What Is Leuprolide?

1. How does leuprolide work?

The Lupron Depot prescribing information describes leuprolide as a nonapeptide, or nine-amino-acid peptide, with more potency than natural GnRH. The body’s own GnRH reaches the pituitary in bursts, and that pulsing pattern keeps the pituitary sensitive. Leuprolide instead provides continuous stimulation, which desensitizes it.

The result unfolds in two stages:

• Flare. LH and FSH climb first. In men, testosterone and dihydrotestosterone (DHT, a more potent androgen) rise; in premenopausal women, estradiol and estrone rise. The label puts the early testosterone increase at about 50% above baseline.
• Shutdown. With continued exposure, LH and FSH fall. Within two to four weeks, testosterone reaches the castrate range in men while women’s estrogen falls to levels typical after menopause.

The label reports that castrate testosterone has been held for more than five years in men with prostate cancer. Leuprolide does not work when swallowed, so every product is injected. For background on why peptides like this are usually injected, see the peptide overview.

2. What forms and doses are approved?

Several products deliver the same active drug on very different timelines. The doses below are the labeled ones, taken from the daily injection label, the Lupron Depot 3.75 mg label, the Lupron Depot 11.25 mg label, the pediatric Lupron Depot-PED label and Eligard’s label.

How long treatment runs for each use

The first FDA approvals were the daily injection, Lupron, on April 9, 1985 (NDA 019010), and Lupron Depot on January 26, 1989 (NDA 019732). The Lupron brand of the daily injection has since been discontinued, while generics remain. DailyMed also lists other leuprolide products such as Camcevi, Fensolvi and Vabrinty (DailyMed product search).

3. How long does leuprolide last in the body?

Leuprolide itself is short-lived. After a 1 mg intravenous dose in healthy men, the daily injection label reports a terminal half-life of about 3 hours, clearance of 7.6 L/h and a volume of distribution of 27 L. Subcutaneous bioavailability is comparable to intravenous, and 43–49% of the drug binds to plasma proteins.

Depot products solve the short half-life by holding the peptide in slowly dissolving polymer microspheres. Blood levels spike shortly after the injection, then settle at a low plateau that lasts the whole interval. The Lupron Depot label gives these figures:

Because each depot releases drug on its own curve, the labels say strengths are not additive. Two 1-month shots are not a substitute for one 3-month shot, and splitting a longer depot does not produce a shorter-acting dose. A generic half-life calculator built on the 3-hour figure would badly misrepresent a depot, whose release profile is set by the formulation.

4. What do the clinical trials show?

Prostate cancer: leuprolide against estrogen therapy

Before GnRH agonists, medical castration often used diethylstilbestrol (DES), an oral estrogen. The Leuprolide Study Group’s 1984 randomized trial assigned 199 men with metastatic prostate cancer to leuprolide 1 mg/day by injection (98 men) or DES 3 mg/day (101 men).

The investigators judged the two treatments equally effective, with fewer side effects overall on leuprolide.

How reliably depots reach the castrate range

The label trials defined castration as testosterone at or below 50 ng/dL (Lupron Depot label).

The 6-month study shows the flare directly. Mean testosterone climbed from 435 to 608 ng/dL during the first week, then fell to 16 ng/dL by week 4.

Endometriosis, fibroids and early puberty

According to the Lupron Depot 3.75 mg label, monthly treatment had stopped menstruation after one month in 74% of women and after two months in 98%. Regular cycles had resumed in 95% by the third month after stopping. In three controlled fibroid trials, average uterine volume shrank 41% and fibroid volume 37%. Uterine size returned to baseline a mean of 8.3 months after treatment ended.

In the main Lupron Depot-PED trial, 55 children with a mean age of 7 were treated monthly for an average of 4 years. By month 1, 96% had a peak LH response under 1.75 mIU/mL on stimulation testing. Half a year after the injections ended, the average peak LH response was back up to 20.6 mIU/mL.

5. What does leuprolide do to muscle, fat and bone?

Removing testosterone shifts body composition in the direction most GLP-1 users are trying to avoid. In Smith and colleagues’ 2002 study, 40 men with non-metastatic prostate cancer received the 3-month 22.5 mg depot for 48 weeks; 32 completed the analysis. Testosterone fell 96.3%.

Age and cancer are not required for this effect. Mauras and colleagues gave six healthy men, mean age about 23, two Lupron injections three weeks apart. Ten weeks later, testosterone had dropped from 535 to 31 ng/dL, fat-free mass from 56.5 to 54.4 kg, body fat had risen from 19.2% to 22.2%, whole-body protein synthesis was 13% lower and leg strength had declined. With only six participants, the study shows direction more than precise size.

These studies did not involve weight-loss drugs, so they cannot say how leuprolide would interact with lean-mass changes during semaglutide or tirzepatide treatment. The broader question of muscle during GLP-1 weight loss is covered in GLP-1 and muscle loss.

Bone

Over 48 weeks, in 47 men with prostate cancer that had not spread to bone, Smith and colleagues (2001) reported that men randomized to leuprolide by itself lost 3.3% of lumbar spine bone mineral density (BMD) and 8.5% of trabecular (inner, spongy) spine BMD. In the arm that added pamidronate, a medicine that protects bone, density did not drop significantly.

Women show the same pattern. The 3.75 mg label gives lower-spine BMD results with and without norethindrone acetate add-back:

The label cautions that part of this loss may not reverse, which is why gynecologic treatment courses are capped.

6. Why do testosterone researchers use leuprolide?

Because it reliably removes the body’s own testosterone, leuprolide lets investigators set testosterone levels by design. In the 5α-Reductase Trial reported by Bhasin and colleagues in 2012, 139 healthy men aged 18 to 50 received Lupron Depot 7.5 mg monthly plus weekly testosterone enanthate at one of four doses (50, 125, 300 or 600 mg) for 20 weeks, with or without the drug dutasteride.

Among men not given dutasteride, fat-free mass changed by 0.8 kg (95% CI −0.1 to 1.7) at 50 mg/week and by 8.1 kg (95% CI 6.7 to 9.5) at 600 mg/week. Those gains reflect the testosterone dose. Leuprolide’s job in the design was to take natural production out of the equation, not to build muscle.

7. What are the side effects and warnings?

None of the labels carries a boxed warning. Most adverse effects follow predictably from very low sex hormones. The Lupron Depot label reports these as the most frequent in its prostate cancer trials:

The label adds reduced sex drive, erectile problems and breast tissue growth to the list. Among women treated for endometriosis, reactions reported in over 10% included hot flashes, headache, vaginitis, depression or mood swings, weight change, nausea, lower libido and dizziness (3.75 mg label).

Tumor flare

In prostate cancer, the early testosterone surge can temporarily worsen the disease. The label lists bone pain, neurological symptoms, blood in the urine and urinary obstruction. In men with cancer in the spine, spinal cord compression can cause paralysis.

Blood sugar, lipids and the heart

Warnings in the labels cover high blood sugar (hyperglycemia), new diabetes, higher blood lipids and fatty liver disease. They also describe reports in men of more heart attacks, strokes and sudden cardiac deaths. In Keating and colleagues’ Medicare analysis covering 73,196 men whose prostate cancer was localized, men treated with GnRH agonists had higher rates of diabetes (adjusted hazard ratio 1.44), coronary heart disease (1.16), heart attack (1.11) and sudden cardiac death (1.16). Because the data were observational, they link the drug class to these outcomes without proving it caused them.

Another labeled concern is that lowering androgens can lengthen the QT interval, a measure of how long the heart takes to reset electrically between beats.

Other labeled warnings and contraindications

• Seizures, in people with or without a prior history.
• Severe skin and hypersensitivity reactions such as Stevens-Johnson syndrome and DRESS.
• Depression and mood changes, with rare reports of suicidal thoughts.
• Pituitary apoplexy, a rare bleed or infarct in the pituitary, mostly within 2 weeks of the first dose; a pituitary adenoma was diagnosed in most reported cases.
• Possible fetal harm. In rabbit studies, one depot injection produced major birth defects in the offspring. The gynecologic products are contraindicated in pregnancy and in undiagnosed abnormal uterine bleeding.
• Hypersensitivity to GnRH, GnRH agonists or product ingredients rules out use of any product.

8. Do hormones and fertility recover after stopping?

Because it shuts down the hormones that drive the testes and ovaries, the label warns that leuprolide can reduce fertility in men and women. Shrinkage of reproductive organs seen in rats was reversible after dosing ended, and the label says normal function usually returns within three months. Lab tests of pituitary and gonadal function can also read abnormally for as long as three months after the final injection, which matters when interpreting results.

Recovery can be much slower in older men after long treatment. Nascimento and colleagues followed 307 prostate cancer patients after they came off hormone-suppressing treatment, which had lasted 17 months on average.

Slower recovery was associated with age above 65 and with treatment lasting more than 6 months. The cohort included androgen deprivation of any kind, so its figures are not specific to leuprolide.

9. Is leuprolide legal, and how does it compare with hCG and kisspeptin?

In the US, leuprolide requires a prescription. It does not appear on the DEA’s Schedule III list of anabolic steroids in 21 CFR 1308.13.

The WADA 2026 Prohibited List bans leuprorelin for male athletes both in and out of competition, in section S2.2.1, which covers peptides that stimulate testosterone in males. The same category covers gonadorelin and other GnRH agonists, LH, hCG and kisspeptin analogs such as kisspeptin-10.

That grouping can mislead. The hCG and kisspeptin-10 guides cover compounds discussed for raising testosterone, while leuprolide’s labeled, sustained effect is suppression, with only a short flare at the start. Anyone comparing these compounds should look at the direction and duration of the testosterone change in each, not just their shared anti-doping category.

10. What can you measure or track on leuprolide?

The labels and trials point to a handful of measurable markers. For each, the treating clinician decides what to order and when.

For people also on a GLP-1 medicine, keeping these records alongside GLP-1 doses makes it easier to tell a clinician what changed and when. A log cannot separate the effects of two drugs started close together, so noting start dates and any other medication changes is what keeps the record useful. The tracker vs spreadsheet guide covers practical ways to keep that history in one place.

11. Leuprolide FAQ

• Does leuprolide increase testosterone?

  Only briefly. Testosterone rises during the first one to two weeks, by about 50% in the label's description, and then falls to the castrate range within about two to four weeks of continuous treatment. Leuprolide is used to switch testosterone production off, not to boost it.

• Is leuprolide legal?

  In the US it is a prescription drug, approved since 1985, and it is not on the DEA's Schedule III list of anabolic steroids. The WADA 2026 Prohibited List bans leuprorelin at all times in male athletes.

• What are the side effects of leuprolide?

  Hot flashes were the most common reaction in the prostate cancer label trials, affecting roughly 57% to 59% of men. Other labeled effects include fatigue, injection site reactions, lower libido, erectile dysfunction, breast enlargement, bone loss, higher blood sugar and lipids, mood changes and, early in treatment, a tumor flare in prostate cancer.

• How long does leuprolide stay in your system?

  Leuprolide given intravenously has a terminal half-life of about 3 hours. Depot injections are built to keep releasing it for 1, 3, 4 or 6 months depending on the product. The label says normal pituitary and gonadal function usually returns within three months of stopping, though some older men after long treatment recover much more slowly.

• Does leuprolide cause muscle loss?

  In a 48-week study of men with prostate cancer, percent lean body mass fell 2.7% and percent body fat rose 9.4% on a 3-month depot. In six young healthy men, fat-free mass fell from 56.5 to 54.4 kg over 10 weeks of testosterone suppression.

• Can leuprolide be used with semaglutide or tirzepatide?

  The sources reviewed here contain no study of leuprolide combined with a GLP-1 medicine. Two label warnings overlap with what GLP-1 users watch: high blood sugar and diabetes, and the loss of lean mass that comes with low testosterone. A prescriber managing both drugs is the right person to judge that combination.

• Does leuprolide affect fertility?

  Yes. The label states it may impair fertility in men and women because it suppresses the whole reproductive hormone axis. Function usually returns after stopping, and leuprolide is contraindicated in pregnancy for the gynecologic products.

• What is the difference between Lupron Depot and Eligard?

  Both deliver leuprolide acetate on 1-, 3-, 4- and 6-month schedules for advanced prostate cancer. Lupron Depot is injected into muscle, while Eligard is injected under the skin. Lupron Depot also comes in strengths for endometriosis, fibroids and, as Lupron Depot-PED, central precocious puberty.

12. Sources