Leuprolide is a hormone-suppressing medication used primarily to treat prostate cancer, endometriosis, uterine fibroids, and early puberty in children. It works by shutting down the body’s production of sex hormones, including testosterone and estrogen, which fuel the growth of these conditions. It is also used in fertility treatments to give doctors precise control over ovulation timing.
How Leuprolide Works
Leuprolide mimics a natural brain hormone called GnRH, which normally signals the pituitary gland to release the hormones that drive sex hormone production. When you first start leuprolide, it actually causes a brief surge in testosterone or estrogen, lasting roughly one to two weeks. This is sometimes called the “flare” effect.
After that initial surge, something counterintuitive happens. The continuous presence of leuprolide overwhelms and desensitizes the pituitary receptors, effectively shutting them down. The pituitary stops sending signals, and the ovaries or testes stop producing sex hormones. The result is a dramatic, sustained drop in testosterone or estrogen to very low levels, sometimes described as a form of chemical castration in the context of prostate cancer treatment.
Prostate Cancer
Prostate cancer is the most common reason leuprolide is prescribed. Most prostate cancers depend on testosterone to grow, so driving testosterone to extremely low levels can slow or halt disease progression. This approach is called androgen deprivation therapy.
The traditional target was testosterone below 50 ng/dL, but more sensitive testing has shown that surgical castration actually brings levels below 20 ng/dL. Many professional guidelines, including those from the European Association of Urology and the FDA, now recognize this lower threshold as the preferred target. In clinical trials, over 99% of patients on one formulation achieved testosterone below 50 ng/dL, and 90% to 96% reached the stricter 20 ng/dL threshold by week six.
Leuprolide for prostate cancer is typically given as a long-acting injection. Formulations range from a monthly shot (7.5 mg) to a six-month shot (45 mg), so your treatment schedule can be tailored to what’s practical for you. Your doctor will monitor testosterone levels periodically to confirm suppression is holding.
Endometriosis
Endometriosis is a painful condition where tissue similar to the uterine lining grows outside the uterus. Because this tissue responds to estrogen, suppressing estrogen with leuprolide can significantly reduce pain, bleeding, and inflammation. The standard regimen is a monthly injection for up to six months.
The tradeoff is bone loss. Without estrogen, bones lose mineral density relatively quickly. In clinical data, women on leuprolide alone lost an average of 3.2% of spinal bone density over 24 weeks and 6.3% over a full year. To counter this, doctors commonly prescribe a small daily dose of a progestin (called “add-back therapy”) alongside leuprolide. With add-back therapy, bone loss dropped to just 0.3% at 24 weeks and 1.0% at one year.
If symptoms return after the first course, retreatment is possible for another six months, but only with add-back therapy included. The total treatment duration should not exceed 12 months because of cumulative effects on bone density.
Uterine Fibroids
Uterine fibroids are noncancerous growths in the uterus that can cause heavy bleeding, pelvic pressure, and pain. Leuprolide shrinks fibroids by cutting off their estrogen supply. It is often used for a few months before surgery to reduce fibroid size and make the procedure easier, or to manage symptoms in women approaching menopause.
Treatment is typically limited to three months for fibroids. Even in that short window, spinal bone density decreased by an average of 2.7% in clinical studies. Because fibroids grow back once estrogen returns, leuprolide is not considered a permanent solution on its own.
Central Precocious Puberty
When children begin developing signs of puberty unusually early (before age 8 in girls, for example), the condition is called central precocious puberty. It happens because the brain’s hormonal signaling system activates too soon, triggering breast development, rapid growth, and bone maturation ahead of schedule. Left untreated, this can lead to shorter adult height and psychosocial challenges.
Leuprolide pauses this process by suppressing the premature hormonal signals. Doctors confirm the diagnosis through a combination of physical signs, blood hormone levels, bone age X-rays, and sometimes a stimulation test that checks how the pituitary responds. Treatment continues until the child reaches a more appropriate age for puberty, at which point the medication is stopped and normal development resumes.
Fertility Treatments
In IVF and other assisted reproduction cycles, leuprolide plays a different role. Rather than being used for long-term suppression, it is given at low daily doses starting about a week before a menstrual period. The goal is to temporarily shut down the body’s own hormone signals so the fertility team can control the timing precisely.
This “downregulation” prevents your body from releasing eggs too early while stimulation medications encourage multiple follicles to grow. Once the follicles reach the right size and hormone levels look good, leuprolide is stopped and a trigger shot is given to induce final egg maturation before retrieval. In some protocols, leuprolide itself is used as the trigger shot, taking advantage of that initial hormone flare to mature eggs while avoiding a risk called ovarian hyperstimulation syndrome.
How It Is Given
Leuprolide comes in several forms. The most common is a depot injection, a slow-release shot given into the muscle. For prostate cancer, four depot options are available: 7.5 mg monthly, 22.5 mg every three months, 30 mg every four months, or 45 mg every six months. For endometriosis and fibroids, the typical formulation is 3.75 mg monthly. In fertility protocols, it is given as a small daily subcutaneous injection, which patients learn to self-administer at home.
Side Effects
Most side effects stem directly from the loss of sex hormones. In both men and women, hot flashes are the most common complaint. Women may experience vaginal dryness, mood changes, headaches, and the bone density loss described above. Men on long-term therapy for prostate cancer often deal with fatigue, reduced libido, muscle loss, and weight gain.
The initial hormone flare during the first one to two weeks can temporarily worsen symptoms. In prostate cancer, this may mean a brief increase in bone pain or urinary symptoms. For this reason, doctors sometimes prescribe a short course of an additional medication to block the effects of that testosterone surge.
Long-term use in men has been linked to increased risks of cardiovascular problems and metabolic changes like higher blood sugar and cholesterol, so periodic monitoring of these markers is standard during treatment.
Who Should Not Take Leuprolide
Leuprolide is contraindicated during pregnancy. It can cause fetal harm and may lead to spontaneous abortion. Women of childbearing age should confirm they are not pregnant before starting treatment. It is also contraindicated in anyone with a known allergy to GnRH-type drugs or any of the inactive ingredients in the formulation, as anaphylactic reactions have been reported.