behind fibroid proliferation, so when you cut off the supply, the tumors lose volume. The result is a temporary, reversible state that doctors sometimes describe as “medical menopause.” Your body behaves as though it has entered menopause — hot flashes and all — but the effect reverses once the drug clears your system. The dosing is either a single 3-month depot injection of 11.25 milligrams or monthly injections of 3.75 milligrams for up to three months, typically combined with iron therapy to address the anemia that heavy fibroid bleeding often causes.
According to data published by the National Center for Biotechnology Information, uterine volume shrinks approximately 50 percent after three months of GnRH agonist therapy. A separate study using goserelin, marketed as Zoladex, confirmed that the greatest shrinkage of about 30 percent occurs in the very first treatment cycle, with continued but more modest reductions in the months that follow. To put this in concrete terms, consider a woman with a uterus enlarged to the size of a 16-week pregnancy due to multiple fibroids. After three months on Lupron, that uterus might shrink to the equivalent of an 8- to 10-week size. That reduction can transform a complex surgical case into a routine one, shorten operating time, reduce blood loss, and in some cases make a minimally invasive myomectomy possible where open surgery would have been the only option.
What the Clinical Evidence Shows — and Where It Falls Short
The numbers from clinical trials are genuinely impressive at first glance. The FDA-approved labeling for Lupron Depot cites that 77 percent of leuprolide-treated patients achieved more than a 25 percent reduction in uterine volume. A peer-reviewed study indexed on PubMed found that mean uterine volume decreased 36 percent at 12 weeks of therapy. These are not marginal improvements. For women bleeding through clothing, missing work, or becoming dangerously anemic, a 36 to 50 percent volume reduction represents a meaningful change in daily life. However, the critical limitation is durability. Fibroids regrow after stopping treatment. The same PubMed study found that the mean time to return to pretreatment uterine size is approximately 8.3 months after cessation of therapy.
Menstrual periods typically resume within two months of the last injection. this means that unless surgery follows the injection window, most women end up back where they started within a year. The injection buys time; it does not buy a cure. There is also the question of who should not use this treatment. Women who are already at risk for osteoporosis face a real dilemma, because GnRH agonists accelerate bone density loss. Treatment is generally limited to three months, with a maximum of six months in select cases, specifically because of this skeletal cost. For a 48-year-old woman approaching natural menopause, three months of medical menopause might be tolerable. For a 32-year-old hoping to preserve fertility and bone health for decades, the calculus is different, and the conversation with her doctor should reflect that.
Pre-Surgical Strategy — Why Doctors Prescribe Injections Before the Operating Room
The primary and FDA-approved use of Lupron Depot for fibroids is not as a standalone treatment. It is approved specifically for the preoperative treatment of uterine fibroids accompanied by anemia caused by heavy uterine bleeding. The logic is practical: a surgeon operating on a smaller uterus with better blood counts faces fewer complications and can often use less invasive techniques. Consider a woman scheduled for a myomectomy — the surgical removal of fibroids while preserving the uterus.
If her largest fibroid is 10 centimeters and her hemoglobin is dangerously low at 8 grams per deciliter, her surgeon might postpone the procedure and prescribe three months of Lupron plus iron supplementation. By the time she reaches the operating room, the fibroid may have shrunk to 6 or 7 centimeters and her hemoglobin may have climbed to a safer 11 or 12. The surgery becomes shorter, the recovery faster, and the risk of transfusion drops considerably. This pre-surgical approach is also used before hysterectomy, particularly when the uterus is so enlarged that a vaginal or laparoscopic approach would otherwise be impossible. Shrinking the uterus with medication can convert what would have been a major open abdominal surgery into a procedure performed through small incisions or through the vagina, with all the recovery benefits that come with less invasive surgery.
Oral Alternatives That Are Changing the Conversation
The pharmaceutical landscape for fibroid treatment has shifted significantly in recent years, and women now have FDA-approved oral options that did not exist a decade ago. Myfembree, a once-daily pill combining relugolix with estradiol and norethindrone acetate, was approved by the FDA for heavy menstrual bleeding associated with fibroids. In the Phase 3 LIBERTY 1 and LIBERTY 2 trials, Myfembree demonstrated a 72 percent response rate, and unlike Lupron, it can be used for up to 24 months. Oriahnn, another oral combination using elagolix with estradiol and norethindrone acetate, offers a similar mechanism as an FDA-approved GnRH antagonist. In Europe, linzagolix received European Medicines Agency approval in June 2022 and launched commercially in Germany in September 2024, with flexible dosing options of 100 milligrams or 200 milligrams that allow physicians to tailor treatment intensity.
The tradeoff between injectables and oral medications comes down to speed versus sustainability. Lupron injections produce rapid, dramatic volume reduction — ideal before surgery. Oral GnRH antagonists like Myfembree offer longer treatment windows and the convenience of a daily pill, but they are primarily aimed at symptom management rather than volume reduction for surgical planning. A woman who needs fibroids shrunk before a myomectomy in three months is still more likely to be prescribed an injection. A woman managing heavy bleeding who wants to avoid or delay surgery may find an oral antagonist more appropriate. Neither choice is universally better; the right one depends on what the treatment needs to accomplish.
Side Effects and the Bone Density Question
The side effect profile of GnRH agonist injections is not trivial, and women deserve honest information before consenting. Because the injection works by inducing a temporary menopause, the side effects mirror menopause itself: hot flashes, night sweats, vaginal dryness, mood changes, headaches, and decreased libido. For some women, these symptoms are mild and manageable. For others, they are severe enough to affect work, relationships, and sleep. The most consequential concern is bone density loss. Estrogen plays a critical role in maintaining bone mineral density, and suppressing it — even temporarily — accelerates bone resorption.
This is why treatment is capped at three to six months. Studies have documented measurable decreases in bone density during GnRH agonist therapy, and while some recovery occurs after the drug is discontinued, the degree of recovery varies. Women with pre-existing osteopenia or risk factors for osteoporosis should have a bone density assessment before starting treatment and should discuss the risks frankly with their provider. A common misconception is that these side effects are a sign the drug is not working or that something has gone wrong. In reality, the side effects are the mechanism. If you are not experiencing some degree of estrogen suppression symptoms, the drug may not be adequately suppressing estrogen, and the fibroids may not be shrinking. That said, the severity of side effects does not correlate perfectly with treatment efficacy, and no woman should be told to simply endure intolerable symptoms without exploring management strategies.
Emerging Research — Collagenase Injections and Direct Fibroid Targeting
While GnRH agonists work systemically by altering hormone levels throughout the body, researchers at Washington University are developing a fundamentally different approach: injecting an enzyme directly into the fibroid itself. Their work uses Clostridium histolyticum collagenase delivered through an injectable hydrogel-copolymer called LiquoGel. The concept is to soften and break down fibroid tissue at the source without disrupting the hormonal environment of the entire body.
This technology is currently in preclinical and ex-vivo stages and has not yet entered human trials. It is not a treatment anyone can access today. But if it eventually proves safe and effective, it would represent a paradigm shift — from managing fibroids by manipulating hormones to dissolving them directly with targeted injections. The uterine fibroid drug market is projected to reach 12.8 billion dollars by 2035, according to a December 2025 report from Astute Analytica, and that kind of investment is accelerating the pace of innovation.
Updated Guidelines and What Comes Next
In 2025, the International Federation of Gynecology and Obstetrics published updated best practice guidance on the medical treatment of uterine fibroids, reflecting the expanding role of GnRH antagonists and the growing body of evidence supporting longer-term medical management. These guidelines represent a meaningful shift from the era when hysterectomy was the default answer for symptomatic fibroids.
The trajectory of fibroid treatment is moving toward more options, more personalization, and less reliance on surgery as a first-line response. Between injectable GnRH agonists for rapid pre-surgical shrinkage, oral GnRH antagonists for longer-term symptom control, and emerging technologies like direct collagenase injection, the next decade is likely to offer women choices that previous generations simply did not have. The key is ensuring that women know these options exist and that the conversation with their healthcare provider starts well before symptoms become an emergency.
Conclusion
GnRH agonist injections like Lupron Depot remain the most effective tool for rapidly shrinking uterine fibroids, delivering a 36 to 50 percent volume reduction in just three months. The clinical data is robust: 77 percent of treated patients see significant shrinkage, and the greatest reduction occurs in the first cycle. But this treatment is a bridge, not a destination.
Fibroids return to their original size within about eight months of stopping therapy, and side effects including bone density loss limit treatment duration. For women and the families who support them, the practical takeaway is this: an injection exists that can meaningfully shrink fibroids in a short window, but it works best as part of a larger plan — whether that plan involves surgery, a transition to oral medications for longer-term management, or watchful waiting as menopause approaches. The decision deserves a thorough conversation with a gynecologist who can weigh fibroid size, symptoms, fertility goals, bone health, and personal priorities. No single treatment is right for every woman, and the best outcomes come from informed, unhurried choices.
Frequently Asked Questions
How quickly do fibroids start shrinking after the injection?
The greatest shrinkage — approximately 30 percent — occurs during the first treatment cycle. Most women begin noticing symptom improvement, particularly reduced bleeding, within the first month, though maximum volume reduction takes the full three months of therapy.
Will fibroids grow back after I stop the injections?
Yes. Clinical data shows that the mean time to return to pretreatment uterine size is approximately 8.3 months after stopping GnRH agonist therapy. Menstrual periods typically resume within two months of the last injection.
Can I use Lupron Depot as a long-term treatment instead of having surgery?
Lupron Depot is FDA-approved for a maximum of three months for fibroid treatment, with some physicians extending to six months in select cases. Longer use is not recommended due to bone density loss. It is primarily designed as a pre-surgical treatment, not a substitute for surgery.
Are there oral medications that work similarly without the injection?
Yes. Myfembree and Oriahnn are FDA-approved oral medications that use GnRH antagonists combined with low-dose hormones to manage heavy menstrual bleeding from fibroids. Myfembree showed a 72 percent response rate in clinical trials and can be used for up to 24 months.
What are the most common side effects of fibroid-shrinking injections?
The most common side effects are hot flashes, night sweats, vaginal dryness, headaches, mood changes, and decreased libido. These occur because the drug works by temporarily suppressing estrogen, creating a reversible menopausal state. Bone density loss is the most significant long-term concern.
Does insurance typically cover GnRH agonist injections for fibroids?
Most insurance plans cover Lupron Depot when prescribed for the FDA-approved indication of preoperative fibroid treatment with anemia. However, coverage varies by plan, and prior authorization may be required. Patients should verify coverage with their insurer before starting treatment.
